外源酸作用下的岩石风化特征及其碳汇效应：以赤水河为例

吴东; 曾艳; 李鹏; 陈敬安; 白晓永; 杨永琼; 冉光荣; 郭旭东; 张紫焱; 李艳

doi:10.12029/gc20250506001

外源酸作用下的岩石风化特征及其碳汇效应：以赤水河为例

Rock weathering and carbon sink effects under exogenous acid forcing: A case study of the Chishui River Basin

摘要

摘要:
研究目的 外源酸加速了喀斯特流域岩石风化并影响碳汇效应。赤水河具有典型的喀斯特地貌特征，研究其流域内水化学特征、溶质来源及外源酸作用，对准确评估喀斯特地区碳汇效应具有重要意义。
研究方法 本研究测定了赤水河干流河水的主要离子浓度，结合离子比值法、Galy模型和质量平衡模型等方法识别流域内岩石风化特征、估算溶质来源贡献以及在外源酸作用下的碳酸盐岩溶蚀比例。
研究结果 结果表明：赤水河流域的pH范围为7.4~9.5，TDS范围为261~365 mg/L；阳离子主要以Ca²⁺和Mg²⁺为主，阴离子包括HCO₃^–、SO₄^2–和NO₃^–。其中，Ca²⁺和Mg²⁺占流域内总阳离子92.3%，HCO₃^–、SO₄^2–和NO₃^–分别占总阴离子的60.3%、28.9%和6.6%，水化学类型主要是HCO₃^––Ca²⁺型或HCO₃^––(Ca·Mg)²⁺型。
结论赤水河流域内的溶质组成主要受水岩作用和人为活动的综合影响。其中，Ca²⁺+Mg²⁺和HCO₃^–主要来源于碳酸盐岩和硅酸盐岩的风化作用，Na⁺、NO₃^–和SO₄^2-等离子浓度主要受生活污水、农业氮肥和矿业活动等人为活动的影响。赤水河上游流域具有典型喀斯特征，河流水化学表现出较高地碳酸盐岩溶蚀特征。此外，在外源酸的影响下，赤水河流域的碳酸盐岩风化速率增加了60.7%，碳汇通量降低了45.0%。因此，评估流域内碳酸盐岩的溶蚀速率和碳汇过程时，人为活动影响及外源酸的作用不可忽视。

Abstract:
This paper is the result of environmental geological survey engineering.
Objective The exogenous acids accelerate rock weathering in karst basins and influence the carbon sink effect. The Chishui River Basin has typical karst landform features, and studying its hydrochemical characteristics, solute sources, and the effect of exogenous acids is of great significance for accurately assessing the carbon sink effect in karst regions.
Methods The major ion concentrations in the mainstream of the Chishui River were determined in this study. Combined with the ion ratio method, the Galy model, and mass balance model, the characteristics of rock weathering in the basin, the contribution of solute sources, and the proportion of carbonate rock dissolution under the effect of exogenous acids were identified and estimated.
Results The results showed that the pH range in the Chishui River was 7.4~9.5, with total dissolved solids (TDS) varying between 261 and 365 mg/L. Cations were dominated by Ca²⁺and Mg²⁺, while anions included HCO₃^–, SO₄^2– and NO₃^–. Specifically, Ca²⁺and Mg²⁺ accounted for 92.3% of the total cations, HCO₃^– accounted for 60.3% of the total anions, SO₄^2– and NO₃^– accounted for 28.9% and 6.6%, respectively. The hydrochemical type was primarily HCO₃^––Ca²⁺ or HCO₃^––(Ca·Mg)²⁺.
Conclusions The solute composition in the Chishui River is mainly controlled by the combined effects of water-rock interactions and human activities. Among them, Ca²⁺, Mg²⁺, and HCO₃^– mainly come from the weathering of carbonate rocks and silicate rocks, while the concentrations of Na⁺, NO₃^–, and SO₄^2– are mainly affected by human activities such as domestic sewage, agricultural nitrogen fertilizers and mining activities. The upper reaches of the Chishui River Basin are characterized by typical karst features, and the river water chemistry shows a high degree of carbonate rock dissolution characteristics. In addition, under the influence of exogenous acids, the carbonate rock weathering rate in the Chishui River Basin increased by 60.7%, and the carbon sink flux decreased by 45.0%. Therefore, when evaluating the dissolution rate of carbonate rocks and carbon sink processes in the basin, the influence of human activities and the role of exogenous acids cannot be ignored.

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