Influential factors and spatial suitability of the method of limestone tablets in karst carbon cycle study in China

As an intuitive way, the method of limestone tablets (MLT) is often used in dissolution rate calculation and carbon cycle research of carbonate rocks. To clarify the influential factors and spatial suitability of MLT in karst carbon cycle study, 30 MLT test sites in China from north to south were collected and the tablets’ dissolution rate (TDR) was analyzed. The results showed that the influence of precipitation on the TDR is more significant than that of the temperature, especially in the impact on the underground tablets. Three typical river basins, i.e., the Nanchuan River karst basin of northern China (NKB), Qingliangsigou loess basin of northern China (QLB), and Wujiang River karst basin of southern China (WKB) were collected as the key research areas to reveal the regional factors of lithology, soil physical–chemical properties, and land use that affect TDR. The results show that the higher the acid insolubility of rocks, the lower is the dissolution rate. Soil CO 2 displayed a positive correlation with TDR in both the northern and southern karst areas of China. Because soil inorganic carbon (SIC) always causes carbon deposits on the tablet surface which made the calculated results of carbon sink inaccurate, the MLT is not suitable for carbon cycle research in the loess area where high SIC is contained. The hydrochemical runoff method may be better selected. In the arid and semi-arid karst basin of northwestern and northern China, the high SIC area should be avoided during carbon sink study with MLT. Graphic abstract