Which scenario best represents non-point-source groundwater contamination?

• A. Pesticides that dissolve and leach through soil after it rains.
• B. Direct discharge from a factory.
• C. A spill from a single drum near a stream.
• D. A leak from a storage tank.

Answer: (A)

Non-point-source groundwater contamination happens when pollutants enter groundwater from many sources over a broad area, typically carried by infiltrating water after rainfall. Pesticides that dissolve and leach through soil after it rains fit this pattern because the contaminant comes from widespread land areas rather than a single discharge point and is moved downward by water into the groundwater. The other scenarios describe point sources: a factory discharging directly from one location, a spill from a single drum near a stream, or a leak from a storage tank—all originating at identifiable sites and releasing contaminants from that single source. The diffuse nature and rainfall-driven movement of the pesticides make this scenario the best example of non-point-source groundwater contamination.