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SECTION
THREE REVIEW OF LITERATURE
Water is the most abundant substance on earth. The oceans alone cover more than
70% of the earth’s surface and contain roughly 1.35 x 109 Km3 of water. Today the
problem is not only one of water availability but of environmental quality and ecological
balance. With increasing industrialization, urbanization & technological advance in all
fields, sources of water are getting more & more seriously polluted. The survival of
Life on Earth will be threatened if, the present rate of pollution continues unabated
(Meadows et al., 1974). These problems grow more acute everyday. About 4 billion
people in 1975 and 2 million more are added everyday. This figure is anticipated to
reach 10 to 16 billion by the year 2050 (UN, 1973). The pressure will be extremely
acute in some areas, but such a growth rate for the population has serious implications
for both developing & developed countries. In the advanced countries, there is the
increasing problem of water quality with resource scarcity. For developing countries,
like, India, which are totally dependent on water for meeting even their food needs,
the problem is extremely serious both from resource and environmental
considerations. It is not generally appreciated that water, though renewable, is a
critical & limited resource. Secondly, increasing irrigation has serious environmental
implications (Worthington, 1976).[27]
The necessity to develop water resources, optimally & urgently, is thus self-evident.
While no doubt, issues & emphases vary from country to country in view of
climatologic, hydrologic, geographic, demographic & economic variations, almost all
nations now agree that, the one single measure for the sustenance of mankind is to
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develop water optimally as a resource and as an environmental component (Water for
Peace, WED-1967). No doubt developmental measures have been initiated in the past
but the needs of the future give a new dimension to all activity in this field. [27]
The oil spillage while its exploration, production & transportation activities has been
affecting the seashore as well as coastal & marine waters and environment. Some
countries have passed resolutions to protect these areas. However, sometimes
accident of marine tanker causes a lot of pollution to the marine environment. Coastal
region has been receiving a lot of attention in the recent years, mainly because of
growth of public awareness about sustainable development of coastal zone &
associated ecological system. Coastal Zone is the major component of ocean
environment, which is most susceptible to the day-to-day kinds of contamination, is
often the province of quality regulatory agencies established by individual nations. The
coastal zone extends from the low-tide line to the 200m-depth contour, tending to
match the geophysical demarcation of the continental shelf. The coastal zone can be
as wide as 1400Kms along some coasts and less than 1Km along others. The average
width of the coastal zone worldwide is about 50Kilometres comprising about 8% of the
surface of the ocean. Species that inhibit the coastal zone has been very resilient to
such natural environmental stresses as wide daily variations in salinity, turbidity,
temperature & UV radiation.[6, 36, 42]
Now, no longer the environment can be subject to indiscriminate exploitation. Hence, it
demands the concept of Sustainable Development. The sustainable development may be
considered as development that meets the needs of the recent, without compromising
the ability of future generations to meet their own needs. It is a process of change in
which the exploitation of resources, the direction of investments, the orientation of
technological development and institutional change are all in the harmony. It enhances
the current & future potential to meet all human needs & aspirations. It is the
combination of the ecology & economy. Hence, sustainable development is a threat for
the maintenance of life supporting system and economic developments. It is based on
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premises of the integrity of the afforestation for the welfare of the mankind. Any
developmental activity achieved at the expenses of environmental degradation is
considered as unsustainable. Important issues of sustainable development are
biodiversity, ecosystem preservation, food security system & population.[42]
The above can be done effectively through local issues and situation which been vast
relevance in the process of development of any region. Sustainable development for
pollution management demands entirely some strategic mechanism which involves local
pollution, local resources, as physical areas of development. Sustainable development is
a development strategy through which any developmental action should not be started
hurriedly. It should be in such a manner that, the same or economic will tolerate. The
technology could cooperate the environment respond positively. The authorities could
coordinate against distortion. Some of the environmental changes, because of pollution
will produce irreversible damage to the ocean, capacity to sustain life. Greater
attention also needs to be given to the understanding of the nature and dimension of
the world’s biodiversity. The multiprolonged development manifestations &
complexities of contemporary man-nature-pollution relationship have raised the vital
question of survival & sustenance. Development processes entitle chronological bonds
of nature & pollution relationship.[42]
Thus, it is clear that, environmental engineering has an increasingly important role to
play in sustained development. Sustainability is a dynamic concept reflecting changing
& evolving needs. Environmental engineers need to integrate a wide variety of
disciplines such as ecology & geography and waste disposal and apply technology to
pressure the ability to meet the long-term objectives.[42] It is more clear from the
excerpts from the UN Secretary General Kofi A. Annan’s address on WED-1997 on a
central theme Life on Earth selected by UNEP, that: Current & emerging
environmental threats facing the world are of such a great magnitude and so universal
in nature that no country, or a group of countries, can hope to tackle them alone. It
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was this realization that would place environmental issues securely on the international
political agenda and thus the UNEP was established.[7]
As we approach the new millennium, we face a range of complex, long-term
environmental problems portending immense consequences for the economic well-being
and security of nations throughout the world: global warming, depletion of the ozone
layer, the decline of biodiversity, the loss of soil and forests, contamination of our
fresh water supplies, vanishing fisheries and the flood of toxic substances entering
our environment & our bodies, threatening our physical & reproductive health.
Five years ago, at the United Nations Conference on Environment and Development in
Rio de Janeiro, governments adopted Agenda-21 and other major international
environmental agreements. We now return to many of the fundamental questions
addressed at Rio. How can we stop the rapid depletion of the world’s resources? How
can we find an equitable balance between the economic, social & environmental needs
of the present and those of future generations? And how can we enhance partnerships
between developed & developing nations, and between governments & civil society, so
that the basic needs of all human beings can be met? I look forward to a truly
comprehensive assessment of these and other questions, and to frank & honest
assessment of our progress – achievements as well as shortcomings. The process of
long-term sustainable development defined by the Earth Summit’s Agenda-21 has to be
implemented.”[7]
Thus, At Rio, in a consensus unique in the history of international relations, the world
leaders agreed on the steps that must be taken now. Agenda-21’ outlines a plan and a
concrete approach to creating environmentally sound & sustainable development. In
concrete & practical terms, sustainable development means a commitment to finding
and using resources that are renewable, and a more careful management of those
resources that are non-renewable. It means choosing products & production processes
that avoid an adverse impact on the environment. It means a greater willingness by
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business to take environmental factors into account. It means respecting biological
diversity in agriculture, and avoiding the excessive use of harmful, energy-intensive
chemicals. It means eliminating public subsidies that encourage the liquidation of our
national environmental heritage. It means addressing the acute poverty that leads
parents to wish forever more children as a buffer against the insecurities of their old
age. It means using preventive diplomacy to avoid the destruction of war and the
waste engendered in the preparation for war”, said UN Secretary General Boutros
Ghali in his message on the occasion of WED-1993.[28]
So, we can say that, to facilitate optimal utilization of the finite natural resources for
ensuring a sustainable benefit stream for a better quality of life, it is essential that
the technology conversion process must be made as possible. This will provide a much
higher output of the productive goods & services from the same national inputs and
consequently reduce wastage that results in pollutants in the gaseous, liquid or solid
form. This policy, therefore, aims at:[43]
i) Adoption, adaptation & promotion of state-of-the-art technologies for waste
prevention and reduction by lesser consumption of raw materials with special
emphasis on indigenous efforts;
ii) Modification & up gradation of the process technologies for optimal utilization
of natural resources;
iii) Adoption of preventive approach for pollution control;
iv) Promotion & use of cleaner technologies; and
v) Ensuring access to cleaner technologies available abroad.
In the WEFO report to the Earth Council in the Engineer’s role & response to
sustainable development it is stated that: By the late 1980’s however, some faculties
in engineering education were adopting courses to increase environmental content. As
facilitators of sustainable development, engineers must acquire the skills, knowledge, &
information that are the stepping-stones to a sustainable future. The promotion of
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sustainable development demands that engineers cultivate an understanding of the
environmental issues, problems & especially risks and potential impacts of everything
we do. Engineering education must instill its students an early respect and ethical
awareness for sustainable development. Moreover, we must strive to promote universal
adoption of a sustainable development ethic, particularly among private & public sector
decision-makers, developers, investors and local, regional, national & international
governing bodies.”[3]
It is further clear from the various environmental awareness programs initiated by
UNEP on the occasion to commemorate WED-1998 with the theme For Life on Earth:
Save Our Sea; the day also honored the United Nations International Year of Ocean-
1998. On sustainable development to abate the environmental pollution, Ian Johnson,
Vice-President & Head, World Bank’s Network for Environmentally & Social
Sustainable Development, said: It took two centuries of environmental degradation
before worldwide concern brought world leaders to Stockholm in 1972 for the first
ever summit dedicated to the Environment. The meeting was a great boost to the still-
young environment and saw the establishment of a new international agency – UNEP –
to keep the environmental flame alive. The UNEP has quietly promoted environmental
management capacity in developing countries and pushed to include environmental
considerations in social & economic policy. But it is not just in East Asia & Latin
America that we have cause for concern. I do not need to rehearse the enormity of
the challenge. The world’s forests continue to be developed at an alarming rate. Urban
pollution takes a huge toll on people’s health. Topsoil is washed away in vast quantities.
Fisheries are depleted devastatingly fast. There is mounting evidence of climate
change. And all kinds of biological species, on land and under water, are threatened – in
many instances with extinction. We need greater international dialogue and co-
operation. The only way that we will succeed in making development more sustainable is
by acting in partnership – with governments, international agencies, the private sector,
local communities, non-governmental organizations and others. We look forward to a
strengthened partnership with a strengthened UNEP in the months & years ahead.”[8, 9]
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Therefore, any activity, either man-made or natural, along the coastal belt generates
anxiety amongst the users on what kind of impact the activity would have on the coast
and on the living conditions of coastal inhabitants. Hence, marine pollution has been on
the focus in the recent past due to increasing oil tanker mishaps in English Channel,
Gibraltar Bay, Malacca Strait & other parts of the World. The first large oil spill was
caused in 1967 by grounding of the tanker Torrey Canyon and the highest ever tanker
mishap caused due to human error in 1989 is the Exxon Valdez during its grounding off
the coast of a National Park. Thus, oil spill from such incidents has cautioned the
Environmentalists & Ecologists that the impact due to discharge of petroleum & its
products on marine life as well as on the environment has produced irreparable damage
to the coastal & marine environment.[3] That is why, a coalition of three conservation
groups, a United Nations agency and the World Bank is calling for major changes in
how the oceans are used because “the entire marine realm, from estuaries and coastal
waters to the open and deep sea, is at risk”. ‘People around the world are catching so
much fish that some stocks may soon disappear’, according to Elliott Norse, a marine
Biologist & Director of the team that published a report on behalf of the coalition.
And pollution from human sources is destroying some of the habitat that nurtures
marine life, he said at a news briefing. Asked to give an example of an area in danger,
he cited that, “the Pacific between Australia, Indonesia & the Philippines having the
richest shallow-water marine life in the world, is an example of an area in danger. In
addition, logging of coastal mangrove forests in the Philippines and the runoff of
nutrient laden waters from farmlands has destroyed the breeding grounds of some
marine life”.[6, 10, 11, 12]
The study, “Global Marine Biological Diversity”, is the first comprehensive report on
the state of the world’s marine life and what can be done to preserve what is left. In
addition to the World Bank, the study was sponsored by the UNEP, the Center for
Marine Conservation, World Conservation Union and the World Wildlife Fund. One
general recommendation to developed countries is that they reduce the oil & other
forms of pollution associated with industrial activities. ‘For their part, developing
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nations should not repeat the North’s wasteful path to prosperity, but should adopt
technologies and economic strategies that can improve economic and social conditions
sustainable without diminishing marine biological diversity’, the report stated. The
report also asks all countries to bar the imports of marine products gathered or made
in ecologically destructive ways.[12]
It has been estimated that nearly 200 ships carrying oil from the Middle East ply
across the Indian Ocean every day, going to the far eastern countries including Japan.
All these ships go closer to the Indian Sub-continent and through the Great Channel
between the Nicobar Islands & Northern Sumatra leading to the Malacca Straits.
Therefore, there are lots of chances of oil spills along this route, which has
extensively studied by the National Institute of Oceanography, India (Qasim, 1991).[2]
For long, beached vessels have been a common sight just off the coasts of
Maharashtra and Goa. Perennial eyesores which the state governments, after
preliminary investigations, preferred to ignore and tour operators made money out of
Hong Kong’s Kowloon Harbor in the 1980 Bond thriller, “The Man with the Golden Gun”.
That may change soon, with New Delhi frowning on the serious environmental hazards
of allowing single-hull old vessels carrying crude oil into its ports. Experts say that,
more than such accident-prone old tankers carry 40% of the crude coming in at the
ports on the western coast. Such accidents, coupled with regular dumping of untreated
organic waste & sewage, have raised oil pollution to alarming proportions in the Arabian
Sea, the common route for nearly 70% of oil movement in the region. As many as four
major beaches in Goa, including Calangute & Candolim, are being given the go-by by
tourists as the water there remains coated with a thin film of oil throughout the year.
Even bilge washing (clean-up of vessel tanks) reaching the coast is wreaking havoc with
Maharashtra’s coastal ecosystem, in the absence of monitoring personnel. Therefore,
these incidents have been the pivotal points in the approach of maritime nations to the
protection of the marine environment through international legislation &
implementation of rigorous requirements concerning the construction and exploitation
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of ships and offshore platforms, limiting the possibility & extent of oil spills. Regional
& bilateral international agreements between neighboring countries have been
concluded, containing contingency plans, describing the means & methods of
cooperation in case of a major spill.[10, 15]
In a study carried out in the year 2000, the Ministry of Environment & Forests
pointed out that oil pollutants, industrial waste & untreated sewage were depleting
oxygen supplies across the entire western coastline. It cited the example of Versova &
Mahim creeks and the Mumbai harbor, where dissolved oxygen at low tide is almost
zero, making the areas unable to sustain aquatic life. As a result, heavy metal
deposition on the seafloor off Maharashtra & Gujarat has increased at an alarming
rate. Metals like cadmium, lead, manganese & zinc have been found in benthic core
samples to depths of up to 45 Cm along with large amount of pesticides, particularly
off the Maharashtra & Goan coasts. The study advocated immediate corrective
measures like, dredging & the removal of contaminated sediments.[15]
Hence, it can be summarized that: the exponential increase in oil consumption, mostly
by the developed and the developing countries – which produce only a small amount of
petroleum they need for their industrial growth and economic expansion – has resulted
in a huge oil transport problem across the oceans. The World Energy production in
1976, for example, was as follows: The OPEC Countries: 51.4%, the Communist
Countries: 21.1%, the remaining Western Countries: 27.2%. The World Energy
Consumption (for 1975) was 5,790 billion ton oil units with a percentage energy
composition as follows: Petroleum- 42.9, Natural Gas- 19.2, Coal- 29.7 & other energy
sources- 8.2. The Western World altogether has consumed about 70% of the total and
the Communist Countries 30%. The percentage distribution of consumption in the
Western World was as follows: Western Europe- 19.5%, North America- 32.6%,
remaining Western World- 17.8%. These numbers & figures of consumption &
production suggest & indicate the followings:[44]
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a) The western industrialized countries produce about 27.2% or less of the World
Energy Sources and consume about 70% or more of the World Energy
Production.
b) The unequal geographical distribution of fossil fuel reserves over the globe
composes & introduces a historical shift of power and decision-making in energy
prices, energy allocation & uses. These are fundamental parameters & factors in
international trade and economic development today.
c) Oil transport through the oceans became a new reality of international trade.
The net oil imports for OECD Countries before the oil crisis of 1972-73 was put
to a level of 2,630 million tonnes, whereas after the oil crisis, the estimate was
lower, about 1,750 million tons. Today’s approximate oil transport estimate was
about 2,200-2,500 million tons. Transportation of these petroleum quantities is
a complex technical & economic problem, requiring cargo tankers 7-8 times
larger in tonnage capacity than the traditional ones of 300-400,000 tons or
more, the inherent risk of tanker breaking, mechanical failure or collision, the
potential spreading of these huge quantities in the ocean and thereby the grave
threat of marine pollution on a large scale are central questions of oil transport
management.
Thus, it is felt for the present thesis work for combating the effect of spilled oil to
aid in the restoration of the coastal environment. No appropriate means could be
undertaken on mitigating the effect of oil-spill unless & until we predict the exact area
covered by the spilled oil under the prevailing Oceanographic & Meteorological
conditions. Before undertaking such type of study, the available literatures were
further surveyed to find out whether any similar type of study in this field has been
carried out in India & Abroad, which is being discussed in chapter two.
42
CHAPTER
TWO BASICS OF OIL SPILL
RESPONSE
2.0 INTRODUCTION
Although oil slicks due to tanker accidents have been found to be of great concern, it
has been estimated that normal operations and usage of oil seems to contribute more
to the pollution load of the aquatic environment as shown in table-2. Usually most of
the oil is carried around the world in the form of crude oil. It is a complex mixture of
hydrocarbons with a wide range of molecular weights. The behavior of different
hydrocarbons is different on the ocean water. Most of the aromatics (about 25%) such
as, xylene, benzene & toluene, will evaporate. These are most toxic of the
hydrocarbons. The left over oil will form tar lumps and may get carried to the shore by
currents where beaches will get contaminated. Some of these lumps will get heavier by
absorbing silt & other particulates and sink to the bottom of the sea, the fate of
which has not been studied extensively. The tarry surfaces can act as ideal collecting
surfaces for pesticide aerosols, thus concentrating toxic materials, which can be
passed through food chains. The tarry residues are degraded by photo-oxidation and
bacterial action (Pryde, 1973).[2]
Thus, oil spill has become a sensitive issue. It makes headlines. It is the focus of
coverage by the media. The image in the public mind is blackened shorelines, fouled
fishing nets & dead sea-birds. The ever-increasing traffic in the straits of Malacca
43
and the intensifying activities in the exploration & development of offshore petroleum
resources in the South China Seas have resulted in increasing incidence of oil spills and
form a major threat to the rich & fragile ecosystem.[45]
Most of the time the world’s 85,000 ships perform their business silently, out of sight
& out of mind. Yet whenever an oil pollution incident occurs which is caused by a ship, it
attracts headlines world over, as we all know. Whether the shipping industry has been
unfairly singled out is somewhat a debatable issue. However, marine pollution despite
the best of efforts & measures will continue to occur. This is a fact of life. There
have been incidents both minor & catastrophic, such as Torrey Canyon in 1967, Amoco
Cadiz in 1978, & Exxon Valdez in 1989, each at intervals of 11 years. Judging by the
time intervals, is the year 2000, i.e. the new millennium, slated for another major
pollution disaster[46] ― and surprisingly it occurred in Indian coast.
