‘Two Major US Aquifers Contaminated by Natural Uranium’
Posted by feww on August 17, 2015
Natural Uranium Contamination in Major U.S. Aquifers Linked to Nitrate: Study
About 2 million people across the Great Plains and California reside above aquifer sites that are contaminated with natural uranium, mobilized by human-contributed nitrate, according to a new study by researchers at the University of Nebraska-Lincoln.
High Plains (HP) and Central Valley (CV) aquifers. The intensity of groundwater contamination via uranium (red) and nitrate (blue) is highlighted in two major aquifers and other sites across the United States. Credit: University of Nebraska-Lincoln
Abstract: Groundwater geochemical data collected from two major U.S. aquifers, High Plains (HP) and Central Valley (CV), revealed naturally occurring groundwater uranium (U) exceeding the U.S. Environmental Protection Agency maximum contaminant level (MCL = 30 μg/L) across 22375 km2 where 1.9 million people live. Analysis of geochemical parameters revealed a moderately strong correlation between U and nitrate, a common groundwater contaminant, as well as alkalinity and calcium [Spearman’s rho (ρ) ≥ 0.30; p < 0.001]. Nitrate is recognized to alter U solubility by oxidative dissolution of reduced U(IV) minerals. Approximately 78% of areas where U concentrations were interpolated above the MCL were correlated to the presence of nitrate (Pearson’s r ≥ 0.5; p < 0.05). Shallow groundwater was determined to be the most susceptible to co-contamination (HP, ρ = 0.46; CV, ρ = 0.52). Together, these results indicate that nitrate, a primary contaminant, should be considered as a factor leading to secondary groundwater U contamination in addition to the recognized role of alkalinity and calcium.
Excerpts from the Introduction: “Uranium (U) contamination of groundwater has been primarily associated with anthropogenic activities such as mining, milling, nuclear testing, and disposal of spent nuclear fuel. However, groundwater U concentrations across the United States exceed the U.S. Environmental Protection Agency (EPA)… The High Plains (HP) and Central Valley (CV) aquifers, two of the largest and most productive aquifers in the world, are among aquifers with high concentrations of dissolved U in groundwater… In addition to being an important source of drinking water, these aquifers are also mined to irrigate 56700 km2 of cropland accounting for 1/6 of all U.S. agricultural annual revenue. Drought has placed an increased reliance on groundwater, impacting not only quantity but also degradation of groundwater quality.
Full paper posted at http://pubs.acs.org/doi/abs/10.1021/acs.estlett.5b00174
Jason Nolan and Karrie A. Weber
Department of Earth and Atmospheric Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska 68588-0340, United States
‡ School of Biological Sciences, University of Nebraska—Lincoln, Lincoln, Nebraska 68588-0118, United States
Environ. Sci. Technol. Lett., 2015, 2 (8), pp 215–220
Publication Date (Web): July 31, 2015
Copyright © 2015 American Chemical Society
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