The formation of acidic deposition is largely from the combustion of fossil fuels and the smelting of sulfide ores. Minor natural sources exist such as the formation of hydrochloric and sulfuric acid from gaseous volcanic eruptions.

There are well over 100 gaseous and aqueous phase reactions that can lead to acid formation and more than fifty oxidizing agents and catalysts may be involved. However, in the simplest terms sulfur in fuels is oxidized to SO2 , and SO2 in the atmosphere is further oxidized and hydrolyzed to sulfuric acid. Most nitric acid is formed by the fixation of atmospheric nitrogen gas (N2) to NOx (NO and NO2) during high temperature combustion emissions, followed by further oxidation and hydrolysis that produces nitric acid in the atmosphere. (more…)

The increased use of fossil energy since the industrial revolution, and especially since 1950, has been the major cause of increased emissions of air pollutants and, correspondingly, many environmental problems. Emissions due to the use of energy are major sources of sulfur dioxide, nitrogen oxides, carbon dioxide, and soot and constitute a large contribution of methane, non-methane volatile organic compounds, and heavy metals. (more…)