7/1/2005 - 6/30/2007
- Martin Shafer, UW-Madison
- Kristie Ellickson, UW-Madison
- James Schauer, UW-Madison
There are widespread occurrences of arsenic concentrations in ground and drinking waters above the maximum contaminant level throughout Wisconsin. Ingestion of inorganic arsenic has been shown to be carcinogenic in the skin, lung and bladder as well as cause skin darkening and arsenic-related corns. Arsenic is a metalloid wih complex groundwater chemistry. It exists mainly in the inorganic form in groundwater and at two oxidation states, although low levels of methylated arsenic V species have been measured. Arsenate (AsV, H3AsO4) is the oxidized form of arsenic and is anionic at relevant groundwater pH ranges. Arsenite (AsIII, As(OH)3) is the reduced form of arsenic and is uncharged at relevant groundwater pH ranges. Arsenite is more toxic to humans and is retained more efficiently in human tissues. Arsenate has a stronger capacity to sorb to aquifer surfaces and is therefore less mobile in groundwater systems. Since mobility, toxicity and mitigation strategies vary with the speciation of arsenic, it is important to identify arsenic release mechanisms in a species-specific (III or V) manner. To this end we propose to perform a meta-analysis on extant groundwater data using multivariate statistical methods. In this analysis we will identify co-varying geochemical analytes and relate these factors of variables to likely arsenic release mechanisms. From this analysis, we intend to identify the most likely inorganic arsenic species (oxidation state III, V) for each identified arsenic release mechanism based on known geochemical mechanisms. Finally, we will directly measure arsenic speciation and important geochemical parameters in 50 of the previously analyzed sites to test our predictions. This is a useful tool for predicting mechanisms driving total arsenic mobilization as well as the most toxic form of arsenic which would assist in health-based decision making.