中国岩溶2025，Vol.44Issue(2)：238-249,12.DOI:10.11932/karst20250203
巫山官渡河流域黑色岩系中镉元素在地下水系统中的迁移特征研究
Study on the migration characteristics of cadmium element in the black shales of the groundwater system in the Guandu River Basin of Wushan area
摘要
Abstract
The Permian black shale in the Wushan area is characterized by high background values of harmful trace elements,among which cadmium(Cd)is particularly prominent.These elements can easily enter groundwater systems through rock weathering,soil erosion,and human activities such as coal mining,thus posing potential threats to regional ecosystems and public health.However,previous studies have predominantly focused on Cd accumulation in soil and crops,while paying less attention to the migration characteristics and pollution mechanisms of Cd in groundwater systems.This study employs a multidisciplinary approach,integrating techniques from geology,hydrology,geochemistry,and environmental science,to systematically investigate the migration characteristics of Cd in the Guandu River Basin.The primary research methods include field surveys,water sampling and testing,data analysis,and geochemical modeling.By examining the pathways and mechanisms of Cd migration from black shale to groundwater,this study reveals the transport patterns of Cd within the rock-soil-groundwater system,clarifies its pollution mechanisms,and provides a scientific basis for environmental protection and resource utilization. Analysis of 40 groundwater samples revealed that eight samples contained detectable levels of Cd,ranging from 0.0001 mg·L-1 to 0.0036 mg·L-1,while Cd was undetectable in the other 32 samples.The pH values of Cd-containing samples ranged from 7.16 to 8.26,indicating neutral conditions.The average sulfate(SO42-)concentration in Cd-containing samples was 67.84 mg·L-1,three times higher than that in Cd-free samples(22.81 mg·L-1),highlighting a strong correlation between SO42-and Cd migration.Additionally,the Total Dissolved Solids(TDS)values in Cd-containing samples ranged from 215 mg·L-1 to 365 mg·L-1,with an average of 268.56 mg·L-1,indicating moderately hard to hard water.Research findings show that Cd-containing groundwater in the Guandu River Basin primarily originates from the karst groundwater system of the Permian black shale.The Gufeng Formation within the Permian System exhibited the highest Cd content.Although Cd remained enriched in soils derived from weathered rocks,its concentration significantly decreased.Cd entered the groundwater system through leaching,which is the main source of Cd in the groundwater of the study area.Coal mining activities have significantly altered the groundwater flow paths and intensified leaching effects,leading to Cd enrichment in mine gushing water.The highest Cd concentration detected was 0.0036 mg·L-1 in gushing water(Sample S131)in an abandoned coal mine,indicating that coal mining activities are a significant anthropogenic factor contributing to Cd contamination.Additionally,TDS values in mine gushing water increased sharply,resulting in water quality deterioration and posing potential environmental risks.The Triassic karst groundwater system can effectively dilute Cd concentrations.This system is characterized by abundant water resources and demonstrates significant dilution effects on Cd concentrations in Permian karst water.For example,Cd was detected in the Longdong Underground River(Sample S039)during both the dry season and wet season,but its concentration was only 0.0003 mg·L-1,which is far lower than that in mine gushing water.This dilution effect effectively reduces the risk of Cd contamination.Geochemical modeling revealed that calcite and dolomite in groundwater are close to saturation,while cadmium sulfate and cadmium carbonate have not yet reached saturation.This indicates that Cd has the potential for further enrichment in groundwater.Cd in rocks mainly exists in carbonate minerals(19％-66％).Analysis of Cd speciation in soil shows that Cd primarily exists in the forms of iron-manganese oxide-bound(25.03％)and residual(24.22％)fractions,with the smallest proportion in the water-soluble fraction(0.63％),indicating that soluble Cd in soils is mostly leached into groundwater through weathering,and soil acidification further enhances the dissolution and migration of Cd. This study elucidates the migration mechanisms and contamination risks of Cd within the black shale-soil-groundwater system,offering essential theoretical support for controlling Cd contamination in similar regions.The findings regarding Cd enrichment in coal mine gushing water provide scientific evidence for groundwater protection and pollution management in mining areas.By clarifying the impact of soil acidification on Cd migration,this study underscores the significance of controlling soil acidification for regional ecological restoration and environmental protection.Additionally,this study also highlights the dilution effect of Triassic karst groundwater on Cd pollution,offering guidance for the sustainable development and utilization of groundwater in the region.The results of this study can serve as a reference for ecological conservation in the Wushan area and other regions characterized by black shale.关键词
官渡河流域/黑色岩系/地下水系统/镉污染/镉迁移Key words
the Guandu River Basin in Wushan area/black shale/groundwater system/cadmium contamination/cadmium migration分类
天文与地球科学引用本文复制引用
刘永旺,朱宗林,李海,柯青青,罗波,刘进,邓鑫钱,张永文..巫山官渡河流域黑色岩系中镉元素在地下水系统中的迁移特征研究[J].中国岩溶,2025,44(2):238-249,12.基金项目
重庆市规划和自然资源局地质矿产勘查类项目(ZC-2021109、21C01719-06) （ZC-2021109、21C01719-06）
