How can runoff contribute to water contamination by pesticides?

Runoff can significantly contribute to water contamination by pesticides primarily through the movement of soil that has adsorbed pesticides. When it rains or when irrigation occurs, water can wash over agricultural fields or treated areas. If these areas have soil that contains pesticide residues, the water can carry these pesticide-laden soil particles into nearby water bodies, such as rivers, lakes, or streams.

This process leads to a dilution of the pesticide in the water but can still result in harmful concentrations that affect aquatic life and water quality. Additionally, the movement of the soil can transport not just the chemical itself but also other contaminants bound to the soil, exacerbating the overall contamination.

Understanding this process underscores the importance of implementing erosion control measures and responsible pesticide application practices to minimize runoff and protect water sources from contamination.