ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    宁镇矿集区岩石风化成土过程中重金属迁移富集特征

    Migration and Enrichment of Heavy Metals During the Weathering Pedogenesis of Rocks in the Ningzhen ore cluster area

    • 摘要: 岩石的风化成土作用造成重金属富集并导致土壤超标是一类特殊的地质成因土壤重金属污染现象,也被称为地质高背景问题,近年来受到学术界的高度关注。为弄清岩石风化成土过程中的重金属的物质来源、释放迁移和富集规律,本研究以宁镇矿集区代表性碳酸盐岩、岩浆岩和碎屑岩风化成土剖面为对象,通过野外调查、岩矿鉴定、相关性分析、上陆壳标准化蛛网图解、化学蚀变指数和质量平衡系数计算等方法,系统研究了重金属在岩石风化成土过程中迁移富集规律。结果表明:各剖面土壤与其下伏母岩具有物源继承关系;在同一气候条件下,重金属在风化剖面中的迁移规律受岩石岩性、剖面化学风化程度和重金属元素在岩石中赋存状态等多因素控制;岩浆岩和碎屑岩剖面土壤重金属表现出继承母岩化学成分组成和含量特征,重金属迁移能力与化学风化程度呈正比。而碳酸盐岩剖面重金属迁移能力与化学风化程度呈反比,导致碳酸盐岩剖面重金属呈现出(岩石)低背景、(土壤)高富集的地球化学特征,其中Cd、As的含量甚至超农用地土壤污染风险管制值,需要加以重视。在上述研究基础上,建立了重金属在岩石风化成土过程中的释放迁移模式。

       

      Abstract: Weathering pedogenesis of rocks can release heavy metals to soil, and further accumulation of heavy metals in soil may exceed the national standard for safety soils. To understand the source, release, transport, and enrichment of heavy metals in the process of weathering pedogenesis, we systematically studied the migration and enrichment of heavy metals during rock weathering in the representative weathering pedogenesis profiles (carbonate rock, magmatic rock, and clastic rock) of the Ningzhen ore cluster area using a combination of field survey, rock and mineral identification, geochemical analysis and statistical analysis. The results showed that the soil of each profile has a provenance inheritance relationship with its underlying parent rock. The heavy metals in the soil of magmatic rock and clastic rock profiles showed similar chemical composition and content characteristics to the inherited parent rock. In contrast, the carbonate rock profile showed the geochemical characteristics of a low content of heavy metals in rocks and a high content in soil. In particular, the contents of Cd and As even exceeded the risk intervention values for soil contamination of agricultural land. It was revealed that the migration of heavy metals in weathering profiles of rocks under the same climatic conditions is controlled by multiple factors, such as rock lithology, the degree of chemical weathering of the profiles, and the occurrence state of heavy metals in rocks. The migration ability of heavy metals in magmatic rock and clastic rock profiles is proportional to the degree of chemical weathering, while the migration ability of heavy metals in carbonate rock profiles is inversely proportional to the degree of chemical weathering, leading to a higher potential for enrichment of heavy metals. Based on the above research, the release and migration pattern of heavy metals in the processes of rock weathering and soil formation was established.

       

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