Which statement is true about groundwater or surface water contaminated by pesticides?

• A. Runoff and erosion are sources of surface water contamination by pesticides
• B. Pesticides contaminate water only through irrigation runoff
• C. Groundwater contamination occurs only near industrial sites
• D. Surface water contamination can be prevented completely by cropping selection

Answer: (A)

The thing this question tests is how pesticides get into water and why surface water is often affected by runoff and soil erosion. When pesticides are applied to fields, rain or irrigation can wash some of the chemicals off the surface into nearby streams, rivers, and ponds. Pesticides can also hitch a ride on soil particles, and as erosion moves soil into ditches and waterways, those pesticides travel with it. This is why runoff and erosion are common sources of surface water contamination.

The other ideas don’t fit because pesticides reach water through more pathways than just irrigation runoff, including rain-driven runoff, drainage, drift, spills, and improper disposal. Groundwater contamination isn’t limited to industrial sites; it can occur when pesticides leach through soil and move down to groundwater beneath agricultural fields. And surface water contamination cannot be prevented completely simply by choosing crops—the risk can be reduced with management, but complete prevention isn’t achievable.