Bacteriogenic Mn oxides: Structure and reactivity with metal cations

COLL 460

Mario Villalobos, marvilla@igiris.igeograf.unam.mx, Environmental Bio-Geochemistry Group, Instituto de Geografía, UNAM, LAFQA, National Autonomous University of Mexico (UNAM), CU México 04510, Mexico, Brandy Toner, btoner@whoi.edu, Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, MS 52, 266 Woods Hole Rd., Woods Hole, MA 02543, and Garrison Sposito, gsposito@nature.berkeley.edu, Division of Ecosystem Sciences, University of California, 137 Mulford Hall #3114, Berkeley, CA 94720-3114.
Bacteriogenic Mn oxides, ubiquitous in terrestrial and marine environments, play critical roles in a broad variety of biological and chemical processes, ranging from photosynthesis to the attenuation of metal contaminants. Pseudomonas putida MnB1, a biofilm-forming bacteria that oxidizes Mn(II) during the stationary phase of growth, has been studied by us and our collaborators as a model organism for biogenic Mn oxide formation in aquatic systems. The oxide produced by MnB1 is a poorly-crystalline birnessite whose negative charge and nanoparticle size lead to an extraordinary adsorptive capacity for metal cations, a property that we and our collaborators have confirmed for the priority metal pollutants, Pb(II) and Zn(II), using X-ray absorption spectroscopy. Adsorbed species were identified at two binding sites, octahedral vacancies in the structure and particle edges. Studies of Zn adsorption in the presence of the biofilm showed that the organic material did not adsorb Zn until all Mn oxide sites were filled. That the biofilm was unable to mask adsorption by the embedded Mn oxide is highly relevant to the natural attenuation of metals.

 

Environmental Interfaces
8:30 AM-12:40 PM, Wednesday, 13 September 2006 Sir Francis Drake -- Empire Room, Oral

Division of Colloid & Surface Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006