Acid rain is an acidic form of rain. It was first observed in Manchester, England. In 1852, Robert Angus Smith found that acid rain was effected by atmospheric pollution.
It happens when pollution enters the atmosphere. In the atmosphere, the chemicals from pollution are absorbed into clouds by water. The chemicals that effect acid rain are Sulfur dioxide and Nitrogen oxides. Then, these acidic droplets fall to the Earth.
There are many industries and manmade processes that cause acid rain. A high amount of Sulfur dioxide comes from fossil fuel combustion. This comes from manmade processes such as driving a car, driving a boat, running a power plant or factory, and flying airplanes. Nitrogen compounds also come from these processes.
Natural processes cause acid rain too. A major natural contributor to acid rain is volcanic eruptions. Volcanoes cause a lot of chemicals in gases to escape into the atmosphere. There are also biological processes around the whole planet that create harmful chemicals.
There are ways to prevent and neutralize acid rain. Coal-burning power plants use flue gas desulfurization (FGD) to neutralize and collect the sulfur dioxide leaving the plant. The FGDs use fans to push the gases into a tower where a limestone mixture is injected. The calcium carbonate in the limestone then combines with the sulfur dioxide to create calcium sulfate, a neutral substance. This substance is then removed from the FGD and is often sold. This is done in power plants to counteract the effects of acid rain.