ACID RAINS

By

Dr.Amir Farooq

Associate ProfessorCivil Engineering Department

The University of Lahore

ACID RAINS

INTRODUCTION.

The term “Acid Rain” was used in 1872

Robert Angus Smith, Chief Alkali Inspector of U.K

Purpose to describe the acidic nature of the rain fallingaround Manchester.

It is defined as precipitation in which pH is below 5.6.

ACID RAIN

dry acid deposition (particulate).

It encompasses

wet precipitation (rain, snow, mist & fog)

FORMATION OF ACID RAINS

Emission caused by burning of fossil fuels(coal, oil and gas)

Key players

Transported by Prevailing wind upto distances as far as 1000 Km.

Rain out and Washout causes formation of rain within and beneath the clouds respectively.

Power Plants,

Smelters,

Factories,

Automobiles &

Large urban areas

Emission rich in SOx, NOx

RAIN - OUT

Within the clouds the process of formation of thedroplets which collect and react with the pollutants iscalled’ rain-out’.

Removal rates by rain-out depend upon

Type of pollutants,

amount of pollutant and

mean size and temperature of the raindrops and snowflakes

WASH-OUT

Important mechanism of removal of particles beneath theclouds takes place by a relatively less important processknown as wash-out

SIGNIFICANCE OF ACID RAINS

Emissions from one country fall on other neighboringcountry.

Japan is being affected from acid rain being originated inChina.

Scandinavia is affected slightly by U.K but severelyimpacted by Czechoslovakia, Hungry, Poland andGermany.

>3/4th acid rain deposition in Norway, Switzerland,Austria, Sweden, Netherlands and Finland is blown fromwestern and eastern Europe.

As a whole Europe and North America remain the world’smost affected large scale regions

Overall emissions of SO2 & NO2 in 1993 were 70 and 27millions tons

IMPATCS OF AICD RAINS.

Effects on Vegetation

Acid rains having pH 3.4 or below damage the leaves ofsensitive crop plants e.g.

Radishes, beets, soybeans and kidney beans.

Injury depends upon

effective dosage,

the concentration and

period of exposure i.e. contact time .

Damages to vegetation through

Leaching of Nutrient

Increasing acidity - mobilize toxic metals

Forests of North America and black forest in Germany havebeen damaged.

Growth problems of forests in Canada, Europe and Sweden

Effects on Vegetation

Damages to Crops leading to Adverse Economic and Social Impacts

Effects on Fresh Waster Ecosystem

Effects on fresh water ecosystem.

Leaching of the toxic heavy metals such (Al, Hg, Mn, Zn & Pb) from the adjacent rocks and lands, which ultimately join the lakes and other surface water sources

Fish in acidified lakes are killed because they lose ions from their plasma and muscle tissues in acidic waters.

Fish also succumbs to toxic concentrations of metals such as Aluminum, Mercury, Manganese, Zinc, and Lead.

In Sweden & Norway, no fish in at least 16,000 lakes & 52,000 have lost buffering capacity.

In Canada around 14,000 acidified lakes are fishless and 150,000 more in peril (danger).

In USA about 9000 lakes are threatened with excess acidity.

Effects on invertebrates and Birds

Loss of species in acidified lakes having pH < 5.4 due todeath of larvae

(mayflies, caddis flies, freshwater shrimps, limpets,snails and beetles)

Depletion of invertebrate species causes fish to starve andits decline.

Heavy metals

Liberation of heavy metals (Al, Hg etc) like

Accumulation of heavy metals released byinvertebrates in tissues of fish and

Enter the food chain.

Reduction in numbers birds

Receive secondary doses of heavy metals via food

Imperfect calcification of eggs and

lay eggs with thin fragile shells

No Effects on skin of human (scaling & burning )

Effects human not in the same way as fish or plants.

Acid rain feels the same as regular rain -- it's even safe to swim in anacidic lake.

