Which pollutants are primarily responsible for acid deposition transported long distances?

• A. Ozone and PM.
• B. Carbon monoxide and lead.
• C. Sulfur and nitrogen pollutants.
• D. Methane and nitrous oxide.

Answer: (C)

Acid deposition that travels long distances is driven by sulfur- and nitrogen-containing pollutants. When fossil fuels burn, sulfur dioxide (SO2) and nitrogen oxides (NOx) are released. In the atmosphere, these gases undergo chemical reactions to form sulfuric acid and nitric acid. These acids can remain aloft, become incorporated into precipitation, or be deposited as dry particles, and the pollutants can be transported by winds before they return to Earth's surface. That long-range transport is what makes distant ecosystems—lakes, forests, and soils—vulnerable to acid rain. The other pollutants listed don’t primarily drive acid deposition: ozone and particulate matter affect air quality and have health/environmental impacts but aren’t the main source of acid rain; carbon monoxide and lead are toxic pollutants with different pathways; methane and nitrous oxide are greenhouse gases with climate-related roles rather than direct acid deposition precursors.