The CO_2 Regime of Soil Profile and Its Reflection to Dissolution of Carbonate Rock

摘要

The studies on the CO2 regime on a soil profile underlain by carbonate rock, the fluctuation of pH and HCO3', and the dissolution of the standard limestone tablets provide us with some new knowledge as follows: (1) CO2 in the soil profile changes with the seasons; (2) Generally, two CO2 concentration gradients, which exist soil-atmosphere and soil-carbonate rock, are formed. However, in winter, only the soil-atmosphere gradient is formed; (3)The dissolution intensity of the limestone tablets relates closely to the CO2 concentration gradient rather than the absolute concentration of CO2; (4) There is larger difference in time between the regime of the pH and HCO3- of karst underground water and the changes of the absolute concentration of CO2 on the overlying soil profile, but the former nearly coincides with the regime of CO2 concentration gradient. The studies demonstrates that the gradient of CO2 concentration, rather than the absolute concentration of CO2 can reflect karst process in the karst dynamic system.