Acid Acid RainRain

What is acid rain?What is acid rain?

Any ppt

→pH value < 5.6

→ acid rain

IntroductionIntroduction1) Wet deposition1) Wet deposition → acidicacidic rain, fog + snowrain, fog + snow a) Rainout: incorporation of materials intoa) Rainout: incorporation of materials into cloud dropscloud drops b) Washout: when materials below the b) Washout: when materials below the cloud are swept out by raincloud are swept out by rain or snow as it fallsor snow as it falls

2) Dry deposition2) Dry deposition → acidic acidic gases + particlesgases + particles

a) Atmospheric pollutants directly contact witha) Atmospheric pollutants directly contact with

the ground, vegetation and buildingsthe ground, vegetation and buildings

b) Gravitational settlingb) Gravitational settling

Causes of acid rainCauses of acid rainMain sourcesMain sources1) Sulphur dioxides (SO1) Sulphur dioxides (SO2)) a) Naturala) Natural - volcanoes - volcanoes - sea spray- sea spray - rotting of vegetation +- rotting of vegetation + plankton plankton (( 浮游生物浮游生物 )) b) Humanb) Human → burning of fossil fuels burning of fossil fuels (coal, oil + natural gas) in (coal, oil + natural gas) in power plants +power plants + factoriesfactories → releases sulphur into the air → combines with oxygen → SO2

SOSO2 2 Emissions from Canada & the Emissions from Canada & the USA in 1998USA in 1998

e.g. In 1998, U.S.’ SOe.g. In 1998, U.S.’ SO22

emissions were 6 emissions were 6

times greater than times greater than

Canada's. Canada's.

2) 2) Nitrogen oxides (NONitrogen oxides (NOXX)) → combustion of fossil fuels in mcombustion of fossil fuels in m

otor vehicles, residential and comotor vehicles, residential and commercial furnaces, industrial and elmercial furnaces, industrial and electrical-utility boilers and enginesectrical-utility boilers and engines

e.g.e.g. a) In HK, 8500 tonnes of SOa) In HK, 8500 tonnes of SO22, 4320, 4320

0 tonnes of NO0 tonnes of NO22 & 5900 tonnes o& 5900 tonnes of particulates are emitted annually f particulates are emitted annually from the fleet of some 424000 licfrom the fleet of some 424000 licensed vehiclesensed vehicles

b) b) In UK, power stations are responsiIn UK, power stations are responsible for 71% of ble for 71% of SOSO22, , 32% of32% of NONO22 33% of33% of COCO22 emissionemission

NOx Emissions from Canada & the USA iNOx Emissions from Canada & the USA in 1998n 1998

e.g. In 1998, by comparison,

U.S. NOX emissions was

11 times more than

Canada's.

.

Formation of acid Formation of acid rainrain

SOSO22 + + NONOX X

→mixed with moisture

→sulphuric acid (H2SO4) &

nitrate acid(HNO3)

→dissolved in rain →falls onto the ground as acid rain

Area affected by acid rainArea affected by acid rain

East N. America

West EuropeSE China

ReasonsReasons

1)↑no. of cities1)↑no. of cities

2)↑population2)↑population

3)↑power plants3)↑power plants

4)↑industries4)↑industries

5)↑traffic5)↑traffic

→ pollutants are produced

Regional pollutionRegional pollution in in

ScandinaviaScandinavia

↑∵↑∵ level of industrialization in UK level of industrialization in UK →↑↑emission of emission of SOSO22

→ Westerlies blow the pollutants from the west of U.K. to Scandinavia and the rest of Europe →→ Scandinavia has been receiving acid rainScandinavia has been receiving acid rain for at least a centuryfor at least a century

Effects of acid rainEffects of acid rain

A. Positive effects (local and short term)A. Positive effects (local and short term)

1) improves visibility 1) improves visibility

2) 2) dissolves some of the atmospheric pollutants dissolves some of the atmospheric pollutants

poisonous to plants and animals poisonous to plants and animals

3)3) washes away dust on the leaves of the urban washes away dust on the leaves of the urban

plants and revitalize photosynthesisplants and revitalize photosynthesis

4) cools the hot concrete surface4) cools the hot concrete surface

B) Negative effectsB) Negative effects

1) Aquatic ecosystem1) Aquatic ecosystem

↑↑ lake acidificationlake acidification

→ fish kills fish kills

stock depletionstock depletion

e.g.e.g. In Sweden, 14,000 lakes cannot support sensitive In Sweden, 14,000 lakes cannot support sensitive aquatic life and 2,200 show no signs of life at all.aquatic life and 2,200 show no signs of life at all.

2) Forest destruction2) Forest destruction Acid rain causes release of metals, e.g. Al, from soil

→ rots plant roots,

attacks leaves

→ forest are destroyed

e.g. a) In UK, 70% of beech trees + 80% of yew trees have

been hit by acid rain.

b) 54% of all trees in Germany

have been hit by acid rain. rain.

c) In some Chinese provincesc) In some Chinese provinces

like Maocaoba, over 90% of the pine trees are dead. like Maocaoba, over 90% of the pine trees are dead.

3) Crop yield drops3) Crop yield drops ∵∵↑↑ acidity acidity e.g. e.g. Acid rain in China causes $260 million in crop damages in the Hunan pro Acid rain in China causes $260 million in crop damages in the Hunan pro

vince alone.vince alone.