When spilled at sea, most oils will normally break up & dissipate as a result of a number
of chemical & physical processes, which are collectively known as weathering. However,
some of the oils may not dissipate quickly and can lead to disastrous consequences. The
subject of oil spills is of great relevance to India in view of the large quantities of
crude oil as well as petroleum products being imported in oil tankers and transported
through pipelines & other means. The topic becomes important also because of
enhanced activity in offshore oil exploration & production. Possibility of a major oil
spill always exists under these circumstances and it can have serious implications due
to inadequate Indian experience in handling large oil spills.[47]
Thus, a fundamental requirement for responding effectively to a crisis or a
threatening situation such as that arising out of a major oil spill is to be fully aware of
all the connected aspects. The subsequent pages of this chapter provide a bird’s view
on salient environment related aspects of marine oil spills. This chapter has been
covered under the following heads:
44
Oil Spill covering hydrocarbon inputs in marine environments, some oil spill
statistics, etc.
Oil Spill Response (OSR) covering brief description of Oceanography,
Definitions of various oil-spill related terminologies, Research works done in
India & Abroad.
2.1 OIL SPILL
Oil spill, generally refers to the discharge of oil in the marine environment (including
estuaries). This is the main source of oil pollution occurring in the world. Every year a
lot of living marine organisms die due to the oil spill. As a result the whole ecosystem
in the biosphere gets affected leading to the imbalance in the environment. Worst
case of oil spill was during the Gulf War - 1991, when millions of gallons of oil were
dispersed in the ocean killing thousands of birds & animals. Human beings are also
added to this pollution. Hence, it is very much necessary to make people aware about
the harms of the oil spill and method to prevent them to happen further.[2]
Accidental spills of oil & other industrial substances into the ocean have put serious
strains on many marine environments throughout the world. Some of these, such as,
the grounding of the Exxon Valdez on 24th March, 1989 on Bligh Reef that resulted in
the spillage of approximately 11.0 million gallons of crude oil into the Prince William
Sound in Alaska, have had catastrophic impacts & long term consequences on local &
regional wildlife, human livelihood and recreational resources. One of the essential
elements of oil spill contingency planning in the coastal & marine environment is the
pre-spill identification and classification of oil-sensitive areas.[36, 48]
Majority of oil spills occurs due to shipwrecks from accidents. The oil pollution usually
comes from both crude & refined petroleum products. Once the crude oil has been
removed from the oil fields, it is transferred to the refinery for breakdown into
45
specific products. This process involves distillation, thermal or catalytic cracking and
subsequent reforming & blending to arrive at wide range of petroleum products or
feed back. The refining process of crude oil essentially involves the use of energy to
separate groups of compounds. One of the first products to be distilled at low
temperature from a crude oil is gasoline, whereas heavier wax or tar fractions are
derived at considerably higher temperature. The most common types of petroleum
products, which are likely to be released to the environment, besides crude oil itself
are Bunker-C, the heaviest distillate fraction with a specific gravity near 1.00,
compounds having C30 range or higher; diesel, the middle distillate fraction specific
gravity 0.825-0.850 having hydrocarbons in C12 – C23 range; kerosene containing
hydrocarbons with C10 – C12 range with a specific gravity of about 0.800 and gasoline
containing hydrocarbons with C5 – C10 range having specific gravity of approximately
0.700. From which it is clear that crude oils & their refined products vary widely
because of their physical & chemical properties, which in turn can greatly influence the
fate and effect of oil released into the marine environment. Each physical & chemical
property of oils must be considered at the time of oil spill response and at the same
time it is important to keep it in mind that these properties continuously change as the
oil weathers with the change of time. Therefore, a series of questions mentioned
below to be answered before taking any kind of response actions:[49]
Heating Point : does the oil is semi-solid or fluid stage?
Boiling Point : will part or all of the oil evaporate?
Flash Point : is there a threat of explosion or fire?
Pour Point : will the oil cool & become semi-solid?
Specific Gravity : will the oil float or sink?
Surface Tension : does the oil tend to spread?
Viscosity : does the oil flow?
Adhesion : will the oil stick to the shoreline material?
Solubility : will the oil evaporate or dissolve or will it be
Toxic to marine-life?
46
Aromatic Content : will the oil be toxic to marine-life?
The definitions of the above terms are given subsequently in the Section-2.2.
2.1.1 OIL INPUTS INTO THE MARINE ENVIRONMENT
Estimation of oil discharged globally into the marine environment is difficult. However,
worldwide annual inputs to the marine system have been estimated since 1970 are
presented in table-2.1 Pollution of marine environment by crude oil or petroleum
products arises from tanker accidents, deballasting operations, tank washing (COW
washing), offshore production, coastal refineries, municipal & industrial wastes (land
based activities), atmospheric fall outs and natural seepages. UNEP (1992) indicates
that the latest estimate of total annual petroleum hydrocarbons that finally reaches
the marine environment is about 2.33 million tones, of which some 15% is due to
accidents related to exploration, production & transportation activities. Almost 50% of
this input is contributed by land-based activities. The oil production in the world over
is 3452 million tones, out of which 2026 million tones are transported to different
parts of the world. The lion share is transported through marine environment. Among
this 45% of the transport originates from Middle East countries and passes through
Arabian Sea, Bay of Bengal & Indian Ocean.[36,49] From this we may be able to assume
the vulnerability of our seas & coastal environment to oil pollution.
In other words, oil around the coastline will arise from one or more of three main
sources:[50]
Accidents due to collision, fire explosion, grounding, well blowout, etc.
Illegal discharge of oil or oily waste and
Accidental spillages while transporting fuel or cargo from ship to ship or ship to
shore, and accidental spillages resulting from the incorrect operation of valves,
etc. on shipboard or at oil terminals. This has been explained in the figure-2.1.
47
Table-2.1: Comparison of Estimates of Petroleum Hydrocarbons annually
entering in the Marine Environment (million tones)
Source MIT
SCEP
Report
(1970)
USCG
Impact
Statement
(1973)
NAS
Workshop
(1973)
FOH
Norway
Report
(1981)
NRC
Report
(1985)
UNEP
(1992)
Marine Transportation 1.13 1.72 2.13 1.50 1.47 0.58
Offshore Oil Production 0.20 0.12 0.80 0.05 0.05 0.04
Coastal Oil Refineries 0.30 -- 0.20 0.20 0.20 --
Atmospheric Depositions 9.00* ? 0.60 0.30 0.30 0.30
Natural Sources ? ? 0.60 0.30 0.25 0.25
Land-based Activities/
Municipal/ Urban/ River
Run-off/ Industrial Wastes
0.45 1.98 2.50 1.00 0.98 1.16
Total 11.08 ? 6.11 3.35 3.25 2.33
* Based upon assumed 10% return from atmosphere.
MIT SCEP = Massachusetts Institute of Technology
USCG = United States Coast Guard
NAS = National Academy of Sciences, USA
FOH = Norwegian Marine Pollution Research and Monitoring Programme
NRC = National Research Council, USA
UNEP = United Nations Environment Programme
Moreover, the oceans have been receiving inputs of petroleum for a long time. The
sources of these inputs are natural seepages of oil from oil reservoirs near the earth
surface & erosion of sediments, such as shale that contain petroleum like
hydrocarbons. These area of natural seepages are depicted in figure-2.2 and the
estimated quantity of inputs to the marine environment is about 0.25 million tones
annually. Thus, low levels of petroleum contamination have existed well before human
use of petroleum. The figure-2.2 also shows broad picture of the global oil tanker
routes and figure-2.3 depicts the international tanker routes to Far East with EEZ
(Exclusive Economic Zone) of India.[49]
48
Big Spills 37
Routine Maintenance 137
Down the Drain 363
Up in Smoke 92
Offshore Drilling 15
Natural Seeps 62
9%12%
33%
2% 7%
37%
Atmosphere
Industrial Discharges and Urban Run-off
Natural Sources
Exploration/ Production
Vessel Operations
Tanker Accidents
Figure-2.1: Pictorial representation of Hydrocarbon
Inputs to the Marine Environment
A. Oil Inputs (in number)
B. Oil Inputs (in %)
49
Figur
e-2.2
: Int
ern
ation
al Oil T
rans
port
Rou
tes
(arr
ows) a
nd t
he loc
ation
of
natu
ral pe
troleum
Seepa
ges
(dot
s) [Num
ber
in b
ox ind
icate
s th
e I
nter
Are
a T
rans
port
ation
of
Oil in
million
ton
es
dur
ing
1999]
50
Floating petroleum residues from Indian Ocean recorded during 1980 to 1981 indicated
a concentration range from 0 - 6.00 mg/m2 with a mean value of 0.59 mg/m2 from
Arabian sea, while in Bay of Bengal tanker route the range varied from 0 - 69.75
mg/m2 with a mean value of 1.52 mg/m2. Since 1990 under Coastal Ocean Monitoring
and Prediction System (COMAPS), a program of monitoring of coastal water quality,
the Department of Ocean Development (DOD), Government of India through different
agencies, monitors the concentrations of petroleum hydrocarbons regularly throughout
the coastal waters of the country. The concentration varied depending on the
influence of coastal activities like ports & harbors, discharges from the urban centers
and other industrial activities in the coastal area. The concentrations of petroleum
hydrocarbons observed within 5 km of Indian coastal waters during 1996 – 2000 are
provided in table-2.2.[49]
Figure-2.3: Indian Exclusive Economic Zone and International
Tanker Routes to Far East
51
Table-2.2: Petroleum Hydrocarbon concentration observed in different
Locations within 5 kms of Indian Waters during 1996-2000
Sl.
No. Location Concentration Range (g/l)
1. Kandla 2.16 – 66.54
2. Bedi 5.28 – 116.20
3. Vadinar 16.28 – 110.80
4. Diu 1.50 – 7.90
5. Alang 2.12 – 8.18
6. Poshitra ND* – 54.30
7. Hazira 0.50 – 3.20
8. Daman 0.90 – 4.70
9. Tarapur 1.20 – 17.00
10. Bassein 0.40 – 5.50
11. Mumbai 0.20 – 3.55
12. Malvan 4.00 – 10.11
13. Marmagoa 3.55 – 15.86
14. Karwar 3.90 – 21.81
15. Mangalore 1.85 – 24.68
16. Kochi 8.10 – 35.42
17. Neendakara 10.40 – 22.50
18. Vizhinjam 2.56 – 14.50
19. Cape Comorin 3.14 – 5.60
20. Mandapam ND – 5.65
21. Vedaranyam 6.97 – 73.40
22. Couum river 0.33 – 77.60
23. Ennore estuary 9.21 –66.50
24. Pulicat 1.41 – 9.95
25. Chilka 0.39 – 0.65
26. Puri 0.05 – 1.40
27. Digha 0.49 – 0.65
28. Kavarati (Lakshadweep) 0.33 – 3.85
29. Minicoy (Lakshadweep) 0.28 – 0.45
30. Phoenix harbour (Andaman & Nicobar Islands) 11.60 – 23.76
* : Not Detectable
52
2.1.2 MAJOR OIL INCIDENTS ACROSS THE GLOBE
AND IN INDIAN WATERS
The table-2.3 given below provides the major oil spill incidents occurred across the
world since 1967 till 1993. On March 18, 1967 the oil tanker Torrey Canyon was
stranded on the Seven Stones Reef in the English Channel and within a period of 10
days discharged her entire cargo of 1,20,000 tones of Kuwaiti crude oil into the sea.
The released oil drifted in three different masses: 30,000 tones drifted up the
English Channel & polluted the north coast of France; 20,000 tones polluted the west
Cornish coast; and eight days later, the ship broke her back & released an additional
50,000 tones which drifted south into the Bay of Biscay. In an attempt to avoid
further pollution, thousands of liters of aviation fuel & napalm along with aerial
bombing of the ship, were used to burn the remaining 20,000 tones of oil.[32, 49]
Table-2.3: Major Oil Incidents across the World
Year Location/ Tanker or Oil Well involved in the
Incident
Qty. of Oil Spilled
(in tones)
Mar. 18, 1967 ‘TORREY CANYON’ (Liberia) polluting southern
English & French coast
119 000
Jan., 1969 ‘SANTA BARBARA’ (USA) affecting the Santa
Barbara platform in California
13 600
June, 1972 CHERRY POINT (Alaska) tanker World Bond
spilled oil at this Production Site affecting US &
Canadian coast
12 000 gallon
Dec. 19, 1972 ‘SEA STAR’ (S. Korea) 115 000
1974 ‘CASTILLO De BELLVER’ 227 000
Jan. 24, 1976 ‘OLYMPIC BRAVERY’ (LIBERIA) 250 000
May 12, 1976 ‘URQUIOLA’ (Spain) 101 000
June 7, 1976 ‘SHOWA-MARU’ (Japan) 230 000
Dec. 15, 1976 ‘HAVEN’ (Cyprus) 40 000
Dec. 15, 1976 ‘VIRGO MERCHANT’ (Liberia) 28 000
53
Year Location/ Tanker or Oil Well involved in the
Incident
Qty. of Oil Spilled
(in tones)
Mar. 16, 1978 ‘AMOCO CADEZ’ (Liberia) got agrounded & broke
into 2 off French coast
227 000
Dec. 31, 1978 ‘ANDROS PATRIA’ (Greece) 40 000
July 19, 1979 ‘ATLANTIC EMPRESS’ (USA) 300 000
Nov. 1, 1979 ‘BURMAH AGATE’ (Liberia) 37 000
Feb. 23, 1980 ‘IRENESS SERENADE’ (Greece) 102 000
May 6, 1983 ‘CASTILLO DE BELLVER’ (Spain) 100 000
Mar. 24,
1989
‘EXXON VALDEZ’ (USA) polluting 1700 kilometers
of southern American coastline & it is the highest
ever tanker mishap caused due to human error
40 000
(10.8 million gallons)
Dec. 19, 1989 ‘KHARG-5 (Iran) 70 000
1989-1990 GULF WAR, Iraqi Crude released to Gulf
affecting entire coastline
Thousands of millions of
gallon
1991 ABI SUMMER, entire crude cargo released to sea 260 000
1991 ‘HAVEN’ (Cyprus) 114 000
Dec. 3, 1992 ‘AEGEAN SEA (Liberia) 720 000
Jan. 5, 1993 ‘BRAER’ (Liberia) 85 000
Jan. 21, 1993 ‘MAERSK NAVIGATOR’ (Denmark) Andaman Slick (50 000)
The table-2.4 provides oil spill incidents that have occurred since 1973 till 1998
around Indian coastal waters. There were no major incidents of oil spill till 1988
except the grounding of vessel Cosmos Pioneer, which has occurred off Gujarat coast
spilling about 3,000 tonnes of oil in 1973 and another major spill occurred around
Kilton Island (Lakshadweep) spilling about 5,000 tones of furnace oil in 1974. There
are a few minor incidents of oil spills ranging from traces to one tone during the period
1975 to 1988. This may either be due to improper monitoring or survey or recording of
the incidents. Four incidents of oil spills occurred in 1989 spilling about 5,500 tones of
oil around Maharashtra & Gujarat coasts. During a span of eight years from 1991 to
1998, 37 incidents of oil spills have occurred with a maximum of eight incidents, which
took place in 1993, in which about 52,188 tones of oil has been discharged into the
Indian waters. However, most of the incidents were not significant, since the quantity
54
of spilled oil were small, except that has occurred off Andaman & Nicobar Island.
Further, the grounding incidents are more significant than collision.[49]
While the Torrey Canyon disaster, and subsequently the Santa Barbara oil spill[32],
focused world attention on the need for more effective control of oil pollution at sea,
big tanker disasters or oil spills, dramatic as they are, are not the major source of oil
pollution. The most serious pollution comes from the thousands of incidents, small but
preventable, or minor pumping and spill from tanker operations, from emptying salt-
water ballasts, pumping bilge water, cleaning oil, and transferring & handling oil
cargoes; it comes from oil spillage which frequently occurs at terminals & onshore
industrial plants, from leaking pipelines, refineries, docks, offshore drilling operations,
sunken tankers & natural oil seeps. While it is difficult to make an estimate of the
total oil influx into the sea from various sources, a minimum estimate of oil spills can
be calculated from the incidence of large accidents and from the operating records of
oil ports.[32]
2.2 OIL SPILL RESPONSE
The coastal marine environment is considered to be one of the most dynamic and
biologically productive environments on the earth. Besides, it varies in nature and
varying from loose muddy to consolidated rocky cliffs particularly, in our country.
Coastal ecosystems around the world, where 90% of the seas living marine resources
spend critical portion of their life cycles, are affected by human beings almost
everywhere and are becoming degraded on a wide scale. Hence, pollution of seas &
oceans has become a matter of concern of world over during the last few decades.
Human activities on land and at sea have increasingly altered the balance of fluxes
between the land & the sea. Nevertheless, in general a significant amount of pollution
is caused by shipping and maritime activities. In terms of tonnage the most important
pollutant resulting from shipping activities is the Oil. According to the statistics
published by International Tanker Owners Pollution Federation (ITOPF), the most
55
common oil pollution incidents, as many as 92% of oil spill occurs during terminal
operations, when oil is being loaded or discharged.[49] The consequences of accidents
may be disastrous to the affected areas depending on the size of the tanker, quality &
quantity of the spilled oil or its products and also closeness of the area of accident to
the coast. Further, oil is an amalgam of thousands of chemicals, each affecting the
marine environment as well as the marine organisms in different ways. The effect of
any given chemical is far from certain. The natural processes like winds, waves, tides &
currents, which may vary in intensity from area to area. Act to disperse the oil, due to
which the given oil spill may be diluted or may remain concentrated in a small area.
Besides, the sunlight & the microorganisms present in the ambient environment may
modify the composition of the oil. Some oil may dissolve in seawater or become
attached to the suspended solid matter, which latter settle down in the sea bottom.
