Which element is often monitored in drinking water to assess the contamination from agricultural runoff?

Monitoring nitrogen in drinking water is crucial for assessing contamination from agricultural runoff due to its prominent role in agricultural practices, particularly in the use of fertilizers. Nitrogen compounds, such as nitrates, are commonly found in fertilizers applied to crops. When it rains or when irrigation occurs, these nitrates can leach into the groundwater or run off into surface water bodies, leading to increased concentrations in drinking water supplies.

High levels of nitrates in drinking water can have significant health impacts, including methemoglobinemia, or "blue baby syndrome," which affects the ability of blood to carry oxygen in infants. As such, tracking nitrogen levels is essential for public health protection. This focus on nitrogen highlights the relationship between agricultural activities and water quality, establishing nitrogen as a key indicator of contamination potential from agricultural runoff.

Phosphorus and other heavy metals like lead and mercury are also important pollutants, but nitrogen’s relevance to agricultural runoff specifically makes it a critical element for monitoring in this context.