南京沿江地区重金属多介质富集特征、来源及生态效应

发布时间：2018-01-23 04:48

本文关键词： 农田土壤重金属空间变异来源解析生态效应风险评价　出处：《南京信息工程大学》2015年硕士论文　论文类型：学位论文

【摘要】：我们国家之前的土壤地球化学调查及部分人的研究已经发现南京沿江地区普遍存在土壤Cd等重金属含量异常现象,但目前对这些重金属异常的成因、生态效应及对人体的健康风险还没有明确的结论。因此,开展“南京沿江地区重金属多介质富集特征、来源及生态效应”的研究具有重要的土壤环境地球化学理论意义,同时对土壤重金属污染的风险评估与环境管理也具有重要的参考价值。本文选取南京沿江地区为研究对象,通过测定并分析表层土壤和沉积物、剖面土壤和沉积物、植物、肥料及大气降尘中重金属含量和同位素比值,揭示了土壤和沉积物重金属异常的空间变异特征；利用多元统计分析、正定矩阵因子分析法(PMF)探究典型农业区表层土壤重金属主要来源,并与Pb稳定同位素比值结果进行对比分析；运用地积累指数法、人体健康风险评价法对土壤、沉积物和作物重金属富集进行生态效应和人体摄入风险评价。结果表明：(1)研究区表层土壤镉(Cd)、砷(As)、汞(Hg)、铅(Pb)、铜(Cu)、锌(Zn)和铬(Cr)平均含量均高于南京市土壤背景值,部分样点土壤Cd、Hg和Cu含量超过了国家土壤环境质量标准的二级标准,在土壤中呈现较高的累积；表层沉积物中Cd、As、Hg, Pb、Cu、Zn和Cd的平均含量分别为0.65、15.8、0.13、42.1、45.8、124和85.3mg/kg、其中As、Pb, Cu、Zn和Cr平均含量超过美国EPA标准。南京沿江流域土壤重金属人为活动系数(AF)略低于富集系数(EF),沉积物重金属AF明显低于EF。(2)根茎中Cd和Pb的含量分别为0.15和0.13mg/kg,水稻中Pb和Cr的含量分别为1.07和6.95mg/kg,叶菜和小麦中Cr的含量分别为0.78和1.39mg/kg,均超过我国食品中污染物限量标准(GB 2762-2012)。根茎类蔬菜中Cd、Pb和Zn的含量高于茄果类和叶菜类,As、Hg、Cu和Cd在叶菜类中含量高于茄果类和根茎类。(3)南京沿江八卦洲农业区及沿江工业区附近重金属含量普遍偏高,八卦洲农业区内除Cr以外,其他表层土壤重金属均呈现东南偏高西北偏低的空间分布特征,与土壤有机质的空间分布规律一致。南京沿江流域上游至下游,沉积物中重金属含量总体呈现增加趋势,且在南京八卦洲农业区及沿江工业区,沉积物重金属含量明显高于其它区域,八卦洲农业区周边沉积物剖面中的重金属含量普遍偏高,且底层沉积物依然具有较高的重金属含量。(4)通过PMF模型得出四个污染源：农业源、降尘源、工业源和自然源,贡献率分别为30.8%,33.0%,25.4%和10.8%,Pb稳定同位素比值法计算大气降尘对土壤Pb累积的贡献率分别为36.8%,与PMF模型计算结果相似。土壤重金属累积和分布状况与研究区的地形、周边工农业布局、风向、交通污染和自然母质有关。(5)工业区沉积物Cd的地累积指数为0.04,达到轻度-中等污染,点位污染率为23.0%。Cd和Hg单项污染潜在生态风险在土壤和沉积物为中等生态危险,水稻中摄入重金属的健康风险明显高于蔬菜和其他作物。
[Abstract]:Soil geochemical investigation and some studies in our country have found that CD and other heavy metals are abnormal in soils along the Yangtze River in Nanjing, but at present, the causes of these anomalies are discussed. There is no clear conclusion on ecological effect and health risk to human body. Therefore, the enrichment characteristics of heavy metals in the Yangtze River area along the Nanjing River have been carried out. The study of source and ecological effects has important theoretical significance in soil environmental geochemistry. At the same time, it has important reference value for risk assessment and environmental management of soil heavy metal pollution. The heavy metal contents and isotopic ratios in soil and sediment, plants, fertilizers and atmospheric dust fall reveal the spatial variation characteristics of heavy metal anomalies in soil and sediment. Using multivariate statistical analysis and positive definite matrix factor analysis (PMF), the main sources of heavy metals in topsoil of typical agricultural areas were explored, and the results were compared with the results of Pb stable isotopic ratios. The ecological effects and intake risk of heavy metals in soil, sediment and crops were evaluated by the method of land accumulation index and human health risk assessment. The results showed that CD ~ (2 +) + CD ~ (2 +) in the surface soil of the study area was 1). The average contents of as, Hg, Pb, Cu, Zn (Zn) and Cr (Cr) were higher than those in Nanjing, and CD in some soil samples were higher than those in Nanjing. The content of Hg and Cu exceeded the second grade standard of national soil environmental quality standard, and showed a high accumulation in soil. The average contents of CD ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) in the surface sediments are 0.65 ~ (15. 8) ~ (0.13) ~ 42.1 ~ (-1) ~ 45.8, respectively. 124 mg / kg and 85.3 mg / kg, in which Aso Pb, Cu. The average content of Zn and Cr is higher than the EPA standard of the United States, and the anthropogenic activity coefficient of heavy metals in the soil of Nanjing River Basin is slightly lower than that of the enrichment factor (EFF). The contents of CD and Pb in the rhizome of the sediment were 0.15 and 0.13 mg / kg, respectively. The contents of Pb and Cr in rice were 1.07 and 6.95 mg / kg, and the contents of Cr in leaf vegetables and wheat were 0.78 and 1.39 mg / kg, respectively. The contents of CD ~ (2 +) Pb and Zn in rhizomatous vegetables were higher than those in eggplant and leaf vegetables. The contents of Cu and CD in leafy vegetables are higher than those in eggplant and rhizome.) the heavy metal content in the agricultural area of Bagua Island along the Yangtze River and near the industrial area along the Yangtze River is generally high, except Cr in the agricultural area of Baguazhou. The distribution of heavy metals in other surface soils was similar to that of soil organic matter in the upper reaches to the lower reaches of the Yangtze River basin, and the spatial distribution of heavy metals in the topsoil was higher than that in the southeast and lower in the northwest. The content of heavy metals in sediments showed an increasing trend, and in the agricultural area of Baguazhou in Nanjing and the industrial area along the Yangtze River, the heavy metal content in sediment was obviously higher than that in other regions. The content of heavy metals in the sediment profile around the agricultural area of Bagua Island is generally high, and the bottom sediment still has high heavy metal content.) through the PMF model, four sources of pollution are obtained: agricultural source, dust source. The contribution rates of industrial and natural sources were 30.8% and 10.8% respectively. The contribution rate of atmospheric dust to soil Pb accumulation calculated by Pb stable isotope ratio method is 36.8, which is similar to that of PMF model. The accumulation and distribution of heavy metals in soil and the topography of the study area. Industrial and agricultural distribution, wind direction, traffic pollution and natural parent material.) the accumulation index of CD in the sediments of industrial area is 0.04, which reaches mildly to moderate pollution. The potential ecological risk of single pollution was 23.0. CD and Hg in soil and sediment. The health risk of heavy metal intake in rice was significantly higher than that in vegetables and other crops.
【学位授予单位】：南京信息工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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