Research On Heavy Metals Pollution And Ecological Risk Assessment In Soil And Sediment In The Changsha Section Of The Xiangjiang River

Because of its persistence, bioaccumulation and toxicity, heavy metal pollution attracts more attention and has been one of the hot research topic on the international environmental scientific community. In recent years, along with coastal industrial "three wastes" and the automobile exhaust emissions, the unreasonable use of city life garbage and sludge, the excessive application of pesticide and fertilizer containing heavy metals,and so on,The content of all kinds of heavy metal pollutant accept soils and sediments of Xiangjiang basin is growing year by year. Study on heavy metal pollution of soil, sediment and plant in Changsha section of the Xiangjiang River, it is helpful to further understand migration and transformation behavior and biological toxicity of heavy metals in the environment, and it provides the basis for the comprehensive prevention and treatment of heavy metal pollution, agricultural production and environmental safety construction.This study first proceeded with the heavy metal content of soil, sediment and plant in Changsha section of Xiangjiang River, investigated and evaluated pollution levels and potential ecological risk of heavy metal of soil and sediment, revealled accumulation characteristics of plant to heavy metal in the area, and through the analysis of correlation of the physical and chemical properties and heavy metal between soil and sediment, it discussed the relationship of heavy metal pollution and influence factors in soil,sediment and plants. The results of the study show that:Soil is acidic and sediment is neutral or weakly alkaline in Changsha section of Xiangjiang River. The area exists different levels of heavy metal pollution. The main contents of heavy metals in soils and sediments is generally higher than the background values in Hunan Province, of which the average content of Cd in soil and sediment is about14times and70times of Hunan background values. According to all kinds of section, the heavy metal content in Zhao mountain in soil and in Xiangjiang bridge in sediment were higher, it presents several combined pollution character of heavy metals in soil and sediment, heavy metal content of moon island is lower. The effective content and biological validity coefficients of Cu, Zn, Pb and Cd in surface soil were greater than the bottom soil. Analysis showed that the pH value of soil and contents of heavy metals in soil and sediment was not related, while the content of soil organic matter and Cu, Zn, Pb, Cd content in soil and sediment was a significant positive correlation. According to potential ecological risk assessment and geo-accumulation index method, the results show that Cd was strong pollution, Cu, Zn and Pb belonged to slight pollution, four kinds of heavy metals pollution levels from heavy to light is the following order:Cd> Pb> Zn> Cu, the potential ecological risk index heavy metals in surface soil is generally greater than the surface sediment. The pollution levels all sampling points in surface and underlying soil are basically consistent, the pollution index in surface soil is generally higher than underlying soil. The pollution leave of Cd in soil and sediment about the entire River is more severe, the average value respectively reached5.60and35.82, especially the pollution leave of Cd in soil and sediment in xiangjiang bridge were very serious, the surface layer and the bottom layer of the comprehensive pollution index reached74.65and74.88. Respectively, the pollution levels of Cu, Zn, Pb in soils and sediments in each sampling point is differ, but failed to reach serious pollution.In addition the low content of Cu in vegetables, the content of Zn, Pb and Cd were higher than the national food vegetables pollutants limited.the content of Cu in plant growth in river floodplain is higher than that in bank. Heavy metal content of Chinese cabbage is higher than several other vegetables. From enrichment characteristics of vegetables to heavy metal, transfer coefficients of all sampling points of Cd was generally high, enrichment coefficients of Cu, Zn, Pb were less than1. The correlation analysis showed that Zn in the surface soil and in soil is significant positive correlation.