Groundwater, the source of water for private wells, is never simply a pure combination of hydrogen and oxygen atoms (H20). It contains many impurities, reflecting the composition of the soils, sand, gravel, and rock through which it travels. Groundwater naturally contains:
- Dissolved minerals such as iron, calcium, magnesium, bicarbonate, chloride, and sulfate
- Gases such as carbon dioxide, oxygen, and nitrogen
- Dissolved organic compounds
As a result of human activity, groundwater can also contain contaminants such as pesticides, nitrate, metals, and volatile organic chemicals (VOCs). Any chemicals that are used or disposed of (purposely or accidentally) on the land surface have the potential to find their way into groundwater supplies.