Groundwater Uranium Origin and Fate Control in a River Valley Aquifer

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• 作者：Andre Banning ; Thomas Demmel ; Thomas R. R眉de ; Michael Wrobel
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：December 17, 2013
• 年：2013
• 卷：47
• 期：24
• 页码：13941-13948
• 全文大小：325K
• 年卷期：v.47,no.24(December 17, 2013)
• ISSN：1520-5851

文摘

Groundwater in a Quaternary gravel aquifer partly exhibits uranium (U) concentrations exceeding the new German drinking water limitation (22% of the samples >10 渭g L^鈥?). 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 渭g L^鈥? 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.