GEOC 41 |
| Ashaki A. Rouff1, Richard J. Reeder1, and Nicholas S. Fisher2. (1) Department of Geosciences and Center for Environmental Molecular Science, SUNY at Stony Brook, Stony Brook, NY 11794-2100, (2) Marine Sciences Research Center and Center for Environmental Molecular Science, SUNY at Stony Brook, Stony Brook, NY 11794-5000 |
| Pb(II) sorption experiments with calcite powders were conducted at ambient pressure and temperature over a pH range of 6.9-9.4. The pH sorption edge correlates well with PbCO30(aq) speciation, alluding to the influence of this metal complex on Pb-calcite interaction. Desorption experiments at pH 7.4, 8.3 and 9.4 demonstrate a subtle residence time effect on metal uptake. Hysteresis is slight at pH £ 8.3, but becomes pronounced at pH 9.4, suggesting the presence of significant irreversibly bound Pb at high pH. Linear combination fits of X-ray absorption near edge spectra for samples sorbed at pH 9.4 confirm an adsorbed component (80%) and non-exchangeable fraction (20%) as co-precipitated Pb. We propose that incorporation occurs as a result of high calcite re-crystallization rates at pH > 8.3. This study highlights the role of aqueous metal complexation on initial Pb uptake, and demonstrates the role of pH in Pb immobilization in calcitic systems. |
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Chemistry of Metals in Terrestrial and Aquatic Systems
1:30 PM-5:10 PM, Monday, March 29, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |