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高校地质学报 ›› 2022, Vol. 28 ›› Issue (6): 787-798.DOI: 10.16108/j.issn1006-7493.2021079

• 表生地球化学专栏 •    下一篇

广西岩溶区土壤铁锰结核重金属富集的地质特征

冯一夫1,廖启林2,季文兵3,任静丽1,季峻峰1,杨忠芳3,卓小雄4,王 磊4,刘媛媛1*
  

  1. 1. 表生地球化学教育部重点实验室,南京大学 地球科学与工程学院,南京 210023;
    2. 江苏省地质调查研究院,南京 210018;
    3. 中国地质大学(北京) 地球科学与资源学院,北京 100083;
    4. 广西土地质量地球化学评价项目办公室,南宁 530023
  • 出版日期:2022-12-20 发布日期:2022-12-20

Geochemical Characteristics of Heavy Metal Enrichment in Soil Fe-Mn Nodules in the Karst Area of Guangxi

FENG Yifu1,LIAO Qilin2,JI Wenbing3,REN Jingli1,JI Junfeng1,YANG Zhongfang3,ZHUO Xiaoxiong4,WANG Lei4,LIU Yuanyuan1*   

  1. 1. Key Laboratory of Surficial Geochemistry, Ministry of Education, School of Earth Sciences and Engineering,
    Nanjing University, Nanjing 210023, China;
    2. Geological Survey of Jiangsu Province, Nanjing 210018, China;
    3. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;
    4. Project Office of Land Quality Geochemical Assessment of Guangxi, Nanning 530023, China
  • Online:2022-12-20 Published:2022-12-20

摘要: 广西岩溶区农田土壤重金属污染形势严峻。该地区土壤含有大量铁锰结核,其主要成分为铁和锰的氧化物,对重金属有着较强的富集作用。铁锰结核伴随着土壤形成过程而产生,也是反映土壤形成过程及成土环境变化的良好载体。研究铁锰结核中重金属的富集特征有助于了解广西岩溶区土壤中重金属元素的富集过程和富集特征。文章对广西柳江和桂平的土壤与其中的铁锰结核进行了成分分析,通过微量元素分析得到铁锰结核对Ni、Cu、Cd、Zn、Pb、Co、Ba、As、Cr等重金属元素的富集特征,通过Ti/Al2O3的比值关系推断了铁锰结核与土壤的物质来源。此外,还对铁锰结核进行了激光共聚焦显微拉曼光谱仪(Laser Microscopic Confocal Raman Spectrometer)、扫描电镜和能谱仪(SEM-EDS)分析。通过铁锰结核内部同心环带状圈层结构及其内部的元素分布周期性变化的特征,推测结核形成机制。铁锰结核的形成固定了大量重金属元素,减轻了土壤重金属污染负担;但如果铁锰结核发生了溶解则会导致Mn及受其控制的部分重金属(Co、Cu、Ni、Ba)重新释放回到土壤,加重重金属污染。

关键词: 广西岩溶区, 铁锰结核, 重金属污染

Abstract: The natural heavy metal contaminant is severe in the Karst area in Guangxi. In this area, the soil contains large quantities of Fe-Mn nodules. Soil Fe-Mn nodules are symbiotic products of soil formation, which is controlled by the environmental conditions. Therefore, Fe-Mn nodules is a good geological record of soil formation and development, as well as historical environmental change. Fe-Mn nodules are composed of ferromanganese oxides, which have strong capacities for heavy metal adsorption. Studying the accumulation characteristics of heavy metals in Fe-Mn nodules will improve understanding the accumulation processes of heavy metals during soil formation and provide scientific support for soil management and treatment. In this study, a series of experiments were conducted using the soil and Fe-Mn nodules from a typical Karst area in Liujiang, Guangxi. Through the determination of trace elements, the analysis shows that Fe-Mn nodules can adsorb Ni, Cu, Cd, Zn, Pb, Co, Ba, As and Cr effectively. We found concentric ring structure and regular distribution of elements in nodules by means of micro measurement methods including Raman spectrum and SEM-EDS. Combined with internal structure and elemental distribution characteristics, the formation mechanism and material source of Fe-Mn nodule was speculated. The formation of Fe-Mn nodules immobilized heavy metals and reduced heavy metal pollution in soil. However, the dissolution of Fe-Mn nodules will release large amount of heavy metals into soil especially those associated with Mn.

Key words: Karst area in Guangxi, Fe-Mn nodule, heavy metal pollution

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