Role of microbial Mn oxide nanoparticles in Zn attenuation in mine-contaminated streams

GEOC 130

Christopher C. Fuller1, John R. Bargar, bargar@slac.stanford.edu2, Yuji Arai, yarai@usgs.gov3, Samuel M. Webb, samwebb@slac.stanford.edu2, and Myriam Perez De la Rosa, myrperes@slac.stanford.edu2. (1) Water Resources Division, U.S. Geological Survey, 345 Middelfield Rd, Menlo Park, CA 94025, (2) Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road, MS 69, Menlo Park, CA 94025, (3) US Geological Survey, 345 Middlefield Rd. MS 465, Menlo Park, CA 94025
Nanolayered Mn oxide coatings of streambed sediments from two circum-neutral pH mine-contaminated streams were characterized using a suite of chemical, spectroscopic, and microscopic techniques to elucidate the mechanisms by which metal contaminants, e.g. Zn, are sorbed and attenuated. At Pinal Creek, AZ, extensive Mn oxide grain coatings are dominated by nanoparticulate Ca-bearing c-disordered hexagonal birnessite (10-Å phyllomanganate) consistent with biogenic origin. TEM images show lateral sheets (100-200 nm) with layer thicknesses of <3 nm. Zn was found to be primarily associated with the birnessite coatings and structurally bound to octahedral vacancies of the hexagonal birnessite, consistent with the observed limited reversibility of sorbed Zn. Dissolution of the host phases likely is required for subsequent re-release of Zn. Speciation of Zn sorbed on microbial Mn oxides forming in High Ore Creek, MT, will be discussed for comparison because of much higher sorbed Zn (Zn/Mn 0.3 to 0.6 molar).
 

The Structure and Reactivity of Nanoparticles in the Environment
9:00 AM-12:00 PM, Thursday, 14 September 2006 Moscone Center -- Room 262, Oral

Division of Geochemistry

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