HR: 0800h
AN: B11B-0402    [Abstracts]
TI: Mercury Release from Soils and Sediments in the Sacramento River Watershed
AU: * Suess, E
EM: elke_suess@gmx.de
AF: Technische Universitat Bergakademie Freiberg, Gustav-Zeuner Str. 12, Freiberg, 09599, Germany
AU: Aiken, G R
EM: graiken@usgs.gov
AF: US Geological Survey, 3215 Marine Street, Boulder, CO 80303, United States
AU: Ryan, J N
EM: joe.ryan@colorado.edu
AF: University of Colorado, Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, CO 80309-0428, United States
AU: Gasper, J D
EM: jgasper@integral-corp.com
AF: US Geological Survey, 3215 Marine Street, Boulder, CO 80303, United States
AB: Mercury released into water from soils and sediments contaminated by cinnabar (HgS) and gold mining is a major environmental concern in the Sacramento-San Joaquin Delta, California. To better understand the conditions resulting in Hg solubilization from these contaminated materials, six soil and sediment samples from the Coastal Range and the Sierra Nevada were subject to batch leaching experiments under varying conditions. Sequential extraction analyses of the soils and sediments indicated that most of the mercury was present as (1) Hg as HgS in samples affected by HgS mining, which occurred in the Coastal Range, (2) Hg bound to metal oxides in a background serpentine soil from the Coastal Range, (3) Hg bound to sediment organic matter in lake sediments from Camp Far West Reservoir, and (4) elemental Hg in a sluice sediment from Starr Tunnel. The effects of pH, ionic strength, inorganic ions (chloride, calcium), simple organic ligands (mercaptoacetic acid, salicylic acid, EDTA), and dissolved organic matter (DOM) on the release of Hg were investigated. Leaching experiments confirmed that the water-soluble fraction was small (9 to 350 ng/L) compared to the amounts of Hg associated with the solid samples (1 to 36 μg/g total mercury); however, these concentrations would be sufficient to result in increased methylation by sulfate-reducing bacteria in wetland systems. An increase in mercury release was observed with (1) increasing pH due to solubilization of soil organic matter, (2) decreasing ionic strength due to colloid stabilization, and (3) increasing chloride concentration due to the formation of complexes with mercury. The presence of calcium strongly inhibited mercury release. Among the organic ligands, mercaptoacetic acid, which binds Hg very strongly, was the most effective at solubilizing Hg. DOM, in the form of organic matter isolates, was also very effective at solubilizing Hg for all samples except the lake sediment sample, with the most aromatic organic matter isolates being the most reactive. The results of this study indicate that DOM is very important in the mobilization of Hg from soils and sediments and will influence the dissolution, mobilization, and bioavailability of mercury in wetlands associated with the Sacramento-San Joaquin Delta area.
DE: 0409 Bioavailability: chemical speciation and complexation
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0478 Pollution: urban, regional and global (0345, 4251)
DE: 0489 Trace element cycling (4875)
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting