文摘
To improve prediction accuracy of the long-term geochemical simulation, we measured carbonate growth rates at carbonated or bicarbonated springs as a natural analogue field of CO2 geological sequestration. Seeding experiments, specially focusing on the effect of the Mg-ion as an inhibitor of calcite growth, indicated that the formation phase changed from calcite to aragonite with an increase of the Mg/Ca ratio, whereas that neither dolomite nor magnesite grew in the present range of the Mg/Ca ratio corresponding to typical aquifer conditions. On the other hand, there was no correlation between the calcite growth rate and the Mg/Ca ratio: the impact of the Mg ion alone seems to be diminished in nature. Regarding this, we also found that the calcite growth rate at field conditions was much lower than the literature values mainly based on laboratory experiments. These results suggest that various other factors besides the Mg-ion affect the natural carbonate kinetics intricately; which in turn can cause a significant error on the predicted timescale of the mineral trapping.