Which of the following is a source of point source pollution?

Point source pollution refers to contaminants that can be traced to a specific, identifiable source. In this context, spills at equipment cleanup sites represent a specific location where pollutants are introduced into the environment. Such spills are characterized by their discrete source, making it possible to pinpoint where the contamination originates, which is the defining feature of point source pollution.

In contrast, the other types of pollution mentioned involve more diffuse sources. Stormwater runoff from fields occurs when rainwater collects pollutants like pesticides and fertilizers as it flows over agricultural land, but it does not originate from a single, identifiable source. Atmospheric deposition refers to pollutants being deposited from the air onto land or water, again lacking a single point of origin. Similarly, runoff from urban areas combines pollutants from various decentralized sources, making it difficult to attribute the pollution to any one specific location. Therefore, spills at cleanup sites clearly exemplify point source pollution due to their identifiable characteristics.