贵阳市白云区农田土壤重金属污染状况及风险评估

发布时间：2018-01-11 03:18

本文关键词：贵阳市白云区农田土壤重金属污染状况及风险评估　出处：《贵州师范大学》2017年硕士论文　论文类型：学位论文

【摘要】：本文以贵阳市白云区农田表层土壤为研究对象,调查农田土壤重金属污染现状,设置了10个采样点,共计100份样品,采用HNO3-HClO4-HF消解法和BCR连续提取法分别对土壤样品重金属总量及形态进行分析测定,并且利用SBET提取方法对重金属生物可给性进行分析测定,依据《土壤农业化学方法》相关方法,对土壤pH及有机质、氮、磷、钾进行分析。采用相关性分析、聚类分析和主成分分析方法分析了土壤重金属的来源及分布特征;采用内梅罗综合指数法、污染负荷指数法及潜在生态指数法对农田土壤重金属污染程度及潜在生态风险进行评价;利用形态分析和生物可给性结果对土壤生物有效性进行分析,并利用所选的理化性质对生物可给量进行多元回归分析,建立预测模型;分别以重金属总量和生物可给量为参考依据,利用USEPA(美国环保署)人体健康风险评价模型对研究区对人体产生的健康风险进行初步估计;旨在为研究区土壤重金属污染防治与修复提供理论依据,结果表明:(1)重金属含量测定结果表明:研究区土壤中元素8种中,除Cd元素外,其余元素均高于采样对照点和贵州省土壤背景值;与国家土壤环境二级标准限值相比,土壤中Ni、Cu、Cd三种元素超标较严重,超标率分别为67.19%、62.5%、35.94%,其次是As、Cr。相关性分析和主成分分析结果均表明,农田土壤重金属有3种来源:第一种来源要素由Cu、Zn、Ni、Hg和Cr构成,可能来源于交通污染和化肥的施用;第二种来源要素由Hg、As和Pb构成,可能来源于当地煤炭燃烧产生的降尘和农药的大量使用;第三种来源要素是Cd,Cd与其它重金属元素的污染来源均不同,可能来源于成土母岩等自然因素。聚类分析结果显示Hg、As和Cd为一类,Cu、Ni和Pb为一类,Zn和Cr为一类。其与主成分分析的统计结果略有差异,其主要原因可能与金属元素间的伴生关系有关。具体的深层次原因还有待于进一步的研究发现。(2)综合三种评价结果来看,内梅罗综合污染指数法和污染负荷指数评价结果均表明,研究区主要受到Cu、Pb、Hg、As的污染,且土壤Cu、Pb、Hg、As均处于轻度至中度污染水平,需高度重视对这4种重金属污染源的控制;潜在生态风险评价结果表明:Hg和Cd是研究区农田土壤的主要污染因子。(3)研究区土壤中除Hg元素的可氧化态所占百分比较高外,其它元素均主要以残渣态形式存在,其中Hg、Cd和Pb活性态所占的比例最高,说明这三种元素能被植物体吸收利用且能参与生物链进行物质循环的那部分活性态含量较高,故Hg、Cd和Pb的危害性较高。土壤As元素活性态所占比例最低其危害性较小。采用RAC风险评估指数法对土壤重金属的生物可利用性进行评价,结果表明,Cd元素的风险程度最高,处于中等风险水平,Zn和Hg次之,均处于低风险水平,Pb、Cr、As和Ni的生物可利用度极低,均处于无风险水平。其中Hg和Pb虽然处于低风险或无风险水平,但由于其活性态所占比例较高,可能会随着土壤pH值、温度、氧化还原电位、有机物种类及含量的改变而发生迁移,最终转化为酸可提取态。因此,土壤中的元素Hg和Pb可能存在一定的潜在风险。(4)研究区农田土壤中金属元素的生物可给性Cd元素远远大于其他元素,并且选择的土壤理化性质对Cd、Zn、As三种元素具有较好的预测效果。(5)分别以土壤中重金属总量和生物可给量为参考依据,对重金属污染物对人体产生的潜在健康风险进行评价;以土壤重金属总量为参考依据时,成人和儿童产生的潜在非致癌风险均可以忽略,但对成人和儿童产生潜在致癌风险不可忽略,尤其是As和Cr元素,以生物可给量为参考依据时,成人和儿童的潜在非致癌风险和致癌风险均处于可接受范围内,可以忽略。
[Abstract]:In this paper, the soil surface of farmland in Baiyun District of Guiyang city as the research object, investigation of soil heavy metal pollution, set up 10 sampling points, a total of 100 samples, the soil samples were used to analyze the morphology of heavy metals and the determination of HNO3-HClO4-HF digestion and BCR sequential extraction method, and the use of SBET extraction method for heavy metal bioavailability for analysis, according to "soil and agricultural chemistry method > correlation method on soil pH and organic matter, nitrogen, phosphorus and potassium were analyzed. By correlation analysis, cluster analysis and principal component analysis method to analyze the distribution and source of heavy metals in the soil; the Nemero index evaluation on pollution and potential ecological risk the degree of soil heavy metals in farmland and potential ecological index and pollution load index method; the speciation analysis and bioavailability results on soil biological effectiveness of Analysis and use of physical and chemical properties of the selected biological multivariate regression analysis to establish prediction model of volume, respectively; total amount of heavy metals bioavailability and quantity as the reference, using USEPA (EPA) human health risk assessment model for health risk research area on the human body are designed to provide preliminary estimates; the theoretical basis for the study area, the soil heavy metal pollution prevention and remediation results showed that: (1) the determination results showed that heavy metal content in 8 kinds of elements in the soil of the study area, except Cd, the other elements were higher than that of the control sample and soil background values of Guizhou province; and the national soil environmental standards of the