What are the two basic causes of non-point source pesticide pollution?

The correct answer identifies runoff and leaching as the two basic causes of non-point source pesticide pollution. Non-point source pollution refers to contaminants that enter the environment from diffuse sources rather than from a single, identifiable source.

Runoff occurs when rainfall or irrigation water flows over the surface of the ground and carries pesticides from fields or treated areas into nearby water bodies, such as rivers, lakes, or streams. This process is particularly significant in agricultural settings where pesticides are widely used.

Leaching, on the other hand, involves the downward movement of pesticides through the soil profile, eventually reaching groundwater. This happens when rain or irrigation water percolates through the soil, carrying soluble pesticides. This contamination can affect drinking water supplies and make it challenging to monitor and manage pesticide levels accurately.

Understanding these mechanisms is crucial for effective environmental management and regulatory practices, as both runoff and leaching contribute significantly to the challenges posed by pesticide pollution, particularly in areas reliant on agricultural production.