Variations in U concentrations and isotope signatures in two Canadian lakes impacted by U mining: A combination of anthropogenic and biogeochemical processes

New Insights into Pb Isotope Fingerprinting of U-Mine Material Dissemination in the Environment: Pb Isotopes as a Memory Dissemination Tracer

“…Similar values have already been observed in the vicinity of U-sites highly contaminated by mining and milling activities. 4,25,26,31,57,58 Importantly, no correlation was observed here between the radiogenic Pb and the U content distributions. For instance, the U-rich C2-5 cm and C4-25 cm levels contain ∼50% of radiogenic Pb, while the same percentage was observed in other layers of the cores with lower U-contents.…”

Diagenetic formation of uranium-silica polymers in lake sediments over 3,300 years

“…1E). The relative behavior of 235 U and 238 U (expressed by δ 238 U) has been described for most chemical reactions (see the review by 39), suggesting that the dominant mechanism here is adsorption of U to colloidal biomass or minerals within the water column (44), and excluding U enrichment in the sediments by diffusion followed by reduction at the sediment-water interface, that would have induced a positive isotopic fractionation (5,45,46). Consequently, since U is correlated to organic carbon (SI Appendix, Fig.…”

“…Combining solid U speciation techniques (X-ray absorption spectroscopy) to high precision isotopic analyses (( 234 U/ 238 U) and δ 238 U), supported by electron microscopy observations, we provide direct evidence for diagenetic aging of noncrystalline U(IV) species in these natural lake sediments. In addition to the description of an original mineralogical transformation, our findings may have important implications for the understanding and longterm management of comparable U-contaminated sites, such as lacustrine sediments downstream U mines (2)(3)(4)(5)(6)(7)(8) and, to some extent, other anoxic environments such as aquifer sediments and peatlands (19)(20)(21)(22)(23)(24)30).…”

“…uranium | noncrystalline species | diagenetic aging | lake sediments | uranium isotopes U ranium (U) mining and milling activities since the midtwentieth century have resulted in the contamination of freshwater bodies (1), such as on-site pit lakes (2) including in some non-U mining districts (3), as well as lakes and reservoirs downstream U mines (4)(5)(6)(7)(8). In these water bodies, the sediments accumulated U because of the development of anoxic conditions that are known to favor U reduction and immobilization as poorly soluble tetravalent U(IV) (9,10).…”

Climate-driven fluxes of organic-bound uranium to an alpine lake over the Holocene

“…In comparison to marine settings, the uranium content of lake sediments is less documented and records more local variations in water oxygenation or U inputs from lake watersheds. Hence, most studies on lacustrine systems have focused on present-day processes of U accumulation at the sediment-water interface in pristine (Chappaz et al, 2010;Och et al, 2016) and U miningimpacted lakes (Dang et al, 2018;Stetten et al, 2018;Wang et al, 2019). Only a few studies have investigated the U distribution in lake sediments over long time scales as a tracer of paleoenvironmental conditions (Edgington et al, 1996;Goldberg et al, 2010;Whitlock et al, 2012;Yang et al, 2015).…”