What role does precipitation play in pesticide movement?

Precipitation significantly influences the movement of pesticides, primarily through the process of runoff and leaching. When it rains, water can wash away pesticides that have been applied to the surface of the soil, especially if the application occurred shortly before the rainfall. This movement can result in pesticides entering nearby water bodies or being carried deeper into the soil profile, potentially affecting groundwater quality.

The other choices do not accurately reflect the role of precipitation in pesticide movement. While precipitation does not help increase pesticide volatility, it can enhance the risk of runoff, which is when pesticides are moved off-site. Likewise, precipitation does not stop pesticide leaching; in fact, it can promote it by saturating the soil and allowing soluble pesticides to move through the soil profile. Finally, precipitation tends to increase, not decrease, soil moisture content, which influences how pesticides are distributed and degraded in the environment. Thus, recognizing that precipitation washes away pesticides into the soil illustrates its critical role in the environmental fate of these chemicals.