What is 'acid deposition'?

Acid deposition refers to the process through which acidic pollutants, primarily sulfur dioxide (SO2) and nitrogen oxides (NOx), are emitted into the atmosphere and eventually deposit back to the Earth's surface through various means, such as rain, snow, fog, or dust. This deposition can lead to a decrease in pH levels in water bodies and soil, causing harm to ecosystems, damaging forests, affecting wildlife, and corroding buildings and structures.

The term captures both wet deposition, which includes acidic rain, and dry deposition, which involves acidic particles settling out of the atmosphere without moisture. Understanding acid deposition is crucial because it highlights the impact of air pollution on environmental quality and the potential harm to natural and human-made systems.

The other options do not accurately capture the essence of acid deposition. The mix of nutrients in water relates more to nutrient pollution or eutrophication, while methods of enhancing soil fertility or forms of water purification focus on improving soil and water quality, rather than the harmful effects of specific pollutants.