CIV 913 Environmental Assessment and Sustainability ESTUARINE AND MARINE POLLUTION

CIV 913 Environmental Assessment and Sustainability

ESTUARINE AND MARINE POLLUTION

ESTUARIES

• Definition.

– A semi-enclosed coastal body of water which has

a free connection with the open sea, and within

which sea water is measurably diluted with fresh

water derived from land drainage.

ESTUARIES

• Mixing is a function of:

– River flow

– Tidal Volume

– Width and Depth of the Estuary.

ESTUARIES

• Characteristics of Mixing

– Stratification (Depends on shape and flows)

• Denser sea water flows upstream in a wedge

shape.

• River water flows out to sea over the top of the

sea water.

ESTUARIES

• Mixing Characteristics.

– Least mixing when QFW >> Qsea

– Stratification causes a salinity gradient.

– Stratification results in higher velocities than in the

highly mixed estuary.

– A vertical salinity gradient results in the upstream

movement of sediment.

ESTUARIES

• Flow

– Due to tides net seaward movement may be small

– e.g. Thames.

• downstream flow high to low water - 15km

• upstream flow low to high water - 13 km

• net seaward flow - 2 km per tidal cycle.

ESTUARIES

• Residence Time

– Can be long eg 30days in the Thames estuary.

– Thus dilution capacity is correspondingly reduced.

– More pronounced oxygen sag.

– Affects migratory fish and macroinvertebrates.

ESTUARIES

• Sedimentation.– Important characteristic of estuaries.

• elevated by salt / freshwater mixing

– Sedimentation of suspended matter.– Flocculation and sedimentation of e.g. clays– Absorption of metals.– Sedimentation of organic matter from river,

material from the sea (and dredging) and waste.– Sediment Oxygen Demand (SOD)

Marine Pollution

MARINE POLLUTIONTypes of Pollution

• Organics• Solids• Pathogens• Metals• Halogenated Hydrocarbons (e.g. PCBs)• Oil• Radioactivity

MARINE POLLUTIONInputs

• Atmospheric deposition

• Rivers

• Direct outfalls

– Sewage

– Industrial

• Solids disposal

• Shipping

MARINE POLLUTIONContamination and Pollution

Pollution.– The introduction by man, directly or indirectly, of

substances or energy to the marine environment, resulting in deleterious effects such as:

• hazards to human health• hindrance of marine activities• impairment of quality (in terms of use) of

seawater• reduction of amenities.

MARINE POLLUTIONInputs

• Many inputs are not deliberate:

– Vegetation and dead organisms from rivers

– Mercury from volcanoes• e.g 5000 to 25000 tpa from volcanoes and weathering of

mercury-bearing ores.

• 8000 tpa from industry and burning fossil fuels.

• Hence knowledge of background concentrations important.

MARINE POLLUTIONRegulation

• International Conventions

– North Sea (Oslo, Paris, North Sea)

– Baltic (Helsinki)

– Mediterranean (UNEP/Barcelona)

– Regional Seas programme (UNEP)

• Scientific Committees recommend areas for

monitoring and control.

MARINE POLLUTIONOil

• Sources of Oil to the Marine Environment.Source Estimate (m tpa)

Anthropogenic

Transportation 1.47 (0.568 spills)

Fixed installations 0.17

Municipal & Industrial WWT 0.90

Urban & river run-off 0.12

Atmospheric fallout(oil-derived) 0.3

Natural

Marine phytoplankton 36,000

Atmospheric fallout 220

MARINE POLLUTIONOil

• Effects of Weathering on an Oil Slick

Evaporation Rapid (24hr)

Dissolution Fairly rapid

Dispersion Rapid early stages

Emulsification Rapid early stages

Photochemical oxidation Dependent on light

Adsorption Dependent on SS

Biodegradation Fairly rapid early stages.

MARINE POLLUTIONOil

• Types of Damage to Marine Organisms.

Organism DamagePlankton Possible growth inhibition of

phytoplankton.

Seaweed Major Damage to inter-tidal species. Rapid recovery. Excessive growth if grazers badly affected.

Invertebrates Large scale mortality due to toxicity and smothering.

Fish Minor effects.

Birds Diving birds badly affected.

Marine mammals Rarely affected. Coastal populations vulnerable.

MARINE POLLUTIONOil

• Treatment Techniques.

Process Comment

Chemical Dispersion enhances degradation. Protects coasts but increases acute toxicity.

Containment Small spills, enclosed/calm waters

Recovery Small spills, calm waters. Disposal problems.

Adsorption/sinking Short term protection/long term benthic contamination.

Burning Fresh oil. Leaves tarry residues.

MARINE POLLUTIONSewage Sludges

• UK ceased disposal of sewage sludge to sea.

• Need to consider hydrodynamics of the disposal site

– dispersive (low concentrations, but larger area

affected). Typical for UK.

– accumulating ( local effects/monitoring)

• Typically reduces diversity, but increases biomass in

the benthic community

MARINE POLLUTIONMonitoring

• Chemical and Biological– Biological - Population Change

• Key species i.e high conservation interest, commercial value, those whose presence or absence has major repercussions on the community.

• Indicator species.– Biological - Community Response

• Preferred. Avoids errors due e.g. to climatic changes.


