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Groundwater Contamination - WorstPollutedorg Reports

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Groundwater Contamination -  WorstPollutedorg  Reports Powered By Docstoc
					GROUNDWATER CONTAMINATION
Description

Groundwater is water located beneath the surface in soil pore spaces and in permeable
geological formations. Sources of groundwater include seepage from the land surface,
such as rainwater, snowmelt and water also that permeates down from the bottom of
some lakes and rivers.1 Fossil groundwater is water that has been trapped in rock
formations over geological time scales. Groundwater is a very important source of
freshwater, making up 97 percent of the world’s accessible freshwater reserves.2 In
addition, about two billion urban and rural people depend on groundwater for everyday
needs.3

Context

 Fresh drinking water makes up only 6% of the total water on Earth and 100% of the
world’s population relies on it. This includes the icecaps and glaciers and if these
sources are subtracted from the total, only 0.3% of the water on Earth is useable for
drinking, and the majority of that is groundwater. Millions of people in the developing
world rely heavily on groundwater, mostly through shallow dug wells. These can easily
become polluted, primarily because of human activities. Such activities can be broadly
categorized into four groups: municipal, industrial, agricultural, and individual sources.4

Municipal sources of groundwater contamination include open dumpsites, poorly
constructed or maintained landfills, latrines and other waste sites. Each of these can
contain a range of pathogens and toxins, including heavy metals that can migrate
downward and contaminate aquifers. Industrial pollution of groundwater can come from
dumping of wastewater or waste, from mining activities and from leakage or spillage
from other industrial processes. Mining primarily affects groundwater through leaching of
mine tailing piles.5 Chemical manufacture and storage similarly present a threat through
leakage. Agricultural contamination comes primarily from overuse of pesticides and
fertilizers that can later seep into groundwater sources.6
Lastly, individuals can also cause groundwater contamination by improperly disposing of
waste.
Motor oil, detergents and cleaners can leak into water sources. Importantly, groundwater
can also be contaminated by naturally occurring sources. Soil and geologic formations
containing high levels of heavy metals can leach those metals into groundwater. This
can be aggravated by over-pumping wells, particularly for agriculture. This is the case in
much of Bangladesh, where groundwater contains high levels of naturally occurring
arsenic. One study indicated that a full one fifth of the population drinks water containing
5 times the arsenic level recommended by the WHO7.

Groundwater pollution differs from surface water contamination in several important
respects. Among them, it does not typically flow to a single outlet. It can affect people
through wells dug in a contaminated aquifer, as it can flow into streams or lakes.
Groundwater pollution also occurs on a different timescale than surface water
contamination. Flow rates vary widely and can be as slow as 2 miles a year. Because of
this, nonpoint source pollution can take years or even decades to appear in wells and
just as long or even longer to dissipate or be converted.
These distinctions depend on topography, hydrology and the sources of groundwater
recharge and have implications for limiting as well as remediating contamination.8

Exposure Pathways

Groundwater pollutants can enter the body directly through water supplies or by eating
foods prepared with contaminated groundwater or grown in fields using contaminated
sources. It may also affect humans when they are in direct contact with polluted waters.

Health Effects

Health effects from groundwater pollution depend on the specific pollutants in the water.
Pollution from groundwater often causes diarrhea and stomach irritation, which can lead
to more severe health effects. Accumulation of heavy metals and some organic
pollutants can lead to cancer, reproductive abnormalities and other more severe health
effects.

What is Being Done

Groundwater is very difficult to remediate, except in small defined areas and therefore
the emphasis has to be on prevention. This is based on protection of sensitive aquifers,
control of discharges and releases and provision of drainage and sanitation systems to
avert pollution discharges. For small areas of highly polluted groundwater, it may be
possible to pump out, treat, and recharge (which is expensive); to treat in-situ – for some
contaminants; or to try to contain the pollution “plume”, physically or chemically.
However, there is continuing degradation of important groundwater aquifers in many
countries, the serious impacts of which are only slowly being appreciated.


1 “What is Groundwater?” U.S. Geological Survey. U.S. Department of the Interior. Last Updated
September 1, 2005. Available at http://pubs.usgs.gov/of/1993/ofr93-643/
2 The World Bank. “Water Resources Management: Groundwater” Accessed on September 15,
2008. Available at http://go.worldbank.org/6YTISD5KR0
3 ibid
4 “Sources of Groundwater pollution.” Lenntech: water treatment and air purification. Available at
http://www.lenntech.com/groundwater/pollution-sources.htm
5 “Sources of Groundwater pollution.” Lenntech: water treatment and air purification. Available at
http://www.lenntech.com/groundwater/pollution-sources.htm
6 “Groundwater pollution.” Marquette County Community Information System. Available at http://
www.mqtinfo.org/planningeduc0020.asp
7 Pearce, Fred. “Arsenic in the Water.” The Guardian. February 19, 1998. Available at: http://
www.lifewater.ca/887805655-arsenic.htm
8 Harter, Thomas. “Groundwater Quality and Groundwater Pollution” ANR Publication 8084,
Division of Agriculture and Natural Resources, University of California at Davis 2003. Available at
http://groundwater.ucdavis.edu/Publications/Harter_FWQFS_8084.pdf

				
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posted:3/17/2010
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