Accumulation, release, and solubility of arsenic, molybdenum, and vanadium in wetland sediments.
This study was undertaken to determine the fate of As, Mo, and V (trace elements, TEs) in the sediments of a constructed wetland in use for the remediation of potentially toxic trace element-contaminated agricultural drainwater. After three years of wetland operation, sediment cores were collected to determine changes in TE concentrations as a function of depth and the effects of varying water column depth. All TE concentrations were highest in the top 2 to 4 cm and decreased with depth. Molybdenum accumulated in the wetland sediments, up to levels of 32.5 +/- 4.6, 30.2 +/- 8.9, and 59.3 +/- 26.1 mg kg(-1) in the top 1 cm of sediment at water depths of 15, 30, and 60 cm, respectively. In the top 2 cm of sediment, As accumulated (28.2 +/- 3.0 mg kg(-1)) only at the 60-cm water depth. Below 2 cm, as much as 10 mg kg(-1) of As was lost from the sediment at all water depths. In most cases, V concentrations decreased in the sediment. In this wetland system, the lowest redox potentials were found near the sediment surface and increased with depth. Thus, in general As, Mo, and V concentrations in the sediment were highest under more reducing conditions and lowest under more oxidizing conditions. Most of the accumulated Mo (73%) became water soluble on drying of samples. This has important implications for systems undergoing changes in redox status; for instance, if these wetland sediments are dried, potentially large amounts of Mo may be solubilized.
Fox
Patricia M
PM
Department of Environmental Science, Policy, and Management-Ecosystem Sciences, 151 Hilgard Hall, University of California, Berkeley, CA 94720-3110, USA.
Doner
Harvey E
HE
D001151:Arsenic / Q000032:analysis; D003247:Conservation of Natural Resources; D005618:Fresh Water / Q000032:analysis*; D019015:Geologic Sediments / Q000032:analysis*; D006801:Humans; D019216:Metals, Heavy / Q000032:analysis*; D008982:Molybdenum / Q000032:analysis; D012995:Solubility; D014639:Vanadium / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*
D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D014639:Vanadium; D008982:Molybdenum; D001151:Arsenic