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Groundwater Contamination
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.