Thus, it is apparent that, crude oil & their refined products, because of their varied
physical & chemical properties, which in turn can greatly influence the fate and
effects of oil released into the environment. Ultimately the effect of oil pollution
depends on the intake of various petroleum chemicals by marine biota.[49]
Table-2.4: Incidences of Oil Spills in Indian Coastal Waters
(from 1973 to 1998)
Date/
Year Location/ Tanker/ Oil Rig/ Pipeline involved in
the Incident with Environmental Impact
Qty. of Oil Spilled
(in Tones)
1973
COSMOS PIONEER off Gujarat (grounding); No
report is available for environmental impact
3 000
1974
TRANSHURON at Kilton Island, Lakshadweep
(accident); Extensive damage to coral reefs around
Kilton Island & deposition of tar balls along the
west coast
5 000
1974 GREEK TANKER off Gulf of Kutch (disappearance);
no report is available
Patches of oil
1979 SEA LEAF Mediterranean at Bay of Bengal
(grounding); no report is available
Not known
1982 SAGAR VIKASH (blow out) Nil
1983 IRANIAN OIL RIGS; Arabian Gulf (attacked by
Iraqi aircraft); damage to planktonic organisms
Film of oil on sea surface
noted
56
Date/
Year Location/ Tanker/ Oil Rig/ Pipeline involved in
the Incident with Environmental Impact
Qty. of Oil Spilled
(in Tonnes)
1984
LAJPAT RAI (SCI Ship); Bombay Harbour (Major
fire on the board of the ship); Unaesthetic
appearance of beaches of Bombay
Less than one tone
June,
1989
MT PUPPY (Maltese tanker); beyond EEZ off
Bombay; oil sank into the sea & no surface
reappearance, however, spilled oil in Bombay
deposited on beach rocks giving unaesthetic
appearance
5 500 tonnes beyond EEZ
off Bombay & 2 tonnes in
Bombay port
22.07.89 SANTA MOHAN; Bombay Harbour (accident); no
significant damage to the environment
Trace amount
04.08.89 MERCHANT VESSELS; off Tarapur; no significant
damage to the environment
Trace amount
29.08.89 MERCHANT SHIP; off Saurashtra coast; no
significant damage to the environment
Trace amount
07.09.91 MT JAYBOLA at Gulf of Mannar; no report is
available
692.5 (Fuel Oil)
14.11.91 ZAKIR HUSSAIN at Bombay; no report is available 40 000 (Crude oil)
22.02.92 Unknown; 40 nautical miles south of New Moore
Island; no report is available
Quantity not estimated
(tanker wash)
06.04.92 SCI TECH HOMMI BHABA; 54 nautical miles west
of Kochi; no report is available
1000 (Gulf crude)
15.08.92 ALBERT EKKA; Madras Harbour;
no report is available
1060 (Kerosene)
17.11.92 MV MOON RIVER; Bombay Harbour;
no report is available
300 (Gulf crude)
21.01.93 MAERSK NAVIGATOR (Danish Super Tanker);
off Nicobar Island; no report is available;
40 000 (Crude oil)
Mar, 1993 ONGC Rig at KUMARADA; off riverine end at
Naraspur; no report is available
Not estimated (Crude oil)
20.04.93 MT NAND SHIV CHAND at Bombay Harbour
(Jawhar Island); no impact report is available
110 (Bombay Crude)
May,
1993
Rupture of ONGC Pipeline; Mortality of Planktonic
organisms, 3km Long Murud beach contaminated
with deposits of 1000 tonnes of Oil leading to
mortality of intertidal fauna
3000 - 6000
10.05.93 MV CELELIA at Bhavnagar; no impact report is
available
98 (Diesel)
17.05.93 BHN PLATFORM at Bombay High; no impact report
is available
5460 (Bombay Crude)
02.08.93 MV CHALLEMGE off New Mangalore Harbour; no
impact report is available
260 (Diesel)
01.10.93 MT NAND SHIV CHAND at Kochi Harbour; no
impact report is available
260 (Bombay Crude)
57
Date/
Year Location/ Tanker/ Oil Rig/ Pipeline involved in
the Incident with Environmental Impact
Qty. of Oil Spilled
(in Tonnes)
22.03.94 MV STOLIDI at 360 nautical miles south-west off
Porbander; no impact report is available
Not estimated (Crude oil)
21.05.94 INNOVATIVE-I off Sacramento Point: no impact
report is available
14 000 (Crude oil)
05.06.94
SEA TRANSPORTER off Sinquerim, Aquada (Goa)
due to Grounding; Unasthetic appearance of beach
due to oil deposition. Mortality of Planktonic
organisms around the grounded area
1025 (Diesel)
20.07.94 MV MAHARISHI DAYANAND at Bombay (Jawhar
Island); no impact report is available
100 (Crude oil)
27.11.94 MV SAGAR off Madras; no impact report is
available
288 (Heavy oil & Diesel)
26.03.95 DRADGER MANDOVI-II off Visakhapattnam; no
impact report is available
200 (Diesel)
24.09.95 MC PEARL off Dwarka; no impact report is available Not estimated (fuel oil)
13.11.95 Unknown at Elliot Beach, Madras; no impact report
is available
Not estimated (tanker
wash)
21.05.96 PREM TISTA (IOC Chartered Barge) off River
Hugly; no impact report is available
370 (Diesel)
16.06.96
MV TUPI BUZIOS off Prongs, Bombay; no impact
report is available
Not estimated (Heavy Fuel
oil)
18.06.96 ZHEN DEN off Bandra, Bombay; no impact report
is available
- do -
18.06.96 INDIAN PROSPERITY off Karanja, Bombay; no
impact report is available
- do -
23.06.96 MV ROMANSKA off Worli, Bombay; no impact
report is available
- do -
16.08.96 MV AL HADI at outer anchorage off Malabar
Coast; no impact report is available
124 tonnes fuel oil & 43.5
tonnes Diesel
25.01.97 Not Known (off Kakinada coast); no impact report is
available
Not estimated (Heavy fuel
oil)
16.06.96 MV TUPI BUZIOS off Prongs, Bombay; no impact
report is available
Not estimated (Heavy Fuel
oil)
18.06.96 ZHEN DEN off Bandra, Bombay; no impact report
is available
- do -
18.06.96 INDIAN PROSPERITY off Karanja, Bombay; no
impact report is available
- do -
23.06.96 MV ROMANSKA off Worli, Bombay; no impact
report is available
- do -
16.08.96 MV AL HADI at outer anchorage off Malabar
Coast; no impact report is available
124 tonnes fuel oil & 43.5
tonnes Diesel
25.01.97 Not Known (off Kakinada coast); no impact report is
available
Not estimated (Heavy fuel
oil)
17.03.97 MV PRABHU PUNI at Haldia Dock area 34 (furnace oil)
58
Date/
Year Location/ Tanker/ Oil Rig/ Pipeline involved in
the Incident with Environmental Impact
Qty. of Oil Spilled
(in Tonnes)
19.06.97 MV ARCADIA PRIDE off Prongs, Bombay; no
impact report is available
Not estimated (Heavy oil &
Diesel)
19.06.97 GREEN OPAL in River Hoogly; no impact report is
available
Not estimated (Bunker
fuel)
02.08.97 MV SEA EMPRESS off Bombay; no impact report is
available
Not estimated (Fuel oil)
14.09.97 HPC Oil Refinery at Visakhapattnam; no impact
report is available
Not estimated (Naphtha &
Diesel)
12.03.98 OFFSHORE PLATFORM at Bombay High; no impact
report is available
Not estimated (Bombay
high crude oil)
01.06.98 SBM off Vadinar; no impact report is available Not estimated (Gulf crude
oil)
08.07.98 MV PACIFIC ACADIAN at Ambuja Port, Kodinar,
Gujarat; no impact report is available
500 (Fuel oil)
[Source: ‘Oil Pollution & the Marine Environment’, CPCB, New Delhi]
The example of theTorrey Canyon & of Exxon Valdez which caused even a bigger
pollution disaster at sea in the eighties, vividly illustrates the potential for damage as
well as the various techniques available for controlling & limiting the disastrous
effects of a major oil spill at sea. For example, the French treated the oil polluting
their coast with 3,000 tonnes of natural chalk with an additive of stearic acid, which
made the chalk oleophilic & hydrophobic, causing the greater part of it to sink or
disperse. Off the Cornish coast, the oil was sprayed both at sea & on shore by
detergents (after the Torrey Canyon spill), the most common being BP1002.
Unfortunately, these detergents proved to be highly toxic for many marine animals &
plants and resulted in killing limpets & other shore animals, especially in inter-tidal
areas. The attempt at burning the oil failed to produce any sustained burning since by
that time the more volatile components of the oil had been lost by evaporation.[32]
Even though different technologies have been developed for combating oil spills in the
marine environment, no single perfect method exists to deal with the problem as the
general knowledge of marine environments, of oil & its behavior when released onto the
water surface, and of the methods & means of response to an oil spill is rather limited.
59
In addition to the technical problems of controlling oil pollution, even organizing its
control was rendered difficult by the international complexities involved. The
Barracuda Tanker Company of Bermuda, a subsidiary of the Union Oil Company of
California, owned the vessel. For Tax purposes the ship was leased by the subsidiary to
the parent company; it was registered in Monrovia and flew the Liberian Flag.[32] The
crew was Greek and the ship was on a charter to the British Petroleum Company.
Before it could be determined who had the legal authority to deal effectively with the
Torrey Canyon disaster, almost two-thirds of the oil had escaped in the marine
environment.[32]
The importance of controlling oil pollution at sea lies not only in its short-term but also
long-term effects on marine life & the environment. Crude oil is one of the most
complex mixtures of natural products with different degrees of toxicity. For example,
at low concentrations, boiling saturated hydrocarbons produces anesthesia & narcosis
and, at greater concentrations, cell damage & death in a wide variety of lower animals,
being especially harmful to larvae and other juveniles of marine life. Higher-boiling
saturated hydrocarbons are not directly toxic though they may interfere with the
nutrition and possible channels of communication between many marine animals.
Aromatic hydrocarbons represent the most dangerous component of petroleum. Low-
boiling aromatics such as benzene, toluene & xylene are very poisonous for human
beings as well as other organisms. It was the great tragedy of the Torrey Canyon
accident that the detergents used to disperse the oil had been dissolved in low-boiling
aromatics; their application actually multiplied the damage to coastal organisms. High-
boiling aromatic hydrocarbons are suspected of being long-term poisons although the
direct carcinogenicity of crude oil and crude oil residues, as in the case of tobacco
smoke, has not yet been conclusively demonstrated.[32]
The short-term effects of an intact cohesive film of crude oil over the water surface
are detrimental for the following reasons:
60
Marine fowl are particularly vulnerable to oil spills and it is estimated that
about 10,000 birds were killed as a result of Torrey Canyon grounding.
Shore properties & beaches can be extensively contaminated. On the north
coast of Brittany, for example, a thick coating of oil remained on the surface of
sandy beaches for a number of years after the original pollution.
Heavy coats of oil can physically damage slow moving crustaceans & inter-tidal
marine life. There is also a particularly deleterious effect on the gill filaments
of fish, preventing the exchange of gases and resulting in anoxia.
The oil film forms a barrier to the transfer of oxygen into the water to support
marine life, particularly planktonic species, which reside less than a half-to-one
meter below the surface.
The long-term effects of oil pollution are twofold. Once incorporated into a particular
marine organism, hydrocarbons are stable and pass through many members of the
marine food chain without alteration, eventually reaching organisms that are harvested
for human consumption. One consequence of this may be the incorporation into food of
materials that produce an undesirable flavor. Far more serious is the potential
accumulation in human food of long-term poisons derived from crude oil, for instance,
carcinogenic compounds. Another effect results from the low level interference of oil
pollution with marine ecology. Oil pollution interferes with natural processes by
plugging taste receptors and distorting natural stimuli, which may threaten some
marine aspects.
Therefore, for anyone involved in combating pollution in marine environments, it is
essential to have some knowledge of these environments (comes under Oceanography)
i.e. the character, amount, fate & persistence of oil on the shoreline and the shoreline-
nature, of typical processes taking place in the oceans and of the interactions with
shores, which are very important factors that determine the implementation of the
response priorities for the clean-up activities. Moreover, these processes will get
more complicated when oil is spilled in large quantities over the surface & may be more
61
seriously disturbed by inappropriate human action than if nature was left to deal with
the oil spill. Hence, the implementation of appropriate action for controlling coastal or
marine oil spills requires a combination of environmental, logistical and operational
knowledge, which are discussed subsequently.[10, 17, 21, 49, 51, 52]
2.2.1 OCEANOGRAPHY
Introduction
Oceanography is the scientific study of the earth’s oceans and their boundaries.
Oceanography means literally ocean mapping; some scientists prefer Oceanology for
this science. The oceans cover 71% of the world’s surface and are interconnected,
separated incompletely by continents, and therefore, comprise a single world Ocean.
Most human beings live on or near the margin of the seas and human history is linked
closely to the oceans. Without oceans, the evolution of life would have been far
different, if it occurred at all. The seas are responsible for much of the global
temperature and climate control, as an important food source, as the key to weather &
climate and as highways for explorers, invaders, & commerce’s. Much of the Earth’s
geological history is recorded in the bottom rocks and sediments of the seas.
Historical Background
Oceanography was at first part of the practical information a naval officer learned,
along with navigation, mathematics, ship operations, etc. Among the first scientific
oceanographers was the versatile American, Benjamin Franking, who in his capacity as
Postmaster General of the United States, used ships’ logs & a thermometer to explain
why mail ships returning from Europe were so often delayed. His work resulted in the
discovery of the Gulf Stream. Oceanography as a modern science developed in the
1800s with the compilation of oceanographic data from ships’ logs. The US Naval
62
officer Mathew Fontaine Maury was among the first to do so systematically, so he is
sometimes called the Father of Oceanography.
Modern Oceanography
Modern oceanography is usually divided into chemical, physical, and biological
oceanography and marine geology. Chemical oceanographers study the equilibrium
between the chemical components & seawater relative to the sediments & atmosphere.
Physical oceanographers are concerned mostly with measurements and mathematical
models intended to predict physical oceanographic phenomena, including currents,
tides, waves, salinity, temperature, density, and the transmission of light and sound in
seawater. Physical oceanographers are often divided into coastal oceanographers, who
deal with processes in the clear waters of the open ocean. Biological oceanographers
are traditionally associated with studying planktonic life and predictions of biological
density & composition relative to physical & chemical regimes. Marine biology, the
study of all living things in the sea, is often considered a branch of biology, rather
than oceanography, but many traditional oceanographers do not make this distinction.
Like physical oceanographers, marine geologists can be divided rather neatly into those
who deal with shallow waters, such as beaches & shoreline processes, and deep-water
geologists. Shallow water marine geologists are closely associated with marine
engineers, who deal with solving problems in marine processes, such as beach erosion,
hurricane protection, shoreline construction, etc. Deep-water marine geologists are
associated more with sea-floor mapping, plate tectonics, and sediment analysis. Marine
geology includes paleoceanography, in which ancient oceans are studied, usually by
analysis of microscopic fossils in deep-water sediments.
Marine Geology
The differences between the earth’s crust on the land versus that under the seas is
largely due to chemical differences in the rocks comprising them. The sea floor is
63
mostly covered by a thick blanket or relatively recent deposits of sediments, largely
sands, silts & clays, but beneath the sediments is a much thicker slab of solid rock
composed mostly of dense, magnesium-rich sematic rocks, especially basalts. Similar
rocks form the underlying core of oceanic islands like Hawaii or the Galapagos, and the
bases of the undersea mountains not high enough to reach the surface. Sediments
likewise mostly cover Continents, but the deeper rocks of continents are composed
mostly of sialic rocks, especially granites, which are high in aluminum & not as dense as
oceanic simantic rocks.
Sediments are classified in various ways; the most familiar classification is by particle
size. Biogenous sediments are the remains of living organisms, such as microscopic
foraminifera & diatoms, or the more massive skeletons of reef-building corals. Atolls
form when corals grow around sinking volcanoes. Coral is colonial animal with a treelike
inner core of calcium carbonate, the same material that composes snails & clams. The
coral animal is carnivorous, but reef-building corals contain microscopic algae
(zooxanthellae), whose photosynthetic metabolism supplement their diet and facilitate
the deposit of calcium carbonate as Biogenous sediment. Such corals, called
hermatypic corals, require warm, well-lit water to prosper; they die in deep water.
Corals first form a fringing reef around the island, which may become a barrier reef
as the system ages. When the volcanic island sinks below the surface, the reef
becomes a circular atoll formation with a shallow lagoon in the middle. The lagoon
forms because too much sediment settles out on the coral animals to allow rapid
growth; most of the rapid coral growth occurs on the edge of the atoll. If the coral
cannot grow fast enough to deposit a reef as fast or faster than the island sinks, the
reef is ‘drowned’ in dark, cold water. Many deep-water guyots in the Pacific have
substantial deposits of fossil coral on & around them.
Near rift zones sediments thin and eventually expose bare lavas of mid-oceanic rises &
ridges. These great undersea ranges of volcanoes extend for thousands of miles, only
rarely reaching the surface to form an island. At the crest of an active ridge there is
64
usually a rift valley near 20 miles wide & several thousand feet deep. Rift valleys may
contain hydrothermal vents, volcanic openings that discharge mineral-rich warm water
that deposits silica, barium, manganese, & other minerals on the margins of the vents.
Populations of bacteria live by oxidizing components of these minerals and support
characteristic populations of animals, they are said to be communities independent of
sunlight, but since they use oxygen derived from sunlight-dependent photosynthesis,
the independence is incomplete. Fracture zones, large faults, cross the rise at near
right angles, displacing segments of the ride-rise system.
Seawater
Coastline & coastal waters are heterogeneous in nature covering different types of
productive ecosystems on the earth. The seawater, being a mixture of many different
types of salts, has virtually the same composition wherever & whenever readings are
taken. In mid-oceans the ratio between these various salts is remarkably constant,
whereas in inshore waters this ratio may vary considerably due to the input of water
by rivers. The density of pure water at 4ºC is 1,000 g/cc or 1,000 kg/m3. If it is
heated or cooled, the density of water decreases. Saline water has a higher density &
lower freezing point than pure water, depending on the content of salts. Wind action
produces a mixed layer on the surface to a depth of 50 to 200 m, which is almost
isothermal in the vertical. A zone below this extends for another 500 to 1,000 m over
which the temperature decreases rapidly. Below this zone there is a deep region of
cold water, in which the temperature decreases very slowly.
The salinity distribution at the surface of the world’s oceans is completely controlled
by rainfall patterns. Regions of high rainfall & low evaporation (tropical regions) have
low salinity due to rainfall dilution of the seawater. Regions of low rainfall &
considerable evaporation (subtropical regions between 20º & 40º latitude) have high
surface salinity. Vertical salinity distribution is related to the density of the water.
65
Less dense water lies above more dense water. A salinity increase of 1% produces the
same density change as a 4C decrease in temperature.
Braking waves at the sea surface aerate the water & dissolve atmospheric gases (O2:
21%; N2: 78%; CO2: 0.03%). The solubility of oxygen (O2), which supports life in aquatic
systems, depends both on the salinity and the temperature. The normal range is from
7x10-6 mg of O2 per kg of water with hot water holding less oxygen. Water can be
supersaturated due to vigorous stirring or as a result of plant photosynthesis, which
converts carbon dioxide into oxygen. This process takes place in sunlight and its
maximum in heavily vegetated waters is reached at noon. Low values of dissolved
oxygen (below 4 ppm) indicate a rapid multiplication of bacteria in salt water, which
depletes the water of oxygen faster than it can be replaced by either the plants or
the atmosphere. Such water is polluted & cannot support aquatic life.
