Geochemical Characteristics And Potencial Ecological Risk Of Heavy Metals In Surfical Soils Of Bortala River Basin, Xinjiang

Seriousness of heavy metal pollution has attracted more and more attention in recent years,the heavy metal pollutants on the human body harmful process is a long-term gradual process and its in vivo enrichment and become persistent pollutants,causing serious environmental problems,such as causing heavy metal poison, lead to cancer, endemic diseases, crop production and crop failure and so on. At present, heavy metal pollution has also spread to the arid area in a disastrous state of Ebinur Lake trail. As a typical inland arid area of Xinjiang closed lake, Ebinur Lake,nearly 50 years,with the development of the basin in industry, agriculture,causing the a series of ecological and environmental problems, a serious threat to the local and surrounding areas of human survival and development. Ebinur Lake main recharge source district Bortala River Basin in the topsoil is selected as the research object, on the basis of field sampling and analysis, the study area in the topsoil Cr, Pb, As, Cd, Ni five elements as the research object, the heavy metal content of soil in the region were preliminary investigation and research,the geo accumulation index method and pollution load index and potential ecological risk index method. Through these index to evaluate the soil heavy metal pollution and potential risks and to improve the ecological environment in the Ebinur Lake Basin and the implementation of strategic planning for sustainable development provides reference and theoretical basis. The main results are as follows:(1) geochemical characteristics of heavy metals in basin soil of Bortala river along the results show:The average value of 5 kinds of heavy metals As, Cd, Ni, Cr, Pb in the study area is 0.45mg/kg, 28.26mg/kg were 20.29mg/kg,53.65mg/kg,28.07mg/kg; the average values of heavy metals exceeded the soil background values for Xinjiang, in which Cd, As, Pb significantly, respectively,to the background value, 3.75 1.81, 1.45 times,showing a strong accumulation trend, and accumulation of Cr and Ni was not significant. From the aspect of variation coefficient,the coefficient of variation of 5 kinds of heavy metals were in the range of 10% to 100%,belongs to the medium variation, indicating that these elements are different in the different sampling sites. From the change of amplitude, maximum amplitude Cd, range is 0.01mg/kg-1.02mg/kg, the maximum value is 102 times the minimum value. The range of Ni range is 10.24mg/kg-41.20mg/kg, the minimum, the maximum value is about 4 times of the minimum.5 kinds of heavy metals by correlation analysis and principal component analysis showed that As and Pb,Cr,Cd,and between Pb and Cr were significantly correlated, indicating that As,Pb,Cr,Cd these 4 kinds of elements have the same pollution source,which is mainly associated with human activities(such as automobile exhaust emissions, industrial pollution, living garbage, application of fertilizers and pesticides).(2) the spatial distribution of soil heavy metals show:The whole study area in the As content of surface soil in 1.72mg/kg-60.34mg/kg, the average value is greater than the local background values, show that the enrichment trend. Cr 10.98mg/kg- 77.01mg/kg is in the range of the average content of soil surface, with the local background Cr value difference was not significant. Content in the surface soil of 10.24mg/kg- Ni in 41.20mg/kg,there is little difference with the local mean value of the Ni background,showed mild enrichment. Cd in the surface soil of the content in the 0.00- 1.02mg/kg,higher than the local background Cd value, the concentration trend. Content in the surface soil of 7.26mg/kg- Pb in 69.35mg/kg,higher than the local background value of Pb, showed that enrichment trend.From the change along the river,along the change of 5 kinds of element concentrations are similar, except Ni, the other 4 kinds of elements were sampled in Hot Springs County in the S4 up to a maximum value, pollution is most serious, which may have relationship with the sampling points of the environment. The heavy metal elements in soil Pb pollution mainly comes from vehicle exhaust emissions, particulate matter in addition to the automobile tire wear can also produce high content of heavy metal Pb,Cd etc.. The agricultural application of phosphorus fertilizer, phosphorus containing compound fertilizer and pesticide were mixed with Pb, Cd, Ni, As, Cr and other heavy metals, and Cd can be used as identification element of the application of pesticides and fertilizers and other agricultural activities.(3) according to the degree of pollution of heavy metals in the soil of the study area geological cumulative index method Cd is the biggest, the most serious pollution, the minimum is Ni, the other three element size sorting is As > Pb > Cr. According to the pollution load index can be obtained,the pollution of Cd coefficient ranged from 0.04 to 8.47, the average value of 3.75, on soil pollution load index of the study area the largest contribution rate, average values of As, Pb, Cr, Ni these 4 elements pollution coefficient were 1.81,1.45, 1.09, 1.05. The scope of pollution load index is 0.39~3.05, average is 1.55. Pollution load index level of 5 elements As, Cd, Ni, Cr, Pb belonged to grade I, is moderate pollution, the regional soil environment is relatively good.The potential ecological risk index, Cr, Ni, Pb potential ecological risk coefficient of single factor elements are less than 40, the maximum damage coefficient Cd,the toxicity is higher than other elements. Each sample point of ecological risk index volatility is relatively large,S4 sampling points in a strong ecological risk. We can see that the degree of potential ecological risk of heavy metals in surface soils of Bortala river basin is in the middle level,or have an impact on the environment,especially the Cd had the greatest effect.