雨热同期的亚热带季风气候促进了岩溶碳汇的发生,受外源水补给的边缘坡立谷是岩溶区碳酸盐岩溶蚀作用强烈的区域,对该区不同类型水的水化学特征研究有助于加深对岩溶固碳作用规律的认识。本文运用数理统计、Piper三线图、Gibbs图和主要离子比值等多种方法,对亚热带典型边缘坡立谷的河流水化学特征、成因及其碳汇效应等进行了分析。结果显示:(1)边缘坡立谷的河水类型主要有外源水、外源水补给的地表河、外源水补给岩溶地下河和岩溶地下水等,其总离子浓度呈递增趋势,岩溶地下水的Ca²⁺浓度平均值为91.06 mg/L,分别是外源水补给地下河水、外源水补给地表水和外源水的2.3、4.3和12.4倍,其中外源水补给的地表河水化学离子浓度变化较大;(2)外源水进入岩溶区后,Ca²⁺和$\mathrm{HCO}_{3}^{-}$浓度逐渐升高,方解石饱和指数逐渐偏正。在亚热带季风区大量降雨导致的水循环加快的情况下,外源水对碳酸盐岩具有较强的侵蚀性;但外源水无论以补给岩溶地下河还是以地表水进入岩溶区后,其与碳酸盐岩的反应时间或接触面积不足,影响了岩溶碳汇增汇的提升。

The concurrent occurrence of rainfall and heat in the subtropical monsoon climate promotes the formation of karst carbon sinks. Border poljes, recharged by allogenic water, are regions with strong carbonate rock dissolution in karst areas. Studying the hydrochemical characteristics of different water types in these regions helps deepen the understanding of karst carbon sequestration processes. This paper employs statistical methods, Piper diagrams, Gibbs diagrams, and major ion ratios to analyze the hydrochemical characteristics, origins, and carbon sink effects of rivers in a typical subtropical border polje. The results show that: (1) The main types of river water in the border polje are allogenic water, surface rivers recharged by allogenic water, karst underground rivers recharged by allogenic water, and karst groundwater. The total ion concentration shows an increasing trend. The average concentration of Ca²⁺ in karst groundwater is 91.06 mg/L, which is 2.3, 4.3, and 12.4 times that of underground rivers recharged by allogenic water, surface water recharged by allogenic water, and allogenic water, respectively. (2) After the allogenic water enters the karst area, the concentrations of Ca²⁺ and $\mathrm{HCO}_{3}^{-}$ gradually increase, and the calcite saturation index shifts positively. In the context of an accelerated water cycle due to heavy rainfall in the subtropical monsoon region, the reaction time of allogenic water with carbonate rocks is insufficient after entering the karst area to strengthen erosion. Whether it is direct infiltration of allogenic water, or karst underground rivers or surface water recharged by allogenic water, it has significant potential for increasing the carbon sink.