HR: 10:55h
AN: B32A-03    [Abstracts]
TI: Biomineralization of Metallic Copper and Copper Sulfide Nanomaterials in a Flooded Soil: Impact on Contaminant Mobility
AU: * Weber, F
EM: faw@env.ethz.ch
AF: ETH Zurich - Institute of Biogeochemistry and Pollutant Dynamics, Universitaetstrasse 16, Zurich, 8092, Switzerland
AU: Voegelin, A
EM: voegelin@env.ethz.ch
AF: ETH Zurich - Institute of Biogeochemistry and Pollutant Dynamics, Universitaetstrasse 16, Zurich, 8092, Switzerland
AU: Kaegi, R
EM: kaegi@eawag.ch
AF: Eawag - Particle Laboratory, Ueberlandstrasse 133, Duebendorf, 8600, Switzerland
AU: Kretzschmar, R
EM: kretzschmar@env.ethz.ch
AF: ETH Zurich - Institute of Biogeochemistry and Pollutant Dynamics, Universitaetstrasse 16, Zurich, 8092, Switzerland
AB: Colloidal nanomaterials may enhance the mobility of strongly sorbing contaminants that are otherwise immobile in soils and sediments. We investigated the formation of biogenic nanomaterials in a contaminated wetland soil upon flooding and microbially-mediated soil reduction using microcosm experiments. Combining electron microscopy and X-ray absorption spectroscopy, we characterized the newly formed nanomaterials and evaluated their effect on the mobility of selected contaminants (Cu, Cd, Pb). In the pore water of the flooded soil, we observed the formation of <20 nm metallic Cu(0) nanocrystals associated with bacterial cells. The Cu(0) nanocrystals grew in size until the onset of microbial sulfate respiration, when Cu(0) started to transform into poorly crystalline hollow Cu sulfide structures on bacteria. Concurrently, we observed the precipitation of <40 nm Cu sulfide nanoparticles dispersed in the pore water. Both Cu sulfide hollow spheres and nanoparticles were apparently mobile and contained substantial quantities of Cd and Pb in addition to Cu, dominating their respective pore water speciation. Over extended periods of flooding, the colloids were slowly removed by deposition following apparent first-order kinetics. We have conducted additional experiments to elucidate the formation mechanism of the bacteria-associated nanomaterials observed. First evidence suggests that the biomineralization of the Cu(0) nanocrystals occurs when Cu(I) released by bacteria, likely exported by homeostasis proteins, disproportionates on the outer cell membrane. Their transformation into hollow structures upon reaction with sulfide is interpreted to result from inward diffusion of vacancies balancing outward diffusing Cu in a Kirkendall-like process. Our results demonstrate that the formation of mobile Cu sulfide colloids enhances Cu, Cd, and Pb mobility in the flooded soil. The findings thus point to a novel pathway for the translocation of chalcogenic contaminants from wetland soils to adjacent surface and groundwater bodies.
DE: 0419 Biomineralization
DE: 0432 Contaminant and organic biogeochemistry (0792)
DE: 0448 Geomicrobiology
DE: 0488 Sulfur cycling
DE: 0489 Trace element cycling (4875)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting