Examining Spatial Distributions of Arsenic and Uranium in Private Drinking Water Wells Along the Connecticut River

Authors: Bryce Mase*, , Meredith Metcalf, Eastern Connecticut State University
Topics: Geographic Information Science and Systems
Keywords: arsenic, groundwater, uranium, fractured rock
Session Type: Poster
Day: 4/4/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

Previous studies of New England associate high concentrations of arsenic and uranium in groundwater with the natural conditions of the bedrock. However, there is no statistical evidence to suggest this is due to natural processes. The Hebron Gneiss, Monson Gneiss, Middletown Formation, and the Brimfield Schist are known to be a concern across Connecticut as many wells intersecting these formations experience exceedances. One-hundred domestic wells within the Deep River Quadrangle were analyzed to further examine the relationship between concentrations of arsenic and uranium in groundwater and the underlying geology. This Quadrangle intersects several of the aforementioned units known to be a concern. Arsenic was present in 7% of the wells sampled yet only 4% exceeded the EPA drinking water standard. Although the Hebron Gneiss has the greatest spatial extent and most samples with arsenic present were in this formation, the average arsenic concentration was less than < 10 μg/L. The greatest average arsenic concentration exceeding the EPA drinking water standard was in the Canterbury Gneiss with only 1 well. The many wells with uranium were randomly distributed but the highest average uranium concentrations were observed in the upper member of the Middletown Formation and Monson Gneiss which corresponds to previous studies. The small percentage of wells contaminated by arsenic and the lack of a correlation with rock type or other water quality parameters indicative of groundwater source characteristics demonstrates the complexity of fractured rock aquifers and the need for detailed well characteristics to better understand fracture flow conditions.

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