What does runoff refer to in the context of pesticides?

Runoff in the context of pesticides specifically refers to the movement of pesticides from their application site into surface water bodies due to water flow. This can occur when rain or irrigation water washes pesticides from fields, gardens, or other treated areas into nearby rivers, lakes, or streams. Understanding this concept is crucial because it highlights the potential for pesticides to contaminate water sources, posing risks to aquatic ecosystems and drinking water supplies.

The other options describe different processes associated with pesticide behavior but do not accurately characterize runoff. The movement of pesticides through the soil pertains to leaching, where pesticides seep into the groundwater. Evaporation of pesticides into the air refers to the volatilization process, where pesticides can transition from a liquid state to vapor. The movement of pesticides back to the application site does not capture the concept of runoff, as it implies a return rather than an outward movement toward surface water. Thus, the correct understanding of runoff is essential for effective pesticide management and environmental protection.