典型岩溶小流域碳酸盐岩风化过程及其碳汇效应  

Weathering process and carbon sink effect of carbonates in typical karst small basin

作　　者：陈发家 肖琼[2,3] 胡祥云 郭永丽[2] 孙平安 张宁[2] CHEN Fajia;XIAO Qiong;HU Xiangyun;GUO Yongli;SUN Ping’an;ZHANG Ning(School of Geophysics and Geomatics,China University of Geosciences(Wuhan),Wuhan 430074,China;MNR&Guangxi Key Laboratory of Karst Dynamics,Institute of Karst Geology,Chinese Academy of Geological Sciences/International Research Center on Karst Under the Auspices of UNESCO,Guilin 541004,China;Pingguo,Guangxi Karst Ecosystem,National Observation and Research Station,Pingguo 531406,China)

机构地区：[1]中国地质大学(武汉)地球物理与空间信息学院,湖北武汉430074 [2]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/联合国教科文组织国际岩溶研究中心,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449-459,共11页Earth Science Frontiers

基　　金：广西自然科学基金项目(2022GXNSFAA035604,2022GXNSFAA035572,2021GXNSFBA075013);中国地质调查项目(DD20230547);国家外专局项目(DL2023055001L);中国地质科学院岩溶地质研究所基本科研业务费项目(2023019,2021001);国家重点研发计划项目(2020YFE0204700)。

摘　　要：碳酸盐岩风化过程是一个吸收大气CO_(2)的过程,具有碳汇效应。利用岩溶区水体的水文地球化学特征揭示碳酸盐岩风化过程、计算流域岩溶碳汇通量是全球变化研究的一个重要方面。以广西柳州官村地下河流域(GGW)为例,2021年4个季度的监测结果表明:(1)HCO_(3)^(-)和Ca^(2+)是主要的阴阳离子,阴阳离子当量浓度和TDS浓度反映了碳酸盐岩强烈的风化作用;(2)水化学时空分布特征显示,GGW的水化学类型为HCO_(3)-Ca型,水岩作用过程除了H_(2)CO_(3)风化碳酸盐岩外,还有H_(2)SO_(4)和HNO_(3)风化碳酸盐岩;(3)在研究H_(2)CO_(3)、H_(2)SO_(4)和HNO_(3)共同参与的水岩作用过程中,用δ13 C DIC计算H_(2)CO_(3)风化碳酸盐岩的CO_(2)消耗量为2.38 mmol·L^(-),CO_(2)净消耗量用[HCO_(3)^(-)]mol-[Ca^(2+)+Mg^(2+)]mol表示,平均净消耗量为1.98 mmol·L^(-),用CO_(2)净消耗量计算出的GGW无机碳汇强度(以CO_(2)计)C m为86.37 t·km^(-2)·a^(-);(4)不考虑外源酸作用,利用水化学径流法计算出的GGW无机碳汇强度(以CO_(2)计)C m为94.49 t·km^(-2)·a^(-),CO_(2)净消耗量是水化学径流法计算的CO_(2)汇量的91.41%;(5)碳汇强度为2008年的1.91倍,研究结果可为人工干预增加岩溶碳汇潜力评估提供一定的参考和借鉴。Carbonate weathering is a process of absorbing CO_(2)from the atmosphere,exhibiting a carbon sink effect.Utilizing the hydrogeochemical characteristics of water in karst areas to reveal the weathering process of carbonate rocks and calculate karst carbon sink fluxes in basins is an important aspect of global change research.A case study of the Guancun Groundwater(GGW)in Liuzhou,Guangxi,with monitoring results from four seasons in 2021,showed that:(1)The main anion in the basin is HCO_(3)^(-),and the main cation is Ca^(2+).The equivalent concentrations and TDS of anions and cations reflect the intense weathering of carbonate rocks.(2)Based on the spatiotemporal distribution characteristics of its hydrochemistry,the GGW belongs to the HCO_(3)-Ca type.Besides the weathering of carbonate rocks by H_(2)CO_(3),the weathering by H_(2)SO_(4)and HNO_(3)also occurs in water-rock interactions.(3)Considering the combined water-rock interaction process involving H_(2)CO_(3),H_(2)SO_(4)and HNO_(3),the average CO_(2)consumption by H_(2)CO_(3)weathering of carbonate rocks is calculated usingδ13 C DIC as 2.38 mmol/L.The net CO_(2)consumption is expressed as[HCO_(3)^(-)]mol-[Ca^(2+)+Mg^(2+)]mol,with an average net CO_(2)consumption of 1.98 mmol/L.The inorganic carbon sink intensity(C m)of the GGW is 86.37 tCO_(2)·km^(-2)·a^(-).(4)However,the inorganic carbon sink intensity(C m)of this groundwater,calculated using the hydrochemical-runoff method,is 94.49 tCO_(2)·km^(-2)·a^(-).The net CO_(2)consumption is 91.41%of the CO_(2)sink calculated by the hydrochemical-runoff method.(5)The carbon sink intensity in 2021 was 1.91 times that of 2008,providing a reference for assessing the potential to increase the karst carbon sink through artificial intervention.

关 键 词：碳酸盐岩风化 官村地下河流域(GGW) 外源酸 CO_(2)净消耗量 无机碳汇强度 

分 类 号：P642.25[天文地球—工程地质学] P641.3[天文地球—地质矿产勘探] P595[天文地球—地质学] P597.2