Groundwater uranium origin and fate control in a river valley aquifer

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Date
2013-10-10
Authors
Banning, Andre
Demmel, Thomas
Rüde, Thomas R
Wrobel, Michael
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American Chemical Society
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Abstract
Groundwater in a Quaternary gravel aquifer partly exhibits uranium (U) concentrations exceeding the new German drinking water limitation (22% of the samples >10 μg L–1). This study assesses relevant U reservoirs and hydrogeochemical processes responsible for U transfer between them. A large data set of solid materials (sediments and soils, 164 samples total) and groundwater (114 samples total) characteristics was created in terms of geo- and hydrochemistry, mineralogy, U microdistribution, and mobilization potential. Results show that U primarily derived from lignitic inclusions in Tertiary sediments is transported to and accumulated (complexation to organic substance and UO2 precipitation) in lowland moor peats of the river valley grown on the aquifer gravels. The alkaline character of the system predefines a hydrogeochemical framework fostering U mobility. Elevated concentrations (up to 96 μg L–1 U) occur downstream of the moor areas and under Mn/NO3-reducing groundwater conditions. Oxic and stronger reduced settings are rather little affected. Supporting previous laboratory studies, this suggests enhanced U mobility in the presence of nitrate also in the field scale. While no anthropogenic U input was detected in the study area, agricultural usage of the moor areas triggers geogenic U release via nitrate fertilization, surface peat degradation, and erosion.
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Keywords
Geological materials , Soils , Uranium , Aquifers , Groundwaters
Citation
Banning, A., Demmel, T., Rüde, T. R. and Wrobel, M. (2013) ‘Groundwater Uranium Origin and Fate Control in a River Valley Aquifer’, Environmental Science & Technology, 47 (24), pp. 13941-13948. doi: 10.1021/es304609e
Copyright
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science and Technology, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/es304609e