What is a common source of nitrates that can contaminate community water supplies?

Nitrates are commonly found in fertilizers and can enter water supplies through runoff, particularly after heavy rain or irrigation. When fertilizers are applied to agricultural fields, not all of the nutrients remain in the soil; some leach into groundwater and surface water, causing elevated nitrate levels in these sources. This runoff often occurs when excess water moves across the landscape, allowing nitrates to migrate into nearby streams, rivers, and even aquifers that contribute to community water supplies.

While wastewater treatment plants can also introduce nitrates, their contributions are typically related to the treatment of sewage rather than agricultural applications. Similarly, industrial discharges and household waste generally do not represent the main pathways for nitrate contamination compared to agricultural fertilizer runoff, making fertilizer runoff the most significant and common source of nitrates affecting community water quality.