湘江（湘潭—长沙段）沉积物重金属含量分布特征及污染评价

发布时间：2018-09-09 08:21

【摘要】：重金属污染物具有毒性强、迁移转化能力强、不易被微生物分解、易累积等特性,严重威胁到人类的生存环境,成为国际环境科学界的焦点。湘江流域是我国重金属污染最严重的区域之一,其污染来源多样,既有成土母质等地质体通过风化作用产生,又有湘江流域上游地区矿产的开懫和冶炼、工业“三废”排放等人为活动产生。本文以湘江(湘潭-长沙段)沉积物为主要研究对象,从易家湾河滩冲积土、老水泥厂底泥、三大桥底泥以及易俗河底泥中重金属含量入手开展重金属元素的污染研究。沿湘江(湘潭-长沙段)布置了4个剖面共取43个样品,对土壤和底泥的pH、有机质含量以及Cr、Cd、As、Pb、Hg等五种重金属元素含量进行了测试分析,探讨了重金属含量的垂向分布特征和沿程分布特征,并对沉积物pH值、有机质与重金属含量做了相关性矩阵分析,最后应用地积累指数法、潜在生态危害指数法和内梅罗综合污染指数法对沉积物中重金属污染进行了评价。研究结果表明:土壤样品的pH在7之下,推测该区为不饱和冲积土,由于受母质影响,土壤pH呈酸性;湘江水的pH在8左右致使底泥样品中pH呈中性至弱碱性。底泥剖面的pH变化幅度与水体的自我净化和采样位置密不可分。垂向分布特征上看,土壤剖面在5-10cm和40-50cm段四种元素都出现了峰值说明当时水体中所含金属已严重超过了水体的自净化能力,沉淀积蓄下来。三个底泥剖面重金属元素垂向分布特征同时说明湘江底泥中重金属污染元素顺序为CdAsPbHgCr。沿程分布特征上看,底泥剖面中0-20cm段受水动力等外界条件影响较大,重金属元素含量大小没有规律;20-60cm段,重金属含量大小顺序为剖面04剖面03剖面01;60-100cm段,剖面03剖面01剖面04。土壤和底泥中各重金属元素间的相关性显示,底泥中各重金属元素的相关性比土壤中重金属间相关性好,说明湘江流域两岸的工业废弃物和人类生活污水的排放有可能是它们共同的污染来源,有机质与重金属元素之间显著的相关性,说明样品中有机质含量影响了重金属的分布与富集。地积累指数法表明:剖面02中各重金属污染程度为:HgCdAsPb,并且对表层土壤0-15cm以及深层土壤40-50cm处造成的污染最大。各重金属对三个剖面不同深度造成的污染程度不同,底泥剖面同时显示污染程度顺序:CdAsPbCrHg。潜在生态危害指数法表明:剖面02各个元素危害程度顺序CdHgAsPb。剖面01、03、04共同显示Cd的潜在生态危害系数对潜在生态危害指数RI贡献率最大,危害程度为CdAsHgPbCr。内梅罗综合污染指数法表明:剖面02中Cd、As和Hg为重度污染,Pb为轻度污染;剖面01、03、04所有元素中,重金属元素Cd、As和Pb为重度污染,Cr表现为轻度污染,重金属元素Hg除剖面01尚清洁外,其他两个底泥剖面为轻度污染。三种评价方法同时说明污染最严重的元素为Cd和As,总体上湘江(湘潭-长沙段)沉积物中重金属污染不容乐观。
[Abstract]:Heavy metal pollutants have the characteristics of strong toxicity, strong ability of migration and transformation, difficult to be decomposed by microbes and easy to accumulate, which seriously threaten the living environment of human beings and become the focus of international environmental science. The Xiangjiang River Basin is one of the most serious heavy metal pollution areas in China. Its pollution sources are various. Both the soil parent material and other geological bodies are produced through weathering, and the mineral resources in the upper reaches of the Xiangjiang River Basin are opened and smelted. Industrial "three wastes" emissions and other man-made activities. In this paper, the sediment of Xiangjiang River (Xiangtan-Changsha section) is taken as the main research object. The pollution of heavy metal elements in the alluvial soil of Yijiawan River, the sediment of the old cement factory, the sediment of the third Bridge and the sediment of the Yi'ou River is studied. A total of 43 samples were collected from 4 sections along the Xiangjiang River (Xiangtan-Changsha section). The contents of pH, organic matter and Cr,Cd,As,Pb,Hg in soil and sediment were measured and analyzed. The vertical distribution and distribution along the path of heavy metal content were discussed. The correlation matrix analysis of pH value, organic matter and heavy metal content in sediment was made. Finally, the method of ground accumulation index was used. Potential ecological hazard index method and Nemero comprehensive pollution index method were used to evaluate heavy metal pollution in sediments. The results show that the pH of the soil samples is below 7, and the soil pH is acidic due to the influence of parent material, and the pH of Xiangjiang River water is about 8, which leads to the neutral to weak alkalinity of pH in the sediment samples. The range of pH in sediment profile is closely related to the self-purification and sampling position of water body. The vertical distribution characteristics showed that the peak values of four elements in the soil profile in 5-10cm and 40-50cm showed that the metals contained in the water at that time had seriously exceeded the self-purification ability of the water body and precipitated and accumulated. Vertical Distribution of heavy Metals in three sediment sections and the sequence of heavy Metal pollution elements in Xiangjiang River sediment is CdAsPbHgCr. According to the distribution characteristics along the course, the 0-20cm section in the sediment profile is greatly affected by external conditions such as hydrodynamics, and the content of heavy metals is not regular in section 20-60cm. The order of heavy metal content is: section 04, section 03, section 01-60-100cm, section 03, section 01. The correlation between heavy metal elements in soil and sediment shows that the correlation of heavy metal elements in sediment is better than that in soil. It shows that the discharge of industrial waste and human domestic sewage on both sides of the Xiangjiang River basin may be their common source of pollution, and there is a significant correlation between organic matter and heavy metal elements. The results show that the content of organic matter affects the distribution and enrichment of heavy metals. The soil accumulation index method showed that the pollution degree of heavy metals in section 02 was 1: HgCdAsPb, and the pollution to surface soil 0-15cm and deep soil 40-50cm was the biggest. The pollution degree of each heavy metal to the three sections is different, and the sediment profile also shows the pollution degree in the order of: CdAsPbCrHg. The potential ecological hazard index method shows that the sequence of damage degree of each element in section 02 is CdHgAsPb.. The potential ecological hazard coefficient of Cd is the largest contribution rate of RI to the potential ecological hazard index (RI), and the degree of damage is CdAsHgPbCr.. Nemero comprehensive pollution index method showed that Cd,As and Hg in section 02 were seriously polluted and lead was slightly polluted, and heavy metal elements, Cd,As and Pb, were slightly polluted in all elements of section 01T03H4. The heavy metal element Hg except section 01 is clean, the other two sediment sections are slightly polluted. The three evaluation methods also show that the most polluted elements are Cd and As,. Generally, heavy metal pollution in the sediments of Xiangjiang River (Xiangtan-Changsha section) is not optimistic.
【学位授予单位】：湖南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X522;X824

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