Explain how acid rain forms and its environmental impacts.

• A. Acid rain is formed by natural rain with no pollutants.
• B. SO2/NOx emissions transform into sulfuric and nitric acids; deposition lowers soils and water pH, harms forests and aquatic ecosystems, and corrodes infrastructure.
• C. It only affects urban surfaces and has no ecological effects.
• D. Acid rain is a myth and does not occur.

Answer: (B)

Acid rain forms when sulfur dioxide and nitrogen oxides released from burning fossil fuels react in the atmosphere with water, oxygen, and other chemicals to produce sulfuric and nitric acids. These acids can return to the surface in rain, snow, or as dry acidic particles, lowering the pH of precipitation and of soils and waters that receive it.

The environmental impacts come from this increased acidity. Soils and freshwater bodies lose their buffering capacity, nutrients are leached away, and toxic metals like aluminum become more soluble, which can harm plant roots and aquatic life. Forests can suffer reduced growth and health as leaves and needles are damaged and nutrient uptake is disrupted. In lakes and streams, acidification can wipe out sensitive species and reduce biodiversity. Acid rain also accelerates the corrosion of metals and the weathering of building materials, including limestone and marble, leading to damage of infrastructure and cultural monuments.

Natural rain without pollutants wouldn’t introduce these strong acids, and the idea that acid rain doesn’t occur isn’t accurate. Acid rain is a real consequence of human-emitted pollutants and their deposition.