Several chemicals cause acid rain, although sulfur dioxide and nitrogen oxide are the primary contributors. Sulfur dioxide and nitrogen oxide contribute largely to the development of acid rain, although several natural sources, such as volcanic eruptions and decaying vegetation, cause acid rain as well.
The creation of acid rain occurs when sulfur dioxide and nitrogen oxide combine with oxygen, water and other chemicals in the atmosphere. The interaction of the gases and chemicals with natural elements creates a solution of sulfuric acid and nitric acid, which lingers in the stratosphere until it evaporates and returns to the Earth’s surface in the form of rain. Sulfur dioxide and nitric oxides are released primarily by power plants and refineries, although they come from factories, buildings and other facilities as well. The gases rise into the atmosphere when burned; they spawn from the combustion of fossil fuels and do not biodegrade upon reaching the ozone layer and stratosphere. In addition to acid rain, these chemicals fall back onto the Earth as fog and snow as well. In dry areas, such as deserts, chemicals mix with dust and smoke to accumulate on the ground in the form of dry deposits. There, they stick to the ground, homes, cars and trees.