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Groundwater Arsenic Contamination in the United States

Groundwater Arsenic Contamination in the United States. GIS Term Project, EWRE Fall 2000 By Hazim Tugun. Outline. Background Objectives Mapping of data/findings related to As in the groundwater Preliminary Conclusions Future work. Background. A gray brittle semi-metal

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Groundwater Arsenic Contamination in the United States

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  1. Groundwater Arsenic Contamination in the United States GIS Term Project, EWRE Fall 2000 By Hazim Tugun

  2. Outline • Background • Objectives • Mapping of data/findings related to As in the groundwater • Preliminary Conclusions • Future work

  3. Background • 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).

  4. Background • 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.

  5. Background • 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.

  6. Objectives • 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.

  7. GW As data from USGS NAWQA

  8. GW As Mapping- Point Theme TAB-delimited ASCII text  .dbf  Event Theme

  9. GW As Mapping- Interpolated Grid Showing hot spots above EPA current 50 ppb limit

  10. Domestic, Public Supply and Recreational Uses of GW 40% of all the sampled GW

  11. Public supply > 50 ppb 1.4% of the public supply GW is above current EPA limit

  12. Counties – GW public supply > 50 ppb

  13. Health Effects- National Atlas Cancer Mortality Rate Data 50% of counties with GW supply > 50 ppb have the highest rates

  14. 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?

  15. 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.

  16. 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.

  17. ??? ???

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