『Abstract
　This study used batch reactors to quantify the mechanisms and rates of calcite dissolution in the presence and absence of a single heterotrophic bacterial species (Burkholderia fungorum). Experiments were conducted at T = 28℃ and ambient pCO2 over time periods spanning either 21 or 35 days. Bacteria were supplied with minimal growth media containing either glucose or lactate as a C source, NH4⁺ as an N source, and H2PO4^- as a P source. Combining stoichiometric equations for microbial growth with an equilibrium mass-balance model of the H2O-CO2-CaCO3 system demonstrates that B. fungorum affected calcite dissolution by modifying pH and alkalinity during utilization of ionic N and C species. Uptake of NH4⁺ decreased pH and alkalinity, whereas utilization of lactate, a negatively charged organic anion, increased pH and alkalinity. Calcite in biotic glucose-bearing reactors dissolved by simultaneous reaction with H2CO3 generated by dissolution of atmospheric CO2 (H2CO3 + CaCO3　→ Ca²⁺ + 2HCO3^- ) and H⁺ released during NH4⁺ uptake (H⁺ + CaCO3 → Ca²⁺ + HCO3^-). Reaction with H2CO3 and H⁺ supplied 〜45％ and 55％ of the total Ca²⁺ and 〜60％ and 40％ of the total HCO3^-, respectively. The net rate of microbial calcite dissolution in the presence of glucose and NH4⁺ was 〜2-fold higher than that observed for abiotic control experiments where calcite dissolved only by reaction with H2CO3. In lactate bearing reactors, most H⁺ generated by NH4⁺ uptake reacted with HCO3^- produced by lactate oxidation to yield CO2 and H2O. Hence, calcite in biotic lactate-bearing reactors dissolved by reaction with H2CO3 at a net rate equivalent to that calculated for abiotic control experiments. This study suggests that conventional carbonate equilibria models can satisfactorily predict the bulk fluid chemistry resulting from microbe-calcite interactions, provided that the ionic forms and extent of utilization of N and C sources can be constrained. Because the solubility and dissolution rate of calcite inversely correlate with pH, heterotrophic microbial growth in the presence of nonionic organic matter and NH4⁺ appears to have the greatest potential for enhancing calcite weathering relative to abiotic conditions.』

1. Introduction
2. Materials and methods
　2.1. Characterization and preparation of calcite samples
　2.2. Model microorganism
　2.3. Growth media
　2.4. Batch experiments
　2.5. Chemical analyses and data treatment
3. Results and discussion
　3.1. Glucose and lactate consumption, bacterial growth, and pH trends
　3.2. Major ion chemistry of the media and reactor solutions
　3.3. Calcite saturation index
　3.4. Microbial growth
　3.5. Equilibrium model for the microbial dissolution of calcite
　3.6. Calcite dissolution kinetics
4. Conclusions and implications
Acknowledgments
Appendix A
References