Which pollutant is mainly produced by burning coal and oil and is linked to acid rain?

• A. Sulfur dioxide
• B. Nitrogen oxides
• C. Ground-level ozone
• D. PM2.5

Answer: (A)

Sulfur dioxide is the pollutant most closely linked to acid rain because sulfur in coal and oil is released when these fuels burn. That sulfur becomes sulfur dioxide (SO2) in the exhaust. In the atmosphere, SO2 can be converted to sulfur trioxide (SO3) and then combine with water to form sulfuric acid (H2SO4). When rain contains this acid, it lowers the rain’s pH, causing acid rain that can harm ecosystems, corrode buildings, and alter soil chemistry.

Nitrogen oxides also contribute to acid rain through the formation of nitric acid, but sulfur dioxide from burning sulfur-containing fuels is the more dominant source in many regions. Ground-level ozone and PM2.5 relate to air quality and health effects, but they are not the primary drivers of acid rain.