title: Geochemical control on uranium(IV) mobility in a mining-impacted wetland.
abstract: Wetlands often act as sinks for uranium and other trace elements. Our previous work at a mining-impacted wetland in France showed that a labile noncrystalline U(IV) species consisting of U(IV) bound to Al-P-Fe-Si aggregates was predominant in the soil at locations exhibiting a U-containing clay-rich layer within the top 30 cm. Additionally, in the porewater, the association of U(IV) with Fe(II) and organic matter colloids significantly increased U(IV) mobility in the wetland. In the present study, within the same wetland, we further demonstrate that the speciation of U at a location not impacted by the clay-rich layer is a different noncrystalline U(IV) species, consisting of U(IV) bound to organic matter in soil. We also show that the clay-poor location includes an abundant sulfate supply and active microbial sulfate reduction that induce substantial pyrite (FeS2) precipitation. As a result, Fe(II) concentrations in the porewater are much lower than those at clay-impacted zones. U porewater concentrations (0.02-0.26 μM) are also considerably lower than those at the clay-impacted locations (0.21-3.4 μM) resulting in minimal U mobility. In both cases, soil-associated U represents more than 99% of U in the wetland. We conclude that the low U mobility reported at clay-poor locations is due to the limited association of Fe(II) with organic matter colloids in porewater and/or higher stability of the noncrystalline U(IV) species in soil at those locations.
authors: Ecole Polytechnique Fédérale de Lausanne (EPFL) - Environmental Microbiology Laboratory (EML) EPFL-ENAC-IIE-EML, Station 6, CH-1015 Lausanne, Switzerland.
authors: Yuheng
authors: Y
authors: Wang
authors: Alexandre
authors: A
authors: Bagnoud
authors: Elena
authors: E
authors: Suvorova
authors: Eric
authors: E
authors: McGivney
authors: Lydie
authors: L
authors: Chesaux
authors: Vannapha
authors: V
authors: Phrommavanh
authors: Michael
authors: M
authors: Descostes
authors: Rizlan
authors: R
authors: Bernier-Latmani
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D003102:Colloids / Q000737:chemistry; D005602:France; D007501:Iron / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008903:Minerals / Q000032:analysis / Q000737:chemistry; D008906:Mining; D016062:Porosity; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry; D013431:Sulfates / Q000378:metabolism; D014501:Uranium / Q000032:analysis* / Q000737:chemistry*; D014867:Water / Q000032:analysis / Q000737:chemistry; D053833:Wetlands
chemical_list: D003102:Colloids; D008903:Minerals; D012987:Soil; D012989:Soil Pollutants; D013431:Sulfates; D014867:Water; D014501:Uranium; D007501:Iron