Acid deposition is the depositing of acid in any form on objects in the environment, be they natural or manmade. In most cases, the acid deposition commonly takes the form of acid rain, which often gets the most attention because it is perceived as being the most dangerous. Other forms include both solids and gasses and, while they may not pose as much risk, they can still be detrimental to objects they touch.
In order for deposition to take place, the acid must first be present in the atmosphere. This most commonly occurs from the burning of coal at electrical generation plants. The coal produces a substance known as sulfur dioxide. Once in the air, it mixes with other elements, mainly oxygen, to become sulfuric acid. Some of this material eventually falls to the Earth.
Acid rain is simply acid deposition in liquid form. The sulfuric acid is found in clouds, which condense and the water droplets eventually become so heavy that they fall. The acid rain can actually fall many miles from where the actual coal plant is located, simply because of wind patterns, and the time it takes the acid to form and fall.
Acid deposition can also happen through the form of acid particulates, which are solids, and acidic vapors, which are gasses. As the acid makes its way back to the planet’s surface, it lands on other objects, such as buildings, trees and lakes. In most cases, these objects are not prepared to deal with the introduction of higher acid levels and therefore are negatively affected.
The main damage is done to buildings and cars, as well as trees and water systems, such as lakes and rivers. Acid deposition can strip paint off buildings and cars, and even lead to structural deterioration. In forests, it can cause trees to die in great numbers as the plants try to cope with a different pH than they prefer. The same is also true of water systems, where fish and other wildlife can be harmed because of the acid deposition.
Stopping acid deposition has therefore become a major concern for many of the world’s countries. Though it may not be possible to completely eradicate coal plants in the near future, switching to cleaner forms of energy without coal, or even using clean coal technologies, can help. For example, acid deposition can be nearly eradicated through the use of scrubbers that remove sulfur from the emissions that coal plants produce.