December 2002
How does acid rain occur?
Acid rain occurs when gases react in the atmosphere with water, oxygen
and other chemicals to form various acidic compounds. Sunlight
increases the rate of most of these reactions.
Acid rain comes in two forms: wet and dry deposition.
Wet deposition refers to acidic rain, fog and snow. As this acidic
water flows over and through the ground, it affects soils, waterways
and a variety of plants and animals.
Dry deposition refers to the acidic gases and particles in the
atmosphere that fall back to earth. According to the U.S. EPA, about
half the acidity in the atmosphere falls in the form of dry
deposition. The wind blows these acidic particles and gases onto
buildings, cars, homes and trees.
http://www.in.gov/idem/4576.htm
The form of precipitation and the amount of water vapor in the
air do affect how acid precipitation and water droplets in the air and
in clouds are.
Generally, the more water drops or snow flakes, the less acidic
the water is, since the acid particles are dissolved and diluted.
http://www.newton.dep.anl.gov/askasci/wea00/wea00117.htm
June 8th, 2007
Pure water has a pH of 7.0. However, normal rain is slightly acidic
because carbon dioxide (CO2) dissolves into it forming weak carbonic
acid, giving the resulting mixture a pH of approximately 5.6 at
typical atmospheric concentrations of CO2.
http://www.epa.gov/acidrain/measure/index.html
Dec. 15, 2009
Power plants spray scrubbers to reduce mercury and contaminants that
cause acid rain—a process that cleans the air but can spell trouble
for organisms living in the water.
http://greatlakesecho.org/2009/12/16/spotty-state-regulations-of-toxic-metals-and-contaminants-in-coal-fired-power-plant-wastewater-prompt-the-epa-to-action/
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