【作者】 张敏；

【导师】 董少刚； 高鹏；

【作者基本信息】 内蒙古大学 ， 环境科学与工程， 2023， 硕士

【摘要】 近年来,在人类活动影响下,自然界的碳循环路径与通量发生了剧烈的改变,从而影响到碳库的储碳效率,产生多余碳的同时使碳库释放出储存的碳（CO₂与CH₄）,造成温室气体的排放,导致全球变暖。地下水作为全球碳循环的参与者,为碳的生物地球化学作用创造了机会。红碱淖作为我国最大的沙漠湖泊,流域内地下水与地表水之间存在着密切的水力联系,地下水在流动过程中发生着溶解性无机碳（DIC）的迁移转化,同时也会向湖泊输入碳。该文将红碱淖流域地下水-湖泊系统作为研究对象,运用数理统计、Durov图、γCl^-/γCa²⁺系数和聚类分析方法,揭示了流域内地下水和湖水的水化学特征及演化规律;建立了地下水碳平衡方程以及地下水-湖水接触界面上的碳质量平衡方程;使用PHREEQC进行水文地球化学反向模拟,计算出地下水-湖泊系统内DIC的迁移转化量并分析影响因素。主要研究结论如下:（1）流域内地下水中占优势的阳离子为Ca²⁺,占优势的阴离子为HCO₃^-;湖水中存在优势阳离子为Na⁺,优势阴离子为Cl^-。地下水在补给、径流和排泄的过程中,优势阳离子逐渐从Ca²⁺向Na⁺方向演化,阴离子逐渐从HCO₃^-向SO₄^2-演化。随着地下水在补给、径流和排泄过程中的径流强度逐渐减弱,红碱淖周边地下水的循环交替条件变差。（2）地下水在流动过程发生水-岩相互作用。其中,方解石沉淀去除的净碳量为267.01t C/a,白云石溶解增加的净碳量为315.69t C/a,大气中CO₂进入地下水参与水化学反应使得净碳量溶解40.55t/a。（3）红碱淖流域年内地下水碳补给量为952.3t/a-1039.03t/a,排泄量为684.99t/a-742.39t/a。若只考虑存在于流动的地下水中DIC增量,那么水岩相互作用下地下水中增加的DIC量为89.24t/a,固碳能力约为（0.21-0.31）g C/（m²·a）;若考虑方解石沉淀增加的“固定”碳,那么在水岩相互作用下地下水实际增加的碳量为356.25t/a,则流域内地下水的实际固碳能力为（0.39-0.49）g C/（m²·a）。红碱淖流域地下水作为一个隐蔽的“碳汇”参与碳循环。（4）地下水向红碱淖排泄的DIC量为287t/a,化学反应生成的CaCO₃为1479t/a,排放的CO₂为647.3t/a,2018年以CaCO₃和CO₂形式从水体中去除的DIC各为176.5t/a;地下水与湖水的混合作用使得红碱淖DIC净减少量为66.1t/a。（5）地下水与湖水的水化学特征,特别是地下水的Ca²⁺浓度、湖水的p H值对地下水与湖水混合过程中碳的迁移转化有重要影响。更多还原

【Abstract】 In recent years,under the influence of human activities,the path and flux of the carbon cycle in nature have undergone dramatic changes,thus affecting the carbon storage efficiency of the carbon pool.The carbon pool releases stored carbon（CO₂and CH₄）while generating excess carbon,resulting in greenhouse gas emissions and global warming.Groundwater,as a participant in the global carbon cycle,creates opportunities for carbon biogeochemistry.Hongjiannao,as the largest desert lake in China,has a close hydraulic connection between groundwater and surface water in the basin.Groundwater undergoes the migration and transformation of dissolved inorganic carbon（DIC）during its flow process,while also inputting carbon into the lake.In this study,the groundwater-lake system in Hongjiannao Basin was taken as the research object.Mathematical statistics,Durov diagram,γCl^-/γCa²⁺coefficient and cluster analysis were used to analyze the hydrochemical characteristics and evolution of the water and lake water in the basin.Based on this,the groundwater carbon balance equation and the carbon mass balance equation at the contact interface between groundwater and lake water were established.The hydrogeochemical reverse simulation was carried out by PHREEQC to calculate the migration and transformation amount of DIC in the groundwater-lake system and analyze the influencing factors.The main conclusions are as follows:（1）The dominant cation is Ca²⁺and the dominant anion is HCO₃^-in groundwater.The dominant cation is Na⁺and the dominant anion is Cl^-.In the process of groundwater recharge,runoff and discharge,cations gradually evolve from Ca²⁺to Na⁺,and anions gradually evolve from HCO₃^-to SO₄^2-.As the runoff intensity of groundwater gradually weakens during recharge,runoff,and discharge processes,the surrounding area of Hongjiannao is a groundwater discharge area with poor circulation and alternation conditions.（2）Water-rock interaction occurs during the flow process of groundwater.Of which,the net carbon removed by Calcite precipitation is 267.01t C/a,the net carbon content increased by the dissolution of dolomite is 315.69t C/a,and CO₂ in the atmosphere enters groundwater and participates in hydrochemical reactions,resulting in a net carbon dissolution of 40.55t/a.（3）The annual carbon replenishment of groundwater ranges from 952.3t/a to1039.03t/a,and its excretion ranges from 684.99t/a to 742.39t/a.If only the DIC increment present in flowing groundwater is considered,the increase in DIC in groundwater under the interaction of water and rock is 89.24t/a,and the carbon sequestration capacity is approximately（0.21-0.31）g C/（m²·a）.If the fixed carbon increased by calcite precipitation is considered,then the actual carbon sequestration（C）of groundwater under the interaction of water and rock is 356.25t/a,and the annual net recharge of groundwater DIC is 566.16t/a-710.29t/a,then the actual carbon sequestration capacity of groundwater in the basin is（0.39-0.49）g C/（m²·a）.As a hidden carbon sink,groundwater in Hongjiannao Basin participates in carbon cycle.（4）The amount of DIC discharged from groundwater to the lake of Hongjiannao at the contact interface was 287t/a,the CaCO₃ generated by chemical reaction was1479t/a,the CO₂ discharged was 647.3t/a,and the DIC removed from the water in 2018was 176.5t/a.The mixing effect of groundwater and lake water results in a net reduction of 66.1t/a in DIC in Hongjiannao.（5）The hydrochemical characteristics of groundwater and lake,especially the Ca²⁺concentration of groundwater and the p H of lake water,have a significant impact on the migration and transformation of carbon during the mixing process between groundwater and lake water.更多还原