Arsenic Species (III, V) Distribution in Wisconsin Groundwaters: Field Measurements and Prediction Using Multivariate Analysis of Geochemical Data Prediction Using Multivariate Analysis of Geochemical Data

Background/Need: The environmental fate, toxicity, and mitigation strategies of arsenic are dependent upon its complex chemical speciation. Thus
critical information pertinent to identification of arsenic release mechanisms can be obtained through studies of arsenic speciation (especially oxidation state). Only trace quantities of organic arsenic species are found in WI groundwaters, thus the study focused on the more toxic and dominant inorganic forms of arsenic (arsenate and arsenite). Arsenate (As V) is the oxidized form of arsenic and is anionic at relevant groundwater pH ranges. Arsenite (AsIII) is the reduced form of arsenic and is uncharged under typical groundwater pH ranges. Arsenate, because of its charge, has a stronger capacity to sorb to aquifer surfaces and is therefore less mobile in groundwater systems than the reduced (arsenite form).

Objectives: The four principal goals of this study were to:

1. 1. 1. Perform a meta-analysis of existing groundwater data for covariation of geochemical analytes and test their association with total and speciated arsenic concentrations using multivariate statistical methods.
      2. Determine the concentrations of arsenic and primary redox-active species [Fe(II/III), nitrate/ammonia, sulfate/sulfide, oxygen, DOC] in Wisconsin groundwaters.
      3. Quantify the occurrence and distribution of arsenic species (III and V) in Wisconsin groundwaters.
      4. Examine relationships between arsenic oxidation state speciation and aquifer geochemistry and test the hypothesis that arsenic speciation can be predicted from aquifer geochemistry.