Dissolved nitrogen (N2) in seawater is not altered by biological changes, except under
unusual conditions. When saturation reaches 127%, fish appear to suffer from
nitrogen-induced diseases. Carbon dioxide (CO2) has a very complicated chemistry that
favors the formation of bicarbonates. The standard measure of gaseous carbon in
natural water is the pH. Pure water has a pH value of 7. Values of pH below 7 denote
acids & the lower the value the stronger the acid. Values of pH above 7 correspond to
alkaline solutions. The pH of surface water is very stable, usually ranging from 8.1 to
8.3 with a direct relation between salinity & pH. This implies a dominance of
bicarbonate in seawater. Plants utilize carbon dioxide and raise the pH, while the
respiration of organisms acts in the opposite direction. Life depends on photosynthesis
and the availability of carbon, oxygen, nitrogen & phosphorous (nutrients) as well as
water. In the oceans these constituent elements are available in solution as dissolved
bicarbonate, phosphate & nitrate. The relative proportions of nutrients used in
photosynthesis are characterized by a chemical equation of the form:
106CO2 + 90H2O + 16NO3 + PO4 + energy 154O2 + protoplasm
66
Thus, incoming light energy of 5.40x109J produces 3.258 kg of protoplasm in the
proportions of 106C, 180H, 46O, 16N & 1P. When this protoplasm is burnt, it releases
5.4x107J of heat energy. Increased urbanization & widespread over-application of
fertilizers has led to increased nutrient loads into the waterways & seas. This
produces high nitrogen loads through urea-based fertilizers and high phosphorus loads
from super-phosphate fertilizers.
The feeding relations of species in the aquatic community delineate an ecosystem,
which is determined by the flow of energy & nutrient materials from the physical
environment to plants. These form the first tropic level, they act as first food
producers and from them to higher tropic levels as consumers (figure-2.4). The rate of
primary supply depends on the supply of light & nutrients. The light energy necessary
for primary production decreases with depth and is limited to surface waters. The
nutrients are recycled from detritus and are most accessible near the bottom. The
two regions overlap in high productivity areas. When sufficient nutrients are present,
then the rate of phytoplankton photosynthesis is proportional to:
the relative photosynthesis rate;
the concentration of phytoplankton present, expressed in terms of chlorophyll
per m3 of water in the water column;
inversely proportional to the extinction coefficient of light.
In upwelling areas, there is an abundance of nutrients for phytoplankton, so primary
production is limited to availability of light & nitrogen. If there is sufficient nitrogen,
then the growth is controlled by the availability of phosphorus. Thus, the growth rate
of an organism is limited by the availability of growth factors, which is the shortest in
supply (Liebig’s law of the minimum: figure figure-2.5). In this example, trace elements
such as copper are in abundant supply, but the rate of primary production will follow
the heavy line and be limited first by iron, then as more iron becomes available by
67
nitrogen & finally phosphorus. Oil spilled on the water surface limits the supply of light
and thus is very harmful to the production of phytoplankton.
Coastal Dynamics
Costal dynamics can be defined simply as those focuses that act to form or change a
shoreline. The coastal zone is probably the most dynamic & complex physical
environment on the earth. For developing practical & effective Oil Spill Response
strategies, it is necessary to understand the forces that contribute to the coastal
zone processes. There are two primary factors that control the character of the
coast, viz, the processes that act on the shore, and the material upon which these
processes act. Thus, it is clear that the character & dynamics of the coastal zone
control the fate of the oil that reaches the coast. Moreover, the shoreline protection
& clean-up responses should be viewed in terms of local & site-specific conditions. The
coastal processes are associated with the winds, waves, tides, currents, ice (in the
cases of temperate & polar regions), temperature, and release of energy, river
discharges & biological processes.
ENERGY
Phytoplankton
Nutrients
Detritus
Figure-2.4: The Tropic Web
68
Definition of Coastal Region / Zone*
Though seaward and landward limits of the coastal region are identified previously by
water depth and wind of land strip, there are two other methods based on which the
coastal region can be characterized:
a) Based on sectional geometry of beachfront.
b) Based on wave deformation.
Definition based on sectional geometry of the beach front:-
Figure-2.6a picturises a typical coastal region. To commence with ‘beach’ is a term
which most of us is familiar and is technically called as backshore. If one stands on the
boundary between water and land, portion on the rear is known as backshore and the
* Source including figures-2.6a & 2.6b: JS Mani, “Coastal & Estuarine Dynamics”, Short Term Course
on Marine Pollution (14 – 16 June, 1999) held at Ocean Engineering Center, IIT – Madras, Chennai.
Figure-2.5: Potential hydrocarbon production areas:- (1) copper; (2) phosphorus;
(3) Nitrogen; (4) Iron; (A) zone of Iron limitation; (B) zone of
Nitrogen limitation; (C) zone of Phosphorus limitation.
C A B
Rat
e o
f Pr
imar
y Pr
oduc
tion
Input Rate of Nutrients
1
2
3
4
69
shore in front of foreshore is termed as foreshore. The portion of water, which is just
in front of foreshore, is termed as nearshore. It is important to mention here that,
the activities of the wave are mostly confined to nearshore and foreshore regions. A
longshore bar and a trough are the characteristics of a coast and are habitual to
appear and disappear in a cyclic fashion.
Definition based on wave deformation:-
Waves reaching the coast, transform themselves in many ways for different reasons.
At this juncture, it is sufficient to know that waves cannot maintain its form all along
its journey from deep to shallow waters and collapses before it reaches the coast.
Destruction of wave from occurs right on the coast and is termed as “Wave Breaking”.
The zone in which this phenomenon occurs is termed as breaker zone (figure-2.6b). In
this process, wave loses its energy, which is transformed into a turbulence causing air-
water mixture to take place at an unimaginably high rate. A zone where air-water
mixture takes place exhibits large surf formation, which is obviously termed as surf
zone.
fore
shore
near shore
inshore
offshore
beach
berms
longshore
trough
longshore
bar
back shore
cliff
Figure-2.6A: Definition of coastal region based on
sectional geometry of beachfront
70
Circulation in the Open Ocean
Three important types of currents are found in the open oceans: drift currents,
thermothaline currents, and geostropic currents. Drift currents are wind-driven
phenomena that occur mostly above the thermocline. The pattern of drift currents is
relatively predictable and determined by the pattern of surface winds. The Ekman
Effect, which results from the interaction of the wind, water, & the Coriolis effect,
complicates the current-generating effect of wind on water. Water at the surface
moves in the same direction as the wind, but in deeper layers the current direction is
refracted slightly to the right or left, depending on the hemisphere. The deeper the
water, the greater the refraction; at some depths the water may flow in the direction
opposite of the wind. The speed of the current generated decreases rapidly with
depth & becomes negligible at 100-150 m. Average movement of water is at right
angles to the wind, to the right in the Northern Hemisphere, to the left in the
Southern Hemisphere. Off western South America, the prevailing winds from the
offshore breaker
zone
surf
zone
swash
zone
beach
berms
bore
longshore
trough longshore
bar
Figure-2.6B: Definition of coastal region based on
nature of wave deformation
71
south produce an Ekman effect to the left of the wind, which blows warm, surface
water offshore. It is replaced by deep, cold, nutrient-rich water. Bringing deep waters
to the surface is called upwelling.
The geostropic currents are illustrated by the Sargasso Sea, the relatively sterile
ocean of the central western North Atlantic. The Ekman Effect forces water from the
North Atlantic gyre toward the center of the Sargasso Sea. A hill of seawater results
with a relief of several meters between the center of the gyre & its edge. The water
in the hill flows outward & downward in response to gravity, but the flow is soon
deflected to the right because of the Coriolis effect. Equilibrium is achieved, whereby
the Coriolis effect exactly balances the outward flow of water; the resulting currents
endlessly circle the center of the Sargasso Sea.
In ocean, currents of almost constant direction & speed, occur in a time period lasting
for months. The influence of the above ocean currents on coastal region is relatively
small compared to other types of currents i.e., coastal currents. As far as coastal
engineer is concerned, it is sufficient to know that, these currents are weak (less than
0.5 m/s) and are less important to coastal studies.
The important currents in the coastal region are: (a) tidal currents, (b) wave generated
near shore currents i.e., longshore currents, rip currents and onshore – offshore
currents. The tidal currents are generated due to tides as the name suggests. These
currents are strong enough particularly, along the coastal region where there is a
drastic change in geometrical shape of the coastline and control the nearshore
phenomena. Due to shallow water depths in the coastal area, few meteorological
factors such as Sunshine, wind and precipitation have strong influence on the coastal
waters compared to that of deep-ocean. As the coastal waters are influenced by fresh
water supplied by the rivers, seasonal change in temperature, salinity etc., cause
density difference and create currents.
72
In addition, more predominant currents that occur in the coastal region are those is
usually inclined with respect to coastline) a longshore current is generated. This
current cannot sustain for an infinite stretch along the coast and survive over short
stretches. To maintain equilibrium, longshore currents travelling along the coast for a
definite stretch return back to sea at appropriate locations. This return flow is
predominantly perpendicular to the coast, is very strong and detrimental to the coastal
swimmers. This current is termed as ‘Rip current’. Figures-2.7A & 2.7B# show the
longshore and rip currents respectively.
# Source: JS Mani, “Coastal & Estuarine Dynamics”, Short Term Course on Marine Pollution (14 – 16
June, 1999) held at Ocean Engineering Center, IIT – Madras, Chennai.
Figure-2.7A: Generation of Longshore currents
73
Wind & Waves
The simplest ocean waves are generated by wind in deep water, i.e., winds are the
controlling factor in wave generation, but also play more direct role in coastal
processes. Sand can be transported by wind, which ultimately can form sand dunes.
During strong winds, sand transported on beaches can evolve large volume of material
and can bury the oil or other stranded material on the beach. Moreover, strong
onshore winds can pile water against the shoreline resulting in ‘storm surge’. These
storm surges can often result in backshore flooding or over-wash on barrier beaches,
where dunes are low and are detrimental to the habitat of coastal region. Factors that
control wave generation are wind velocity, duration of wind in one direction and the
distance or area of water body over which the wind blows. Thus, the level of wave
energy at the shoreline and the mechanical processes that occurs as waves break or
swash runs up ashore have a direct bearing on the physical dispersion of oil on the
water surface in the near-shore zone. These processes also govern the mixing of oil &
water and formation of emulsion such as chocolate mousse.
Figure-2.7B: Rip currents
74
Within storms, high winds throw the water into a steep, sharply peaked, irregular
surface called sea. As the winds diminish, the waves become rounded & smoothed by
friction and undergo dispersion, sorting by speed. Well-dispersed waves form into a
train of similar waves, called swell, all of which travel in about the same direction. Each
wave of a train of swell has a high point, the crest, & a low trough. The length of the
wave is measured as the distance from crest to crest (or trough to trough) between
members of the train as shown in the Fig.-2.4. The length of time it takes for each
wave to pass a stationary point is the period; the number of waves that pass that point
per unit time (waves per minute, for example) is the frequency, People on a coast often
have warning of a storm over the horizon because the interval between waves coming
ashore increases; the fastest waves, which arrive first, have the longest period. As a
wave of swell passes a boat in deep water, the boat rises & falls, describing a circle in
space, but with little net movement; as in a swinging pendulum (i.e., harmonic motion)
there is a cyclic movement, but little expenditure of energy. Energy generated by a
storm transmitted in this way without loss for hundreds of miles and expanded
violently as the wave breaks on a distant shore.
The velocity of a series of waves of this type is a function of the wavelength; the
longer the wave the more rapidly the wave travels. The height of a wave is the vertical
distance between crests & troughs as shown in figure-2.8, half the height is the
amplitude. The energy available in a wave of swell is proportional to the square of its
height. A wave of 2 m height, for example, has four times (2 times 2) the energy of a 1
m wave. Wave height is determined by (a) the velocity of the wind generating it and (b)
how great a distance the wind is allowed to generate the wave. The latter distance is
called the fetch of a wave. Lakes are seldom large enough to have a large fetch, so
really high waves are found on large lakes. As fetch increases, so does the wave
height, until a maximum wave height is achieved for the velocity of the generating
wind. A sea with waves as large as that wind velocity can produce is a fully developed
sea. The wave characteristics and direction of water particle movement are shown in
75
figure-2.9** and different types of ocean waves are shown in the figure-2.10**. An
observed profile of waves in a sea is shown in figures-2.11A to 2.11C**.
Waves reaching coastal region from deep waters, undergo various types of
transformations leading to lateral flow of wave energy, very important phenomenon as
far as coastal equilibrium is concerned. Types of wave deformations are as follows##:-
i) Wave Refraction
ii) Wave Diffraction
iii) Shoaling and Wave Breaking
iv) Wave Run-up & Run-down
Transformation of waves in shoaling water involves a change of wave height, length and
celerity with depth. When waves move shoreward from deep water and approach the
shoreline at an angle, wave crests tend to conform to the bottom contours. This is
because the inshore portion of the wave travels at a lower celerity than the portion in
deeper water. The extent of wave refraction depends on relative magnitude of water
** Source: S. Neelamani, “Wave Hydrodynamics”, Short Term Training Program on Ocean Engineering
(14 – 25 May, 2001) held at Department of Ocean Engineering, IIT- Madras, Chennai. ## Source: Footnote on page-68
y
C Direction of Propagation
Wave Amplitude
Wave Height
SWL
o
z
x
η
Crest
Trough
Bottom, z = -d
Wave Length
d = Water-depth
Figure-2.8: Ocean Wave propagation
[SWL= Still Water Level; C = Wave Celerity; and η = Surface elevation of wave at any
point along the wave length.]
76
depth to wavelength. At shallow depths, refraction occurs for waves oblique to seabed
contour.
Figure-2.12A shows wave refraction pattern for waves approaching from deep to
shallow waters. Convergence and divergence of the wave rays is an indication of
increase and decrease in wave heights respectively. In general, wave rays converge
near the headland and diverge in bays.
Figure-2.9: Wave characteristics and direction
77
Diffraction of water waves is a process by which energy flow laterally along wave
crest. Figure-2.12B shows the phenomena of wave diffraction due to presence of an
island in intermediate waters, located at a distance away from shore. Diffraction is a
common phenomenon around islands and can create substantial disturbance to the
coastal region which adds further to the dynamic nature of the coast.
Condition for wave breaking is dependent on the maximum wave steepness at which the
wave can remain stable. Breaking waves are generally classified as spilling, plunging or
surging depending on beach slope and wave steepness. In principle, plunging breaker
occurs when the crest velocity exceeds celerity of the wave, spilling breaker occurs
when the crest velocity remains approximately equal to that of the wave celerity and
surging breaker occurs when the base of the wave surges up the beach before the
crest can plunge forward.
Figure-2.10: Different types of ocean waves
78
Figure-2.11: An observed profile of waves in a sea – (A) Such a complicated
Wave pattern can be described as consisting of many different
sets of sine waves; (B) all superposed. The lower-frequency
waves contain more energy than the higher-frequency ones;
(C) The energy in a wave is proportional to its height
79
As waves approach shallow water, certain transformations take place, depending on
water depth and at one stage the waves become unstable and breaks. The wave
breaking is generally followed by uprush of water mass along the beach slope. In
coastal engineering this phenomenon is termed as wave run-up. The wave run-up (R) is a
function of wave height (H), wavelength (L), beach slope, and water depth (h). each
time wave runs up the beach, huge quantum of seawater is set to flow back to the sea
in the form of wave run-down due to gravity. This situation creates very high degree
of turbulence near beachfront. Flow directions due to incoming wave, run-up and run-
down are shown in figure-2.13. Figure-2.14 depicts the wave characteristics in deep
and shallow waters.
Figure-2.12: (A) Wave refraction around a headland;
(B) Wave diffraction around an island
Figure-2.13: Wave run-up and run-down
80
Shallow-Water Waves
These are waves in depths less than half of the wavelength (figure-2.15). As waves
enter from deep water they ‘feel bottom’, and undergo changes: (a) they slow; the
velocity becomes a function of the water-depth & independent of the wave length; (b)
they increase in height, caused by slowing without much loss of energy; (c) the
direction of travel is refracted in the direction of shallower water. The shallow water
waves become more regular because the waves having longer period capture shorter
ones. When the water becomes about as shallow as the wave height, the waves become
too high for their wavelength and they break. Breaking waves expend stored energy
and may cause erosion & other damage. Waves may be reflected, sent in a new
direction, by large structures, such as sea walls. Waves are diffracted when they
enter a bay through a narrow strait or channel in a breakwater; from inside the bay all
waves appeal to originate from the strait.
Standing Waves
These are waves that oscillate in a relatively enclosed basin. In a large lake, for
example, wind may produce a standing wave, or seiche (pronounced as seesh). In the
simplest seiche the waves sloshes from one end of the lake to the other, like water in
a bathtub. An antinode is there, where the vertical motion is maximum; a node is there,
Figure-2.14: Wave characteristics in deep and shallow waters
81
where there is no vertical motion. Figure-2.16+ shows some of the standing wave
patterns.
(A) (B)
(C) (D)
Figure-2.16: (A) Standing wave pattern; (B) First Harmonic standing wave
Pattern; (C) 2nd Harmonic standing wave pattern;
(D) 3rd Harmonic standing wave pattern
+ Source: http://www.id.mind.net~zona/mstm/physics/waves/standingWaves/standingWaves.html
u
+
w = 0 u ≠ 0
Bottom, z = -d
u o
u
SWL o
+ +
Shallow-water Wave or
Transitional-water Wave Deep-water Wave
Figure-2.15: Shallow & Deep-Water Waves
82
Internal Waves
These are large, slow waves, which propagate along a density gradient, along the
thermocline, for example. They have long wavelengths, low amplitude, low energy and
travel slowly compared to surface waves. They are never visible to a casual observer,
but are usually measured by systematic measurements near the propagating interface.
They may be generated by whales or ships or by other phenomena and are important in
submarine direction. Capillary waves or cats’ paws are ephemeral waves with short
wavelengths (1-3 cm), which are generated at the water surface as the result of wind.
These are waves, which are so small that gravity is unimportant and the restoring
force is capillarity instead of gravity.
