HR: 14:25h
AN: B12D-04    [PDF]
TI: The Effects of Microbial Surface Attachment on the Dissolution Kinetics of Plagioclase Feldspar
AU: * Conrad, P G
EM: conrad@jpl.nasa.gov
AF: Jet Propulsion Lab, California Institute of Technology, M/S: 183-301, 4800 Oak Grove Dr., Pasadena, CA 91109 United States
AU: Luttge, A
EM: aluttge@mail.rice.edu
AF: Dept. of Earth Science, Rice University, MS-126, 6100 Main Street, Houston, TX 77251-1892
AB: The rate of mineral dissolution can be influenced by the attachment of microbes to a mineral surface. We have previously reported the effect of Shewanella oneidensis (MR-1) biofilm formation on the dissolution kinetics of calcite, dolomite and rhodochrosite, where the organisms completely control dissolution kinetics by recognizing high-energy surface sites overlying screw dislocations and attaching to those sites, inhibiting the opening of etch pits and significantly retarding dissolution. Note that calcite and dolomite are not known to possess nutritional significance for MR-1; and while this facultative anaerobe can reduce both Mn and Fe, our experiments were all conducted with aerobic organisms. In recent experiments, we have observed that this inhibitory effect requires the cells to be alive; dead cells do not prevent the opening of etch pits and subsequent dissolution of the carbonate crystals under conditions in which they would otherwise dissolve. Now we report on the effects of the MR-1 biofilm formation on the more slowly dissolving end-member plagioclase feldspar, anorthite (CaAl$_{2}$Si$_{2}$O$_{8}$). The influence of organisms on feldspar weathering rates, in particular the Ca-rich plagioclases, has been the subject of considerable interest because of their crustal abundance and role in the maintenance of atmospheric CO$_{2}$. (Schwartzman and Volk, 1989, Schwartzman, 1995 and others). Our methodology of direct observation of microbial attachment, biofilm propagation and effects on mineral dissolution provides a quantitative measure of biological contribution to weathering of single crystal minerals for subsequent use in biogeochemical modeling.
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 4805 Biogeochemical cycles (1615)
DE: 4825 Geochemistry
DE: 4840 Microbiology
SC: Biogeosciences [B]
MN: 2003 Fall Meeting