| Due to the properties of their strong toxicity,migration ability,easy to accumulation and non-biodegradation,Heavy metal pollutant is great harm to the natural environment living.Therefore,increase attention has been given these compounds.Xiangjiang River is one of China’s rivers most contaminated by heavy metals.The sources of pollution are full of diversity,such as geologic bo dy by weathering,the mining and People’s activities such as industrial "three wastes” emissions.This passage sets the sediment of Xiangtan and Changsha section of Xiangjiang River as the research object,from the heavy metal content of the river alluvial soil of Yijiawan,the sediment of old cement factory,Three bridge and Yisuhe,and carries out the heavy metal element pollution research.Forty-three representative samples of four profiles are selected in River Sediment profile of Xiangjiang River Xiangtan and Changsha(from upriver to downriver)including the pH value,organic matter content and the concentration of heavy metals including Cr,Cd,As,Pb,and Hg are evaluated.Discussed the vertical distribution characteristics and along the distribution characteristics of heavy metal content,and had a correlation matrix analysis between the sediment of pH,organic matter and the heavy metal content,and last the methods of Index of Geoaccumulation,Potential ecological risk evaluation and Nemerow comprehensive pollution index evaluation are applied to evaluate the heavy metal element contamination of sediment in Xiangjiang River.The results show that:The pH of river alluvial soil is less than 7,it is speculated that the area is unsaturated alluvial soil,due to the effect of geologic body,the pH presents acidity;the pH of Xiangjiang river water isaround 8,lead the pH of sediment samples is neutral to weak alkaline.Variations of the pH in sediment profile is closely connected with the self-purification of water and sampling position.From the vertical distribution characteristics,this four elements of 5-10 cm and 40-50 cm in soil profile appeared maximum value show ing that the concentration contained in the water is serious more than the water self-purification ability,the precipitation accumulating to the sediment.The vertical distribution characteristics of heavy metal elements in this three sediment profile illustrate that the order of heavy metal contamination is Cd>As>Pb>Hg>Cr.For the distribution characteristics,the section of 0-20 cm in sediment profile is greatly influenced by outside conditions such as hydrodynamic,there is no feature for heavy metal element content;in 20-60 cm,the order of heavy metal content is profile 04>profile 03> profile 01;in 60-100 cm,the order of heavy metal content is profile 03>profile 01> profile 04.The correlation of heavy metal elements between in soil and sediment shows that the correlation of heavy metals in sedimentis well thanthat in soil,it illustrates that the industrial waste and human sewage discharge besides the xiangjiang river may be their common sources of pollution,the significant correlation between organic matter and heavy metals shows that the organic compounds in the sample affected the distribution and enrichment of heavy metals.Accumulated index method shows that the level of heavy metal pollution in profile 02:Hg>Cd>As>Pb,the 0-15 cm and 40-50 cm pollution is the heaviest.The heavy metal pollution degree of different depth of the three profile is differen t,sediment profile shows that the order of pollution levels at the same time :Cd>As>Pb>Cr>Hg.Potential ecological risk method shows that the level of heavy metal pollution in profile 02:Cd>Hg> As>Pb,for the heavy metal element Cd,Profiles 01,03,04 shows the contribution of potential ecological harm coefficient to potential ecological harm index RI is the largest at the same time,the order of heavy metal harmful degree is Cd>As>Hg>Pb>Cr.Nemerow comprehensive pollution index method shows that it is severe poll ution for Cd,As and Hg in profile 02,Pb is light pollution.Cd,As and Pb is severe pollution in each sediment profile,Cr is light pollution,the heavy metals Hg is cordon in profile 01,in the other two sediment profiles is light pollution.Three evaluation methods show that the most polluted elements are Cd and As,on the whole,the heavy metal pollution in sediment of Xiangjiang River(Xiangtan and Changsha)is not optimistic. |
