Under what soil conditions are pesticides more likely to leach through soil?

The correct answer is based on the characteristics of the soil mentioned and their impact on pesticide movement. Sandy soil has larger particles and greater drainage capacity, which allows water—and any dissolved pesticides—to move through it more rapidly compared to heavier soils like clay. When combined with low organic matter, there is less binding capacity for the pesticides, making it easier for them to leach away from the soil particles and into deeper layers or groundwater.

Furthermore, if groundwater is shallow, any leaching that occurs in sandy soil has a higher chance of reaching the groundwater quickly, posing a risk of contamination. The combination of sandy soil, low organic matter, and shallow groundwater creates an environment where pesticides are more likely to move downward through the soil profile toward aquifers.

In contrast, other options introduce factors that would generally inhibit leaching. High organic matter in sandy soils may provide binding sites for pesticides, thereby reducing their mobility. Heavy clay soils are dense and retain water, slowing down the movement of both water and dissolved substances, including pesticides. Finally, deep groundwater implies a longer distance pesticide residues must travel, often enabling more time for degradation and adsorption processes to occur before reaching the aquifer.