Soil loss in karst area is divided into surface soil loss and soil leakage. The binary and three-dimensional hydrogeologic structure in karst area provides space condition for its soil leakage. Different from surface soil loss, soil leakage is the transport and deposition of soil from the surface to the underground space. The strong karstification provides multifarious paths for soil leakage. Due to the complexity and variability of loss paths, the diversity and interactivity of influencing factors and the multi-interface nature of subsurface hydrological processes, a quantitative analysis of soil leakage in karst area is always one of the important issues in soil erosion research and one of the difficult questions in soil erosion forecasting and monitoring. Focused on influencing factors of soil leakage, this study is aimed at analyzing the effects of environmental factors such as soil properties, vegetation, rainfall characteristics, terrain feature and human activities on soil leakage. For quantitative tracing of sediment source in such levels as runoff plots, cave catchment area and watershed in spatial scale, four main quantitative methods about evaluating soil leakage in karst area, such as simulated runoff plot method, cave drip tracer method, traditional model method and composite fingerprinting, have been analyzed and compared. These four quantitative research methods have their own advantages and limitations. The simulated runoff plot method can quickly and intuitively monitor the soil leakage at a small spatial and temporal scale. However, its result is highly sensitive to external environmental factors such as rainfall and physical and chemical properties of soil. The cave drip method can only trace the soil loss that occurs by cave dropping water, which is quite different from the actual loss in the cave catchment. However, as a new leakage research method, it provides a new idea for leakage monitoring. The determination of soil leakage at watershed scale mainly includes model method and fingerprinting identification method. The traditional model method can directly monitor the leakage at the watershed scale, but there are some limitations in practice. First of all, the traditional method requires clear underground runoff outlet in the basin and no exchange and superposition between underground runoff and surface runoff. Secondly, it is requested that the surface and underground sediment production and drainage only occur in the basin without the disturbance by other basins. Thirdly, for the traditional model method, the underground or surface runoff sediment discharge should be monitored at fixed points, and the accuracy of sediment amount is greatly affected by the location of monitoring point and monitoring time. To some extent, fingerprinting identification method can be used to solve some problems of traditional model method, but it also has some limitations such as the selection of sediment sources, the screening of fingerprinting factors and the correction of retention of them. In this paper, the future study focuses on soil leakage in karst area are also pointed out by analyzing the problems of research on soil leakage. The collation of quantitative research on soil leakage in karst area provides a reference for exploring the driving mechanism of soil leakage and for further studying the coupling relation between soil leakage and environmental factors.

The dynamic changes of different components in water carbonate system (CO₂+HCO$_3^{-}$+CO$_3^{2-}$) can be characterized by Revelle factor which can not only reflect the buffering capacity of weak-basicity water to absorb atmospheric CO₂, but also reflect the buffering effect of CO₂ degassing on H⁺ during water acidification. Compared with the marine system, the Revelle factor in the surface water carbonate system has a larger variation range. However, the study on the variation of buffering factors in the dynamic transformation of carbonate components in freshwater system is still very limited. This study selected the Chetian river located in Eastern Jinsha county, Guizhou Province as the research area. Through the analysis of multiple buffering factors, the buffering effect of the surface water carbonate system on AMD input was discussed. The results will help to further understand the DIC cycle process and the CO₂ source-sink relationship in surface water in the karst area of medium-high sulfur coal mine. Based on the 13-month sampling analysis from November 2020 to November 2021, the equations of Revelle factor—γ_DIC, β_DIC, ω_DIC, γ_Alk, β_Alk and ω_Alk—were established to characterize the relationship between acid-base chemical balance of water and the dynamic variation of carbonate components. Results show that when the Revelle factor is at the maximum, the buffering capacity of the water carbonate system is the weakest. In the marine system, the maximum value of Revelle factor appears at pH 7.50, and the seawater sample data are mainly distributed on the right side of this factor, reflecting the absorption and buffering capacity of the ocean to atmospheric CO₂. When the pH is in the range of 6.35-8.38, the carbonate balance in surface water mainly reflects the conversion between CO₂ (aq) and HCO$_3^{-}$, and CO$_3^{2}$⁻ is almost negligible. Due to the influence of AMD input, all data in the Chetian river fall on the left side of the maximum value, with a variation range of 1.00-51.96, which is shown as the buffering of CO₂ degassing on H⁺. In acidic water with pH<6.35, DIC is gradually dominated by CO₂ (aq), and the sensitivity of Revelle factor is reduced. The buffering factors such as γ_DIC, β_DIC, ω_DIC, γ_Alk, β_Alk and ω_Alk, based on the binary equations of pH and DIC concentration, can be used to further elaborate the relative variation of CO₂ (aq), H⁺ and CO$_3^{2}$⁻ on DIC concentration and alkalinity. It can be found that the six buffering factors show a good response to the dynamic transformation of carbonate components during water acidification. When pH is equal to 8.38, the six factors have extreme values, reflecting the low buffering capacity of water carbonate system. At pH>6.35, β_Alk is linearly related to the concentration of CO₂ (aq). With the improvement of acidification degree, β_DIC can respond well to the buffering of chemical equilibrium of carbonate system to H⁺. When pH is less than 6.35, with the gradual increase of the proportion of CO₂ (aq), the water carbonate system is no longer in a closed environment, and the carbon transport at the water-gas interface and water-rock interface is enhanced. When the CO₂ degassing is dominant, the absolute value of these buffering factors becomes larger; when the erosion of carbonate rocks by H⁺ is the dominate process, the absolute value of these buffering factors become smaller.