Acid Deposition

• Acids and Bases

• Chemical Processes and Sources

• Deposition Processes

• Acid Deposition Distribution

• Environmental Effects➔ Health Effects

➔ Lakes and Forests

• Abatement

Depositionprocesses Sulfur

sources

Anthropogenic Natural/Biogenic

Rainacidity

pH

Distribution

Threats

Lakes

Forests

Urbaninfrastructure

Studies andpolitics

People

Abatement

Alt. fuels

Alt. energygeneration

Acidchemicalprocesses

Acid Deposition

Reduceemissions

pH• Solution: substance dissolved in water

• p H: index of acidity or alkalinity of asolution

• pH difference of 1.0 is 10· difference inacidity

pH = 7.0: neutral

pH < 7.0: acidic

pH > 7.0: basic or alkaline

Typical pH Values

1 2 3 4 5 6 7 8 9 10 11 12 13

Batteryacid

Colabeverage

Tomato juiceAcid rain

Natural rain

Bakingsoda

Ammonia

Lye

A C I D B A S ENeutral

Vinegar Distilled water

Sulfur Chemistry

Fossil fuel(C + S)

Natural SOX

Combustion(adds O to C

and S)

SOX fi … fi SO3,g

Dissolve inliquid water

H SO2 4,aq

Sulfuric acid

SO3,g H O,2 v+

H SO2 4,g/p

Natural Sulfur Sources

Volcanoes SO2

Organic Decay H S fi … fi SO2 2

Anthropogenic Sulfur

FossilFuels(C+S)

Coal1–6% S

Oil1–2% S

Gas0.5% S

• Electricity• Industrial

• Other

61.70%

31.60%6.70%

Other Acidic SpeciesNO + H O2 2

Nitric acid (HNO )3

Organic acids

Hydrogen chloride (HCl)

Natural

Anthropogenic Incineration ofPVC plastics

Volcanic HCl

Methyl chloride (CH Cl)from ocean

3

Acid Deposition Processes• Wet deposition: liquid water removes

acidic species from atmos.

Acidgases

(Runoff)

Rain, snow scavenging Acid gases

Cloud, fog droplets

Washout

Rainout

Watercoat

Acid

. .

. . . .

. ..

.. .

.. . . . . .

Acid

• Dry deposition: no liquid waterinvolved

pH of Rain

Unpollutedrain

CO2,g

H CO2 3,aq(Carbonic acid)

pH ~ 5.6

SOX

H SO2 4,aq

Acid rain

pH < 5;typ. 4 to 4.5

(Sulfuric acid)

Regional Transport of Acids

SO source regions2

SW to NEflow

SO receptorregion

2

Adirondack Mts.

LocalNOx inSo. Cal.

2

Precipitation pH, 1996

SO Health Effects

• Effect of SO gas on respiratorysystem (ch. 7)

2

➔ Taste

➔ Odor

➔ Slight Bronchial constriction

➔ Inflammation of mucous membranes

• SO + aerosol particles worsethan SO alone

22

X

High-altitudelakes

Low-altitudelakes

Water sourcefilters thru

soil; buffered

Little orno soi l

buffering

Water source =direct precip.

and runoff

West: alkalinelimestone soi l

East: acidicgranite soi l

Freshwater Acidification

Feedback

• Effects

➔ Aquatic plants and fish stunted,reproduction impaired

➔ Metallic ions (e.g., aluminum,copper, lead) leach from soils intolakes

Growth/reproduction ratesuppression ordeath of trees

Susceptible regions?

Downwindof sulfursources

Highelevation

Eastern regionsof continents(west-to-eastprevail ing wind)

Long-term contactwith acidifiedclouds/fog

Thinner soils,less buffering

E. Europe, NE U.S., SE Canada

Forest Decline

Abatement

Dispersion

Locatedownwind, notupwind ofsensitive areas

Tal ler stacks

Abatement

Low-sulfur fuel

Oil, gasLow-sulfurcoal

Solvent-refined coal

Coal gassification

Abatement

Reduce emissions

Modifiedcombustion

Scrubbers

Abatement

Lake andsoil buffers

Clean-up