two limit in soil in Ni, Cu, Cd three elements exceed the standard seriously exceed the standard rate were 67.19%, 62.5%, 35.94%, followed by As, Cr. correlation analysis and principal component analysis results showed that soil heavy metals have 3 sources: the first one The source of elements by Cu, Zn, Ni, Hg and Cr, may be derived from traffic pollution and chemical fertilizer; second sources of elements by Hg, As and Pb, may use a lot of local sources of coal combustion dust and pesticide; third kinds of source elements are Cd, Cd and other pollution sources heavy metal elements were different, may be derived from the parent rocks and other natural factors. The results of cluster analysis showed that Hg, As and Cd as a class, Cu, Ni and Pb for a class, Zn and Cr as a category. The statistical results of principal component analysis and the associated relationship may be slightly different, the main reason with the metal elements between the deep-seated reasons. The specific are needed to further study. (2) three comprehensive evaluation results, Nemero comprehensive pollution index and pollution load index evaluation results show that the study area mainly by Cu, Pb, Hg, As pollution, and soil Cu, Pb, Hg As, in Mild to moderate pollution levels, need to pay great attention to the control of the 4 kinds of heavy metal pollution; ecological risk assessment results showed that Hg and Cd are the main pollution factors of farmland soil. (3) in the soil of the study area except Hg element oxidizable percentage is relatively high, the other elements are mainly in residual form, including Hg, Cd and Pb activity had the highest proportion of these three elements can be absorbed by plants that use and can participate in the activity content of chain material recycling is higher, so Hg, Cd and Pb high hazard. Soil As element active state the lowest percentage of its less harmful. The RAC risk assessment method of biological index of soil heavy metal availability evaluation, the results show that the degree of risk of Cd elements in the middle of the highest risk level, Zn and Hg, are at a low risk level, Pb, Cr, and As Ni bioavailability is very low, are at no risk level. The Hg and Pb while at low or no risk level, but because of its active state of higher proportion, may with the soil pH value, temperature, redox potential, organic matter content and types of the change of migration, the final conversion for the acid extractable soil. Therefore, the elements of Hg and Pb may have some potential risks. (4) the study area of farmland soil metal elements in the bioaccessibility of Cd elements is far greater than other elements, physical and chemical properties of Cd, Zn and As of the soil, the three elements has good prediction effect. (5) respectively in the total amount of heavy metals in soil and biological feed for reference, to evaluate the potential health risk of heavy metal pollution on the human body; the amount of soil heavy metal for reference, adults and children have the potential non carcinogenic risk It can be ignored, but the potential carcinogenic risk to adults and children can not be ignored. Especially when As and Cr elements are used as reference, the potential non carcinogenic risks and carcinogenic risks of adults and children are acceptable, which can be ignored.

【学位授予单位】：贵州师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53;X825

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