What causes acid rain?

Acid rain is primarily caused by the release of sulfur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere, which often result from human activities such as burning fossil fuels, including coal. When these gases are emitted, they undergo chemical reactions in the atmosphere, leading to the formation of sulfuric and nitric acids. These acids can then mix with rainwater, resulting in precipitation that has a lower pH than normal, which is termed acid rain.

The significance of this process lies in its broader environmental impact, as acid rain can harm ecosystems, damage buildings, and affect human health. The connection between human activities, particularly those related to energy production and industrial processes, clarifies why the release of sulfur and nitrogen from burning coal is understood as a primary cause of acid rain.

The other options relate to environmental issues but do not contribute directly to the phenomenon of acid rain in the same way. Natural mineral deposits may affect local water chemistry but are not adequate to create the chemical compounds involved in acid rain. Excessive use of fertilizers can lead to runoff that causes water pollution but does not produce acid rain, and industrial waste dumped in rivers poses different environmental threats that do not include the acidification of precipitation.