The occurrences of Ca2UO2(CO3)3 complex in Fe(II) containing deep groundwater at Forsmark, eastern Sweden
2017 (English)In: Procedia Earth and Planetary Science, ISSN 1878-5220Article in journal (Refereed) In press
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 175μg/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, 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.
Place, publisher, year, edition, pages
Ca-uranyl-bicarbonate complex, groundwater, uranium, luminescence spectrometry, 234U/238 1. Introduction U AR, reducing conditions
Research subject Geology
IdentifiersURN: urn:nbn:se:su:diva-135738OAI: oai:DiVA.org:su-135738DiVA: diva2:1048608
15th Water-Rock Interaction International Symposium, Évora, Portugal, 16 - 21 October 2016