【摘要】：重金屬污染物具有毒性強(qiáng)、遷移轉(zhuǎn)化能力強(qiáng)、不易被微生物分解、易累積等特性,嚴(yán)重威脅到人類的生存環(huán)境,成為國際環(huán)境科學(xué)界的焦點(diǎn)。湘江流域是我國重金屬污染最嚴(yán)重的區(qū)域之一,其污染來源多樣,既有成土母質(zhì)等地質(zhì)體通過風(fēng)化作用產(chǎn)生,又有湘江流域上游地區(qū)礦產(chǎn)的開懫和冶煉、工業(yè)“三廢”排放等人為活動(dòng)產(chǎn)生。本文以湘江(湘潭-長沙段)沉積物為主要研究對象,從易家灣河灘沖積土、老水泥廠底泥、三大橋底泥以及易俗河底泥中重金屬含量入手開展重金屬元素的污染研究。沿湘江(湘潭-長沙段)布置了4個(gè)剖面共取43個(gè)樣品,對土壤和底泥的pH、有機(jī)質(zhì)含量以及Cr、Cd、As、Pb、Hg等五種重金屬元素含量進(jìn)行了測試分析,探討了重金屬含量的垂向分布特征和沿程分布特征,并對沉積物pH值、有機(jī)質(zhì)與重金屬含量做了相關(guān)性矩陣分析,最后應(yīng)用地積累指數(shù)法、潛在生態(tài)危害指數(shù)法和內(nèi)梅羅綜合污染指數(shù)法對沉積物中重金屬污染進(jìn)行了評價(jià)。研究結(jié)果表明:土壤樣品的pH在7之下,推測該區(qū)為不飽和沖積土,由于受母質(zhì)影響,土壤pH呈酸性;湘江水的pH在8左右致使底泥樣品中pH呈中性至弱堿性。底泥剖面的pH變化幅度與水體的自我凈化和采樣位置密不可分。垂向分布特征上看,土壤剖面在5-10cm和40-50cm段四種元素都出現(xiàn)了峰值說明當(dāng)時(shí)水體中所含金屬已嚴(yán)重超過了水體的自凈化能力,沉淀積蓄下來。三個(gè)底泥剖面重金屬元素垂向分布特征同時(shí)說明湘江底泥中重金屬污染元素順序?yàn)镃dAsPbHgCr。沿程分布特征上看,底泥剖面中0-20cm段受水動(dòng)力等外界條件影響較大,重金屬元素含量大小沒有規(guī)律;20-60cm段,重金屬含量大小順序?yàn)槠拭?4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屬元素間的相關(guān)性顯示,底泥中各重金屬元素的相關(guān)性比土壤中重金屬間相關(guān)性好,說明湘江流域兩岸的工業(yè)廢棄物和人類生活污水的排放有可能是它們共同的污染來源,有機(jī)質(zhì)與重金屬元素之間顯著的相關(guān)性,說明樣品中有機(jī)質(zhì)含量影響了重金屬的分布與富集。地積累指數(shù)法表明:剖面02中各重金屬污染程度為:HgCdAsPb,并且對表層土壤0-15cm以及深層土壤40-50cm處造成的污染最大。各重金屬對三個(gè)剖面不同深度造成的污染程度不同,底泥剖面同時(shí)顯示污染程度順序:CdAsPbCrHg。潛在生態(tài)危害指數(shù)法表明:剖面02各個(gè)元素危害程度順序CdHgAsPb。剖面01、03、04共同顯示Cd的潛在生態(tài)危害系數(shù)對潛在生態(tài)危害指數(shù)RI貢獻(xiàn)率最大,危害程度為CdAsHgPbCr。內(nèi)梅羅綜合污染指數(shù)法表明:剖面02中Cd、As和Hg為重度污染,Pb為輕度污染;剖面01、03、04所有元素中,重金屬元素Cd、As和Pb為重度污染,Cr表現(xiàn)為輕度污染,重金屬元素Hg除剖面01尚清潔外,其他兩個(gè)底泥剖面為輕度污染。三種評價(jià)方法同時(shí)說明污染最嚴(yán)重的元素為Cd和As,總體上湘江(湘潭-長沙段)沉積物中重金屬污染不容樂觀。
[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.
【學(xué)位授予單位】：湖南科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：X522;X824

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