Which of the following represents nonpoint-source pollution?
Waste from a pig farm pollutes a nearby stream. Fertilizers added to fields in Illinois and Iowa leach into the Mississippi River, leading to high levels of nitrogen in the water. During heavy rains, untreated sewage spills from a treatment plant directly into a nearby river. Attendants at a service station dump used oil into a nearby stream.
The example that represents nonpoint-source pollution is:
Fertilizers added to fields in Illinois and Iowa leach into the Mississippi River, leading to high levels of nitrogen in the water.
Nonpoint-source pollution comes from multiple, diffuse sources rather than a single, identifiable source. In this case, the fertilizers applied to fields contribute to pollution as they wash off into the river, making it difficult to pinpoint a specific source of the pollution. The other examples provided are instances of point-source pollution, where the pollution can be traced back to a specific location or source.