The Occurrences of Ca₂UO₂(CO₃)₃ Complex in Fe(II) Containing Deep Groundwater at Forsmark, Eastern Sweden

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• 作者：E.-L. Tullborg^a ; ^{evalena@terralogica.se} ; J. Suksi^b ; G. Geipel^c ; L. Krall^d ; L. Auqué ; ^e ; M. Gimeno^e ; I. Puigdomenech^d
• 关键词：Ca-uranyl-bicarbonate complex ; groundwater ; uranium ; luminescence spectrometry ; 234U/238U AR ; reducing conditions
• 刊名：Procedia Earth and Planetary Science
• 出版年：2017
• 出版时间：2017
• 年：2017
• 卷：17
• 期：Complete
• 页码：440-443
• 全文大小：1254 K
• 卷排序：17

文摘

Elevated U concentrations, most evident in a section ∼500 mbsl, have been measured in deep Fe(II)-containing groundwater at Forsmark, eastern Sweden and have prompted detailed geochemical and isotopic investigations. The highest U contents (up to 175 μg/L) are associated with HCO3− of 120-135 mg/L and Ca2+ of 900-1050 mg/L. Geochemical modelling shows that elevated dissolved U can be stabilized by Ca-uranyl-carbonate complexes. Indeed, time resolved luminescence spectrometry confirmed the Ca2UO2(CO3)30 complex, which is identified in deep reducing groundwater for the first time. U isotopes have been monitored in several sections with high U, and show stable but fracture specific activity ratios (ARs) around 1.5 to 2, although the U concentration varies. This is explained by mobilization of a solid phase with the same AR present in the fracture system close to the sampled sections. The AR >1 in this solid phase indicates a Quaternary age.