HR: 11:50h
AN: B12A-07 [Abstracts]
TI: Quantification of Biogeochemical Mineral Dissolution Rates in the Vadose Zone
AU: * Green, E
EM: lis@eps.berkeley.edu
AF: Department of Earth and Planetary Science, 307 McCone Hall, UC Berkeley, Berkeley, CA 94709
United States
AU: Banfield, J F
EM: jill@eps.berkeley.edu
AF: Department of Earth and Planetary Science, 307 McCone Hall, UC Berkeley, Berkeley, CA 94709
United States
AB:
Most mineral dissolution experiments are typically carried out in batch or flow-through reactors with very high ratios of
solution to mineral, or continuous flow. These conditions are unlikely to support growth of most microorganisms typical of
the soil environment and do not simulate realistic soil water compositions. To address these issues, we conducted mineral
dissolution experiments in flow-through reactors modified to more closely reproduce conditions in the vadose zone. Within
these reactors, crushed mineral samples sit on a polypropylene mesh surface. Periodically, solution is sprinkled over the
sample, collecting in pore spaces between mineral grains and flushing out pore waters from the last application. In our
initial experiments, apatite was dissolved in pH 5 solution containing 1 mM oxalate, with flushing events involving 7 mls of
solution occurring every 8 hours. Ca and P were released from dissolving apatite in approximately equal molar amounts, with
a rate of 2.0 +/- 0.15 * 10-10 mol/m2/sec for Ca, and 2.3 +/- 0.20 *10-10 mol/m2/sec for P. The measured
rates are significantly slower than those measured for apatite dissolution at pH 5 in batch reactors (1.1*10-7,
Valsami-Jones et al., 1998; 2*10-9 mol/m2/sec for a solution containing 1mM oxalate; Welch et al, 2002). We infer
that dissolution rates are suppressed between flushing events by the presence of water films with higher saturation indices.
These results provide a benchmark for comparison to measured rates of biogeochemical dissolution of apatite in the presence
of cultures of Acidobacteria, a common soil microorganism.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0463 Microbe/mineral interactions
SC: Biogeosciences [B]
MN: Fall Meeting 2005