What are common indicators of nitrate contamination in water?

Elevated nitrate levels above 10 mg/L are a key indicator of nitrate contamination in water. The U.S. Environmental Protection Agency (EPA) has established a maximum contaminant level for nitrate in drinking water at this threshold to protect public health. Nitrates, which can come from agricultural runoff, septic systems, and natural sources, can cause health issues, especially in infants, where they may lead to methemoglobinemia, or "blue baby syndrome." Therefore, when monitoring water quality, exceeding this level is a significant red flag and indicates the need for further investigation and potential remediation efforts. Understanding this threshold is essential for recognizing pollution sources and protecting both human health and the ecosystem.

The other options, while they can indicate various water quality issues, do not specifically relate to nitrate contamination as definitively as elevated nitrate levels do. Cloudy water can result from sediment or biological activity, low pH levels indicate acidity not directly tied to nitrates, and the presence of certain algae species may signal nutrient imbalances but does not pinpoint nitrate specifically.