Which process describes groundwater contamination when recharge water carries dissolved chemicals through the soil profile into the water table?

• A. Runoff
• B. Leaching
• C. Filtration
• D. Evaporation

Answer: (B)

Leaching is the downward movement of dissolved chemicals through the soil profile with infiltrating recharge water until they reach the water table. When rainfall or irrigation water percolates through soil, it can carry soluble pesticides, nutrients, or other contaminants down to groundwater, bypassing much of the surface filtration and entering the aquifer. This downward transport is exactly how groundwater becomes contaminated during recharge events. Runoff stays on the surface and doesn’t reach the water table. Filtration describes the soil’s ability to remove some contaminants as water moves, not the primary transport of contaminants to groundwater. Evaporation involves water turning into vapor at the surface and does not move dissolved contaminants into groundwater.