GEOC 152 |
| F. Grant Ferris1, R. Martinez1, and K. Pedersen2. (1) Department of Geology, University of Toronto, 22 Russell Street, Toronto, ON M5S 3B1, Canada, (2) University of Göteborg, Göteborg, Sweden |
| Bacteriogenic iron oxides (BIOS) composed of 2-line ferrihydrite embedded with intact and fragmented bacteria were digested using a sequential technique. Hydroxylamine was used to remove the hydrous ferric oxide fraction. Subsequent nitric acid and hydrogen peroxide digestion removed the sample’s bacterial component. On a dry weight basis, the BIOS consisted of 64.6 + 1.8 % ferrihydrite, and 34.5 + 1.8 % bacterial cell organic matter. ICP-AES analysis showed enrichment of Al, Cu, Cr, Mn, Sr and Zn in the solid versus aqueous phase (log 10 Kd values ranged from 1.9 to 4.2). Within the solid phase Al (70%), Cu (78%) and Zn (78%) had a strong preference for the bacterial fraction whereas Cr (60%), Mn(100%) and Sr (79%) were associated with ferrihydrite. Acid-base tritration data from the BIOS and bacteria were fitted using FOCUS pKa spectroscopy to assess surface reactivity. The bacterial pKa values were similar to those of previous studies for intact and fragmented bacterial cells. The BIOS pKa spectrum was deconvoluted to remove overlapping binding site contributions from the bacteria fraction. The result was similar to the discrete MUSIC spectrum of lepidocrocite, where all three pKa values reported were recovered. Bacterial and iron oxide fractions contributed 37.3, 5.5, and 57.1, and 18.3, 34.9, and 46.7 % of their normalized total site densities withn pKa ranges of 4.18 to 4.80 + 0.37, 6.53 to 7.89 + 0.45, and 9.51 to 9.75 + 0.68 respectively. Corresponding values of 22.6, 33.3 and 44 % for the BIOS composite indicated a net decrease in bacterial site density contributions, suggesting the presence of iron oxide and bacterial surface chemical interactions. |
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Microbially Mediated Manganese and Iron Oxidation in the Biosphere
1:45 PM-6:20 PM, Wednesday, March 31, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |