Which statement about soil pH and acid rain is true?

• A. Acid rain can increase soil pH.
• B. Acid rain can decrease soil pH.
• C. Soil pH is unaffected by acid rain.
• D. Soil pH only changes with irrigation water.

Answer: (B)

When acidic pollutants from rain enter the soil, they bring in acids such as sulfuric and nitric acids that release hydrogen ions into the soil solution. The pH scale measures how concentrated these hydrogen ions are, so adding more H+ makes the solution more acidic and lowers the pH. This is why soil pH decreases with acid rain, not increases. Over time, the soil’s buffering capacity and loss of basic cations (like calcium, magnesium, and potassium) can amplify this drop, making conditions more acidic and altering nutrient availability. So the statement that acid rain can decrease soil pH is the accurate one, reflecting how acid inputs shift the soil toward acidity rather than neutrality or basicity.