长江流域水体稳定同位素分馏特征及碳水循环  

Fractionation of stable isotopes and the carbon-water cycle in Yangtze River

作　　者：原雅琼 孙平安[1,2,3] 于奭 何师意[1,2,3] YUAN Yaqiong;SUN Ping’an;YU Shi;HE Shiyi(MNR&Guangxi Key Laboratory of Karst Dynamics,Institute of Karst Geology,Chinese Academy of Geological Sciences,Guilin 541004,China;International Research Center on Karst Under the Auspices of UNESCO/National Center for International Research on Karst Dynamic System and Global Change,Guilin 541004,China;Pingguo,Guangxi Karst Ecosystem,National Observation and Research Station,Pingguo 531406,China)

机构地区：[1]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,广西桂林541004 [2]联合国教科文组织国际岩溶研究中心/岩溶动力系统与全球变化国际联合研究中心,广西桂林541004 [3]广西平果喀斯特生态系统国家野外科学观测研究站,广西平果531406

出　　处：《地学前缘》2024年第5期409-420,共12页Earth Science Frontiers

基　　金：广西自然科学基金项目(2022GXNSFAA035572);国家重点研发计划项目(2020YFE0204700);国家自然科学基金项目(42377069,42177075);中国地质科学院基本科研业务费项目(2022001);中国地质调查项目(DD20230547,DD20221820)。

摘　　要：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CO_(2)),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、δ^(18)O、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δ^(18)O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,δ^(13)C 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CO_(2)参与碳酸盐岩风化使δ^(13)C DIC值显著增加;夏秋季季风期降雨爆发,降水导致δD和δ^(18)O急剧下降,同时利于土壤CO_(2)累积和碳同位素值下降,并使得水体δD、δ^(18)O和δ^(13)C 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 CO_(2)),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 examinesδD,δ^(18)O,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 inδD andδ^(18)O 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,andδ^(13)C DIC values are primarily controlled by the relative contributions of carbonic acid weathering and sulfuric/nitric acid weathering of carbonate rocks to 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 CO_(2) participating in the weathering of carbonate rocks,significantly increasingδ^(13)C DIC values.During the summer and autumn monsoon rains,the rapid decline in precipitationδD andδ^(18)O,coupled with soil CO_(2) accumulation and the decrease in carbon isotope values,leads to a decrease inδD,δ^(18)O,andδ^(13)C 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.

关 键 词：δD和δ^(18)O δ^(13)C DIC 碳水循环 水库 长江流域 

分 类 号：X143[环境科学与工程—环境科学] P595[天文地球—地球化学] P597.2[天文地球—地质学]