湖南典型地区土壤中铅等元素污染来源探讨

发布时间：2018-04-29 13:49

本文选题：有害元素 + 来源识别　；参考：《中国地质大学(北京)》2016年硕士论文

【摘要】：随着国家经济建设步伐不断加速,由人类活动造成的Pb等有害元素在环境中积累现象日趋严重,人为污染造成的有害元素富集具有较高的危害性,在自然成土过程中表层土壤也会富集有害元素,但此类有害元素危害性较低,因此识别土壤中有害元素来源具有非常重要的意义。本论文在湖南地区选取了以板岩和花岗岩为成土母质的两类土壤,并分别选择表层土壤中Pb等重金属元素高于深层的区域作为污染区,表层土壤中Pb等重金属元素接近于深层的区域作为背景区。对比分析同一母质下背景区剖面与污染区剖面理化指标、矿物组成及有害元素含量的特征,通过相关分析探究理化指标对有害元素分布的影响,并通过富集系数、重金属形态、磁化率及铅同位素等方法对表层土壤中的Pb等有害元素进行来源解析。通过本文研究得出以下结论:在土壤理化性质方面,研究表明研究区土壤质地受控于母岩类型,pH和化学风化指数(CIA)受控于气候,表层土壤具有较高的有机碳和阳离子交换量(CEC),花岗岩母质的粘土矿物组合为高岭石+伊利石+绿泥石+蒙脱石,板岩母质土壤黏土矿物组合为高岭石+伊利石+蒙脱石;土壤剖面有害元素的分布特征表明以板岩为成土母质的污染区表层土壤有害元素含量显著高于深层土壤;背景区表层土壤有害元素含量略高于深层土壤。以花岗岩为成土母质的污染区表层土壤有害元素显著高于深层土壤,背景区表层土壤有害元素含量接近于深层土壤;经分析可知有害元素的垂向分布特征主要受元素地球化学行为的控制,并受土壤性质的影响;以Ti作为参比元素,通过富集系数法估算污染区土壤剖面上人为源输入有害元素的量,结果表明不同成土母质污染区土壤剖面上表层土壤中有害元素人为源输入的量比较大,对有害元素形态的研究可见污染区土壤剖面中活动态比例明显高于背景区土壤剖面,污染区剖面磁化率高于背景区,且与有害元素含量呈较好的正相关性,铅同位素组成研究显示污染区表层土壤中Pb同位素组成主要与大气干湿沉降相似,系统对比表明污染区表层土壤受到人为源污染较为严重,且存在较大生态风险。
[Abstract]:With the accelerating pace of national economic construction, the accumulation of harmful elements such as Pb caused by human activities in the environment is becoming more and more serious, and the enrichment of harmful elements caused by man-made pollution is highly harmful. In the process of natural soil formation, the surface soil will also enrich harmful elements, but such harmful elements are less harmful, so it is very important to identify the sources of harmful elements in the soil. In this paper, two types of soils with slate and granite as parent material were selected in Hunan Province, and heavy metal elements such as Pb in surface soil were selected as polluted areas respectively. The heavy metal elements such as Pb in the surface soil are close to the deep layer as the background area. The characteristics of physical and chemical indexes, mineral composition and harmful element contents in background section and polluted area under the same parent material were compared and analyzed. The effects of physical and chemical indexes on the distribution of harmful elements were explored through correlation analysis. The sources of harmful elements such as Pb in surface soil were analyzed by magnetic susceptibility and lead isotope methods. In this paper, the following conclusions are drawn: in terms of soil physical and chemical properties, the study shows that the soil texture in the study area is controlled by the climate, which is controlled by the parent rock type pH and chemical weathering index (CIAA). The clay mineral assemblage of granite parent material is kaolinite Illite chlorite montmorillonite and slate parent soil clay mineral assemblage is kaolinite Illite montmorillonite. The distribution characteristics of harmful elements in soil profile showed that the harmful elements content in surface soil of polluted area with slate as parent material was significantly higher than that in deep soil, and that in surface soil of background area was slightly higher than that in deep soil. The harmful elements in the surface soil in the polluted area with granite as the parent material were significantly higher than those in the deep soil, and the contents of harmful elements in the surface soil in the background area were close to those in the deep soil. The vertical distribution of harmful elements is mainly controlled by geochemical behavior of elements and affected by soil properties, and Ti is used as reference element. The enrichment coefficient method was used to estimate the amount of harmful elements in the soil profile of contaminated area. The results showed that the amount of harmful elements in the surface layer of soil profile was large. The study on the morphology of harmful elements showed that the dynamic ratio of soil profile in contaminated area was significantly higher than that in soil profile of background area, and the magnetic susceptibility of polluted section was higher than that of background area, and there was a good positive correlation with the content of harmful elements. The study of Pb isotopic composition showed that the Pb isotopic composition in the surface soil of polluted area was mainly similar to that of atmospheric dry and wet deposition. The systematic comparison showed that the surface soil of polluted area was seriously polluted by man-made sources and had a large ecological risk.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X53

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