Diffuse pollution, such as runoff, is categorized as which?

• A. Fluxes
• B. Nonpoint source pollution
• C. Groundwater
• D. Hydrologic cycle

Answer: (B)

Nonpoint source pollution is contamination that enters water bodies from many diffuse sources across the landscape, not from a single identifiable discharge. Diffuse pollution like runoff fits this because when rain or irrigation water flows over soils, roads, and crops, it picks up nutrients, sediments, pesticides, and other pollutants from numerous locations and carries them into rivers, lakes, or groundwater. There isn’t one outlet to point to; the pollution results from widespread inputs over a broad area, which is the hallmark of nonpoint source pollution. This differs from flux, which is simply the rate at which pollutants move, not where they come from. Groundwater is a medium that can transport pollutants, not a pollution-source category. The hydrologic cycle describes the global movement of water, not a pollution source. So runoff is a classic example of nonpoint source pollution.