4) Human health4) Human health→ contaminated fish + drinking water supplies passed on to contaminated fish + drinking water supplies passed on to people through the food chainpeople through the food chaine.g.e.g.a) Sweden, 1000 lakes with high concentration of mercury esp. Pregnant woa) Sweden, 1000 lakes with high concentration of mercury esp. Pregnant wo

men’s fetuses men’s fetuses (( 胎兒胎兒 )) are sensitive to mercury poisoning are sensitive to mercury poisoningb)b) Sweden, drinking water with high levels of copper causes diarrhea (Sweden, drinking water with high levels of copper causes diarrhea ( 腹瀉腹瀉

) in young children ) in young children → harms liver, kidneysharms liver, kidneysc)c) Norway, aluminum from acid rain Norway, aluminum from acid rain pre-smile dementia ( pre-smile dementia ( 痴呆痴呆 ))d)d) N. America & Canada, in 1982, 51000 people die from Sulfur pollutionN. America & Canada, in 1982, 51000 people die from Sulfur pollutione)e) Others: respiratory problems, asthma(Others: respiratory problems, asthma( 哮喘哮喘 ), dry coughs + brain damage), dry coughs + brain damage

5) Material and visibility5) Material and visibility→ corrodes buildings, monuments,

bridges and highways

→ reducing the life expectancy

of properties + infrastructure

e.g.e.g.

a) In Europe, structures like The Acropolis in Greece and In Europe, structures like The Acropolis in Greece and

Renaissance buildings in Italy, as well as several churches andRenaissance buildings in Italy, as well as several churches and

cathedrals have suffered visible damage.cathedrals have suffered visible damage.

b) In the Yucatan peninsula in Mexico, and in places in South America, ancient Mayan b) In the Yucatan peninsula in Mexico, and in places in South America, ancient Mayan Pyramids are being destroyed by acid rain.Pyramids are being destroyed by acid rain.

. .

SolutionSolution1) Legislation1) Legislation

Examples: Examples:

a) In HK , Air Pollution Control Regulation (Fuel Restriction) has been very successful + SOa) In HK , Air Pollution Control Regulation (Fuel Restriction) has been very successful + SO 2

have been reduced by about 40% on average.have been reduced by about 40% on average.

b) In HK, between 1992-97, emissions of SOb) In HK, between 1992-97, emissions of SO2+ NOx were reduced by banning the use of high s+ NOx were reduced by banning the use of high s

ulphur fuels, using natural gas for power generation. As a result, the total amount of SOulphur fuels, using natural gas for power generation. As a result, the total amount of SO 2 e e

mitted was reduced by 54 % in 1992 -97, and NOx emitted was educed by 44 % in 1992 -97.mitted was reduced by 54 % in 1992 -97, and NOx emitted was educed by 44 % in 1992 -97.

..

2) Economic Emission Strategy2) Economic Emission Strategye.g.e.g.In USA, the Emission Trading Policy (1982) sold In USA, the Emission Trading Policy (1982) sold the right to pollutethe right to pollute

But, strict controls But, strict controls → ↑ ↑ production costs may drive industries to areaproduction costs may drive industries to area where there is less controlwhere there is less control

3) Installation of advanced anti-pollution equipm3) Installation of advanced anti-pollution equipmentsents

e.g. e.g. Power plants in H.K. have adopted flue-gas Power plants in H.K. have adopted flue-gas desulphrization to↓SO2 emission by 90% and water desulphrization to↓SO2 emission by 90% and water injection techniques to↓Nox emission by 75% injection techniques to↓Nox emission by 75%

4) Education4) Education

i) encourage people to adopt waste reductioni) encourage people to adopt waste reduction

and recycling programmes should be launched and recycling programmes should be launched

→ ↓ ↓pollutants emitted from incinerationpollutants emitted from incineration

ii) encouragement and promotion towards ii) encouragement and promotion towards

environmental conservationenvironmental conservation

5) Transport5) Transporti) Construct mass transport system which is more i) Construct mass transport system which is more efficient + uses cleaner fuelefficient + uses cleaner fuele.g.e.g. MTR, KCR MTR, KCRii) Encourage drivers to turn off engine while waitingii) Encourage drivers to turn off engine while waitingiii) Encourage drivers to install catalytic converter to reduce NOx emiiii) Encourage drivers to install catalytic converter to reduce NOx emi

ssionssione.g. e.g. By the end of 1998, 75 By the end of 1998, 75% of petrol cars were fitted with 3-way cat% of petrol cars were fitted with 3-way cat

alytic converters and using unleaded petrolalytic converters and using unleaded petroliv) Encourage people to use unleaded petrol, LPG andiv) Encourage people to use unleaded petrol, LPG and bio-dieselsbio-dieselse.g. e.g. No diesel taxi will be allowed after 2006No diesel taxi will be allowed after 2006v) Encourage people to use public transport instead of v) Encourage people to use public transport instead of driving their own cardriving their own car

6) Better and proper city planning6) Better and proper city planningi) Highly polluting industries should be separated i) Highly polluting industries should be separated from residential zones by buffer.from residential zones by buffer.ii) Highly polluting industries should be relocated toii) Highly polluting industries should be relocated to less populated areas.less populated areas.iii) Highly polluting industries must be carefullt sitediii) Highly polluting industries must be carefullt sitede.g. e.g. Power plants in Tsing Yi, Lamma I sland + TapPower plants in Tsing Yi, Lamma I sland + Tap Shek Kok are all located at the western side of Shek Kok are all located at the western side of H.K., which are the downwind sides of the urbanH.K., which are the downwind sides of the urban area since the prevailing wind is easterlyarea since the prevailing wind is easterly Yet, it is sometimes criticized that the city Yet, it is sometimes criticized that the city planners are simply shifting pollution problem planners are simply shifting pollution problem from one part of the city to the other.from one part of the city to the other.

ConclusionConclusionWhether it is effective, depends on:Whether it is effective, depends on:

1) availability of capital1) availability of capital

2) advanced technology2) advanced technology

3) inter-departmental coordination3) inter-departmental coordination

4) cooperation among government, 4) cooperation among government,

industrialists andindustrialists and

citizenscitizens