Tsunamis
These are large waves generated by tectonic disturbances, such as earthquakes or
volcanic explosions. They have very long wavelengths & long periods and travel very
rapidly, often over 100 Knots (1 Knot = 0.5144 m/sec). Although a seagoing vessel will
seldom notice a passing tsunami because of the low amplitude relative to the period,
tsunamis can be destructive when they come into shallower water because the height
may increase to 100 feet or more. Tsunamis are always shallow water waves because
one-half of their wavelength is always much less than the depth of the ocean, the path
& speed of a tsunami is influenced by the bathymetry of the sea floor and the Coriolis
effect. After a tectonic event the resulting tsunami can be predicted as to its time of
arrival at distant areas, but the height is much more difficult to predict, complicating
civil defense measures. Tsunamis are often destructive and may cause great loss of
life, for example, tsunamic or tsunamigenic earthquake occurred in 1960 on the Shelf
of Makurazaki coast of Chily decay of the initial crest due to scattering of tsunami
waves caused by sea mounts. Again in 1985 at Chily the same disaster happened.
83
Tides
Tides are the regular rise & fall of the sea surface produced by the movements of the
moon, sun, and to a much lesser degree, the planets. Tides are generated by the
interaction between gravity & the centrifugal forces caused by the rotation of any two
bodies around one another. Figure-2.17$ picturises the concept of tide generation. If
the earth were covered uniformly by water there would be two tidal crests forced to
travel around the world at a speed equal to that of the moon (about 1000 mph), each
crest with a wavelength of half the circumstances of the earth. On the real earth,
however, seas vary in depth and the continents get in the way of the tidal wave. The
result is a complex set of oscillations set up in the ocean basins, normally with a period
of about half a lunar day (half of 24 hours 40 minutes). The crest of an arriving tide
forms a line along which tides always arrive at the same time. Such curves are called
co-tidal lines. For example, parts of Angola and Southern Brazil lie on the same co-
tidal line, so high & low tides will occur simultaneously in both places. In some oceans,
including the northern Atlantic, tides rotate in a huge circle around a central
amphidromic point, where co-tidal lines intersect. The amphidromic point is the node
of a giant standing wave and there are no tides there.
Because each interaction of the earth with an astronomical object produces a tide, the
actual tide recorded in the seas can be resolved into a series of harmonics, or “partial
tides”, one for each interaction. One of the most important harmonics is the one
generated by the moon, the lunar semidiurnal harmonic, with a period of 12 hours 20
minutes. The lunar semidiurnal harmonic determines the time of arrival of most tides,
although tides with a period of 24 hours 40 minutes dominate in some parts of the
world, in the US Gulf Coast, for example. The solar semidiurnal harmonic complicates
tides because it has a period of exactly 12 hours. When the sun & moon are both
pulling in the same direction, the harmonics are added and the tides are more extreme
than usual; this is a time of spring tides. During spring tides the sun, moon & earth are
$ Source: Footnote in page-68
84
roughly in line (syzygy) and the moon is either full or new. When this harmonics oppose
one another, the tides are less extreme and are called neap tides; at this time the sun,
moon & earth are at right angles to one another (quadrature) and a half moon is
showing. Spring & neap tides follow one another at an interval of about one week. For
instance, semi-diurnal tide with large diurnal inequality & varying amplitude dominates
all along the Gulf of Kutch as shown in the Table-2.5. Types of tide form are given in
the figure-2.18++.
Figure-2.17: Concept of tide generation
Tides vary greatly in amplitude because of the shape of the ocean basins in which they
are generated. Places near amphidromic points (Tahiti, for example) have small tides of
only an inch or so. Other sites, such as the northern end of the Gulf of California, are
++ Source: Footnote in page-68
85
shaped so that they resonate in time with the arrival of the tidal crest; the result is
very large tides, 40 vertical feet or more between high & low tide. Tidal movements in
relatively enclosed seas may generate dangerously strong tidal currents, whose
direction & time of arrival can be predicted in much the same way as tides; tidal
current tables are produced in many areas where tidal currents interfere with inshore
shipping.
Table-2.5: Tidal Elevations (m) in the Gulf
Ice
Ice is a modifying factor on regional wave climates especially in temperate & Polar
Regions. The major effect of the presence of the ice is to prevent or dampen the wave
generation. The degree to which waves are modified depends on the period of
presence of ice & on its distribution. This factor is irrelevant in tropical marine
environment like Indian marine waters.
Shoreline Types
The shoreline dynamics can be cyclical or non-cyclical. Various types of coastal
processes erode, transport & deposit coastal sediments developing a variety of forms
& features. Some of these changes occur cynically in response to variation in tides or
Station MLWS MLWN MSL MHWN MHWS
Okha +0.41 +1.20 +2.04 +2.96 +3.47
Sikka +0.71 +0.71 +3.04 +4.35 +5.38
Kandla +0.78 +1.81 +3.88 +5.71 +6.66
Navalkhi +0.78 +2.14 +4.15 +6.16 +7.31
MLWS = Mean Low-Water Spring
MSL = Mean Sea-Level
MHWS = Mean High-Water Spring
MLWN = Mean Low-Water Neap
MHWN = Mean High-Water Neap
86
to periodic variations in wave energy level. On the other hand, changes in the shape &
form of beaches largely a fluctuation in wave energy levels, which are usually evident
on low energy coasts, where a single storm may results in more charge & more
sediment transport during the storm than which occur on predominantly sandy
beaches. On any coast, where waves, tides, wind or ice act upon sediment, there is a
constant redistribution of material and constant changes in beach characters. The
stable & dynamic conditions of beaches must be considered if any attempt to predict
the fate of the stranded oil on the beach. Other physical processes associated with
the rivers, gravity as well as biological processes that govern mangroves, coral reefs &
marshes depending on the area or location supplement the above-cited processes.
Based on the form & process, the most useful classification of the shoreline was
provided by Davis (1972), is given below:
Group-1 : Cliffs, Shore platforms (high tide & low tide platforms).
Group-2 : Beaches, Spits & Barrier Island, and Lithified
Beaches (Beach Rock) and Coastal Dunes.
Group-3 : Deltas, Estuaries, Lagoons, and Tidal Flats.
Group-4 : Salt Marshes, Mangrove Swamps, and Coral Reefs.
Some of the shorelines are shown in figures-2.19A to 2.19G$$.
The physical features & processes of each of the major shoreline types, which are
designated to bring together the key elements of processes, materials & oil so that
the interactive relationship can be defined in the context of the fate of stranded oil.
$$ Source: http://archive.orr.noaa.gov/shor_aid/shore.html
87
Figure-2.18: Types of tide form
88
Figure-2.19A: Coarse-grained sand beaches Figure-2.19B: Gravel beaches
Figure-2.19C: Exposed tidal flats Figure-2.19D: Exposed rocky shores
89
Figure-2.19E: Mixed sand and gravel beaches Figure-2.19F: Mangroves
Figure-2.19G: Barrier Island
90
2.2.2 ORIGIN, PHYSICAL & CHEMICAL PROPERTIES OF OIL
Origin
We are living in an ‘OIL AGE’. Nothing can dislodge oil from its pride of place until
nuclear energy or solar energy is available in abundance & at cheap rates to meet man’s
daily needs. Oil has by far been the biggest industry in the most industrialized
countries in the world. It has more than any other material factor, influenced world
politics and the conduct of international relations in the past half a century. Defense
in the modern world is inconceivable without oil. It is difficult to think of a country’s
fate with its oil supplies cut off for a day. An oilman goes to the wilderness, the
desert, and the mountains and even under the seas to look for oil. In this, he is not
dictated by his whims & fancies. The knowledge of Geology is there to guide him.
Man’s scientific investigation has lead to certain conclusions about the origin of oil.
Scientists agree that, Petroleum or Rock Oil widely known as Crude Oil, originated &
lies trapped deep under the earth’s surface (it may be beds of ancient seas or inland
salt water lakes). How it got there is very interesting: Plants & Animals that lived
millions of years ago on earth (the earth we live in is more than two thousands million
years old), died and were covered with layers & layers of sand & sedimentary rock,
preserving their energy within their cells. Under pressure & temperature these turned
into tiny droplets that accumulated in impervious rock beds. This accumulation forms a
dark blackish liquid called Petroleum. The word ‘Petroleum’ is derived from the Greek
words Petra (= rock) & Oleum (= oil), as its origin is associated with rocks. It was first
discovered when it seeped to the surface in small quantities. Today gigantic oil wells
with huge drilling bits bore deep through the earth’s surface till they strike a store of
Gas & Oil floating on water (figure-2.20). Thus, Oil is made to gush out and collected in
large quantities, from where it is sent to the refinery. This method of pumping out of
oil from rock bed is known as Onshore Drilling. Oil is sometimes found under the ocean
91
bed too! The method of pumping out of oil from ocean bed is known as Offshore
Drilling.[4, 33]
Therefore, Crude oil & Natural gas are naturally occurring, complex mixture of organic
components originated from organic matters of both plants & animals, which
accumulated in the grained oxygen deficient sediments under special geological
conditions of high temperature & pressure over different periods of earth’s history.
These sediments eventually transform into shale, limestone & sandstone, collectively
forming the sedimentary rock, which is porous & permeable in nature, where oil can
move freely through the pores. Since physical properties & chemical composition of
oils from different areas & from different depths of the same reservoirs vary, an
exact definition of oil is not possible considerably. Crude oil contains tens of thousands
of different chemical components, mainly hydrocarbons, since they are composed of
entirely of elements like carbon & hydrogen. Other groups of components also contain
A. Offshore Drilling B. Onshore Drilling
Figure-2.20: Oil Exploration
92
sulphur, nitrogen & oxygen and some heavy metals such as vanadium, nickel, arsenic &
lead. Typical chemical composition of crude oil is shown in Table-2.6.
Physical Properties
Naturally occurring petroleum (crude oil), which can have a wide range of physical &
chemical properties, even from different wells within the same field, used by human
beings after it has been fractioned into variety of refined products. Knowledge of
properties of oil is essential to understand how oil may behave when it is spilled. For
example, the very light volatile crude oil may be flammable & hazardous and it may
rapidly evaporate, whereas, the heavy crude or asphalting product may be semisolid
and very stable. However, the physical properties of oil will vary greatly depending on
local (ambient) environmental conditions and may deviate from values reported for
standard conditions. The most important physical properties of oil from a spill
response viewpoint include the followings:[10, 49]
Melting Point A wide range of world’s crude oil shows that the melting points vary
from –43C to +43C. The melting point of oil can be significant in the event of an oil
spill because high melting point restricts the tendency of the oil to spread, especially
at low temperatures.
Boiling Point The boiling point is the temperature at which each fraction of
hydrocarbon evaporates. Many of the light (low boiling) fractions evaporate at
temperature less than 20C and would undergo a phase change from liquid to gas at
ambient temperature. As these light fractions evaporate the remaining oil is reduced
in volume and become denser & more viscous (one-third of the total volume of spilled
Kuwait crude was lost through evaporation during Amoco Cadiz oil spill in 1978).
Flash Point As a safety parameter, the flash point is critical. It is the lowest
temperature at which the fractions of oil will ignite, when exposed to an ignition
source such as sparks or other fire sources. A serious hazard may also exist if air
93
temperatures are above the boiling points of light fractions in spilled crude oil or
refined products.
Table-2.6: Chemical Composition of Crude oil
Sl. no. Composition % Weight
1. Carbon 84 – 87
2. Hydrogen 11 – 14
3. Sulphur Trace - 3
4. Oxygen Trace - 2
5. Nitrogen Trace - 1
6. Water Trace - 1
7. Heavy Metals Trace - 0.1
Pour Point The pour point is the lower temperature at which the oil will flow and
below which it acts as a semisolid substance. This is very important property in
evaluating whether or not the oil penetrate beach sediments since the ambient
temperature vary from place to place and also diurnally or seasonally, which may
influence the existence of the stranded oil in fluid or semisolid state. The pour point
ranges from -57C to +32C, but majority of the oils have a pour point below 0C and
therefore, are fluid above the freezing point. Even in cold temperature the light
volatile oils remain liquid, on the other hand, the heavier products such as Bunker C
(No.6 fuel oil) will frequently become solid on the sea surface, but may flow, when
stranded on the shore.
Specific Gravity The specific gravity or the density of the oil normally determines
the buoyancy of spilled oil in the seawater. If a density gradient exists in water
column, the oil sinks below the water surface to level at which the densities of both oil
and seawater are equal. Most of the oils have specific gravity less than 1.0 allowing
them to float on the surface. Heavy crudes & fuel oils, or lighter oils that are
weathered substantially may have gravity greater than that of the surface waters.
Surface Tension The surface tension controls the rate of spreading of oil slick. Oils
having a low surface tension spreads more rapidly so that a greater surface area of
94
spilled oil is exposed to natural weathering (evaporation). Ambient temperature
partially controls the surface tension. This, in turn, increases the rate of spreading.
Viscosity It is a measure of the resistance of oil to flow or to its internal cohesion.
This property controls the rate at which the slick spreads and the degree to which oil
can penetrate into the beach sediments. High viscosity oils are semisolid or tarry,
where as light fluid oils have low viscosity values. The major controlling factor of
viscosity is the temperature and as it increases the oil becomes less viscous, can
penetrate into the beach sediment more rapidly & spread more easily exposing greater
surface areas for weathering & other natural processes.
Stickiness Another important property is the stickiness when spilled oil reaches
shoreline. This is the adhesive characteristic in terms of the ease with which non-
sticky oils could be fleshed from surfaces using low-pressure water jets.
Solubility Solubility determines the rate at which the spilled oil will dissolve in
seawater, which is almost invariably low. Solubility is of considerable importance in
evaluating potential spill impacts on living marine biota.
Chemical Properties
Most crude oils contain over 95% hydrocarbons.[49] However, in certain cases the
hydrocarbon content can be as low as 50%. Hydrocarbons are divided chemically into 3
general groups viz., aliphatic, napthenes & aromatic hydrocarbons. Aliphatic
hydrocarbons are compounds of open chain, straight or branched carbon skeleton.
These may be fully saturated with hydrogen and are known as Alkanes (paraffins) or
may be deficient in hydrogen and are known as unsaturated compounds. Paraffins are
compounds that contain one to more than 80 carbon atoms and may be straight chained
or branched. Components with lesser than five carbon atoms are gases, compounds
with 5 to 16 carbon atoms are liquid and compounds with 17 or more carbon atoms are
viscous or solid. Those with carbon atoms between 22 & 35 are called petroleum wax.
Napthenes, saturated or unsaturated alicyclic hydrocarbons are also known as
cycloparaffins containing one or more ring structures in the carbon chain. In the crude
95
oil, the saturated components are dominant. Saturated napthenes occur particularly, in
refined oil products originating from different thermal & catalytic cracking processes.
Aromatic hydrocarbons contain one or more benzene rings. The simplest compounds
are benzene & toluene. One type of aromatic hydrocarbons, which occurs in many crude
oils, is the naphthalene, in which aromatic rings are linked together through two
common carbon atoms. Other compounds include phenanthrene and benzoapyrenes.
Other components are mentioned earlier are containing nitrogen, sulphur & oxygen.
Crude oil also contains trace metals, usually coupled with organic compounds and more
than 50 elements have been identified. Asphaltenes and resins are fractions usually
used in characterization of crude oil and heavier oil products. These compounds from
oils of different origins usually have different chemical composition and are relatively
high molecular weight compounds.
2.2.3 BEHAVIOUR OF OIL IN MARINE ENVIRONMENTS
The Oil (crude) or petroleum products, spilled on the sea is subjected to a series of
diverse processes that distribute the products in the environment (Fig.-2.21), and
simultaneously cause changes in its physical properties & chemical composition.
Therefore, for anyone involved in combating pollution in marine environments, it is
essential to have some knowledge of these environments, of typical processes taking
place in the oceans and of the interactions with shores. These processes will get more
complicated when oil is spilled in large quantities over the surface and may be more
seriously disturbed by inappropriate human action than if Nature was left to deal with
the oil spill.[10, 49]
Seawater is a complex solution of dissolved minerals, elements & salts. As water (H2O)
is a compound of hydrogen & oxygen, these two are the most abundant elements.
Sodium chloride (NaCl) forms the majority of dissolved salts, with magnesium, calcium
96
& potassium chlorides and carbonates forming the rest. The primary processes by
which these changes, also called degradation or weathering, that take place are
spreading, dispersion (i.e., mixing) & diffusion, sedimentation, biodegradation,
dissolution & advection, emulsification, evaporation & photo-oxidation.
The factors controlling the weathering processes are the properties of the oil and
environmental conditions like, weather, sea conditions, particularly sea-state or
roughness, wind & temperature. Once weathering is initiated & it continues, the
properties of oil change at the same time, simultaneously the oil is subjected to
drifting, spreading or sinking. The persistence of oil is primarily the function of oil’s
exposure to wave action & the wave-energy levels at the shoreline. In the absence of
wave action, weathering is primarily a function of biodegradation, oxidation & clay oil
flocculation. The energy available is the controlling factor at which the natural
dispersion occurs. This energy can be either thermal or mechanical or as a result of
biochemical processes. The thermal energy is related to air & water temperature,
0
PHOTO-OXIDATION
SPREADING
DRIFT
EVAPORATION
DISSOLUTION
DISPERSION
EMULSIFICATION
SEDIMENTATION
BIODEGRADATION
Figure-2.21: Weathering processes verses Time elapsed since a Spill
(Time width represents relative magnitude in relation to
other Active processes) (Wheeler 1978)
1 10 DAY 100 WEEK MONTH 103 104 YEAR
TIME (HOURS)
(n-ALKANES)
(AROMATICS)
C15 C14 C13 C12
C9 C8 C7 C6
C11
(LATERAL) (VERTICAL)
97
which increases the degradation processes. Mechanical energy is a function of waves,
currents & winds that cause dispersion & breakdown of oil. Biochemical energy is mainly
breakdown of oil by microbial actions. The relationship between weathering and
persistence of oil, inputs of energy and the properties of oil are depicted in figure-
2.22.
A pictorial presentation of the oil spill processes in the marine environment is provided
in figure-2.23. Oil exposed to the marine environment could be summarized as, during
the first day the principal processes that occur are spreading, evaporation &
dispersion of oil particles into the water column. Some dissolution and atmospheric
photolysis may occur, but this affects only a small fraction of the spilled oil.
Evaporation proceeds until 25% of the spilled oil may have evaporated after 2 to 5
days. Subsequent photolytic oxidation in the atmosphere is probably fairly good. As
the spill spreads and thus an increasing fraction of the oil is dispersed into the water
Evaporation
+
Photo-Oxidation
+
Dissolution
+
Biodegradation
Thermal Energy
+
Mechanical Energy
+
Biological Energy
INPUTS OF ENERGY
+
PROPERTIES OF OIL
WEATHERING
and
PERSISTENCE
Physical properties of Oil
+
Chemical properties of Oil
+
Volume of Oil
+
Surface Area of exposed Oil
+
Effect of Oil on energy factors
Figure-2.22: Factors that affect the degradation (weathering
& persistence) of spilled oil
98
column and in many cases the surface slick may disappear. However, it is suspected
that a considerable fraction of the oil remains on the surface eventually becoming tar
balls, which may be stranded on the beaches. Biodegradation of dissolved & dispersed
oil probably become significant during the first year. Small amounts of oil that sink to
the bottom, or are ingested by animals of various tropic levels. Now the processes are
discussed below.
