Role of calcite on carbon cycle in global scale

本研究研究了方解石在pH5下的溶解，磷酸盐浓度范围很广（1.0 × 10^<-6>-5.0 × 10^<-1>摩尔）。结果表明，磷酸盐离子在低浓度时对方解石的溶解速率起抑制作用，但在高浓度时（约大于10^<-4>摩尔），随着磷酸盐离子的增加，方解石的溶解速率增加。从不同磷酸盐浓度下的实验，以及高浓度磷酸盐下方解石表面的SEM显微照片可以得出结论：(1)对于低浓度的磷酸盐离子，其对方解石表面的化学吸附（可用Langmuir等温线方程描述）使反应面积变小，方解石的溶解速度变慢；(2)磷酸盐离子对方解石表面的氢离子浓度起缓冲作用，其作用表现为方解石溶解速度的增加。

This study investigates dissolition of calcite at pH5 over a wide range of phosphate concentration (1.0x10^<-6>-5.0x10^<-1> molar). The result is that the phosphate ions act as an inhibitor on the dissolution rate of calcite at low concentration, but at high concentration (about upper 10^<-4> molar), the calcite dissolution rate increases as phosphate ions increasing. From the experiments at various phosphate concentration, also SEM photomicrographs of the calcite surface under high concentration of phosphate, it was concluded : (1) for low concentration of phosphate ion, its chemical adsorption, which can be described by a Langmuir isotherm equation, to the calcite surface makes the reaction area smaller, and the dissolution rate of calcite slower, (2) phosphate ions act as a buffer of the hydrogen ion concentration at the calcite surface and its effect appears as rate increasing of the calcite dissolution.