What is the primary contaminant of concern in groundwater and what is the reasoning behind it?

The primary contaminant of concern in groundwater is nitrate due to its solubility and ability to easily enter groundwater systems. Nitrate originates from various sources, including agricultural fertilizers, septic systems, and animal waste. Its soluble nature means that, when nitrates are applied to the soil or released into the environment, they can readily leach through the soil and into the groundwater.

Once in the groundwater, nitrate can pose significant health risks, particularly to vulnerable populations such as infants. High levels of nitrate in drinking water can lead to methemoglobinemia, or "blue baby syndrome," where the oxygen-carrying capacity of blood is reduced. This makes the presence of nitrate a significant public health concern, prompting monitoring and regulations to manage its levels.

While other contaminants like phosphorus, ammonium, and certain forms of carbon may have environmental impacts, they do not exhibit the same widespread and direct health implications caused by nitrate in groundwater. Thus, the solubility and ease of entry into water systems underscore nitrate as the primary contaminant of concern.