1. Emission of Precursors:
* Sulfur dioxide (SO2): Primarily released from burning fossil fuels (coal, oil) in power plants, industries, and vehicles.
* Nitrogen oxides (NOx): Released from combustion processes, especially in vehicles and power plants.
2. Atmospheric Reactions:
* SO2 and NOx react with water, oxygen, and other chemicals in the atmosphere. These reactions form sulfuric acid (H2SO4) and nitric acid (HNO3).
* Sunlight plays a crucial role in these reactions, acting as a catalyst.
3. Acid Deposition:
* The sulfuric and nitric acids form tiny droplets that are carried by wind and rain. These acidic droplets fall to the earth as acid rain, snow, fog, or dry particles (acid deposition).
Key Chemical Reactions:
* SO2 + H2O → H2SO3 (sulfurous acid)
* H2SO3 + O2 → H2SO4 (sulfuric acid)
* NOx + H2O + O2 → HNO3 (nitric acid)
In Summary:
Acid rain is a result of chemical reactions between sulfur dioxide and nitrogen oxides released into the atmosphere, leading to the formation of sulfuric and nitric acids. These acids are then deposited to the earth as acid rain or other forms of acid deposition.
