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Are You Informed About Acid Rain? “Acid rain" is simply rain which is acidic. The rain becomes acidic because of gases which dissolve in the rain water to form various acids. Rain is naturally slightly acidic and thus it has a pH of around 6.0 and in some parts of the world it can be as low as 4.0 (this is typical around volcanoes, where the Sulphur dioxide and hydrogen Sulphide form Sulphuric acid in the rain).Before the Industrial Revolution, the pH of rain was generally between 5 and 6, so the term acid rain is now used to describe rain with a pH below 5. Acid rain is a broad term used to describe several ways that acids precipitates from 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 how acidic the water is, the chemistry and buffering capacity of the soils involved, and 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. The wind blows these acidic particles and gases 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. (Figure.1) Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds.
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