If a pesticide is persistent in soil, which environmental process is most associated with its movement through the soil?

If a pesticide is persistent in soil, which environmental process is most associated with its movement through the soil?

• A. Leaching
• B. Runoff
• C. Vapor drift
• D. Spray drift

Answer: (A)

Leaching is the downward movement of a substance through soil with percolating water. When a pesticide is persistent, it remains intact long enough to be dissolved in water and carried down through soil pores as rainfall or irrigation infiltrates. This makes leaching the main way such a chemical moves through the soil, potentially reaching deeper layers or groundwater. Runoff moves pesticides along the soil surface with surface water and does not describe movement through the soil profile. Vapor drift and spray drift involve movement in air during or after application, not movement within the soil itself.

Leaching is the downward movement of a substance through soil with percolating water. When a pesticide is persistent, it remains intact long enough to be dissolved in water and carried down through soil pores as rainfall or irrigation infiltrates. This makes leaching the main way such a chemical moves through the soil, potentially reaching deeper layers or groundwater.

Runoff moves pesticides along the soil surface with surface water and does not describe movement through the soil profile. Vapor drift and spray drift involve movement in air during or after application, not movement within the soil itself.