Biogeochemical Mechanisms of Selenium Exchange between Water and Sediments in Two Contrasting Lentic Environments

• Published in: Environmental science & technology Vol. 45; no. 7; pp. 2605 - 2612
• Main Authors: Martin, Alan J, Simpson, Stephanie, Fawcett, Skya, Wiramanaden, Cheryl I. E, Pickering, Ingrid J, Belzile, Nelson, Chen, Y.-W, London, Jacqueline, Wallschläger, Dirk
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-04-2011
• Subjects: Applied sciences; Biogeochemistry; Carbon - analysis; Characterization of Natural and Affected Environments; Ecological and Environmental Phenomena; Environment; Exact sciences and technology; Fresh Water - chemistry; Geologic Sediments - chemistry; Hydrogen-Ion Concentration; Nitrogen - analysis; Oxidation-Reduction; Pollution; Recycling; Sediments; Selenium; Selenium - analysis; Selenium - chemistry; Selenium - metabolism; Spectrum analysis; Vegetation; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - metabolism; Sediment water interaction; XANES spectrometry; Pollutant behavior; Environmental factor; Lentic environment; Vegetation effect; Selenium Organic compounds; Interstitial water; Trace element; Biogeochemistry; Water pollution; Selenium; Speciation; Organic compounds
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es103604p

The biogeochemical mechanisms of Se exchange between water and sediments in two contrasting lentic environments were assessed through examination of Se speciation in the water column, porewater, and sediment. High-resolution (7 mm) vertical profiles of <0.45 μm Se species across the sediment-water interface demonstrate that the behavior of dissolved Se(VI), Se(IV), and organo-Se are closely linked to redox conditions as revealed by porewater profiles of redox-sensitive species (dissolved O2, NO3 −, Fe, Mn, SO4 2-, and ΣH2S). At both sites Se(VI) is removed from solution in suboxic near-surface porewaters demonstrating that the sediments are serving as diffusive sinks for Se. X-ray absorption near edge spectroscopy (XANES) of sediments suggests that elemental Se and organo-Se represent the dominant sedimentary sinks for dissolved Se. Dissolved Se(IV) and organo-Se are released to porewaters in the near-surface sediments resulting in the diffusive transport of these species into the water column, where between-site differences in the depths of release can be linked to differences in redox zonation. The presence or absence of emergent vegetation is proposed to present a dominant control on sedimentary redox conditions as well as on the recycling and persistence of reduced Se species in bottom waters.