Which term describes the downward movement of pesticide through soil and into groundwater?

• A. Drift
• B. Leaching
• C. Runoff
• D. Volatilization

Answer: (B)

Leaching is the downward movement of pesticide with water through soil toward groundwater. When a pesticide is soluble or not strongly bound to soil particles, rainwater or irrigation can carry it down through the soil profile and potentially reach the water table. This distinguishes it from drift, which is air movement of pesticide during or after application; runoff, which is water moving across the surface carrying pesticides away; and volatilization, which is the pesticide turning into vapor and moving into the air. Leaching is more likely in sandy, low-organic-matter soils and under heavy rainfall or irrigation, especially for highly soluble pesticides. To reduce leaching risk, choose products with lower leaching potential, apply under appropriate conditions to avoid heavy rainfall, and manage soil properties to increase sorption, such as maintaining organic matter.