Which of the following is an example of a point source?

• A. Urban stormwater
• B. Air emissions
• C. POTW discharge and industrial discharge
• D. Runoff from fields

Answer: (C)

Distinguishing point sources from nonpoint sources in water pollution is about identifying whether pollutants enter water through a single, identifiable outlet. A point source is a discrete discharge, like a pipe or outfall from a facility, where you can trace the pollution to one location and regulate it through a permit system.

Discharges from a wastewater treatment plant or an industrial facility fit this idea perfectly because they come through a specific outlet that releases treated or untreated water into the water body. That single source makes it a point source.

The other options are diffuse in nature. Urban stormwater and runoff from fields originate from many places over large areas, so there isn’t one outlet to point to. Air emissions relate to air pollution rather than a direct, single water discharge, so they don’t form a point source for water pollution.