What soil texture has an increased risk of groundwater contamination?

• A. Sandy soils
• B. Clay soils
• C. Silty soils
• D. Loamy soils

Answer: (A)

Understanding how soil texture affects groundwater contamination risk comes down to how easily water and dissolved pesticides move through the soil. Sandy soils have large pore spaces and high permeability, so water drains downward quickly with little chance for pesticides to be adsorbed or slowed. This rapid leaching increases the likelihood that residues reach the groundwater, making sandy soils the highest risk. Clay soils, with tiny pores and lots of surface area, tend to adsorb pesticides and slow water movement, reducing leaching to groundwater. Silty and loamy soils are intermediate—they drain slower than sand and provide more sorption than sandy soils, so their groundwater contamination risk is lower than sandy but higher than dense clay under similar conditions.