How does acid deposition affect soil chemistry and nutrient availability?

• A. It increases soil pH and base cations.
• B. It leaches base cations (Ca, Mg, K), lowers soil pH, increases aluminum toxicity, reducing microbial activity and nutrient availability.
• C. It has no effect on soil chemistry.
• D. It only affects surface water, not soils.

Answer: (B)

Acid deposition lowers soil pH and triggers leaching of base cations from soil surfaces. The extra hydrogen ions displace calcium, magnesium, and potassium from exchange sites, and these base cations are washed away by water moving through the soil. As the soil becomes more acidic, aluminum becomes more soluble, increasing soluble Al3+ in the soil—this can damage root tips, hinder root growth, and interfere with nutrient uptake.

These chemical changes also slow down soil biology. Microbial communities and their nutrient-mining processes operate less efficiently in acidic conditions, so mineralization and overall nutrient cycling decline. With fewer readily available nutrients and a damaged root system, plants struggle to acquire essential elements, leading to reduced nutrient availability. So the combined effects of lower pH, loss of base cations, increased aluminum toxicity, and diminished microbial activity explain how acid deposition degrades soil chemistry and nutrient access.