What is leaching in the context of pesticide pollution?

Leaching is the process by which water, often through precipitation or irrigation, carries contaminants from the soil's surface downward through the soil profile and can result in the movement of these contaminants into the groundwater. In terms of pesticide pollution, leaching is particularly significant because it can transport pesticide residues beyond the application site, potentially entering and polluting groundwater sources. Understanding leaching is crucial for managing pesticide application practices to minimize environmental impacts and protect water quality.

The other concepts presented in the choices refer to different processes. For instance, water loss through the soil surface pertains to evaporation and surface drainage rather than contaminant movement. The removal of nutrients from the soil focuses on soil fertility dynamics, not specifically on the transport of pesticides. Surface runoff is a process where water flows over the soil surface, carrying pesticides, but it does not involve the downward movement towards groundwater, which is central to the definition of leaching.