• Limitations of Toxicity Testing of Marine Pollution

– valency changes, alter form.– metal salt solubility. (Lead citrate>>Lead nitrate)– organic complexes of heavy metals>>inorganic

compounds eg mercury (but NOT arsenic)– oil (dissolved and particulate components)– chlorinated hydrocarbon pesticides

• low solubility in water, particulate ingestion important


• Sub-Lethal Effects and Biomarkers

– Non-specific pre-cancerous growths on flatfish (e.g. observed for

sewage sludge, oil and titanium dioxide).

– Skeletal deformities in fish e.g. herring affected by chlorinated

hydrocarbons, oils and heavy metals.

– Detoxification mechanisms

• formation of metalothioneins to complex metals (urchins,

crabs, seals, rockfish)

• production of mixed function oxygenases in livers of fish due to

exposure to lipophilic organic compounds


• Analysis of Community Responses.

– Use soft sediment invertebrates.

– Diversity

• Univariate analysis e.g. number of species per unit area,

• Graphical methods e.g. abundance-biomass comparison

(comparison of sites, but does not differentiate the actual

species).

– Species composition.

• Multi-variate statistical analysis e.g. comparison of

similarities of species in different samples.

MARINE POLLUTIONPollutant Hazards

• Sewage and Sewage Sludge

– Affects coastal waters.– Reduced diversity, increased biomass in

sediments.– Can get oxygen depletion e.g. New York Bight, the

German Bight and some Norwegian fjords.– Nutrient addition - Eutrophication.– Changing nutrient balance affects distribution of

plankton, and can stimulate production of toxins.


• Sewage and Sewage Sludge

– Direct infection, and contamination of sea food.• Most terrestrially derived bacteria and viruses die

within 12-24hrs in the sea.– due to UV, high salt concentrations, low concentrations of

antibiotic inorganic and organic chemicals.

• Some enter a dormant phase, not measured in routine tests. Can become active when ingested by bathers.

– Control bathing and shellfish waters.


• Persistent Organic Compounds.– e.g. List I Substances. Persistence, bioaccumulation potential and

toxicity.– Few studied in the marine environment e.g. halogenated compounds.

• organochlorine pesticides (DDT, dieldrin, aldrin and endrin, lindane, hexachlorobenzene). Lipophilic.

• Banned in developed economies.• Still widespread in emerging and developing economies due to

low cost.– Dioxins.– 2,4,5 Trichlorophenoxyacetic acid (Agent Orange)– PCBs. Type important. Coplanar most toxic. Effects sub-lethal.

Widespread in the marine environment.


Persistent Organic Compounds

• Effects.– Primary production rates of plankton reduced at >

1 mg/l

– Fish 96 hr LC50 1-100mg/l

– Typical concentration in seas at pg/l and ng/l levels i.e. much below the acute concentrations.

– Effects mainly eggshell thinning in birds and reproductive abnormalities in mammals eg seals in the North and Baltic seas.


• Distribution of PCBs Between Different Environmental Compartments.

Environment PCB Load(t) % of Load

Land&Coast

Sediment 130000 35

Sea Water 2400 0.64

Other 10700 2.6

Open Ocean

Sea Water 230000 61

Sediment 110 0.03

Other 1060 0.73


• Trace Metals– Take account of metal speciation and condition of organism.

– Mercury• Important marine species: Elemental, divalent and methyl

mercury.• Key factors

– high affinity for organics, hence accumulates in marine biota.

– inorganic mercury may be bio-converted to methyl mercury.

– Accumulates in fine-grained coastal sediments.


• Lead– Main inputs to the sea are from the air.– Long range effects due to this airborne pathway– Main effects seen in coastal environments with a

build-up of lead in sediments.– Lead in the marine environment presents a

negligible source to humans.


• Tin– A potentially serious marine pollutant.– Organotin compounds provide the hazard (e.g. tri-

butyl tin oxide TBTO)– Main uses, PVC stabilisers and biocides (anti-

foulants on ships)– Two main sources

• bacterial methylation of inorganic tin.• leaching of aryl and alkyl tin from ant-fouling

paints.


• Tin (contd)– Harmful responses in a number of marine

organisms.

– Commercial stocks e.g. Pacific oysters, dogwhelks, farmed slamon.

– Concentrations believed to affect shellfish– 0.01 ug/l– Causes reduced growth in young POs and

loss of fertility in female DWs


• Tin (contd)

– Acutely toxic to planktonic organisms. e.g. mollusc larvae at 1.0mg/l

– Banned in mariculture installations and on boats < 25 m in EU, USA, Australia, NZ

– Rapid recovery (few years) of dogwhelks following the ban.


• Radionuclides– natural potassium-40– detectable at great distance from discharge– accumulation in sediments– local ecological impact

• bottom dwelling fish• shellfish (human health risk)

– international pressures on nuclear industry• Sellafield


• Conclusions.– Widespread anthropogenic effects can be

detected, even in remote regions.– Main impacts are in coastal waters.– Control of risks associated with marine

pollution is increasing, but still has a long way to go.

Documents

CIV 913 Environmental Assessment and Sustainability ESTUARINE AND MARINE POLLUTION