喀斯特地区典型风化剖面重金属超标程度及元素迁移特征研究
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摘要
我国西南喀斯特地区是著名的重金属元素地球化学异常区。除了人类活动所导致的土壤污染问题以外,地质背景很可能是造成土壤重金属超标的重要因素。为了弄清岩石风化和成土过程中重金属的释放规律及其环境效应,本次研究以贵州省罗甸县典型的碳酸盐岩和碎屑岩风化剖面为载体,采用实地调查、地球化学测试分析等手段,结合质量平衡系数的计算方法对研究剖面的重金属元素超标程度及元素迁移规律展开调查。研究结果表明:碳酸盐岩比泥质岩具有更高的重金属元素释放潜能,其风化和成土过程向环境中释放重金属的量与风化壳的发育程度有关。研究区石灰土剖面重金属元素超标程度严重,且以Cd和As的超标程度最大。地带性黄壤中Cr、Ni元素的富集很可能与剖面发育过程中铁氧化物的沉淀富集有关。综合分析认为岩性不同所导致的风化速率的差异很可能是造成碳酸盐岩和泥质岩剖面重金属淋失程度差异的主要原因。而且,重金属元素在风化剖面中的迁移规律受元素自身地球化学性质、母岩类型和风化壳发育程度等多重因素控制。
The karst area in southwest China is a famous geochemical anomaly region of heavy metals. Besides human activities, the regional geological background could be another significant factor for which results in excessive heavy metals in soils. In order to figure out releasing rules and environmental effects of heavy metals during weathering and pedogenesis processes of rocks, investigations of excessive degrees and migration rules of heavy metals in representative weathering profiles of carbonate and clastic rocks in the Luodian County, Guizhou, were carried out using field surveys, geochemical analyses and mass balance calculations. The results show that, compared to clastic rocks, carbonate rocks have higher potential to release heavy metals, and that the amount of heavy metals released from carbonate rocks by either weathering or pedogenesis process is closely related to the weathered crust development degree. In the study area, concentrations of heavy metals in calcareous soil profiles exceed the national standards remarkably, especially of Cd and As. The enrichments of Cr and Ni in yellow soils are probably associated to the precipitation and enrichment of iron oxides during the development processes of weathering profiles. The difference of weathering rates caused by different lithology is probably the main reason for the difference of heavy metal leaching degrees between carbonate rocks and mudstone profiles. Moreover, the migrations of heavy metals in weathering profiles are controlled by their geochemical properties, parent rock types and development degrees of weathered crusts.
The karst area in southwest China is a famous geochemical anomaly region of heavy metals. Besides human activities, the regional geological background could be another significant factor for which results in excessive heavy metals in soils. In order to figure out releasing rules and environmental effects of heavy metals during weathering and pedogenesis processes of rocks, investigations of excessive degrees and migration rules of heavy metals in representative weathering profiles of carbonate and clastic rocks in the Luodian County, Guizhou, were carried out using field surveys, geochemical analyses and mass balance calculations. The results show that, compared to clastic rocks, carbonate rocks have higher potential to release heavy metals, and that the amount of heavy metals released from carbonate rocks by either weathering or pedogenesis process is closely related to the weathered crust development degree. In the study area, concentrations of heavy metals in calcareous soil profiles exceed the national standards remarkably, especially of Cd and As. The enrichments of Cr and Ni in yellow soils are probably associated to the precipitation and enrichment of iron oxides during the development processes of weathering profiles. The difference of weathering rates caused by different lithology is probably the main reason for the difference of heavy metal leaching degrees between carbonate rocks and mudstone profiles. Moreover, the migrations of heavy metals in weathering profiles are controlled by their geochemical properties, parent rock types and development degrees of weathered crusts.
引文
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[2] 孙晋伟, 黄益宗, 石孟春, 等. 土壤重金属生物毒性研究进展[J]. 生态学报, 2008, 28(6): 2861-2869.
[3] Sun Y, Zhou Q, Xie X, et al. Spatial, sources and risk assessment of heavy metal contamination of urban soils in typical regions of Shenyang, China [J]. Journal of Hazardous Materials, 2010, 174(1-3): 455.
[4] 郭笑笑, 刘丛强, 朱兆洲, 等. 土壤重金属污染评价方法[J]. 生态学杂志, 2011, 30(5): 889-896.
[5] 骆永明. 金属污染土壤的植物修复[J]. 土壤, 1999, 31(5): 261-265.
[6] 蔡美芳, 李开明, 谢丹平, 等. 我国耕地土壤重金属污染现状与防治对策研究[J]. 环境科学与技术, 2014, 37(S2): 223-230.
[7] Viard B, Pihan F, Promeyrat S, et al. Integrated assessment of heavy metal (Pb, Zn, Cd) highway pollution: bioaccumulation in soil, graminaceae and land snails [J]. Chemosphere, 2004, 55(10): 1349-1359.
[8] 何腾兵, 董玲玲, 刘元生,等. 贵阳市乌当区不同母质发育的土壤理化性质和重金属含量差异研究[J]. 水土保持学报, 2006, 20(6): 157-162.
[9] 何邵麟, 龙超林, 刘应忠, 等. 贵州地表土壤及沉积物中镉的地球化学与环境问题[J]. 贵州地质, 2004,21(4): 245-250.
[10] 龙家寰, 刘鸿雁, 刘方, 等. 贵州省典型污染区土壤中镉的空间分布及影响机制[J]. 土壤通报, 2014(5): 1252-1259.
[11] 范成五, 张邦喜, 秦松, 等. 贵州麦西河沉积物及土壤中重金属分布特征及污染评价[J]. 湖北农业科学, 2012, 51(20): 4485-4490.
[12] 吴攀, 刘丛强, 张国平, 等. 碳酸盐岩矿区河流沉积物中重金属的形态特征及潜在生态风险[J]. 生态与农村环境学报, 2004, 20(3): 28-31.
[13] 谢代兴, 杨杨, 苏春田,等. 滇东南石灰土重金属超标程度及潜在生态危害评价:以三迭系至寒武系地层土壤为例[J]. 贵州农业科学, 2015, 1: 162-166.
[14] Nesbitt H W. Mobility and fractionation of rare earth elements during weathering of a granodiorite [J]. Nature, 1979, 279: 206-210.
[15] Chadwick O A, Brimhall G H, Hendricks D M. From a black to a gray box-a mass balance interpretation of pedogenesisi [J]. Geomorphology, 1990, 3: 369-390.
[16] 王世杰, 季宏兵. 碳酸盐岩风化成土作用的初步研究[J]. 中国科学(D辑), 1999, 29(5): 441-449.
[17] 李艳丽.贵州碳酸盐岩红色风化壳稀土富集与分异的机理研究[D].中国科学院研究生院(地球化学研究所),2004.
[18] 刘英俊, 曹励明, 李兆麟,等. 元素地球化学[M]. 北京:科学出版社,1984: 1-548.
[19] 李小平, 王继文, 赵亚楠,等. 城市土壤中铅地球化学过程与儿童铅暴露的关系[J]. 国外医学医学地理分册, 2016, 37(2): 85-92.
[20] Fordham A W, Norrish K. Electron microprobe and electron microscope studies of soil particles [J]. Australian Journal of Soil Research, 1979, 17(3): 283-306.
[21] Ayoub G M, Mehawej M. Adsorption of arsenate on untreated dolomite powder [J]. Journal of Hazardous Materials, 2007, 148: 259-266.