摘要
地下水是表层土壤碳库的重要碳排泄项,准确评估地下水碳循环量对区域碳均衡研究意义显著。评估地下水碳循环量首先需要确定地下水中的碳元素的来源,并分析碳迁移转化过程。以塔里木盆地主要支流流域为研究区,分析地下水主要溶质的水化学来源及迁移转化特征,结果表明,地下水中的碳元素主要来源于水分入渗过程而非径流过程,即地下水碳主要来源于表层土壤碳库,而其他主要元素多来源于径流过程中的矿物溶解,这是判定地下水碳循环量能否视为碳汇的关键;在地下水径流过程中,随着溶解总固体(TDS)的增加,重碳酸根离子可能进一步转化为碳酸盐及游离二氧化碳,从而会降低高TDS地下水中的碳含量,这部分样本需要在评估方法中加以甄别。以此为基础,结合各片区地下水循环量,建立地下水碳汇评估方法并进行评估,结果显示,塔里木盆地7个主要支流地下水碳汇量约为151×10^(4)t/a(以碳计),这部分碳汇是表层土壤碳库最主要的排泄途径之一,其碳汇贡献较大,是陆地碳平衡的重要组成,不容忽视。
Groundwater is usually downstream of the soil layer,which is one of the most important carbon reservoirs in the terrestrial ecosystems.Assessing the source,migration and transformation processes of carbon in water cycling system is of importance to accurately estimate groundwater carbon sink,which may has significant implications for the study of regional carbon balance.In this study,474 groundwater samples were collected in Tarim Basin,including 461 groundwater samples from the circular oasis area around the basin,3 samples as a set of stratified groundwater data in desert areas and 10 samples of different rivers.Samples were analyzed to determine the source,migration and transformation of carbon in groundwater system of Tarim Basin.It showed that the carbon in groundwater mainly originates from the water infiltration through soil layer in the vadose zone rather than the dissolution of carbonate minerals in the aquifer system,revealing that soil carbon pool is the primary source of carbon elements in groundwater.This is the key to determining whether groundwater carbon cycling becomes a carbon sink.Meanwhile,the mineral dissolution during the process of groundwater runoff is the main source of other major elements in groundwater,for example,chlorine,sulfur,potassium,sodium,calcium and magnesium.Moreover,the migration and transformation process of carbon in the aquifer systems is vital to determine the hydrochemical variation and controlling mechanism of carbon sink in groundwater.As the total dissolved solid(TDS)in groundwater increases during the runoff process,bicarbonate may be converted into carbonates and free carbon dioxide under the water-rock interactions,and thus more carbon are trapped in deep aquifers,which can increase the total carbon sink amount in groundwater.At the same time,this process will reduce the carbon content in the groundwater samples with high total dissolved solids,which needs to be taken into account in the evaluation methods.Finally,a new estimation method of groundwater carbon sink was established by considering the amount of groundwater circulation and carbon contents in different drainage areas.The method was used to estimate the groundwater carbon sink in the study areas.The results indicate that the groundwater carbon sink of the seven main drainage areas in the Tarim Basin is about 1.51 million tons per year(counted by carbon).The case study suggested that the groundwater carbon sink is one of the most important subsequent components of soil carbon pool,which may strongly influences the terrestrial carbon sink system and is crucial for global carbon balance.
作者
马洪云
刘江
王化齐
李成柱
马红娜
李艳娥
MA Hongyun;LIU Jiang;WANG Huaqi;LI Chengzhu;MA Hongna;LI Yane(Xi′an Center of China Geological Survey(Northwest China Center for Geoscience Innovation),Xi′an 710119,China;Xi′an Center of China Geological survey,Shaanxi Engineering research Centre of Water resources and Environment,Xi′an 710119,China;Xi′an Center of China Geological Survey,Key Laboratory for Groundwater and Ecology in Arid and Semi-arid Regions,Xi′an 710119,China)
出处
《生态学报》
北大核心
2025年第15期7248-7256,共9页
Acta Ecologica Sinica
基金
新疆第三次科学考察项目(2022xjkk0300)
陕西省重点研发计划一般项目(2024SF-YBXM-562)。
关键词
塔里木盆地
地下水
水化学分析
碳循环
碳汇评估
Tarim Basin
groundwater
geochemical analysis
carbon cycle
carbon sink assessment
