Nearly any activity that releases chemicals or wastes into the environment, either intentionally or accidentally, can pollute groundwater. When a contaminant is released into the environment, it can (depending on its physical, chemical, and biological properties) soak into the soil and leach into groundwater. It may also contaminate surface water that feeds aquifers holding groundwater.
Some natural sources, such as rocks and soils, contain substances that can contaminate water, like an excess of minerals or decaying organic matter. However, most groundwater contamination is caused by human activity. Residential, municipal, commercial, industrial, and agricultural activities can all impact groundwater quality.
Common sources of contamination include leaks, spills, and releases of chemical, hazardous, and toxic substances from:
- Industrial containers,
- Septic systems,
- Aboveground and underground storage tanks,
- Landfills and surface impoundments,
- Underground pipelines,
- Pesticides and fertilizers, and
- Underground injection wells.
