Sunlight increases the rate of most of the SO2 and NO reactions. The result is a mild solution of sulfuric acid and nitric acid. "Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry.
- Wet deposition - refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depend on many factors, including:
- the acidity of the water;
- the chemistry and buffering capacity of the soils involved;
- the types of fish, trees, and other living things that rely on the water.
- Dry deposition - refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition.
- Acidic particles and gases are blown by the wind onto buildings, cars, homes, and trees.
- Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone.
Process of Acid Deposition
Prevailing winds blow the compounds that cause both wet and dry acid deposition across state and national borders, and sometimes over hundreds of miles. Please watch the 1:22 presentation below to learn more about the process of acid deposition.