Which of the following is NOT a potential source of nitrate contamination in water supplies?

Nitrate contamination in water supplies primarily arises from activities that introduce nitrogen compounds into the environment. Agricultural runoff is a significant source as fertilizers used in farming contain high levels of nitrates that can leach into nearby water sources. Industrial discharges can also contribute nitrates, especially if industrial processes involve the use or disposal of nitrogen-rich compounds. Similarly, residential sewage can lead to nitrate contamination due to the breakdown of organic materials that contain nitrogen, which can then seep into groundwater or nearby water bodies.

In contrast, forest conservation typically does not contribute to nitrate contamination. Healthy forest ecosystems can actually help mitigate nitrate levels by absorbing excess nutrients from the soil through plant uptake and reducing runoff. Thus, forest conservation is generally associated with the protection of water quality rather than its degradation. This distinction makes it clear why it is not considered a potential source of nitrate contamination compared to the other options listed.