摘要
离子吸附型稀土矿开采导致矿区水土环境遭受严重的氮污染,但矿山排水影响下水体中硝酸盐(NO_(3)^(-)-N)的分布、迁移转化过程及污染来源仍缺乏系统研究。以江西赣南足洞离子吸附型稀土矿区下游地表水和地下水为研究对象,结合水化学分析及多同位素技术(δ^(18)O-H_(2)O、δ^(15)N-NO_(3)^(-)和δ^(18)O-NO_(3)^(-)),研究了水体中NO_(3)^(-)-N来源及转化过程,并借助MixSIAR模型定量评估了各污染源的贡献率。结果表明,区内水体呈弱酸性、低矿化度特征,地表水以SO 4-Ca型为主,80%地下水为HCO_(3)-Ca型;地表水的总氮(TN)及NO_(3)^(-)-N、氨氮(NH_(4)^(+)-N)浓度显著高于地下水,表明其氮污染与采矿活动密切相关。空间上,氮来源与开矿使用高氨氮卤水密切相关,矿山开采活动对地表水氮污染影响显著。土地利用类型分布表明,地表水和地下水氮的来源不同,地表水氮源主要是林地中的矿山排水,而地下水氮主要来源于耕地上的农业活动。δ^(18)O-H_(2)O、δ^(15)N-NO_(3)^(-)和δ^(18)O-NO_(3)^(-)同位素组成特征及其分馏系数分析表明,地表水和地下水均以硝化作用为主。利用δ^(15)N-NO_(3)^(-)和δ^(18)O-NO_(3)^(-)及其重建值进行端元分析显示,SW1的NO_(3)^(-)-N主要来源于铵态氮,即采矿活动排出的高NH_(4)^(+)-N水;SW2受到采矿和农业活动的共同影响,其来源包括铵态氮、土壤氮和污水粪肥,GW主要来源于土壤氮和污水粪肥。MixSIAR定量结果表明,矿山排水对靠近开采区的地表水(即SW1)的NO_(3)^(-)-N贡献率平均值超过50%,其中65%~94%NO_(3)^(-)-N来源于矿山排水中原生NO_(3)^(-)-N的直接贡献,而在远离开采区的地表水中(即SW2),矿山排水的NO_(3)^(-)-N贡献值递减至约30%。不确定性分析UI 90显示,大气降水的贡献率最为稳定,矿山排水、粪肥污水和土壤氮的贡献率存在较大的变异性。本研究揭示了离子吸附型稀土矿区硝酸盐污染的形成机制,为矿区氮污染的精准管控提供了科学依据。
Mining of ion-adsorption rare earth elements(REEs)has caused severe nitrogen pollution in water and soil.However,the distribution,migration and transformation,and pollution sources of nitrate(NO_(3)^(-)-N)in water bodies affected by such drainage remains insufficiently studied.This study investigated the origins and transformations of NO_(3)^(-)-N in surface water and groundwater downstream of the Zudong ion-adsorption REE mining area in southern Jiangxi,China,using hydrochemical analysis and a multi-isotope(δ^(18)O-H_(2)O,δ^(15)N-NO_(3)^(-) and δ^(18)O-NO_(3)^(-))approach.The contribution of various sources was quantitatively assessed using the MixSIAR model.The results showed that surface water and groundwater were weakly acidic and were characterized by low TDS values.Surface water was predominantly of the SO 4-Ca type,whereas 80%of the groundwater samples were of the HCO_(3)-Ca type.The concentrations of total nitrogen(TN),NO_(3)^(-)-N,and NH_(4)^(+)-N in surface water were significantly higher than those in groundwater,indicating that nitrogen pollution in surface water was closely related to mining activities.Spatially,nitrogen sources were closely related to mining activities that utilized ammonium-nitrogen-rich brine,which posed a significant nitrogen pollution risk to surface water.Distributions of land-use types indicated that nitrogen sources in surface water differed from those in groundwater.Nitrogen in surface water primarily originated from mine drainage in forested areas,whereas nitrogen in groundwater was mainly derived from agricultural activities on cultivated land.The compositions ofδ^(18)O-H_(2)O,δ^(15)N-NO_(3)^(-),δ^(18)O-NO_(3)^(-)and fractionation coefficients revealed that nitrification was the dominant process in both surface water and groundwater.End-member analysis based on measured and reconstructedδ^(15)N-NO_(3)^(-)andδ^(18)O-NO_(3)^(-)values suggested that NO_(3)^(-)-N in SW1 was primarily derived from ammonium nitrogen discharged from mining activities.In contrast,NO_(3)^(-)-N in SW2 was influenced by both mining and agricultural activities,with contributions from ammonium nitrogen,soil nitrogen,and sewage manure.NO_(3)^(-)-N in groundwater mainly originated from soil nitrogen and sewage manure.Quantitative assessment using the MixSIAR model indicated that mine drainage contributed over 50%(mean value)of the NO_(3)^(-)-N in SW1(surface water nearest to the mining area).Of this contribution,65%to 94%originated from the native NO_(3)^(-)-N present in the mine drainage;while in surface water farther from the mining area(SW2),mine drainage contributed approximately 30%of the NO_(3)^(-)-N.Uncertainty analysis(UI 90)showed that the contribution of atmospheric precipitation was the most stable,while the contributions of mine drainage,sewage and manure,and soil nitrogen exhibited significant uncertainty.This research elucidates the formation mechanism of NO_(3)^(-)-N pollution in ion-adsorption REE mining areas and provides a scientific basis for the precise prevention and control of nitrogen pollution.
作者
韦春伊
余圣品
白细民
刘海燕
王振
葛勤
陈功新
周仲魁
孙占学
郭华明
WEI Chunyi;YU Shengpin;BAI Ximin;LIU Haiyan;WANG Zhen;GE Qin;CHEN Gongxin;ZHOU Zhongkui;SUN Zhanxue;GUO Huaming(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;Jiangxi Provincial Key Laboratory of Genesis and Remediation of Groundwater Pollution,School of Water Resources and Environmental Engineering,East China University of Technology,Nanchang 330013,China;Hydrogeological Brigade of Jiangxi Geological Bureau,Nanchang 330224,China;Nanchang Key Laboratory of Hydrogeology and High Quality Groundwater Resources Exploitation and Utilization,Jiangxi Institute of Survey&Design LTD.,Nanchang 330224,China;School of Water Resources and Environment,China University of Geosciences(Beijing),Beijing 100083,China)
出处
《地学前缘》
北大核心
2026年第1期121-134,共14页
Earth Science Frontiers
基金
国家自然科学基金项目(42262029,42302284)
江西省自然科学基金项目(20232BAB203066,20232BAB213068)
江西省重点研发计划项目(20212BBG71011)
南昌市水文地质与优质地下水资源开发利用重点实验室开放课题(20252B21)
东华理工大学放射性地质与勘探技术国防重点学科实验室开放基金(2022RGET15)。
关键词
稀土矿
氮污染
硝化作用
贝叶斯同位素混合模型
分异富集
rare earth mine
nitrogen pollution
nitrification
Bayesian isotope mixture model
fractionation and enrichment
