The Relationship Between Deuterium Excess and Uranium Groundwater Concentrations in Whitehall, Montana

Authors

  • Daniel P. Wight Environmental Science Department, University of Montana Western, Dillon, MT 59725
  • Eric G. Dyreson The Mathematics Department, University of Montana Western, Dillon, MT 59725

Abstract

Uranium can become elevated in the environment and pose a human health risk to water resources. Therefore, it is important to understand the origin, transport and concentration of uranium in the environment. With this exploratory study we propose that deuterium (δ2H) excess may be a viable way to study uranium groundwater concentrations that originate from the surface. The Boulder Batholith of southwestern Montana has been associated with varying levels of uranium. The Whitehall, MT area includes the Boulder Batholith as a geologic unit. We collected 23 water samples and compiled data from a study done by the United States Geological Survey (USGS) within the area of Whitehall, MT. With a linear regression we show that there is a significant negative relationship between deuterium excess and uranium water concentrations. As expected we showed that there is a significant positive, linear relationship between uranium water concentrations and nitrate water concentrations. As expected we also showed that there is a significant positive, linear relationship between calcium carbonate and uranium groundwater concentrations for the compiled USGS data. The results of a Wilcoxon rank sum test showed that median uranium concentration for wells close to ponds is 14.5 μg/L higher for our data added to the USGS data. These results may be consistent with a model that involves insoluble uranium being transported in suspension and settling out in ponds where an influx of nitrates and/or carbonates react to produce higher concentrations of water-soluble forms of uranium. We suggest that the relationship found between uranium concentration and deuterium excess in water samples may be related to the higher rates of evaporation in ponds. Thus, in this specific hydrologic environment of valley ponds close to the Boulder Batholith source, deuterium excess may serve to help predict levels of uranium concentrations.

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Published

2019-12-31

Issue

Section

Environmental Sciences and Engineering [Articles]