Spreading
The first process that occurs after the oil spill is spreading of the products over the
surface in the form of thinning film. In the calm sea the spreading is controlled by
gravitational force in the initial stage and also by the surface tension-viscosity
relationship, which is independent of spill volume. Surface currents & local winds
control the movement of oil slick on the surface water and thus the slick increases its
area rapidly. Figure-2.24*# shows the spreading of oil on surface waters. This area
eventually becomes constant, as further enlargement is limited and offset by natural
forces. Once the oil spill has thinned and the surface forces begin to play an important
role, the oil film is no longer continuous and uniform, but becomes fragmented by winds
and waves into patches and windows.
The spreading must complete with emulsification. The effect of water in oil
emulsification increases with time and greatly increases the viscosity of the remaining
slick, which reduces the tendency of the slick to spread. Thus, the spreading is a self-
retarding process. It accelerates the evaporation and leads to increased viscosity &
pour point of the oil.
*# Source: Figure-1.8 of “Oil Spill Response in the Marine Environment”, JW Doerffer
99
Figur
e-2.2
3: Diagr
ammatic
Sum
mary
of
Fate
of
Spilled O
il in
the M
arine
Env
iron
ment
100
Evaporation
Evaporation is one of the important processes, which reduces the quantity of oil from
spill. It is a process by which the low & medium molecular weight components of low
boiling points are volatized into atmosphere. Volatile hydrocarbons of boiling points
less than 20C undergo evaporation & photolysis. The time needed for the lighter
components to evaporate depends on the vapor pressure and composition of the oil,
surface area, & thickness of the oil spill and on wind & temperature. Evaporation is
most intense during first few hours. Lighter hydrocarbon fractions of the oil
containing approximately 13 carbon atoms or less, comprising around 40%, are
subjected to evaporation during first 24 hours immediately after the oil spill.
Evaporation, therefore, selectively depletes the lower boiling components of the oil,
increasing the specific gravity as the oil loses its volatile fraction. The process can
contribute to the formation of thick residuals, oil sludges, and finally the possible
formation of tar balls. In either case, the specific gravity of the remaining oil
Figure-2.24: Three Phases of Oil Slick Spreading
102 103 104 105 106 107
103
104
105
106
Time after Spill (seconds)
Slick
Diamete
r (c
m)
101
increases and the residual oil may become denser than seawater leading to the
possibility of sinking. Evaporation can be an important means of preventing toxic
components from entering into the marine ecosystem. However, higher ring aromatics,
some of which are less volatile, involved in long-term toxicity, are potentially
hazardous components. At the same time, it is also seen that the lower molecular
weight hydrocarbons, which are susceptible to evaporation loss, are also the most
soluble. The process of evaporation is more in tropical seawaters. However, as
mentioned elsewhere in this report in case of polar conditions, evaporation does not
occur under ice, so that some components that would normally evaporate would achieve
higher concentrations in the water column under ice. The amount of oil that evaporates
also depends on the area covered by the oil. This is, in turn, connected with the
spreading process of the oil in the seawater.
Dispersion (Mixing) & Diffusion
In addition to evaporation & spreading processes the most important process
simultaneously occurring is dispersion or mixing of oil from the surface into the
underlying water masses. This process is probably the most important single oil spill
process governing the amount of oil in water column. Dispersion is largely occurring due
to breaking waves or white capping. The breaking waves mix parts of the slick into the
underlying water masses in the form of larger or smaller oil droplets. These droplets
rise towards the surface as a result of buoyancy, while turbulence tends to prevent oil
from rising. The smallest oil droplets are those which are most affected by turbulence
and those may reach relatively greater depth. The Fig.-2.25 shows the mixing of an oil
film into the underlying water masses.
Factors contributing to the formation of the characteristic trail of their oil film
observed after oil spills at sea, the so called blue sheen include the spreading and
mixing of oil with water, which subsequently rises to the surface at another area away
from where it has disappeared. Because the oil on surface layers generally drifts
102
Figure-2.25: Mixing of Oil film into the underlying Water layers
OIL PARTICLES OIL FILM
BREAKING WAVES
faster than oil mixed with water. Therefore, the latter returns to the surface at
another area away from where it has disappeared. Because the oil on surface layers
generally drifts faster than oil mixed with water. Therefore, the latter returns to the
surface behind the oil slick, which remained on the surface. The loss of oil in a given
period is termed as the rate of dissipation. The Table-2.7 shows the natural rate of
dissipation, which is controlled by wind speed & wave action.
The oil/ water interfacial tension affects globulation & coalescence, but does not
affect dispersion (transport of oil droplets into the water column. The use of chemical
dispersants to accelerate this dispersion process i.e., for lessening the adverse
effects of oil spills will depend on the following factors:
Effectiveness of a given dosage of dispersant on a given oil slick;
Diffusion (i.e., spreading in every direction) of dispersed oil & dispersant into
the water column and subsequent processes including dissolution, volatilization,
degradation and interaction with suspended & bottom sediments;
103
Effects of dissolved & particulate oil & dispersant on the water column and
benthic biota.
Table-2.7: The natural rate of Dissipation of Oil
from the Surface & Wind speed
Dissolution & Advection
Dissolution is a physical process by which the low molecular hydrocarbons as well as
some of the more polar non-hydrocarbon compounds are lost by the oil to water. The
rate of this process is controlled not only by wind & condition of the sea, but also by
the physical properties & chemical composition of the oil. Although this process does
not start immediately, it has long-term effects as well. It is also established that the
oxidation processes constantly produce polar compounds from hydrocarbons in the oil,
which are more soluble than the original products. Mostly the low molecular weight
components, namely the aromatic compounds have the greater solubility. However, over
a short period of time, losses of highly soluble aromatics in solution will be minor as
compared with evaporation. About 1% of the spilled oil may get dissolved, dispersed or
suspended in seawater. All these processes occur quite fast in warm seawater
simultaneously as compared with cold marine environment. The dissolved hydrocarbons
are predominately aromatic in nature, whereas the dispersed ones are probably
deficient in aromatics. Dissolved components of the oil would probably act by diffusing
into the vital fluids & organs of marine organisms, thus giving toxic effect. On the
other hand, if the oil particles are of the same size as the usual food size, the
organism may accidentally ingest large quantities of oil or particles may coat & block
the surface of respiratory organs, thus giving a different type of toxic effect.
Wind speed 7 m/s
(Breeze)
7-12 m/s
(Strong Breeze)
14-20 m/s
(Gale)
> 20 m/s
(Storm)
% of oil dissipated from
the surface per day
7 7-23 24-45 46-60
104
The petroleum hydrocarbons are removed from the sea surface by wave-produced
sprays & bursting of bubbles. The process transfers hydrocarbons into the
atmosphere, which is also controlled by wind speed, see state and the extent to which
have breaking and white cap formation are suppressed by oil films, which in turn is
dependent largely on film thickness and the horizontal extent of the film. This is
further accelerated by solar radiation, which can cause formation of polar, surface
active molecules in the film. The transfer process is more effective in relatively thin
films. Most of the particles from the atmosphere are redeposited in the ocean. The
annual estimated quantity of such fallout is about 0.25 million tonnes and its deposition
may be from at distance ranging few meters, to several hundred kilometers from the
source. It is interesting to note that the components may have undergone
photochemical breakdown while airborne. In this regard it can be noted that: the
values of Time-series concentrations of selected lower molecular weight aromatics
dissolved in a water column were obtained from wave tank experiments (JW Doerffer,
1992). The peak concentrations of dissolved compounds occur approximately 8 to 12
hours after the initial release of the oil to the water surface. The concentration then
drops off in an exponential manner, reflecting the loss of these compounds by
evaporation from both the slick & the water column and the removal of dissolved
components by advection (water mass transport i.e., the horizontal & vertical flow of
sea water as a current). The early time-series concentrations of total aromatics are in
the range of 10 to 100 parts per billion (ppb). After a relatively short time these
concentrations resulting from advection & diffusion quickly yield values in the low
parts per trillion levels in an open ocean spill. These predictions are in agreement with
measured values in subsurface water column samples collected within 2 to 3 kilometers
of the slick generated during the 1979 IXTOC I blowout in the Bay of Campeche (Gulf
of Mexico).
105
Sedimentation or Sinking
Most oils are less dense than seawater and even after evaporation. It is only under
exceptional cases that oil density will exceed that of seawater. Rough seas may also
increase the chances of oil to be absorbed on or mixed with particulate matter such as
sand, salt, clay & organic detritus, and eventually settle down on the bottom, when the
seas become calmer. Its absorption by solids renders the oil more susceptible to auto-
oxidation and also too microbial action. On burial of these hydrocarbons in the
reducing sediments, oxidation process becomes reduced.
Table-2.8: Characteristic appearance & quantity of oil film on water
Appearance of oil film Thickness of oil
film (x 10-3 mm)
Quantity of oil film
on water/km2
liters tones
Visible only during favourable conditions 0.05 50 0.04
Visible silver sheen 0.10 100 0.08
First observable colour 0.15 150 0.12
Easily visible pale strips of colour 0.30 300 0.24
Dark colour 1.00 1000 0.80
Deep dark colour 2.00 2000 1.60
Sedimentation or Sinking
Most oils are less dense than seawater and even after evaporation. It is only under
exceptional cases that oil density will exceed that of seawater. Rough seas may also
increase the chances of oil to be absorbed on or mixed with particulate matter such as
sand, salt, clay & organic detritus, and eventually settle down on the bottom, when the
seas become calmer. Its absorption by solids renders the oil more susceptible to auto-
oxidation and also too microbial action. On burial of these hydrocarbons in the
reducing sediments, oxidation process becomes reduced.
106
Photo-Oxidation
The chemical reactions occurring in the petroleum are mostly oxidative in nature.
Since the oil floats on the surface, a major portion of the oxidation occurs on the sea
surface. Reduction reaction takes place when the material is carried to or released to
the sea bottom, where the oxygen content is very low.
Chemical Degradation
The chemical degradation is largely the result of photo-oxidation of hydrocarbons.
The oxidized compounds are more soluble in water than the original ones. The dominant
degradation process of hydrocarbons in the atmosphere is photolysis. Photolytic
process is significant at the sea surface. Photolysis (above 3200 A) is thought to
afford an initiating mechanism for the oxidation of larger, more complex molecules
(auto catalytic oxidation) as well as polymerization, hydrocarbon formation & removal,
and tar ball formation. This process can be very important in that the chemically
altered hydrocarbon may be more toxic and soluble than its parent and the “oxidized
form may be subjected to faster biodegradation. The effect of photochemical
degradation only become significant alters first day or so. Further, it was also
established that chemical weathering influence the viscosity. Several crude oils
increased their viscosities by decimal power after few days of exposure. Solar
oxidation also causes the polymerization of hydrocarbons.
Aerosol Formation
Under rough sea conditions with high winds, substantial quantities of oil may be
conveyed into the atmosphere as aerosol sprays and may be transported some distance
and even on land.
107
Biological Fates
The biological fate of oil stresses is on two aspects. The first concerns those factors,
which change and remove hydrocarbons & its products from the ambient water. The
second concerns the biota as a physical reservoir that takes up and holds the oil. The
indigenous microbes play a dominant role in the first case and macro communities are
most important in the second case.
Microbial Degradation
It was known that a large number of microorganism including bacteria, moulds & yeast
are capable of breaking down hydrocarbons and there are reasons to believe that
bacteria is the most important degrader of oil in sea water. Microbial organisms, in
particular, bacteria use petroleum hydrocarbons as a food source. The biochemical
process is related primarily to oxidation and results in the breakdown of the
hydrocarbon compounds to produce carbon dioxide, water, and biomass & partially
oxidized biologically inert byproducts. Generally, biodegradation rate is slow and it
largely depends on the ambient temperature & on the surface area of the exposed oil.
As the residence time of the oil on the water increases, biological processes begin to
operate and rapidly gained significance. Over 90 species of microorganisms are capable
of degrading the oil by biological oxidation has been identified. The degradation
depends upon the ambient water temperature & on the presence of certain volatile
fractions in the spill and some components are either bacterial or bacteriostatic. The
most important factor, which influences the biodegradability of hydrocarbons, seems
to be the molecular configuration. Alkanes are attacked by more microbial species and
support more growth than either aromatic or napthenic compounds. Within the alkane
series normal compounds are more susceptible to microbial oxidation than branched
chain compounds. Nutrient limitation, specifically, phosphates & nitrates, is a major
factor that effects degradation of petroleum in the marine environment.
108
Uptake By Microorganisms
A considerable portion of petroleum hydrocarbons is dissolved or absorbed in
particulate matter because the partition coefficient favors the solution of
hydrocarbons in the lipids of detritus. Detritus then would carry the adsorbed or
dissolved hydrocarbon to the sea floor to be consumed by benthic organisms or it may
be consumed by the pelagic filter feeders while in suspension. The gill tissues of
mussels followed by transfer of hydrocarbons to other tissues take up dissolved
hydrocarbons. It was also reported that phytoplankton absorb hydrocarbons. On the
other hand, the surface zooplankton take up large quantities of petroleum
hydrocarbons from heavily polluted surface film. Studies also have indicated some
storage of hydrocarbons in the liver of marine fish and in the hepatopancreas of
several invertebrates, since liver & hepatopancreas are generally high in lipid. From the
metabolic fate of various forms of petroleum hydrocarbons present in the food web
and in aquatic organisms was examined, it is impossible to evaluate the fate of
persistent low concentration of petroleum pollution in the marine environment.
Even though marine biota may be severely affected by the presence of oil, it is neither
a major reservoir for spilled oils nor is it a major factor in influencing the distribution
pattern of spilled oil. Therefore, the marine biota except the microorganisms have
minor role in deciding the fate of spilled oil. However, it is proper to mention that once
the accumulation or concentration of petroleum is shown to occur within marine
organisms the pathways for passage and magnification of oil within the marine food
chain has opened up.
Tar Ball Formation
The residual oil on the sea surface tends to form tar balls. It is the product of
different degrees of physical, chemical and biological weathering of petroleum, which
vary considerably in size ranging from a few millimeters in diameter up to several
109
centimeters. Some samples are soft & others are quite hard, almost brittle and many
incorporate sand & small particles. The occurrence of such petroleum residues/ tar
balls/ tar lumps on beaches or on ocean surface are well documented. The samples
showed a wide variety in chemical composition. The saturated hydrocarbon composition
ranged from 1.6 to 56.1% and asphaltene contents from 8.8 to 54.7%. The hard brittle
tar ball samples have undergone appreciable chemical & biological oxidation in addition
to physical weathering. They contain low amounts of saturated hydrocarbons (<10%) &
greater amounts of nitrogen – sulphur – oxygen containing compounds and asphaltenes.
In hard tar balls, the content of C15 to C25 hydrocarbons decreased relative to the
hydrocarbon fraction above C25. The effect of oil pollution in Indian Ocean can be
seen on the beaches in the form of deposition of tar balls. The intensity & frequency
depends on the winds & surface current especially during monsoon season. In 1981 an
estimation has been made that the floating tar balls in the surface layers of the
Arabian sea would be about 3700 tones, while along the tanker route across the
southern Bay of Bengal the quantity would around to 1100 tones.
Behaviour Of Oil With Shoreline Types
The physical factors on the Shore that alter the degradation of oil are given in the
table-2.9.
World oil production is estimated to be near 2,800 million tonnes per year and of this,
at least 60% is transported across the ocean. The loss in transportation has been
estimated to be about 0.1% of the total oil shipped. The actual oil influx into the ocean
is higher since the figure does not include accidents during production on offshore
sites, return to the ocean of petroleum products as untreated municipal wastes, and
the incomplete combustion of marine fuels. Thus even the estimate made in January
1975 by the US National Academy of Sciences of 6.1 million tonnes per year of oil
influx into the ocean will be a substantial under-estimation. Clearly, a major effort
110
needs to be made to control and remove this oil pollution. The following section brings
out this effort in the field of research work in India & Abroad.
The table-2.10 provides the behavior of spilled oil in the coastal zone with shoreline
types.
Table-2.9: Behaviour of Oil with Shoreline Types
Factors that reduce impact and increase
rates of physical breakdown
& Degradation of oil
Factors that increase impact and reduce
rates of physical breakdown
& Degradation of oil WAVES:
Increasing wave energy levels
Mix or breakdown oil in breaker, surf
& Swash zones
Use of sediment as abrasive tools
Redistribution of erode oil on the
Shore
Reflected waves mix or breakdown oil
& may prevent oil from reaching the
Shoreline
Decreasing wave energy levels
Burry oil by beach accretion or by
longshore migration of sediments
Reduce temperature of oil
Throw oil above the normal level of
Wave activity by the splashing actions
of breakers
WINDS:
Increase rate of evaporation
Increase dispersion of surface slicks
Redistribute sediments & burry oil on
the backshore
Generate storm surges and oil is
deposited in lagoons (by over-wash) or in
backshore
Onshore winds trap on coast during
surge deposition, then occurs above level
of normal wave activity when water level
lowers
TIDES:
Lower water level cause deposition of
oil in section that would later be subject
to wave or current action
High water levels cause deposition of
oil above normal limits of wave or current
action
Oil can be carried into marsh surface
CURRENTS:
Increase dispersion of oil in water
Transport oil offshore
Concentrate oil in eddies & other
areas of low currents
Transport oil to previously unaffected
areas
111
Table-2.10: Shoreline types and fate of Oil Spill
Sl.
