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生态学杂志 ›› 2021, Vol. 40 ›› Issue (8): 2289-2301.doi: 10.13292/j.1000-4890.202108.007

• 农田地质高背景重金属污染专栏 • 上一篇    下一篇

地质高背景地区土壤中不同粒径铁锰结核地球化学特征

季文兵1,2,3,杨忠芳3*,尹爱经1,2,芦园园1,2,应蓉蓉1,2*,杨琼3,刘旭3,李博3,段轶仁3,王珏3,王懿铮3,余涛4,吴天生5,张起钻6   

  1. (1生态环境部南京环境科学研究所, 南京 210042; 2国家环境保护土壤管理与污染控制重点实验室, 南京 210042;3中国地质大学(北京)地球科学与资源学院, 北京 100083; 4中国地质大学(北京)数理学院, 北京 100083;5广西壮族自治区地质调查院, 南宁 530023;6广西壮族自治区地质矿产勘查开发局, 南宁 530023)
  • 出版日期:2021-08-10 发布日期:2021-08-10

Geochemical characteristics of Fe-Mn nodules with different sizes in soils of high geological background areas.

JI Wen-bing1,2,3, YANG Zhong-fang3*, YIN Ai-jing1,2, LU Yuan-yuan1,2, YING Rong-rong1,2*, YANG Qiong3, LIU Xu3, LI Bo3, DUAN Yi-ren3, WANG Jue3, WANG Yi-zheng3, YU Tao4, WU Tian-sheng5, ZHANG Qi-zuan6   

  1. (1Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China; 2State Environmental Protection Key Laboratory of Soil Environmental Management and Pollution Control, Nanjing 210042, China; 3School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China; 4School of Science, China University of Geosciences, Beijing 100083, China; 5GuangxiInstitute of Geological Survey, Nanning 530023, China; 6Guangxi Bureau of Geology & Mineral Prospecting & Exploitation, Nanning 530023, China).
  • Online:2021-08-10 Published:2021-08-10

摘要: 研究地质高背景地区土壤中不同粒径铁锰结核地球化学特征,有助于厘清岩溶地区土壤中铁锰结核对重金属异常富集的影响及对重金属吸附固定的主控因素。本研究以广西南宁市和崇左市大新县表层土壤大样(0~20 cm)为对象,筛分出不同粒径的铁锰结核(0.3~0.5、0.5~1、1~2、2~4、4~6、6~8、>8 mm)和对应土壤(<2 mm)样品进行化学分析,研究不同粒径铁结核和锰结核重金属元素变化和主控因素以及重金属(Cd、Cr、Cu、Ni、Pb、Zn)在铁锰结核和对应土壤中的分布分配规律。结果显示:铁结核和锰结核中,随着粒径变化,Fe2O3与Cr元素显示同步变化趋势,而MnO2与Cd、Cu、Ni、Pb、Zn等重金属变化趋势同步,重金属元素随粒径变化特点反映了铁锰结核形成及生长过程中铁元素控制着Cr元素的地球化学行为,而锰元素控制着Cd、Cu、Ni、Pb、Zn元素的地球化学行为。通过计算土壤中铁锰结核重金属元素含量的贡献比例,在铁结核中平均贡献比例为Cr(47.76%)>Cd(24.91%)>Pb(18.44%)>Cu(16.26%)>Zn(14.77%)>Ni(10.41%),而在锰结核中平均贡献比例为Cr(45.25%)>Cd(37.94%)>Pb(25.86%)>Cu(15.59%)>Zn(13.79%)>Ni(12.15%),说明岩溶区土壤中大部分重金属实际是被固定在铁锰结核中,且生物活性很低。因此,对高地质背景区土壤进行生态风险评价时,应扣除固定在铁锰结核中的重金属,这样才更科学更精确。

关键词: 岩溶区, 铁结核, 锰结核, 地球化学行为, 重金属元素

Abstract: Understanding the geochemical characteristics of different particle sizes of iron-manganese nodules in soils of high geological background areas is helpful to clarify the effects of iron-manganese nodules on the abnormal enrichment of heavy metals and the main controlling factors of heavy metal adsorption and fixation in soils in karst areas. The surface soil samples (0-20 cm) were collected in Nanning City and Daxin County in Chongzuo, Guangxi. The samples of iron-manganese nodules with different particle sizes (0.3-0.5, 0.5-1, 1-2, 2-4, 4-6, 6-8, and >8 mm) and corresponding soils (<2 mm) were screened out for chemical analysis. The main aims of this study were to examine the variation and controlling factors of heavy metals in iron-manganese nodules with different particle sizes, and clarify the distribution of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) in iron-manganese nodules and corresponding soils. The results showed that Fe2O3 and Cr in iron-manganese nodules displayed synchronous dynamics, while MnO2 presented a synchronous dynamic with Cd, Cu, Ni, Pb, and Zn with changes of particle sizes. The characteristics of heavy metals with changes of particle sizes reflected the formation and growth process of iron-manganese nodules. Iron affects the geochemical behavior of Cr, while manganese affects the geochemical behaviors of Cd, Cu, Ni, Pb and Zn. We calculated the percentage of mass (PM) of iron-manganese nodules to the element concentrations in soil. The PM of iron nodules was in an order of Cr (47.76%) > Cd (24.91%) > Pb (18.44%) > Cu (16.26%) > Zn (14.77%) > Ni (10.41%), while the PM of manganese nodules was in an order of Cr (45.25%) > Cd (37.94%) > Pb (25.86%) > Cu (15.59%) > Zn (13.79%) > Ni (12.15%). Those results indicate that a large number of heavy metals in the soil of karst area are actually fixed by the nodules in the ironmanganese nodules, with quite low biological activities. Therefore, heavy metals fixed by the iron-manganese nodules in the total amount of soil should be deducted in the assessment of soil ecological risk in high geological background areas, which would be more scientific and accurate.

Key words: karst area, iron nodule, manganese nodule, geochemical behavior, heavy metal.