Which of the following is an example of non-point source pollution?

Non-point source pollution refers to pollutants that originate from multiple diffuse sources rather than a single, identifiable source. Runoff from agricultural fields is a prime example of non-point source pollution, as it often involves a variety of contaminants, such as fertilizers, pesticides, and sediments, which are washed into water bodies by rainfall or irrigation. This type of pollution is challenging to trace back to a specific point, making it difficult to manage or regulate effectively.

In contrast, industrial discharge, sewage treatment plants, and ballast water discharge are examples of point source pollution, where contaminants can be traced to a single, identifiable location or facility. Industrial discharge comes from factories, sewage treatment plants handle wastewater in a centralized manner, and ballast water discharge involves the release of water from ships that can introduce invasive species. Each of these sources can be directly monitored and regulated, unlike the diffuse and widespread nature of the pollutants from agricultural runoff.