What kind of contamination is it?
Groundwater is rain water or water from surface water bodies, like lakes or streams, that soaks into the soil and bedrock and is stored underground in the tiny spaces between rocks and particles of soil. Groundwater pollution occurs when hazardous substances come into contact and dissolve in the water that has soaked into the soil.
How did it get there?
Groundwater can become contaminated in many ways. If rain water or surface water comes into contact with contaminated soil while seeping into the ground, it can become polluted and can carry the pollution from the soil to the groundwater. Groundwater can also become contaminated when liquid hazardous substances themselves soak down through the soil or rock into the groundwater. Some liquid hazardous substances do not mix with the groundwater but remain pooled within the soil or bedrock. These pooled substances can act as long-term sources of groundwater contamination as the groundwater flows through the soil or rock and comes into contact with them.
How does it hurt animals, plants or humans?
Contaminated groundwater can hurt animals, plants, or humans only if it is first removed from the ground by manmade or natural processes. In many parts of the world, groundwater is pumped out of the ground so it can be used as a source of water for drinking, bathing, other household uses, agriculture, and industry. In addition, groundwater can reach the surface through natural pathways such as springs. Contaminated groundwater can affect the quality of drinking and other types of water supplies when it reaches the surface. Contaminated groundwater can affect the health of animals and humans when they drink or bathe in water contaminated by the groundwater or when they eat organisms that have themselves been affected by groundwater contamination.
How can we clean it up?
Different approaches are used to clean up contaminated groundwater. Sometimes polluted groundwater is pumped from the soil or bedrock, treated to remove the contamination, and then pumped back into the ground. If contaminants are released into the groundwater slowly, large amounts of groundwater need to be pumped to remove a relatively small amount of contamination. In this case groundwater contamination is addressed by containing the contamination in a limited area to keep it from harming animals and plants. Still other types of contamination can be left in the ground without active pumping and treatment. In these cases, contaminants are reduced to non-toxic concentrations by natural biological, chemical, and physical processes before the contamination reaches the surface.