What are common routes through which pesticides can contaminate groundwater?

The correct answer identifies leaching, spills, and improper disposal as common routes through which pesticides can contaminate groundwater.

Leaching occurs when pesticides applied to the soil filter down through the soil profile and potentially reach groundwater. This process can be exacerbated by factors such as soil composition, moisture levels, and the chemical properties of the pesticide itself.

Spills can happen during the handling or application of pesticides. If pesticides are spilled on the ground without proper containment, they can seep into the soil and travel down to the water table, resulting in contamination.

Improper disposal practices, such as discarding leftover pesticides or washing application equipment near water sources, can also lead to pesticides entering groundwater supplies. All three methods highlight the importance of responsible pesticide management to prevent groundwater contamination.

The other options involve processes that are either less directly related to groundwater contamination or irrelevant to the contamination mechanisms in the context of pesticide use.