Chapter 12.3 outline Acid Precipitation = acid rain

What causes Acid precipitation

rain, sleet, snow that is more acidic than normal

when fossil fuels are burned they release primary pollutants SO2 and NOx, oxides of sulfur and nitrogen

these combine with water in the air and form surfuric and nitric acids

flows into streams, rivers and lakes

kills living things including plants and animals

pH (power of hydrogen) scale is used to measure how acidic or basic a substance is

lower #s are more acidic, 7 is neutral, higher #s are more basic

each # increase indicates a 10 fold increase in H+ concentration

pure water has pH of 7.0

normal rain has pH of 5.6, slightly acidic because CO2 in air forms carbonic acid

often acid rain occurs downwind of large cities and industries

plants and animals have evolved to live within a particular pH range, evolution takes very long time (thousands or millions of years)

How acidic precipitation affects soils and plants

Acidification – increase in the concentration of acid, lowers the pH

Causes some nutrients to dissolve and wash away

Causes aluminum and other toxic metals to be released by soil and absorbed by plants

Also causes root damage

SO2 in water vapor (fog) clogs the openings on the surface of plants (suffocating them)

Acid precipitation and aquatic ecosystems

Acidic water can kill plants, fish and other animals

Causes aluminum to leach out of soil and into the water, accumulates in the gills of fish and interferes with oxygen and salt exchange, fish slowly suffocate

Acid shock – very quick change in pH due to snow melting in spring,  large fish kills

Affects reproduction of fish and amphibians, produce fewer eggs and many do not hatch

Off spring that do survive often have birth defects and cannot reproduce

To offset the acidification some states spray powdered limestone (basic) to neutralize acidic lakes. Not feasible to do this with all lakes and streams.

Acid precipitation and humans

release of aluminum and mercury from the soil can pollute our food and poison our body

may also cause respiratory (breathing) problems in children

hurts the fishing industry and forestry

can dissolve calcium carbonate in building materials and monuments (Michael Angelo’s David) made of marble and black crusts to form on historic Greek monuments

International Conflict and Cooperation

Acid precipitation often falls (downwind) 100s of kM away from the source of the pollution – crosses state and international boundaries, making it necessary for countries to work together, be good neighbors, to solve problems.