Name a potential source of nitrates in drinking water.

Nitrates in drinking water typically originate from agricultural activities due to the use of fertilizers that contain nitrogen compounds. When it rains, excess fertilizer can wash off fields into nearby water sources, leading to elevated levels of nitrates. Agricultural runoff is a significant contributor because it often contains high concentrations of these nutrients, especially in areas where intensive farming practices are common. Fertilizer application directly adds nitrates to the soil, and practices such as over-fertilization or improper timing of application can exacerbate the issue, resulting in contamination of groundwater and surface water supplies.

While other sources like industrial discharge and urban runoff can introduce various pollutants into water systems, they are not as predominant in the specific aspect of nitrate contamination as agricultural activities are. Household waste can contribute nutrients as well, but the scale and concentration of nitrates related to agricultural runoff are considerably higher, making it the primary concern for water treatment facilities monitoring drinking water quality.