Study On Heavy Metals Pollution Of Top Soil And Cropper In The Northern Slope Of Tianshan Mountains

With the implementation of the western development strategy,Xinjiang's industry and agriculture have been rapid development,however,industrial development and agriculture modernization will inevitably lead to the pollution of surrounding environment.Agriculture is the most important industry of Xinjiang's economy;Safety soils could ensure the safety of agricultural products,and protect people's health.Heavy metals are the most widespread soil pollutants that are most difficult to degrade and repaired.This study selected Xinjiang Changji Hui Autonomous Prefecture and Urumqi as a research area.The contents of Cd,Co,Cr,Cu,Ni,Pb,and Zn,soil physical and chemical properties were measured.The risk of heavy metal pollution in the study area was evaluated and the source of heavy metal pollution was analyzed by mathematical method.The local crops were sampled and analyzed,and analyzed the distribution and transfer of heavy metals.The main conclusions are as follows:The surface soil of the northern slope of Tianshan Mountains is alkaline,low fertility and low water content,showing the characteristics of saline soil in arid area.The average contents of Cd,Co,Cr,Cu,Ni,Pb,Zn and Hg were 1.27,14.55,44.63,33.79,22.96,7.95,63.37 mg.kg-1 and 0.10 mg.kg-1,respectively.The concentration of Cd,Cu and Hg has exceeded the background values of Xinjiang;Cd exceeded the national secondary standards of soil.Co,Cr,Ni,Pb and Zn are unaffected by human activities,while Cd,Cu and Hg are main affected by human activities.The Cd concentrated in Urumqi Dabancheng District agricultural area and Fukang coal mines and other small industrial areas,the Hg concentrated in the coal and industrial areas surround,the Pb mainly concentrated in the population density and traffic developed Area and the surround of Fukang coal mine.The spatial distribution of Co,Cr,Ni and Zn was similar,and concentrated in the mining area,tourist area and industrial area.Cu concentrated in several locations where agricultural production was developed.Coefficient of variation showed that heavy metals in the study area may be affected by human activities indicates that the heavy metals in the study area may be affected by human factors.Evaluation the risk degree of heavy metals pollution in soil references the soil background values in Xinjiang.The enrichment factors showed that Pb and Ni were in the non-enrichment state,Co,Cr,Cu,and Zn are in a slightly enrichment state,and both Cd and Hg were in an enrichment state.The geo-accumulation index indicated that Co,Cr,Cu,Ni,Pb and Zn were in a non-polluted state,Cd was moderate to strong pollution state,Hg was moderate pollution state,and 66.1% of Cu was in a no pollution state,33.9% were in mild-moderate pollution.The potential ecological risks of Cd and Hg are the main contributors to the comprehensive potential ecological risks.The potential ecological risk of the northern slope of the Tianshan Mountains is high,19.8% samples were moderate risk,30.5% samples were high risk,and 49.3% of samples the potential ecological risks were extremely high.The soil of the study area can be divided into three categories,the first kind of samples were seriously polluted by Cu,mainly concentrated in the farmland area;the second category of samples mainly concentrated in the tourist area and industrial area Hg and Cd pollution was serious;The third types of samples were concentrated in the developed areas of transportation and industry,Hg and Cd pollution were also very serious.The principal component analysis and correlation analysis of heavy metals were carried out Co,Cr,Cu,Ni and Zn were the same as the first principal component(PC1),Cd and Hg were the same as the second principal component(PC2),Pb was the third principal component(PC3),The three principal components can explain most characteristic of the eight heavy metals.The PCi(i = 1,2,3)were calculated by entropy method,and the spatial distribution of different principal components was analyzed.Co,Cr,Cu,Ni and Zn mainly came from biomass and organic fertilizer.Hg and Cd mainly came from industrial and domestic waste,maybe have the trend of transmission through river irrigation;Pb mainly came from industrial production and automobile exhaust emissionsCotton and corn haven't super-enrichment ability for heavy metals,and the transport capacity of cotton to heavy metals was basically stronger than corn;the leaves of cotton and corn have higher transport capacity and enrichment ability to trace elements of Cu and Zn than other parts;The roots of cotton and corn have stronger ability to enrich Cd,Co and Pb than other tissues.The roots and stems of cotton have synergistic effect on the uptake of Cd and Pb,The absorption of Cd,Zn and Pb in corn rhizome had synergistic effect.The composition of heavy metals in different tissues and different tissues was very different.