Oelkers,E.H., Golubev,S.V., Pokrovsky,O.S. and Benezeth(最初と二番目のeの頭に´),P.(2011): Do organic ligands affect calcite dissolution rates? Geochimica et Cosmochimica Acta, 75, 1799-1813.

『有機配位子は方解石の溶解速度に影響するか?』


Abstract
 Steady state Iceland-spar calcite dissolution rates were measured at 25℃ in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO2 sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA4-, succinate, D-glucosaminate, L-glutamate, D-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of <0.05 mol/kg of these organic anions changes calcite dissolution rates by less than a factor of 2.5 with the exception of citrate and EDTA4-. The presence of 0.05 mol/kg citrate and EDTA4- increases calcite dissolution rates by as much as a factor of 35 and 500, respectively, compared to rates in organic anion-free solutions. Further calcite dissolution experiments were performed in the presence of organic polymers similar to bacterial exudates, cell exopolysaccharides, and analogs of microbial cell envelopes: alginate, lichen extract, humic acid, pectin, and gum zanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.』

1. Introduction
2. Theoretical background
3. Experimental methods
4. Results
5. Discussion
 5.1. Relative effects of organic ligands on calcite dissolution rates
 5.2. Modeling of ligand-effected carbonate mineral dissolution
 5.3. Geological applications
6. Conclusions
Acknowledgments
References


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