QAL Laws & Regulation Practice Exam

Rainfall is the environmental condition that increases the risk of pesticide leaching into groundwater. When it rains, particularly if the rainfall is heavy or occurs shortly after the application of pesticides, water can infiltrate the soil and carry dissolved chemicals down through the soil profile. This process can lead to contaminants reaching the groundwater supply, especially in areas where the soil is sandy or has low organic content, as these conditions allow water to move more rapidly through the soil.

The timing and amount of rainfall are critical factors in this process; even a light rain can be enough to mobilize pesticides if they have been recently applied or are present in the upper soil layers. In contrast, conditions such as high temperatures, low humidity, and snowfall typically do not have the same immediate effect on the movement of pesticides into groundwater. High temperatures may increase evaporation rates and reduce the amount of water that can lead to leaching, while low humidity can also contribute to less soil moisture. Snowfall may initially introduce moisture, but it often does so in a much more gradual manner as the snow melts, which can reduce the risk of rapid leaching compared to rain.