中文关键词岩溶流域洪水过程岩石风化水化学特征碳通量漓江 英文关键词karst watershedflood processrock weatheringhydrochemical characteristicscarbon fluxLijiang River Basin

作者	单位	E-mail
原雅琼	中国地质科学院岩溶地质研究所, 自然资源部、广西岩溶动力学重点实验室, 桂林 541004 西南大学地理科学学院, 重庆 400715	yyqiong@karst.ac.cn
孙平安	中国地质科学院岩溶地质研究所, 自然资源部、广西岩溶动力学重点实验室, 桂林 541004	safesun@163.com
苏钊	广西壮族自治区水文水资源桂林分局, 桂林 541001
于奭	中国地质科学院岩溶地质研究所, 自然资源部、广西岩溶动力学重点实验室, 桂林 541004
钟丽华	广西壮族自治区水文水资源桂林分局, 桂林 541001
何师意	中国地质科学院岩溶地质研究所, 自然资源部、广西岩溶动力学重点实验室, 桂林 541004
徐茜	广西壮族自治区水文水资源桂林分局, 桂林 541001

中文摘要 岩溶流域河流水化学对暴雨/洪水过程有着快速响应，是岩溶碳循环的重要过程，不应忽视.本文通过2015年11月8~12日阳朔断面洪水过程水化学特征的动态监测，分析了各主要离子变化特征和影响因素，计算不同来源无机碳浓度和通量.结果表明，阳朔断面洪水过程各阶段水化学类型为Ca-HCO₃型.水化学离子主要源自碳酸盐岩风化，同时有硅酸盐岩风化、降雨及人类活动的贡献.洪水过程中，受控于水文过程，碳酸盐岩风化强度先急剧减弱后缓慢加强，HCO₃^-、Ca²⁺和Mg²⁺的浓度也呈现一致的变化趋势.而SO₄^2-、Cl^-、Na⁺和K⁺动态变化主要受大气降水和人类活动的影响.碳酸风化碳酸盐岩是无机碳的主要来源，平均占总无机碳74.3%；因硫酸/硝酸的输入，硫酸/硝酸风化碳酸盐岩在洪水过程中对无机碳的贡献明显增加，最高可达31.7%.阳朔断面地质碳汇通量在洪水前、第一次洪水过程和第二次洪水过程分别为1.28×10⁸、5.28×10⁸和11.52×10⁸ g·d^-1.洪水前地质碳汇通量与年平均通量相当，而洪水过程数倍于年平均通量.并且，因两次洪水过程碳酸盐岩风化强度存在显著差异，第一次洪水过程地质碳汇通量在相同流量情况下仅为第二次洪水过程的58%. 英文摘要 The hydrochemistry of river water in a karst basin has a rapid response to the rainstorm/flood process, which is an important process of the karst carbon cycle and should not be ignored. Based on the dynamic monitoring of the hydrochemical characteristics of the flood process in the Yangshuo section on November 8-12, 2015, the dynamic change in the main ions and the influencing factors were analyzed, and the concentration and flux of inorganic carbon from different sources were calculated. The results showed that the hydrochemistry types in different stages of the flood area belonged to the Ca-HCO₃ type. The ions were mainly sourced from carbonate weathering, and affected by silicate weathering, rainfall, and human activities. Because of the hydrological process, the weathering strength of carbonate rocks sharply weakened at the beginning of the flood, and then gradually increased. The concentrations of HCO₃^-, Ca²⁺, and Mg²⁺ sharply decreased at the beginning of the flood, then gradually increased, and continued to increase in the second flood process because of the waterlogging in the karst system. Because of the waterlogging, the reaction time between water and rock become longer; thus, the concentrations are higher. The dynamic changes in SO₄^2-, Cl^-, Na⁺, and K⁺ were mainly affected by precipitation and human activities. At the beginning of the flood, the concentrations of SO₄^2-, Cl^-, Na⁺, and K⁺ increased because the runoff takes more ions sourced from activities. The concentrations of SO₄^2-, Cl^-, Na⁺, and K⁺ decreased with the decrease of easily transported substances. At the lowest point of concentration, SO₄^2- and Cl^- were mainly sourced from precipitation, and Na⁺ and K⁺ were mainly sourced from precipitation and silicate weathering. The weathering of carbonates by carbonic acid was the main source of inorganic carbon, accounting for 74.3% of total inorganic carbon on average. Because of the input of sulfuric/nitric acid, the contribution of the weathering of carbonates by sulfuric/nitric acid to the inorganic carbon cannot be ignored, and the contribution increased significantly in the flood, up to 31.7%. The geological carbon sinks before the flood, and during the first and second flood processes in the Yangshuo section were 1.28×10⁸, 5.28×10⁸, and 11.52×10⁸ g·d^-1, respectively. The geological carbon sink before the flood was equal to the annual average flux, whereas the geological carbon sink in the flood process was several times that of the annual average flux. Moreover, because of the significant difference in the weathering strength of carbonate rocks during the two floods, there was also a significant difference in the amount of geological carbon sink under the same discharge.

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