No. Shoreline type Behaviour of spilled Oil
ROCKY COASTS:
1. Cliff/ rock
outcrops
Spilled oil is not absorbed if it reaches the shore
On steep coast the rock face prevent oil from being
stranded on shoreline
Oil does not adhere on wet surfaces
Oil deposits at higher levels by the flood tide
Stop of the cliff determines the thickness of the stranded
oil
Oil collects in the crevices rock pools & in regular surfaces
of the cliff
Natural dispersion occurs to the oils of the rock surfaces in
intertidal zone
Oil may be buried in the base of the cliff
2. Intertidal rock
platforms
Oil can be stranded on rock surfaces, hollows, crevices, &
tide pools
Light oils may be re-floated with the rising tide
Heavy oil can be deposited & not re-floated with the tide
Oil trapped/ absorbed by the intertidal vegetation may be
subsequently released during flood tide
Oil trapped in crevices or hollows that contain coarse
sediment can form local patches of asphalt payment that
erode very slowly
3. Man-made
shoreline
Oil would penetrate the man-made sediments
On steep vertical structures any stranded oil may flow down
and stain would likely to remain
On protective structures the hydraulic & abrasive action of
waves rapidly removes the stranded oil
UNCONSOLIDATED COASTS:
4. Sandy beaches Mobile sediment can trap oil
Stranded oil above the spring tide level remain unaltered by
coastal process
Oil can be trapped in the sand dunes
Light oil penetrates into the sandy beach
Oil stranded in the lower water zone are likely to be re-
floated by tides and carried land ward or sea ward
Oil can be buried during the period of erosion & deposition
Heavy oil may not penetrate into the sediment
As the mud content increases the oil retention decreases
112
5. Sandy gravel
(mixed)
shoreline
Oil can be buried by normal process of erosion & accretion
If the oil penetrates the beach and remains there to leach
into the intertidal zone it will be there for years
The rate of natural cleaning would depend on wave energy
levels
Clay oil flocculation removes the oil
6. Gravel/ Cobble
or Pebble/
Cobble
shoreline
Oil deposited on the ridge would be buried
Oil-mixed sediment beach forms asphalt pavement
Oil in sediment, the concentration of asphalt pavement are
2-5%
7. Intertidal mud
flats
Spilled oil including light oils do not penetrate into the mud
flats
Open burrow holes allow accumulation
Light medium oils may be flushed from the surface area by
the tidal cycle
If spilled oil quantity is large it can effect the burrowing
animals
Heavier oil could be deposited & can effect the fauna
Deposit feeder can ingest oil contaminated sediment
If the sediment is oiled it may take years to flush naturally
The residence time of buried oil depends on redox condition
& microbial degradation
8. Intertidal sand
flats
Light & medium oil can penetrate through the surface
sediment and can persist extensive length of time
Spill of light oil in the sheltered sand flat could remain oiled
for several years and recovery is a slow process
9. Marshy
beaches/ coast
Oil deposits along the outer edge of the marsh
Once the oil is stranded on the upper edge of the marsh it
may take years to biochemical breakdown
Fresh or light oil penetrate the surface of marsh and may
effect the root system of vegetation
Heavy or weathered oil would not penetrate the substrate
The damage potential are not only to plants & animals but
also to birds
113
2.2.4 RESEARCH WORK DONE IN INDIA & ABROAD
From 1978 – 1987:
MJ Roux (1979) studied about the fate of a pollutant on the sea surface based on two
phenomena – (i) The process of oceanic dispersion & (ii) 3 types of wind-induced drift.
The developed model is best suited for a theoretical case. TS Murthy, et al. (1979)
studied on Numerical simulation of the movement and dispersion of oil slicks in the
upper St. Lawrence estuary based on two field experiments conducted in November,
1972. The developed model on the subject only computes the trajectory of an oil slick
due to tidal currents, winds & random variations in the wind field.[17]
Anon (1980) studied about computer watch on oil slicks, which predicts the movement
of an oil slick is available from Offshore Environmental Systems Limited, it locates the
source of pollution and predicts environmental impact. T. C. Gloersen (1980) developed
a computer-programming package for statistical evaluation of the consequences of one
or more oil spills. It is particularly suited for statistical analysis of physical fate of oil
spills at sea.[17]
KS Aravamudan, et al. (1981) studied on break-up of oil on rough seas. In this study, an
attempt has been made to integrate the existing theoretical & experimental
information regarding behavior of oil spills in the ocean based on the principal
phenomena: combined spreading & evaporation, the interaction of waves within the
slick with the slick and formation of oil droplets, dispersion of droplets in the water
column and finally the formation & dispersion of slickiests due to turbulence in the
ocean.[17]
M. Darras (1982) also developed numerical models for the prediction of oil stick
movements at sea considering the spreading & dispersion of oil sticks at sea occur in 3
phases → spreading with gravity forces with the resistance of inertia & with the
114
resistance of interfacial friction; and impact of surface tension with the resistance of
interfacial friction. This model also takes care of the effects of winds & currents on
the oil-slick movement. But this model is unable to predict exact time-bound area
coverage by the spilled oil. SE Herbes & GT Yeh (1982) developed a numerical model to
predict dissolved aqueous concentrations of phenolic contaminants resulting from
accidental spillage of synthetic oil into a river. The model (termed SOPTRAN, for
Synthetic Oil Pollutant Transport) simultaneously solves algorithms for processes of
oil slick spreading, oil evaporation, phenolic dissolution, advection & dispersion using an
implicit integrated compartment method. The model was used to simulate a
hypothetical 300m3 (80,000 gallons) accidental release of a coal liquid from a barge
into a large navigable river under both instantaneous & non-instantaneous (i.e. leakage)
spill scenarios. SE Soerstroem, et al. (1982) studied about drifting & spreading of oil
based on experimental oil release on Haltenbanken, Norway in 1982. In this study
drifting & spreading of oil information on physical environment, decay of oil, mixing of
oil in water, oil spill surveillance, warning & simulation and numerical modelling are
collected. Multidisciplinary field experiments were carried out at Haltenbanken, north
Norway, during the period July – August, 1982 to examine the drift & dispersal of oil
in the sea surface & water column and to investigate the conditions regarding microbial
oil degradation & the resulting ecological effects. In this study, drift of the oil layer,
the disintegration & the vertical distribution of oil in the water-masses were
monitored and simulated models were used to predict the outcome. Biological
investigations were carried out to examine the microbiological conditions, dynamic
conditions in the pelagic ecosystem and to estimate the productivity of the ecosystem.
(Published in cooperation with the Norwegian Marine Pollution research & Monitoring
Program, Oslo, Norway).[17]
JCJ Nihourl (1983) developed a non-linear mathematical model for the transport &
spreading of oil slicks. This model differs from previous ones by its capability of taking
simultaneously gravity, surface tension, friction & weathering processes of the oil into
account and by the introduction of a new parameterization of surface tension &
115
friction, better adapted to real field conditions. The model is summarized by an
evolution equation – describing oil transport and spreading – for the oil layer’s
thickness. This equation contains all essential features of the phenomenon and can be
solved numerically for any oil spill situation whether the released volume is large or
small. JW Dippner (1983) presented a mathematical model, which simulates oil spill
movements. The numerical framework is done with a Lagrange tracer technique. The
model includes drift by wind & tidal currents, spreading & dispersion by turbulent
diffusion. The results are compared with the measurements during the Bravo Ekofisk
blowout in April 1977 in the North Sea. He (1984) also formulated a current & oil drift
model (a semi-implicit model) for the German Bight, where the possibilities of tanker
accidents and the processes occurring after an oil spill are discussed. This numerical
model is designed, consisting of 2 parts – a circulation model & an oil drift model. The
result of the circulation model is an atlas of the currents in the German Bight. The oil
drift model gives an impression of the complex & difficult advection processes in shelf
sea areas. The results show the dimension and intensity of oil pollution in the case of
small accidents. He (1985) again studied & developed a deterministic numerical model
in Oil Patch Simulation Package (OIPASIPA) for the simulation of the drift & fate of
oil spills, which is useful for quantitative oil spill contingency planning. The model is
based on Lagrange tracer technique that includes drift by currents & wind’s spreading
and horizontal dispersion by turbulent diffusion & shear currents. Evaporation of
different sorts of crude oil is calculated as a function of temperature & wind. Natural
dispersion effects are simulated by an empirical relationship between wind speed &
rate of natural dispersion.[17]
PG Kurup (1983) studied oil slick drift trajectories for hypothetical spills in the
Arabian Sea. Of the 732 spills studied, 135 spills may pollute the Indian coast with
varying intensity. The period: May – September provides more chances of severe oil
deposition on the West Coast of India. T. Audunson (1983) presented a Technical
paper in which the fate of oil slicks on the sea is discussed. The drift of oil is
dependent on several factors such as winds, waves & currents. The spread &
116
weathering of oil depends on evaporation, mixing in the upper layers of water,
formations of emulsions, etc. The present status in the description of these processes
in relation to their application to numerical models is discussed. TK Jensen (1983)
presented a technical paper on modelling Oil Spills. A number of oil spill models have
been developed in recent years, and many have shown their usefulness in contingency
planning, clean-up operations, and environmental impact assessments. None, however,
takes fully account of all oil fate-governing processes, categorized as advection,
spreading, evaporation, dissolution, emulsification, dispersion, auto-oxidation,
biodegradation, & sinking/ sedimentation. This paper discusses these processes and
suggests some topics for further investigations that will improve oil spill fate
predictions. T. Yangi, et al. (1983) developed a numerical model to simulate the
dispersion of drift cards in a coastal sea. The result of this numerical experiment
coincides well with that of a field experiment at Harima-Nada in the Seto Inland Sea,
Japan. This model can also be used/ applied to the dispersion of pollutants such as oil
spill bounded to the sea surface.[17]
Falconer (1984, 1986) developed a hydrodynamic model as well as solute transport
model based on Quick scheme provided by Leonard (1979) to predict pollute
transportation in the seas, which can give good results in offshore situations, but can
lead to significant errors when applied to coastal regions.[18]
JM Lo (1985) developed a computerized mathematical model for predicting short-term
movement and spreading of slicks in the coastal waters of Kuwait. He along with M. Al-
attiah also developed a computerized mathematical model to predict long-term
movement & spreading of oil slicks in the coastal waters of Kuwait, which includes
statistical oil pollution risk data for the whole coast of Kuwait. The data can be used in
the strategic planning for routing tankers & other vessels and in the selection of sites
for Ports & Terminals, so oil pollution risk to sensitive areas along the coast would be
minimized. J.R. Bennett, et al. (1985) developed a series of computer programs to
assist in forecasting the movement of oil spills, floating & submerged debris, or other
117
objects in the open waters of the Great Lakes. A numerical circulation model is used to
calculate the lake currents based on observed winds for the previous day and wind
forecasts for following days. The current field may be examined or stored for future
reference. Conservative particles may then be released into the lake by specifying the
initial location, wind effect percentage, & current effect percentage. Another program
predicts the trajectories of the particles and allows the user to examine particle
locations at a given time, or the trajectory of a single particle. The system is intended
to be used primarily by the National Oceanic and Atmospheric Administration (NOAA)
and the US Coast Guard for guidance in operational spill response and search & rescue
operations in the open water areas of the lakes, where the currents are due mainly to
the large-scale wind-driven circulation.[17]
A time dependent, 2- dimensional numerical model has been developed by TS Murthy &
MI El-Sabh (1985), to simulate the movement of oil slicks in the inner Gulf of the
Kuwait Action Plan (KAP) Region. Initially, the oil is assumed to spread under the action
of gravity, inertia & surface tension forces; but most of the movement is due to the
currents in the water column due to wind-driven circulation & tides. The output from
tidal & storm surge numerical models for the Gulf are used as input for the oil slick
model which computes the trajectory, as well as, the area by the oil slick, as a function
of time. Realistic values for the amount of crude oil being discharged into the water
as well as appropriate values for the winds & tides were used. The numerically
simulated results show reasonable agreement with the observations. It was then
concluded that wind is the primary agent in the movement of oil slicks.[17]
AJ Elliot, et al. (1986) studied about shear diffusion & the spreading of oil slicks by
controlled releases of oil in the southern North Sea. Here, various Empirical methods
have been used and good agreement has been found between observed & predicted
slicks when the shear diffusion processes are represented. C. Ambjoern (1986)
developed a fully operational forecasting system as a part of the combating
organization. However, some specific data, like locality information, time of spill &
118
thickness of the oil is manually added to the calculation. The output of the system can
predict the spreading & different positions of the spilled oil up to 4 days ahead
counted from the starting point. ER Gundlach, et al. (1986) studied for development of
a coastal oil spill smear model, Phase-1: Analysis of available & proposed models. The
report is a collaborative & multidisciplinary effort to determine the best combination
of algorithms and models representing surf zone currents & sediment transport, oil
weathering, and oil/ shoreline interactions for use in a unified, interactive coastal Oil
Spill (Smear) model. The purpose of the Smear model is to produce stochastic
predictions of oil spill composition, amount & spatial distribution across & along a beach
as a function of time.[17]
D. Mackay, et al. (1987), studied about the drop size & dispersant effectiveness only.
VR Neralla (1987), discussed a Nomogram method for predicting the movement of oil
slicks incorporating advection & spreading processes.[17]
From 1988 – 1996:
In the recent years the study of the environment has become increasingly important.
This is a result of the present-day economic expansion, which brings about a
tremendous pollution problem of ground & surface waters and of the atmosphere. It
has become clear that it is a necessity to use adequate models in order to trace out
the consequences of accidents in seas & estuaries that lead to pollution of the waters.
In the paper presented by Van-Stijn & Praagman (1988}, the authors discuss two
numerical techniques that are particularly suited for the calculation of the transport
of pollutants in realistic simulations. This model is unable to predict exact area
covered by the spilt oil in real situations.[17]
JR Payne, et al. (1989) developed a predictive model that describes the qualitative &
quantitative weathering of spilled Crude oil & refined Petroleum products in the
presence of first-year & multi-year ice only.[17]
119
SA Joynes (1990) studied the horizontal diffusion of a buoyant pollutant in coastal
waters, which examines the motion and spreading of a buoyant oil pollutant in the near
shore environment with particular regard to the wave height field. Major oil spills,
which occur from damaged tankers, such as the Torrey Canyon in 1967, need to be
monitored and assessed for clean-up purposes. Literature on the fundamental
processes which drive an oil slick in Coastal waters is reviewed and a numerical
prediction model was developed. In this model, a time-dependent Fickian advection-
diffusion equation is applied which predicts the position & concentration levels of the
slick. Regular waves with heights in the range 0.06 to 0.1 m & periods of 0.8 to 1.3 secs
were considered as the inputs for the model solution. However, the developed model by
Joynes did not sufficiently consider small-scale eddies feeding off the rip current,
which would increase the lateral spreading of the slick. It is recommended therefore,
that modelling of the Fickian-diffusion equation may be further improved using
turbulence terms obtained from a k- epsilon turbulence model. The effect of wave
height on the diffusion of oil needs also to be examined more extensively. He along
with AGL Borthwick (1992) also carried out a laboratory study of oil slicks subjected
to near shore circulation. This paper compares results from a simple numerical
simulation of small-scale oil slick advection and spread (based on an equation of species
coupled with wave-induced currents) with laboratory test data from a 3.5 x 6.0 m wave
basin containing a sinusoidal beach profile. The numerical model predicted reasonably
the near shore circulation patterns and the movement of the oil slick. Even so,
important discrepancies occurred due to reflections from the experimental beach &
the effect of surface tension-viscous spreading which were not included in the
mathematical formulation. It should be noted that the small-scale results presented
herein couldn’t be scaled up to prototype slicks that cover several surf zone widths. A
model system is presented for the prediction of the drift & spreading of oil in the
German Bight by S. Dick & KC Soetze (1990). The main parts of the system are a
hydrodynamic-numerical circulation model of the North Sea & German Bight, and an oil
drift & dispersion model. The circulation model consists of 3 nested & interactively
coupled models, which reach the highest resolution (1 nautical mile) in the coastal area
120
of German Bight. The 3-dimensional model of the coastal area has 4 layers, and
simulates the flooding & falling dry of tidal flats. For the computation of the oil
dispersion a Lagrange method is used, which requires that a particle cloud represent
the substance examined. Thus, it can be inferred that this model is a complex one for
handling in the real situation.[17]
HT Shen, et al. (1991), developed two computer models named ROSS & LROSS for
simulating oil slick transport in Great Lakes connecting channels. These models can be
used for slicks of any shape originating from instantaneous or continuous spills in
rivers & lakes only with or without ice covers. L. Papa (1991) calculated the circulation
in the Ligurian Sea and studied the dispersion & transport of the oil spilled from the
tanker Haven during the period 11 - 25 April, 1991 in the Gulf of Genoa, using 3-
dimensional mathematical model. The field of residual currents was also determined in
order to evaluate the transport of oil towards the open sea. But the actual area of oil
spreading after the spill was higher than the predicted area from the model.[17]
AH Al-Rabeh, et al. (1992) also studied on modelling the fate & transport of Al-Ahmadi
oil spill. Over the period January – May, 1991 Iraqi forces, occupying the State of
Kuwait, caused a massive amount of oil to be released in the waters of the Arabian
Gulf. The models were developed based on the trajectory analysis which may/ may not
give accurate result in some cases. Geng, et al. (1992) studied about the tidal flow in
Zhoushan sea area and provided a model that can be further used with a set of models
to predict the transport of oil spill.[17]
CR Ryu, et al. (1993) studied on numerical modelling of oil dispersion in the coastal
waters. The aim of this study is to give an overview of existing oil spill models that
deal with the physical, chemical & biological aspects of fate/ behavior of spilled oil,
and to develop a feasible, sophisticated, design purpose model of oil spill in the coastal
waters. The applicability & feasibility of the model are discussed by comparative
applications of the typical conventional model and the developed model to the
121
Southeast coastal waters of Korea. Martinez & Harbough (1993) developed a
hydrodynamic model to predict pollute transportation in the seas only, which cannot
give good results for coastal regions. ML Spaulding, et al. (1993) configured an oil spill
response model for operation on a personal computer, was simulated to predict the oil
trajectory and fate in the northern Arabian Gulf from the Mina Al-Ahmadi spill. Wind
data necessary as input to the model was generated by Monte Carlo procedures from
an analysis of historical data or provided by wind forecasts. Current data was provided
by hydrodynamic model of the Gulf. The model was applied in forecast & hindcast
modes to predict the transport and fate of the Mina Al-Ahmadi (Sea Island), which
started on 19th January 1991. Model predictions were compared to the observations
of slick size & arrival times at key locations along the Saudi Arabian coast. The model
correctly predicted the spill path & size but over-estimated the rate of transport in
the forecast mode. Hindcasts were in better agreement with the observations.[17]
Angang Lou, et al. (1994) presented the prediction of oil spill track and studied its
dispersion over the sea, using the Euler-Lagrangian method. This model is only suitable
for the prediction of near-shore spilled oil.[17] G. Puttaramaiah (1994) also presented a
brief overview of the dispersion phenomenon. The results of field investigations &
mathematical & physical model studies are presented as case studies. In the case of
both buoyant & dense fluids, turbulent mixing caused by ambient tidal currents has
been observed to promote dispersion & transport of pollutants. Need is indicated for
understanding the dispersion characteristics of dense fluids.[53] GS Durell, et al.
