摘要
溶解无机碳(DIC)是研究流域水体碳循环的重要指标之一。泸江流域内岩溶断陷盆地发育,水文地质条件独特,是研究流域水体碳迁移转化的良好选区。为了研究泸江流域河流水体水化学类型及DIC的来源问题,分析了该流域雨季14个地表水点、8个暗河点、10个泉点的水化学和碳同位素采样数据。结果表明:(1)流域内水化学类型主要是HCO_(3)-Ca型,属于“碳酸盐岩风化型”;(2)通过分析离子关系图进一步确定了SO_(4)^(2-)与NO_(3)^(-)参与了流域岩石风化过程;(3)基于离子比值法计算得出,碳酸风化碳酸盐岩贡献比例平均为68.8%,硫酸/硝酸风化碳酸盐岩贡献比例平均为27.2%,硅酸盐岩风化对HCO_(3)^(-)贡献比例平均为3.9%,泸江流域水体岩石风化过程中,以碳酸风化碳酸盐岩为主;(4)根据碳同位素法验证,与实测值相比,暗河水和泉水理论平均值δ^(13)C_(DICTh)比较接近,而地表水则过于偏正,说明地表水中DIC来源不仅由岩石风化控制,还有河流水体内部的生物地球化学过程。相比较而言,地表河流处城镇化严重且存在明显农业活动,受人类活动影响显著。
The watershed carbon cycle is an important part of the global carbon cycle,playing an important role in seeking global carbon sinks that have been missed.Dissolved inorganic carbon(DIC)is one of the important indicators for studying the carbon cycle of water bodies in the basin.As an important component of terrestrial ecosystems,karst water bodies containing high DIC concentrations play an important role in the global carbon cycle.The Lujiang river basin,a typical development area of karst graben basin,is an applicable place for us to study the carbon migration and transformation of water bodies.In order to study the hydrochemical types and sources of DIC in the rivers of the Lujiang river basin,sampling data of hydrochemistry and carbon isotope from 14 surface water points,8 underground river points,and 10 spring points during the rainy season were analyzed.It is believed that exploring the proportional contribution of DIC sources in different water bodies may help to understand the sources and cycles of groundwater DIC under the influence of human activities,providing scientific references for water resource management.Firstly,this study determines the hydrochemical types of different water bodies through the Piper trilinear map and Schukalev classification.The results show that regardless of the type of water body in the study area,the hydrochemical type in the drainage basin is mainly HCO_(3)-Ca,belonging to the"type of carbonate rock weathering".Due to the long interaction time between water and rock,the rock weathering in groundwater is more obvious than in surface water.Secondly,the analyses of ion sources in water bodies by Gibbs plot indicate the consistency in the hydrochemical composition,changes,and origin mechanisms between groundwater and surface water.The controlled mechanism belongs to the leaching type of rock weathering".Thirdly,due to the widespread distribution of carbonate rocks in the study area,an analysis has been conducted on carbonate rock dissolution in order to distinguish the relative contribution of limestone and dolomite dissolution to the chemical ion compositions of water bodies in the watershed.It is found that there are additional sources of Mg^(2+)and Ca^(2+)in the surface water of the Lujiang river basin,while other acids participate in the chemical weathering reaction in the water bodies of the underground river points and spring points.Furthermore,it is determined that SO_(4)^(2-)and NO_(3)^(-)are involved in the rock weathering in the basin,which has caused a large disturbance to the hydrochemical characteristics of water bodies in the basin.The Lujiang river basin is mixed with carbonate and silicate rocks.Therefore,the main sources of HCO_(3)^(-)in water are classified into three types:carbonate rocks weathered and dissolved by carbonic acid,carbonate rocks weathered by sulfuric acid/nitric acid,and silicate rocks weathered by carbonic acid.Based on the quantitative analysis by ion ratio method,carbonate rocks weathered by carbonic acid contribute average 68.8% to HCO_(3),carbonate rocks weathered by sulfuric acid/nitric acid 27.2%,and silicate rock weathered by carbonic acid 3.9%.During the weathering process of water bodies in the Lujiang river basin,carbonate rocks are mainly weathered by carbonic acid.Finally,the verification by carbon isotope method has been compared with the measured values to show that the theoretical average values of underground river water and spring water δ^(13)C_(DIC_Th)are relatively close,while the values of surface water are positive too,indicating that the source of DIC in surface water is not only controlled by rock weathering,but also by biogeochemical processes within river water bodies.In comparison,the areas of surface rivers are more significantly affected by human activities with severe urbanization and agricultural activities.
作者
李丹阳
张连凯
李灿锋
王晓宇
王兴荣
杨镇飞
钱龙藤
LI Danyang;ZHANG Liankai;LI Canfeng;WANG Xiaoyu;WANG Xingrong;YANG Zhenfei;QIAN Longteng(Kunming Natural Resources Comprehensive Investigation Center,China Geological Survey/Technology Innovation Center for Natural Ecosystem Carbon Sequestration Engineering,MNR,Kunming,Yunnan 650100,China;China University of Geosciences(Beijing),Beijing 100083,China)
出处
《中国岩溶》
CAS
CSCD
北大核心
2024年第1期92-104,共13页
Carsologica Sinica
基金
中国地质调查局地质调查项目(ZD20230111)。
关键词
水化学特征
溶解无机碳
碳同位素
离子比值法
hydrochemical characteristics
dissolved inorganic carbon
carbon isotope
ion ratio method
