Acid Rain

Acid Rain

pH value – the measure of the acidity and alkalinity of a solution, range from 0 to 14

pH 7 is neutral

pH>7 = alkaline

pH<7 = acidic

Natural rain in Hong Kong is about pH 6.

Natural rain in Central Europe is pH 4.3,

N. Europe, N. America and Japan is 3.5

Situation

• Acid rain(Acid deposition)– Wet deposition: acidic rain, fog, hail and snow – Dry deposition: acidic gases and particles

• Acid rain: pH > 5.5– Normal rain ~ pH 5.5 (CO2 dissolves in rain water

weak Carbonic acid)– Acid rain can be as acidic as vinegar and lemon

juice

• One of the Global Problems – Widely spread (Prevailing winds disperse the

pollutants far away from the sources)– problem between national borders or frontier

What is the acid What is the acid rain ?rain ?

Acid Rain is caused when sulphur dioxide (SO2) and nitrogen oxides (NOx) chemically react with other substances in the atmosphere to form acidic compounds.Sunlight increases the reaction rate.

They fall to the earth in wet and dry form.

Causes of acid rain [2]

• Main acid rain causing chemical

Sulfuric acid H2SO4

Nitric acid HNO3

Nitric Oxides (nitric oxide NO

& nitric dioxide NO2)

Sulfur dioxideSO2

Acid Rain

Where do air pollutants come from ?

Oil refineries,the use of coal in the production of electricity, from base-metal smelting, and from fuel combustion in vehicles.

Causes of acid rain [3] - sources

Natural source of sulfur dioxide --Volcanic Eruption

Industry -- emission of acidic gases (e.g. smelting plant & power plant)

Transportation -- source of acidic gases,

mostly nitric oxides

Causes of acid rain [4]

Chemical Process in Atmosphere

O2

NOx

SO2 H2SO4

HNO3

oxidationoxidation

O3energy

dissolutiondissolution2H+ + SO4

2-

H+ + NO3-

Effects of Acid Rainthe acidification of lakes and streams forest damage decay of buildings and paint an increase in public health problems

LAKES AND STREAMS an acidity of between 6 and 8. Acid rain can cause a pH of as low as 3 in some places. cause to kill certain aquatic plant and animal life.Increase concentration of mercury, aluminium, manganese, lead and zinc in water.Norway and Sweden suffered most because no chalk and limestone (Geology)

Effects of acid rain [2] - water bodies

Lake - can be acidified easily as low water flow

When the water bodies is acidified, most of the

aqueous species cannot survive and so the

biodiversity decreases

This chart shows the different levels of acidity that certain lifeforms can handle.

FORESTSAcid rain causes direct damage to trees at high elevations, especially the red spruce. As shown in this picture from the EPA, large areas of forests have died. This occurs mainly in the very severe cases of acid rain, those causing a pH of 4 or less. Acidic soil causes the leaching of the nutrients from soil

Effects of acid rain [3] - forests

• Plant injury

• Soil acidified– Further affect plant reproduction and growth

Massive injury of plants by acid rain

MATERIALS•damage certain materials ( limestone and marble)

•dissolves calcium carbonate in the stone

•forming crystals with stone and break apart stone

Effects of acid rain [4] - materials

Marbles eroded by acid rain

Status worn out by acid rain

PUBLIC HEALTH~ affect through both the water and the atmosphere.

the pH of soil decreases,

~ the mobility of metallic compounds ( aluminum and

mercury) increase

~ make them easily transported into the water system

~ lead to the contamination of not only the water

~ also the contamination of edible fish. And crops

Effects of acid rain [5] - human health

• Effects are usually indirect– lung cancers, bronchitis, emphysema and

asthma– caused by inhalation

Acid Rain in the United States and Canada

Acid rain is a large problem in the Eastern U.S. and Canada.This is mainly because emissions rise high into the atmosphere and are carried by the strong winds from the West, falling out with precipitation in the East.

Prevention:Reduce acidic gases emission [1]

• Good practice in fossil fuels combustion– low sulphur coal used in power plants– scrubbers used to remove sulphur dioxide from

exhaust gas– catalytic converters in vehicles reduce nitrogen

oxides emission

Prevention:Reduce acidic gases emission [2]

• Application of clean energy resources– nuclear power, hydropower, wind and

geothermal energy– high combust-efficient biomass fuel used in

vehicles

Wind-powered electricity plant

Mitigation:Restore damaged environment

• Liming– neutralize acidity in lakes and streams– however, not effective in damaged soil and

watershed– expensive

Improvements

~set up some regulations / law

~use Calcium carbonate / lime to neutralize the lakes and streams

Local actions1984 Sweden $25 million to neutralize lakes1985 USA 3-7 billions to controlEncourage the industries to install some environmental facilities such as scrubber, electrostatic precipitator or using low sulphur content diesel, washing coal before use by tax break or by subsidization.

Individual actions

• Energy consumption is the main cause– energy conservation help to avoid the problem

Is acid rain a serious problem in Hong Kong?

Serious in some districts because of factories and acidic rain may have been emitted from the factories or brought from China causing pipelines rusting, paint peeling, kills trees and causing people suffer from respiratory diseases (bronchitis and asthma).However, Hong Kong has few historical building and sculptures.No large lakes or rivers with big fish populations.Little farming, no large forest.

To what extent do you think that acid rain in Hong Kong is caused by nearby territories, for example, mainland China?

If acid rain in Hong Kong is caused partly by China, who should bear the responsibility and costs of combating it, and how would you justify your view?

What would be the likely difficulties encountered in negotiation with China?

Discussion• What are the natural sources of acid rains?• How acid rains affect economic and agricultural activit

ies?• Can you show some evidences about buildings being d

estroyed by acid rain?• Use of the nuclear power is a way to reduce the proble

m of acid rain, but is nuclear power an environmentally friendly fuel?

• What are some actions that individual can take to conserve energy & to reduce the problem of acid rain?

• Referring to section 1.1 Air Pollution, what is the trend of concentration of sulphur dioxide and nitrogen dioxide in Hong Kong? What is the implication of the trend on the problem of acid rain in Hong Kong?

Convention on Long-range Transboundary Air Pollution, adopted on 13.11.1979, entered into force on 16.3.1983.

Protocol to the 1979 Convention on Long-range Transboundary Air Pollution on Long-term Financing of the Cooperative Programme Monitoring and Evaluation of the Long-range Transmission of Air Pollutions in Europe (EMEP), adopted on 28.9.1984.

Protocol to the 1979 Convention on Long-range Transboundary Air Pollution on the Reduction of Sulphur Emisssion or their Transboundary Fluxes by at least 30%, adopted on 8.7.1985.

International Efforts

Relevant websites• Acid Rain 2000

(http://www.brixworth.demon.co.uk/acidrain2000/)

• U.S. Environmental Protection Agency - Acid Rain Program(http://www.epa.gov/airmarkets/acidrain/index.html)

• The site of Environment Canada - Atlantic Region(http://www.ns.ec.gc.ca/aeb/ssd/acid/acidfaq.html)

• EcoNet's Acid Rain Resources(http://www.econet.apc.org/acidrain/)