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Groundwater Arsenic Groundwater Arsenic Contamination in the United Contamination in the United StatesStates
GIS Term Project, EWRE
Fall 2000
By Hazim Tugun
OutlineOutline
Background Objectives Mapping of data/findings related to As in
the groundwater Preliminary Conclusions Future work
BackgroundBackground
A gray brittle semi-metal Naturally exists throughout the earth’s crust
(often as Arsenic Sulfide, Metal Arsenates or Arsenites).
Has many oxidation states, As(III) or As(V).
BackgroundBackground
Main sources: Natural: From dissolution of naturally existing
minerals/ores or soils, upflow of geothermal water.
Man-made: Industrial effluents, copper smelting, atmospheric deposition.
Adsorption-desorption, precipitation-dissolution with other environmental factors determine fate/transport in water.
BackgroundBackground Human exposure via food, water and air. Regulated under EPA Drinking Water
Standards: 50 ppb current limit 5 ppb proposed.
Acute or chronic health effects: Skin lesions, skin, bladder, other internal
cancers, upon prolonged exposures. Poisoning / death can result upon ingestion of
60 ppm in drinking water.
ObjectivesObjectives Create a map to show the geospatial distribution
of groundwater Arsenic concentrations in the United States.
Use this distribution as a foundation to make general characterizations, if possible, of groundwater arsenic contamination with respect to: Variations in the magnitude of contamination. Possible sources of contamination. Health effects.
GW As data from USGS NAWQA
GW As Mapping- Point ThemeTAB-delimited ASCII text .dbf Event Theme
GW As Mapping- Interpolated GridShowing hot spots above EPA current 50 ppb limit
Domestic, Public Supply and Recreational Uses of GW
40% of all the sampled GW
Public supply > 50 ppb1.4% of the public supply GW is above current EPA limit
Counties – GW public supply > 50 ppb
0
200
400
600
800
1000
1200
1400
Ars
enic
Con
c. (
ppb)
1
Counties with Highest Max. GW Arsenic Conc.
Churchill / NV
Washington /ID
Worcester / MA
Yavapai / AZ
San Bernardino / CAEPA LIMIT = 50 ppb
Health Effects- National Atlas Cancer Mortality Rate Data50% of counties with GW supply > 50 ppb have the highest rates
Preliminary Conclusions Western parts of the US seem to have
higher GW As concentrations. May be due to more natural sources than
man-made sources. Will become more clear when sources are
looked at. Exposure to As in GW from public
supply > EPA limit is about 1.5%. Significant?
Preliminary Conclusions Health data is not very helpful in seeing
patterns. Inadequate specific data in terms of the
causes of cancer. Definitely needs further research / detailed epidemiological data.
Probably, other factors, such as simply smoking, wipes out the effects that may be observed just due to exposure to low levels of As in GW.
Future Work
Look at more health data. Incorporate possible sources of As
contamination in the GW of US. Soils/Mineral Data from SSURGO. EPA Toxic Release Information System.
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