Aerosols or mist having size < 0.8 Um (containing commonly used acidssuch as sulfuric, nitric, hydrochloric and hydrofluoric acid are the mostharmful and cause damage to lungs.

Dry Deposition of Sulfate and Nitric acids Acid rains can cause prematuredeath due to respiratory diseases such as bronchitis and asthma andheart attack.

Heavy metals (Cd, Hg, Al etc) become soluble in acidified lakes andstreams and enter the food chain to ultimately affect the human health.

Acid rains liberate or dissolve metals like Aluminum and irons, incatchment area of water supplies thus increasing the concentration ofAluminum in water supply.

At concentration ranging from 1000 to 2000 ppm, Aluminum causessoftening of bones, deposits (Plaques) containing Aluminum in brainsthe“Alzheimer ‘s disease “ and chronic renal failure.

Effects on Human Health

Effects on Buildings, Monuments, Sculptures and materials etc

Limestone and marble suffer most from acid rains.

Sandstone and granite may become discolored.

Structural and building materials including steel may also deteriorateunder attack from acid rains.

Acid deposition speeds up natural weathering caused by rain, sun,snow and wind

Severely affected monuments of that have been severely affected byacid rains include Washington monument in Washington D.C. andStatue of Liberty, New York and damages to historic sites in Venice,Rome, Athens, and all across Europe.

Sulphur pollution damaged the Taj Mahal i.e. indicative of acid rainimpacts in developing countries.

Acid rain also mars (damages) automotive paint. The auto industryconsiders acid deposition one type of corrosive environmental fallout,along with tree sap, pollen and bird droppings. Acid markings leaveirregular, etched (engraved) shapes on horizontal surfaces.

Fixing needs Repainting of cars--------

Limestone and marblesuffer most from acidrains.

Sandstone and granitemay become discolored.

Top 5 Endangered Heritage Sites - Acid Rain

1. Leshan Giant Buddha, Mount Emei (China, Buddhist)

2. Acropolis Of Athens (Greece, Ancient Greek)

3. Taj Mahal (India, Mughal Islam)

4. Dampier Rock Art Complex (Australia, Australian Aboriginal)

5. Longmen Grottoes (China, Buddhist)

CONTROL OF ACID RAINS.

Fuel desulphurization, which removes sulphur from coal burning.

Fluidized bed technology, which reduces SO2 emissions during combustion; and

Flue gas desulphurization,

CONTROL OF SO2 & NOx.

Use of technologies to reduce SO2 emissions from fossil fuels.

Similar approached can also be adopted to reduce emission of NOxfor industrial establishments

Catalytic converters and lean-burn engines have been applied toNOx emissions from motor vehicle engines

Individuals can contribute directly by conserving energy (Larger useof use energy – more use of fossil fuels for energy production – moreacid deposition problem)

Car pool, Purchase less NOx producing cars, employ heat insulation, control energy losses & Less /Conservative use of energy

Botkin, D and Keller, E(1995) Environmental Science, earth as a Living Planet,Jojn Wiley and Sons. Inc.New York

Brown, L. T. et al., (1996) Vital Signs theTrends that are Shaping OurFuture. Worldwatch Institute. W.W. Norton andCo., London

Cornwell, A. (!993) Environmental Concerns, Cambridge UniversityPress, Cambridge.

John Mink (2009), Top 5Endangered Heritage Sites -Acid Rain,

CyArk Europe | 152 Morrision Street | TheExchange | Edinburgh EH3 8EB | UKt: +44 131 200 6024 | e: info [at] cyark.org

Kemp, D.D. (1994) Global Environmental Issues, A ClimatologicalApproach, Routledge, London

Middleton, N. 91995) The Global Casino, An Introduction toEnvironmental Issues. Edward Arnold, London

Miller, G.T.Jr. (1994) Environmental Problems and Solutions

Wadsworth Publishing Co., Balmont, California.

Raven, P.H. et al., (1993) Environmental Saunders College PublishingLondon

References