Date of Graduation

7-2015

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor

Phillip D. Hays

Committee Member

Ralph K. Davis

Second Committee Member

Celina Suarez

Keywords

Earth sciences; Bauxite; Bauxite, ar; Geochemistry; Groundwater; Metal mobilization; Water quality

Abstract

The Wilcox Aquifer of Bauxite, AR contains bauxite ore deposits that may contribute heavy metals to groundwater. Twenty-four wells were sampled for aluminum, iron, manganese, zinc, lead, barium, nitrate, sulfate, sodium, alkalinity, calcium, magnesium, chloride, pH, total organic carbon, and total dissolved solids. A Wilcoxon Rank-Sum compared the similarity of the three geographic areas covered in the study. All parameters for wells in Bauxite and Sardis failed to reject the null hypothesis, signifying that wells all occupy the Saline Formation. 2/3rds of the parameters from BFI261 and the Bauxite region did not agree, suggesting the two areas do not occupy the same unit.

Groundwater in Bauxite is a sodium bicarbonate-type with a pH range of 3.12-7.91 and large concentrations of iron and manganese alongside low concentrations of other ions. Nitrate reduction, iron reduction, cation exchange with clays, and low pH are the primary controls on dissolved species concentrations. Trends between dissolved metals, versus pH, and sulfate were similar. Despite low solubility, large concentrations of aluminum are present in waters around bauxite mines, suggesting that high aluminum concentrations for MW-4D, MW-9D, UNKN1 and UNKN3 represent bauxite deposits. Median iron concentration was 0.194 mg/L with values up to 15.3 mg/L in private wells. Median aluminum concentration was 2 µg/L, but increased up to 330 µg/L. Toxic concentrations of lead, antimony, and cadmium were limited to BFI261. Low sulfate concentrations outside BFI261 suggest that acid mine drainage is not present and low pH indicates that bauxite tailings do not play a major role in heavy metal concentrations.

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