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Title:Variations in U concentrations and isotope signatures in two Canadian lakes impacted by U mining: A combination of anthropogenic and biogeochemical processes
Authors:Wang, Wei (Author)
Dang, Duc Huy (Author)
Novotnik, Breda (Author)
Phan, Thai T. (Author)
Evans, R. Douglas (Author)
Files:This document has no files. This document may have a phisical copy in the library of the organization, check the status via COBISS. Link is opened in a new window
Language:English
Work type:Not categorized (r6)
Tipology:1.01 - Original Scientific Article
Organization:UNG - University of Nova Gorica
Abstract:Temporal and vertical variations in uranium (U) concentrations and U isotope (δ238U, ‰) signatures were examined in sediment cores collected seven times over a one year period, from two lakes in Ontario, Canada, which are contaminated with U by historical mining activities. Bow Lake is holomictic, experiencing seasonal anoxia, while the sediments of meromictic Bentley Lake are permanently anoxic. Average annual peak concentrations of U in Bow Lake subsurface sediments were approximately 300 μg L−1 and 600 μg g−1 in porewater and bulk sediments, respectively. Similar ranges of concentrations (900 μg L−1 and 600 μg g−1, respectively) were observed in Bentley Lake sediments. The exceedingly high levels of U observed in the porewaters of both lakes, as well as the seasonal variability in U levels, challenge the traditional paradigm regarding U chemistry, i.e., that reduced U(IV) should be insoluble under anoxic conditions. The average annual δ238U ‰ values at the sediment-water interface of both lakes were similar (i.e., 0.47 ± 0.09‰ and 0.50 ± 0.16‰, relative to IRMM-184). The deep sediments in both Bentley Lake and Bow Lake record U isotope composition with a typical fractionation of 0.6‰ relative to the surface water, confirming authigenic U accumulation, i.e., negligible contribution of particulate material from the tailings. Also, the δ238U values in porewater have an average offset of ca. −0.1‰ relative to bulk sediments in anoxic zones and are reversed in the oxic sediment layer.
Keywords:Uranium Isotope composition Uranium tailings Biogeochemical cycling Redox chemistry
Year of publishing:2019
Number of pages:58-67
Numbering:506, 2019
COBISS_ID:5460987 Link is opened in a new window
URN:URN:SI:UNG:REP:BBQZTVK6
DOI:https://doi.org/10.1016/j.chemgeo.2018.12.029 Link is opened in a new window
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Title:Chemical Geology
Year of publishing:2019

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