岩溶碳循环具有快速的动力学反应过程,对环境变化敏感,水循环可影响岩溶碳循环的两个驱动因子(水和CO₂),是岩溶碳循环的重要影响因素。通过2016年6月和10月长江干流、主要支流、水库、湖泊的采样测试,分析了δD、δ¹⁸O、无机碳含量和同位素分馏特征及控制因素,揭示了长江流域水循环对岩溶碳循环的影响特征。结果表明:长江流域水体δD和δ¹⁸O的空间变化表现出大陆效应、纬度效应和海拔效应,并随降雨的季节性变化而变化;无机碳主要源自碳酸盐岩风化,δ¹³C_DIC值主要受碳酸风化碳酸盐岩和硫酸/硝酸风化碳酸盐岩对$\mathrm{HCO}_{3}^{-}$的贡献比例控制。长江流域水文过程可显著影响岩溶碳循环,上游冻土区土壤冻结时,幔源和大气源CO₂参与碳酸盐岩风化使δ¹³C_DIC值显著增加;夏秋季季风期降雨爆发,降水导致δD和δ¹⁸O急剧下降,同时利于土壤CO₂累积和碳同位素值下降,并使得水体δD、δ¹⁸O和δ¹³C_DIC值均下降;水文过程可影响“生物碳泵”作用,平水期“生物碳泵”作用更强,水库的分层效应也更显著。

The karst carbon cycle exhibits rapid dynamic responses and is sensitive to environmental changes. The water cycle can influence the two driving factors of the karst carbon cycle (water and CO₂), making it an important influencing factor. This study analyzes samples collected in June and October 2016 from the main stream, major tributaries, reservoirs, and lakes of the Yangtze River. The study examines δD, δ¹⁸O, inorganic carbon content, and isotope fractionation characteristics and controlling factors, revealing the impact of the water cycle on the karst carbon cycle in the Yangtze River Basin. The results show that the spatial variation in δD and δ¹⁸O compositions in the Yangtze River Basin’s water bodies reflects continental, latitudinal, and altitudinal effects, and varies with the seasonal changes in rainfall. Inorganic carbon mainly originates from the weathering of carbonate rocks, and δ¹³C_DIC values are primarily controlled by the relative contributions of carbonic acid weathering and sulfuric/nitric acid weathering of carbonate rocks to $\mathrm{HCO}_{3}^{-}$. Hydrological processes in the Yangtze River Basin significantly impact the karst carbon cycle. In the upstream permafrost region, soil freezing results in mantle-derived and atmospheric CO₂ participating in the weathering of carbonate rocks, significantly increasing δ¹³C_DIC values. During the summer and autumn monsoon rains, the rapid decline in precipitation δD and δ¹⁸O, coupled with soil CO₂ accumulation and the decrease in carbon isotope values, leads to a decrease in δD, δ¹⁸O, and δ¹³C_DIC values in the water. Hydrological processes also affect the “biological carbon pump” effect, which is stronger during normal flow periods, and the stratification effect in reservoirs becomes more pronounced.