(1994) carried out an Inter-laboratory comparison of physico-chemical characteristics
of weathered oils & emulsions describing the transfer of technology necessary for
evaluating the weathering behavior of oil from IKU Petroleum Research of Trondheim,
Norway to Battle Ocean Sciences, Duxbury, Massachusetts. The Heidrun Crude oil is
used for the study.[17] S. Kapoor & HS Rawat (1994) outlined about the Indian west
coast oil spills - A remedial preparedness. In this paper, the problem of combating an
oil slick in Indian waters was systematically studied/ discussed using bench scale
studies.[54] S. Venkatesh & TS Murthy (1994) carried out a numerical simulation of the
122
movement of the 1991 oil spills in the Arabian Gulf. The output from the modified
version of a hydrodynamic numerical model developed earlier by El-Sabh & Murthy
(1988) has been used to hindcast the movement & dispersion of oil slicks in the
Arabian Gulf during part of the period of January to March 1991. While other studies
on numerical simulations of this event pertain mainly in the Al-Ahmadi spill, the
present study simultaneously examines the movement of oil from not only this source
but also from Mina Al-bakr and clearly delineates the impact of oil from each of these
sources. The numerical model is used for computing the currents due to tides, winds &
bathymetric influences. WR Turrel (1994) presented a retrospective view on the
modelling, the Brayer oil spill. Finally the paper considers the developments required to
improve the modelling of similar incidents in the future.[17]
A. Maure, et al. (1995) studied & formulated numerical model using the finite element
& finite difference methods on the behavior of crude oil spills in shallow bodies of
water in Llancanelo saltwater lake in the south of the Mendoza province, Argentine.
The final goal of the study is to predict ecological impacts of petroleum contamination
and to evaluate remediation actions proposed to overcome these impacts. ML Spaulding
& E. Howlett (1995) designed a shell based approach to marine environmental
modelling, to predict oil transport & fate, dispersion & bottom deposition of
particulate materials from drill fluid & sewage effluent discharges, wave dynamics in a
small harbor, and water quality impacts from combined sewer overflows into an urban
estuary. Extensions of the system to other environmental modelling problems are
described. They along with VS Kolluru & EL Anderson (1994) had also developed a 3D
oil spill model known as WOSM/ OILMAP and was applied to the Brayer Oil Spill, which
occurred off the southern coast of Shetland Island in January, 1993. The model
simulations clearly show the importance of entrainment, subsurface transport, &
resurfacing of oil and accurate representations of the current field in the vicinity of
the grounding site & to the south of Shetland island in accurately hindcasting the spill.
P. Sebastian, et al. (1995) presented a numerical model, for the simulation of the
123
physiochemical weathering processes of an oil spill at sea based on state-of-the-art
models.[17]
HR Fuentes, et al. (1996) carried out a study in which, experimental design & results
are described on the effect of weathering of Arabian Crude oil on its stimulated
dispersion in saline water. The results of this study have provided fundamental
informations to enhance future experimental efforts and to assist in the conceptual
development of eco-toxicological assessments of oil spills. JF Meyer & RF Cantao
(1996) studied on the movement of oil slicks in coastal seas: mathematical model &
numerical analysis of an introductory case study, which is one of the sub-projects of a
greater effort for the creation of an official manual for organizing protection &
cleaning activities. Besides presenting a model, acceptable simplifications are
discussed, and an algorithm is presented for numerical approximation and
computational simulations in the Sao Sebastian Channel region, in Sao Paulo, Brazil. ML
Spaulding, et al. (1996) formulated an integrated monitoring & modelling system to
support oil spill response. System performance is illustrated by the simulation of the
trajectory of oil tracking buoys during two experiments performed in the lower west
passage of Narragansett Bay. Simulation results using several forecast procedures,
with or without real-time data, are presented. Meteo-France has national &
international responsibilities concerning marine pollution fighting (P. Daniel, 1996).
Meteo-France is engaged within the World Meteorological Organization (WMO) with
Marine Pollution Emergency Response Support System (MPERSS). Because of these
engagements, Meteo-France developed an oil spill response system. This system is
designed to simulate the transport of oil in 3- dimensions.[17]
From 1997 – 2000:
C. Zhang, et al. (1997) developed a 3-D numerical model of oil spills based on the
particle approach. In this model, the advection process was simulated with determined
method and the eddy dispersion was simulated with the stochastic method. The results
124
out of the model solution indicated that the error of the drift direction between the
modelled results and the data from the man-made satellite of the oil spills is less than
20 degree and the area covered by the thicker part of the oil spill is agreement with
the satellite data. JA Galt, et al. (1997) provided a current pattern analysis for oil
spills (a case study using San Francisco Bay) → during oil-spill events the movement &
spreading of the pollutant is of critical interest to responders and there are always
demands for forecasts of the future position of oil. For floating portions of the spilled
oil that are constrained to remain on the surface, the 2D Kinematics analysis of the
flow patterns are used. The results of this kinematics analysis can be used to identify
likely collection areas for floating oil and to provide location maps for the effective
placement of recovery equipment. During an actual spill caused by the Cape Mohican in
San Francisco Bay (late Oct, 1996), the planning response for clean up efforts and the
development of insights on the movement of oil patches were enhanced by the results
of the current pattern analysis. Rosso & Rosman (1997) developed a numerical model
for floating contaminants transport in coastal regions. This model is developed only to
estimate the velocities at the free water surface which are dominant factors for
pollutants/ oil slicks movements/ spreading, as because the spreading of floating
contaminants, such as oil, with density smaller than that of the water, depends
strongly on the flow velocities at the free water-surface. In coastal areas the tides &
the wind shear stresses exerted on the free water surface are the main driving forces
of the carrying flow. In this model an alternative methodology is presented instead of
traditional tri-dimensional (3D) models methodology, known as hydrodynamic quasi-tri-
dimensional (Q3D) numerical model. This model is developed for large-scale flows
assuming that the water-column has little or no satisfaction and the density gradients
are negligible. RT Cheng, et al. (1997) developed a nowcast numerical model for
hazardous material spill prevention and response, San Francisco Bay, California, The
NOAA installed Physical Oceanography Real-Time System (PORTS) in San Francisco
Bay, California to provide real-time observations of tides, tidal currents, and
meteorological conditions. Data assimilation techniques, which are common in numerical
weather predictions, have been adopted to derive boundary conditions for the
125
nowcasting model. Nowcast numerical modelling techniques and the results from this
model is specific for the study of tides & tidal current distributions in San Francisco
Bay or for future analysis in this regard.[17]
J. Hasegawa, et al. (1998) presented a technical paper which describes a new
simulation technique for diffusion phenomena over the sea-surface using Cellular
Automata. The technique presented in this paper is capable of making prediction of oil
dispersion from tankers come into collision or stranded on rocks. L. Zheng (1998)
studied & formulated a 3-dimensional comprehensive numerical model to simulate the
behavior of oil & gas spills that originate as jets/ plumes in deep water. This model is
used to simulate the field experiments conducted by IKU in the North seas in 1996 &
1997 and compared with the field data; a scenario simulation using the model is
presented to demonstrate the model capability. He along with PD Yapa (1998)
presented a companion paper for the development of a 3-dimensional numerical model
to simulate the behavior of buoyant oil jets that result from the underwater
accidents. The numerical model was developed based on a Lagrange integral
technique.[17] L. Zhiwei, et al. (1998) developed a numerical model to simulate the
transport and fate processes of spilled oil with the Random Walk Technique. In the
model, the PLUME-RW dispersion model developed by HR Walling Ford is used to
simulate the Oil movement. The model is only suitable for oil spill contingency
planning.[55]
Bao-Shi Shiau (1999) presented a simulation model of oil spill spreading on the coastal
waters of Kaoshiung Harbour in Twain wherein it is mentioned that: Fay (1969) had
proposed a mathematical relation to describe the spread of oil slicks on a calm sea;
Waldman, et al. (1973) investigated the spreading & transport of oil slicks on the open
ocean considering wind, waves, & currents; Shen & Yapa (1988) modelled the transport
of oil slick in rivers - their models accounted for oil’s mechanical spreading, water
currents in river, river bank conditions, oil evaporation, & oil dissolution; in the year
1995, the developments of oil spill model for Korean & Japan coastal waters have been
126
made ― their models are too complicated, it is uneasy to use these models. In this
paper as written by Bao, a simple & easy-to-use model is presented to simulate the oil
spreading on the coastal waters. Simulation results of the oil spreading on the coastal
waters are rather good in comparison with the satellite image. It can be employed to
evaluate the environmental impacts on the coastal waters of the harbour on the oil spill
accidents occur.[23] FS Daling, et al. (1999) studied about Weathering of Oils at Sea in
which Model & Field data comparisons are made.[17]
KA Burns, et al. (1999) studied about dispersion and fate of produced formation water
(PFW) constituents in an Australian Northwest Shelf shallow water ecosystem.
Basically, this was a study of PFW discharged into a shallow topical marine ecosystem
on the Northwest Shelf of Australia. A combination of oceanographic techniques,
geochemical tracer studies, chemical & biological assessment methods, and dispersion
modelling was used to describe the distribution and fate of petroleum hydrocarbons &
added nutrients discharged from an offshore Production platform. The study is only a
benchmark to help in predicting the effects of further oil industry expansion in this
pristine Coastal region.[56] M. Read, et al. (1999) made an overview of the sate-of-the-
art in oil spill modeling, focusing primarily on the years from 1990 to 1999. In this
review, knowledge of the relationship between oil properties, and oil weathering &
fate, and the development of models for the evaluation of oil spill response strategies
are summarized. Future directions in these and other areas are indicated.[17] Rosso, et
al. (1999), developed a hydrodynamic model for oil spill transport in coastal regions: An
application to Guanabara Bay, Rio de Janeiro, Brazil. In this work, the issue is in the
forecasting of spreading plumes resulting from possible accident scenarios with
variable tides & wind conditions associated with a pipeline yet to be built across a
section of Guanabara Bay, Rio de Janeiro, Brazil. In this model a 3D numerical
hydrodynamic model for homogeneous & large-scale flow developed by Rosso & Rosman
(1997), was used. This model is composed of 2 modules: a depth-averaged of 2D
hydrodynamic (2DH) module, through which the free surface elevation is computed,
and a 3D module that computes the flow field. The surface gradients and the bottom
127
shear stresses couple the two modules, and an extra coupling is also granted by forcing
the depth-averaged velocities to match in both modules. The 3D module uses the
water surface elevations obtained in the 2DH module. And in its turn the 2DH module
gets the bottom shear stresses from the vertical velocity profiles, calculated in 3D
module. A particle tracking model developed by Horita & Rosman, 1997, was used to
simulate the dispersion of the pollutants.[20] S. Sugioka, et al. (1999) carried out a
numerical simulation of an oil spill in Tokyo Bay, after an oil spill accident happened in
Tokyo Bay on 2nd July, 1997. About 1500 m3 of crude oil was released on the sea-
surface from the Japanese tanker Diamond Grace. An oil spill model is applied to
simulate the fate of spilled oil. The Lagrange discrete parcel method is used in the
model. The model considers current advection, horizontal diffusion, mechanical
spreading, evaporation, dissolution and entrainment in stimulating the oil slick
transformation. In this model, grid size is taken as 1 km in the calculation domain and
the residual flow simulated by a 3-D hydraulic model & observed wind data are used
for advection. The simulated oil spreading distribution is validated with the
observations from satellite remote sensing.[17]
Qiao Bing (2000) presented a paper on oil spill model development and application for
emergency response system. The paper introduces systematically the developing
principle of CWCM1.0 Oil Spill Model based on Lagrange system and oil spill fate
processes in environment, reviews two oil spill incidents of East Ambassador in
Jiaozhou Bay and Min Fuel 2 in the mouth of Pearl River, and designs the predictable
system simulating oil spill applied in contingency plans. It is indicated that CWCM1.0
has met preliminary the demands for functions of precision simulating & predicting oil
spill, and can plan an important role to support oil spill response.[57]
EXECUTIVE SUMMARY
Therefore, from section-2.2.4 it can be summarized as:
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(a) Most of the investigators during 1978 – 1987, like Dippner (1983, 1984 & 1985),
Bennett, Sehwab & Lynn (1986), Yangi, Tsukamoto, Inoue & Okaichi (1983), have
studied mainly the fate/ overview of oil spill and its containment. Only few of
them, like Dippner (1983, 1984 & 1985), Aubin, El-Sabh & Murthy (1979) have
studied the spreading & dispersion characteristics of oil spill by simulation
technique & Lagrange tracer technique, which do not give the complete result.
Also the results of the model developed by Dippner (1983) show the dimension
& intensity of oil pollution only in the case of small accidents. Only, Falconer
(1984, 1986) developed a hydrodynamic model as well as solute transport model
based on Quick Scheme provided by Leonard (1979) to predict pollute
transportation in the seas which can give good results in offshore situations,
but can lead to significant errors when applied to coastal regions. Aravamudan,
et al. (1981) studied on break-up of oil on rough seas. The model developed by
M. Darras (1982) is unable to predict exact time bound area coverage by the
spilled oil. JM Lo & M. Al-Attiah (1985) developed a computerized model, which
includes statistical oil pollution risk data and can be used in the strategic
planning for routing tankers & other vessels, in the selection of sites for Ports
& Terminals. The models developed by JR Bennett, et al. (1985) are too
complicated in their application & process, and predict the trajectories of the
particles. In the model developed by TS Murthy & MI El-Sabh (1985), the initial
assumptions were wrong, and subsequently the model has been refined number
of times during model solution, which is a cumbersome job. Moreover, wind is
not only the primary agent for oil slick movement, simultaneously viscosity of
the oil & tidal characteristics also play a vital role in the movement of oil slicks.
(b) During 1988 – 1996, Researchers like Meyer & Cantao (1996), Ryo, Chang & Lee
(1993), Van Stijn & Praagman (1988) have also studied the dispersion of oil into
the seas and provided mathematical models based on simulation techniques. The
model presented by Van-Stijn & Praagman (1988) is unable to predict exact area
coverage by the spilt oil in real situations. In the model represented by Joynes
(1990) a wave height in the range 0.06 to 0.1 m & periods of 0.8 to 1.3 s were
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considered, whereas, any wave height with any wave periods can be used while
model solution under discussion in the present thesis paper (this model was
validated with the area having more than 2.0 m of wave height with an wave
period of more than 6.0 s. Borthwick & Joynes (1992) have studied a small-scale
oil slick in laboratory. Papa (1992) has studied the behavior of oil spilled (during
the period 11 – 25 April 1991 from the tanker Haven. Spaulding, Odulo & Kolluru
(1992) have provided a hybrid model to predict the entrainment and subsurface
transport of oil. Geng, et al. (1992) studied about the tidal flow in Zhoushan sea
area and provided a model that can be further used with a set of models to
predict the transport of oil spill. Similarly, Dick & Soetze (1990) formulated an
operational model based on ‘particle cloud’ to predict the drift & spreading of
oil for the German Bight. Bao-Shi Shiau (1992), investigated on the prediction
of pollute transportation on the coastal waters using Lagrange discrete parcel
algorithm, which cannot be extended in the deep seas. Shen & Yapa (1988)
modeled the transport of oil slick in rivers only, which is unfit to use to predict
the oil-plume movement in seas/ coastal waters. Martinez & Harbough (1993)
developed a hydrodynamic model to predict pollute transportation in the seas
only, which cannot give good results for coastal regions. A. Maure, et al. (1995)
formulated a numerical model to investigate the behavior of crude oil spill
models that deal with the physical, chemical & biological aspects of fate/
behavior of spilt oil in the coastal waters only. Venkatesh & Murthy (1994)
simulated the movement of the 1991 oil spills in the Arabian Gulf (Gulf War,
1991).
Spaulding, et al. (1994) simulated a model on the hindcast the transport and
fate of the Brayer oil spill (January, 1993). Meteo-France developed an oil spill
(Daniel, 1996) response system to simulate the transport of oil in 3- dimensions.
Lou, et al. (1994), investigated the oil spill track prediction & its dispersion over
the sea using the Euler-Lagrangian method, which is suitable only for near-shore
oil spills. Joynes (1990) studied about the horizontal diffusion of buoyant
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pollutants in the near-shore environment occurred from major oil spills from
damaged tankers, like Torrey Canyon in 1967, for monitoring & assessing for
clean-up purposes. In this study, he considers waves having short wave height &
short wave period. Kapoor & Rawat (1994) outlined about the Indian west coast
oil spills – A remedial preparedness. In the same year, Puttaramaiah provided an
overview of the dispersion phenomenon and Mascarenhas analyzed the relative
environmental hazards of developing oil in different regions of the Bombay
High.
(c) During 1997 – 2000, Investigators like Sugioka, Kojima, et al. (1999) studied oil
spill in Tokyo Bay. Rosso, et al. (1999) developed only a hydrodynamic model for
floating contaminants transport in coastal regions, which was applied to
Guanabara Bay, Brazil. Reed, et al. (1999) summarized & discussed about the
state-of-the-art in oil spill modellings, focusing primarily on the years from
1990 to 1999. Zheng (1998) proposed a mathematical relation to simulate the
behavior of oil & gas spills that originate as jets/ plumes in deep water. In the
same year he along with Yapa presented a companion paper using a 3D numerical
model to simulate the behavior of buoyant oil jets that result from the
underwater accidents; these models can not be used for prediction of normal oil
spill spreading in the coastal & oceanic regions. Zhiwei, et al. (1998) presented a
model based on random Walk technique, which is only suitable for Oil Spill
Contingency Planning. S. Sugioka, et al. (1999) studied on the Japanese tanker
Diamond Grace oil spill & provided a 3-D model to simulate the fate of spilled
oil. Normally, the calculation in 3-D models is a tedious job, but the model under
discussion in the present thesis paper is a 2-D model where calculations are
very simple & easy to use; moreover, here grid size is taken as 100x100 m to
obtain more realistic result.
Thus, from the above literature survey it surfaces that, no extensive research works
have been carried out for prediction of the oil-spill spreading in the coastal region
particularly, in Indian context. Only, few Indian Researchers namely, TS Murthy (1979,
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1985, 1988), KS Aravamudan (1981), PG Kurup (1983), G. Puttaramaiah (1994), S.
Kapoor & HS Rawat (1994), S. Venkatesh & TS Murthy (1994) studied about the oil
pollution in marine environment. Amongst them, Aravamudan (1981) studied on break-up
of oil on rough seas; Kurup (1983) studied oil slick drift trajectories for hypothetical
spills in the Arabian Sea with reference to West Coast of India; Kapoor & Rawat
(1994) outlined about the Indian west coast oil spills. Therefore, keeping in view the
facts as enumerated above, in the present thesis work, an attempt has been made to
build a simple & easy-to-use state-of-the-art mathematical model to numerically
predict the area covered by the spilt oil in the coastal waters in real situations which
can also be efficiently & effectively applied to mitigate the effect of oil spill in the
deep seas.
