太原市城区周边土壤污染特征分析及等级评价

发布时间：2018-10-05 16:36

【摘要】：近几十年随着我国社会和经济的高速发展,土壤污染问题变得越来越严重,对农产品质量、大气质量、水的质量和人类身体健康都造成了很大的威胁。本文以2013年在太原市城区周边采集得到的171个土壤样品的重金属、有机氯农药(OCPs)和多环芳烃(PAHs)的实测值为数据来源,对土壤污染状况进行研究。在对各污染元素的含量进行统计分析的基础上,用相关分析、单因子指数、内梅罗综合污染指数、景观指数对重金属的污染特征进行分析；对有机氯农药和多环芳烃的异构体组成特征进行分析,并对比太原市与其他地区的污染程度；采用随机森林模型,对重金属、有机氯农药和多环芳烃及综合污染程度分别进行评价。得到的主要研究结果有：(1)太原市城区周边土壤中重金属元素含量介于山西省元素背景值和国家土壤标准二级标准值之间,而有机氯农药和多环芳烃的含量均介于国家土壤一级和二级标准之间。太原市城区周边土壤污染较轻,不是非常严重。(2)8种重金属元素中,Hg元素的变异系数最大,为1.04；而变异系数最小的As元素也达到了0.33,可见太原市城区周边土壤中各重金属元素含量的空间差异性较大。(3)对重金属元素的单因子污染指数和内梅罗综合污染指数进行计算和分析发现：Cd和Hg元素的污染比较严重,单因子污染指数分别达到了2.4和4.72,综合污染指数的平均值也达到了3.59,可见太原市城区周边的土壤重金属污染较为严重。(4)通过景观指数对土壤重金属污染空间分布情况进行分析,发现太原市城区周边的土壤重金属污染大部分属于轻度和中度污染,且不同等级的斑块连通性较好,空间差异性较大。(5) OCPs总量的中位数为70.43 μg/kg,变异系数达到了1.05。对土壤中有机氯农药的各异构体进行分析发现：α-HCH、β-HCH、γ-HCH和δ-HCH分别占总HCH的13.88%、51.95%、11.47%和14.79%；(DDD+DDE)/DDT比值均值为0.75。(6)16种多环芳烃的总和的平均值为3574.12μg/kg。各多环芳烃有机物的变异系数都在1以上,二氢苊、葸和芘三种化合物的变异系数分别达到了2.35、2.05和2.04。对其物质组成进行发现分析发现,致癌性化合物在PAHs总量中所占的比例较大,且污染多来自于化石燃料的不完全燃烧。(7)用随机森林算法对土壤污染进行评价,结果显示171个土样中重金属污染评价等级属于1、2、3、4的样点分别占总样点的4.68%、87.13%、8.19%和0%,可见大部分属于2级污染。其中31个土壤样品中重金属、有机氯农药污染和多环芳烃污染等级属于1、2、3、4的样品个数分别为3、21和1,21、8以及18,6、0和2,1、2和9。由此可见,31个样点中多环芳烃污染相对于有机氯农药污染较为严重,并且两种污染严重的样点均集中在太原市西部的化工企业聚集区。
[Abstract]:With the rapid development of our society and economy in recent decades, soil pollution has become more and more serious, which poses a great threat to the quality of agricultural products, air quality, water quality and human health. Based on the measured values of 171 soil samples collected around Taiyuan City in 2013, the soil pollution was studied by using the measured values of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) (PAHs). Based on the statistical analysis of the contents of each pollution element, the pollution characteristics of heavy metals were analyzed by correlation analysis, single factor index, Nemero comprehensive pollution index and landscape index. The isomer composition characteristics of organochlorine pesticides and polycyclic aromatic hydrocarbons (PAHs) were analyzed, and the pollution levels in Taiyuan and other areas were compared. Organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) were evaluated respectively. The main results are as follows: (1) the content of heavy metal elements in the soil around Taiyuan City is between the background value of Shanxi Province and the national soil standard. However, the contents of organochlorine pesticides and polycyclic aromatic hydrocarbons (PAHs) are between the first and second grade of national soil standards. The pollution of soil around Taiyuan City is relatively light and not very serious. (2) the coefficient of variation of Hg element is the largest among the eight heavy metal elements, which is 1.04; The As element with the smallest coefficient of variation also reached 0.33. It can be seen that the spatial difference of the contents of each heavy metal element in the soil around Taiyuan City is great. (3) the single factor pollution index of heavy metal elements and the comprehensive pollution index of Nemero are increased. The calculation and analysis showed that the pollution of the elements of CD and Hg was serious. The single factor pollution index reached 2.4 and 4.72 respectively, and the average value of comprehensive pollution index reached 3.59. It can be seen that the soil heavy metal pollution around Taiyuan City is serious. (4) the spatial distribution of soil heavy metal pollution is analyzed by landscape index. It was found that most of the heavy metal pollution in the soil around Taiyuan city was mild and moderate pollution, and the patch connectivity of different grades was better, and the spatial difference was great. (5) the median of total OCPs was 70.43 渭 g / kg, and the coefficient of variation was 1.05. The isomers of organochlorine pesticides in soil were as follows: 伪 -HCH, 尾 -HCH, 纬 -HCH and 未 -HCH accounted for 13.88%, 51.95% and 14.79% of total HCH, respectively, and the mean value of (DDD DDE) / DDT ratio was 0.75. (6) the sum of 16 polycyclic aromatic hydrocarbons (PAHs) was 3574.12 渭 g / kg. The coefficient of variation of polycyclic aromatic compounds (PAHs) was above 1, and the coefficients of variation of dihydroacenaphthene, anthracene and pyrene were 2.35 and 2.04, respectively. It was found that carcinogenic compounds accounted for a large proportion of the total PAHs, and most of the pollution came from the incomplete combustion of fossil fuels. (7) the random forest algorithm was used to evaluate the soil pollution. The results showed that the samples of 171 soil samples with the grade of heavy metal pollution were 4.68% 87.138.19% and 0%, respectively, and most of them belonged to grade 2 pollution. The number of heavy metals, organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in 31 soil samples were 30.21 and 1C21 / 8, respectively. It can be seen that the pollution of polycyclic aromatic hydrocarbons (PAHs) is more serious than that of organochlorine pesticides (OCPs) in the 31 sample sites, and the two serious samples are concentrated in the chemical enterprise accumulation area in the western part of Taiyuan.
【学位授予单位】：山西大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53;X825

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