碳酸盐岩风化和成土过程的重金属迁移富集机理初探及环境风险评价  

Heavy Metal Migration and Enrichment Mechanism and the Environmental Risks during the Weathering and Soil Formation of Carbonate Rocks

作　　者：王秋艳 文雪峰[1] 魏晓 刘鸿雁[1] WANG Qiuyan;WEN Xuefeng;WEI Xiao;LIU Hongyan(College of Agriculture,Guizhou University,Guiyang 550025,China)

机构地区：[1]贵州大学农学院,贵阳550025

出　　处：《地球与环境》2022年第1期119-130,共12页Earth and Environment

基　　金：环境地球化学国家重点实验室开放课题(SKLEG2021212);国家自然科学基金项目(41473027、42067028、41563011);贵州大学引进人才科研项目[贵大人基合字(2017)53号]。

摘　　要：为了探究碳酸盐岩在风化和成土过程中重金属元素迁移规律及重金属的富集机理,本次研究以贵州省都匀市及其周边地区寒武纪地层出露的碳酸盐岩风化剖面为研究对象,采用碳酸盐岩酸不溶物的提取试验研究重金属在基岩中的赋存特征,并结合质量平衡法探索重金属的迁移特征,初步讨论了土壤中重金属的富集机制及其环境影响。研究结果表明:碳酸盐岩风化过程中Ca、Mg元素大量淋失所导致的体积和质量的巨大损失,是造成风化土壤重金属相对富集的主要原因;而部分碳酸盐岩风化过程中释放的重金属以多种形式滞留于残积土中,导致土壤中重金属富集程度增加。研究区部分碳酸盐岩风化剖面重金属含量严重超标,其中以Cd和As超标程度最为严重。重金属元素在碳酸盐岩风化剖面中的迁移规律受气候、剖面发育程度、元素地球化学性质和重金属在碳酸盐岩不同矿物相中的分配特征等多重因素控制。综合分析认为碳酸盐岩风化和成土过程中重金属显著富集的特征很可能是喀斯特地区土壤重金属超标的重要驱动机制,建议地方政府及相关部门在规划和发展农业产业时,要高度重视Cd和As超标的风险,加大对喀斯特地区地表径流和地下水重金属污染的监控力度。In order to explore the migration and enrichment mechanisms of heavy metals during the weathering and soil-forming process of carbonate rocks, the outcropped weathering profile of carbonate rocks in Cambrian strata in Duyun City and its surrounding areas of Guizhou Province was taken as the research object, and the occurrence characteristics of heavy metals in bedrock were studied by using the extraction test of acid insoluble matter of carbonate rocks. Combined with the mass balance method, the migration characteristics of heavy metals were explored, and the enrichment mechanism of heavy metals in soil and its environmental impact were discussed. The results showed that the large volume and mass loss caused by the leaching of Ca and Mg elements during the weathering of carbonate rocks is the main reason for the relative accumulation of heavy metals in the weathered soils. The heavy metals released during the weathering of some carbonate rocks remain in the residual soil in various forms, leading to the increase of the enrichment of heavy metals in the soil. The content of heavy metals in some weathering sections of carbonate rocks in the study area exceeds the standard seriously, especially Cd and As. The migration of heavy metals in weathering profiles of carbonate rocks is controlled by multiple factors, such as climate, profile development, element geochemical properties and distribution characteristics of heavy metals in different mineral facies of carbonate rocks. Comprehensive analysis shows that the characteristics of significant enrichment of heavy metals in the process of carbonate weathering and soil formation are likely to be an important driving mechanism for excessive heavy metals in karst soil. It is suggested that the local government and relevant departments should pay great attention to the risk of excessive Cd and As in the planning and development of agricultural industry, and strengthen the monitoring of surface runoff and groundwater heavy metal pollution in karst areas.

关 键 词：碳酸盐岩 土壤 重金属迁移富集特征 超标情况 

分 类 号：P5121[天文地球—地质学]