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The biogeochemical behaviour of selenium in two lentic environments in the Elk River Valley, British Columbia Martin, Alan J.; Wallschläger, Dirk; London, Jacqueline; Wiramanaden, Cheryl I. E.; Pickering, Ingrid J.; Belzile, Nelson; Chen, Yu-Wei; Simpson, Stephanie
The biogeochemical behaviour of selenium (Se) in two lentic environments (Goddard Marsh (GM) and Fording River Oxbow (FRO)) was assessed through detailed examination of Se speciation in bottom water, porewater and sediment components. The depositional environments at GM and FRO differ with regards to organic matter content, organic matter sources (as revealed by C:N ratios) and redox character. X-ray absorption near edge spectral (XANES) data suggest that elemental Se and organo-Se represent the dominant hosts for Se at GM and FRO. At both sites, the vertical distributions of dissolved Se species in porewater are closely linked to the profiles of redox-sensitive metabolites. Porewater profiles indicate that the sediments at GM and FRO are serving as diffusive sinks for Se through in situ adsorption/precipitation of Se in suboxic horizons. Although the sediments at both sites serve as net sinks for dissolved Se, interfacial peaks in dissolved selenite (SeIV) and organo-Se demonstrate these species are recycled back into the water column. The conditions present at GM are more favourable for the recycling of reduced Se species. Such observations can be linked to subtle differences in redox conditions as illustrated by profiles of redox-sensitive species (dissolved NO₃-, Fe, Mn, SO₄²- and ΣH₂S). These differences have important implications to both the recycling of reduced Se species into the water column and Se uptake by aquatic biota. Implications with regards to Se management, bioremediation and biologically availability (food chain transport) are discussed.
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