地学前缘 ›› 2023, Vol. 30 ›› Issue (3): 505-514.DOI: 10.13745/j.esf.sf.2022.9.3

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贵德盆地高氟地下水稀土元素特征及其指示意义

王振1(), 郭华明2,*(), 刘海燕1, 邢世平2   

  1. 1.东华理工大学 水资源与环境工程学院, 江西 南昌 330032
    2.中国地质大学(北京) 水资源与环境学院, 北京 100083
  • 收稿日期:2022-06-30 修回日期:2022-08-19 出版日期:2023-05-25 发布日期:2023-04-27
  • 通讯作者: *郭华明(1975—),男,教授,主要从事水文地质学方面的教学与科研工作。E-mail: hmguo@cugb.edu.cn
  • 作者简介:王 振(1990—),男,博士,讲师,主要从事水文地球化学方面的教学与研究工作。E-mail: wzhen@ecut.edu.cn
  • 基金资助:
    国家自然科学基金项目(41222020);国家自然科学基金项目(41672225);中央高校基本科研业务费项目(2652013028);博士科研启动基金项目(DHBK2019098);博士科研启动基金项目(SHT201901);地下水循环与环境演化教育部重点实验室开放基金项目(K20220002)

Geochemical characteristics of rare earth elements in high-fluoride groundwater in the Guide Basin and its implications

WANG Zhen1(), GUO Huaming2,*(), LIU Haiyan1, XING Shiping2   

  1. 1. School of Water Resources and Environment Engineering, East China University of Technology, Nanchang 330032, China
    2. School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China
  • Received:2022-06-30 Revised:2022-08-19 Online:2023-05-25 Published:2023-04-27

摘要:

高氟地下水是我国乃至国际社会面临的最严重的环境地质问题之一。尽管众多的研究学者已对高氟地下水形成机理开展了广泛的研究,但高氟地下水中稀土元素的分异特征和迁移规律能否指示地下水中氟的富集过程尚不完全清楚。本研究聚焦高氟地下水广泛分布的贵德盆地,通过野外调查取样、室内测试和综合分析以及水文地球化学模拟相结合的技术手段,探究了含水层中氟和稀土元素的分布特征和迁移规律。研究发现贵德盆地地下水中氟的平均浓度为2.67 mg·L-1,75%的地下水样品中氟浓度高于1.5 mg·L-1,且沿地下水流程呈现出上升趋势。PHREEQC计算结果表明,地下水中氟主要以自由态F-的形式存在(浓度99.5%)。XRD 和SEM-EDS的结果表明含水层沉积物中的主要矿物为石英(含量52.9%~56.5%)和斜长石(含量19.8%~21.8%),且斜长石已发生化学风化作用。贵德盆地地下水中稀土元素浓度较低(0.052~0.267 μg·L-1),且主要以LnCO3+和Ln(CO3)2-无机络合形态存在(含量>99%,Ln代表稀土元素)。地下水稀土元素北美页岩归一化模式表现为轻稀土元素相对于重稀土元素富集,且具有轻微的Ce负异常和显著的Eu正异常特征。地下水中氟和稀土元素的迁移均受到含水层中铁氧化物矿物的还原性溶解和长石类矿物的非全等水解过程的影响,且地下水中稀土元素的富集过程在一定程度上可以指示地下水中氟的富集过程。研究成果拓展了稀土元素在高氟地下水研究中的应用,可以为识别和揭示高氟地下水的分布和富集机理提供依据。

关键词: 高氟地下水, 稀土元素, 贵德盆地, 水-岩相互作用, 元素迁移和富集

Abstract:

High-fluoride groundwater is one of the most serious environmental geological problems in China and abroad. Although the formation mechanism of high-fluoride groundwater has been studied extensively by many researchers, it is not completely clear whether chemical speciation and migration characteristics of rare earth elements (REEs) in high-fluoride groundwater are indicative of the fluoride enrichment process. This study focused on the Guide Basin where high fluoride content groundwater is widely distributed, and explored the distribution and migration processes of fluoride and REEs in aquifer by field sampling, laboratory testing and comprehensive geochemical analysis, combined with hydrogeochemical simulation. It was found that the average fluoride concentration in groundwater was 2.67 mg·L-1—with 75% of samples higher than 1.5 mg·L-1—and showed an upward trend along the groundwater flow path. PHREEQC calculation results showed that fluoride mainly occurred as free F- in groundwater (99.5%). XRD and SEM-EDS results showed that the main minerals in aquifer sediments were quartz (52.9%-56.5%) and plagioclase (19.8%-21.8%) that has undergone chemical weathering. REE contents in groundwater samples were low (0.052-0.267 μg·L-1), and REEs mainly occurred as LnCO3+ and Ln(CO3)2- (>99%)(Ln represents REEs). NASC-normalized REE patterns showed that LREEs were enriched relative to HREEs, with slight negative Ce anomaly and obvious positive Eu anomaly. Migration of fluoride and REEs in groundwater was affected by reductive dissolution of iron oxide minerals and inhomogeneous hydrolysis of feldspar minerals, and, to certain extent, REE enrichment process was indicative of fluoride enrichment in groundwater. This research expanded REE applications in the study of high-fluoride groundwater and provided a reference for identifying high-fluoride groundwater distribution and revealing fluoride enrichment mechanisms.

Key words: high-fluoride groundwater, rare earth elements, Guide Basin, water-rock interaction, elemental migration and enrichment

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