Acid Deposition

Two Forms… Wet Refers to acid rain, fog, sleet, cloud vapor and snow. Dry Refers to acidic gases and particles.

Two main contributors to acid deposition:

1. Sulfur Dioxide (SO2) Sulfur in the atmosphere comes from burning bituminous coal, smelting, and organic decay. 90% is from human sources.

2. Nitrogen Oxides (NOx) Major sources of nitrogen oxides include gasoline engines, power stations and industry.

Acid Rain Normal rain is slightly acidic and has a pH of about 5.6 Any rainfall has a pH value less than 5.6 is defined as ACID RAIN

Chemical Rxns involved in the formation of acid rain. CO2 + H2O  H2CO3 (carbonic acid) (this is why rain water is naturally slightly acidic) SO2 + H2O  H2SO3 (sulfurous acid) NO2 + H2O  HNO2 + HNO3 (nitrous acid) (nitric acid) Chemical Rxns involved in the formation of acid rain.

Acidic Precipitation Wind Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3) Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts Wet acid deposition (droplets of H2SO4 and HNO3 dissolved in rain and snow) Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts) Sulfur dioxide (SO2) and NO Nitric oxide (NO) Acid fog Farm Lakes in deep soil high in limestone are buffered Ocean Lakes in shallow soil low in limestone become acidic

Effects on the Environment Areas affected the most are where buffering capacity is low. Ex. Soils formed from granite Soils formed from limestone (CaCO3) have a greater buffering capacity therefore acid rain does not have as large of an impact http://cica.indiana.edu/projects/Biology/movies.html

Aquatic environments In areas where buffering capacity is low, acid rain also releases aluminum from soils into lakes and streams Aluminum is highly toxic to many species of aquatic organisms. At pH 5, most fish eggs cannot hatch. Lower pH levels can cause increased stress levels, lowering body weight and size. Some acid lakes have no fish. http://cica.indiana.edu/projects/Biology/movies.html

Forests Acid precipitation dissolves the nutrients and helpful minerals in the soil washes them away before trees and other plants can use them to grow. Acid precipitation also causes the release of substances that are toxic to trees and plants, such as aluminum, into the soil. The leaves of plants are also damaged.

Mountains Acid clouds greatly affect mountains in the eastern U.S. NC New England

Mongolia Germany

Flip through the next slides to see the progress that has been made

Manmade structures are also affected

Sulfate Ion Concentrations1985-2004 1986 1984 http://nadp.sws.uiuc.edu/amaps2/

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