Pollution And Potential Ecological,Health Risk Assessment Of Heavy Metals In Farmland Soils Of Oasis In The Lower Reaches Of Kaidu River,Xinjiang

Soil environmental safety is the basis of land resources development,utilization and protection,as well as the guarantee of food security.Heavy metals in soil can affect not only the main function of soil,prevent the normal growth of the vegetation and the safety of the whole ecosystem,but also affect human health through the cycle of various types of ecosystem,which has attracted more and more attention.Taking into account the lack of related researches on the heavy metal pollution risk of farmland soils in Xinjiang,in this study,the pollution of heavy metals in farmland soils of oasis in the lower reaches of the Kaidu River were studied.A total of 98 soil samples were collected,contents of eight heavy metal elements including arsenic(As),cadmium(Cd),chromium(Cr),copper(Cu),Manganese(Mn),nickel(Ni),lead(Pb)and zinc(Zn)were determined.The pollution characteristics,spatial distribution patterns,main sources and potential ecological,human health risks of heavy metals in farmland soils of the study area were analyzed based on multi-statistical methods,the single factor pollution index,the pollution load index,the comprehensive pollution index,the geo-accumulation index,the potential ecological risk index,the ecological risk warning index,and the human health risk assessment model.Results of this study can provide a scientific and theoretical basis for soil environmental safety and sustainable development of farmlands in the study area.The main results of this study are as follows:(1)The mean contents of As,Cd,Cr,Cu,Mn,Ni,Pb and Zn in farmland soils did not exceed the second grade of the National Soil Environmental Quality of China.The average contents of Cd,Cr,Ni,Pb and Zn were exceeded by 1.75,1.32,1.36,3.40 and 5.14 times,respectively,of the background values for irrigation soils in Xinjiang.The accumulation of As in soil of 0～20 cm soil layer was obvious,and the accumulation of Zn in 20～40 cm soil layer was obvious,whereas the contents of other elements in each soil layer is similar.(2)The average value of the single pollution index of eight heavy metals in farmland soils in the study area could be ranked as:As,Mn,Cr,Cu,Ni,Zn,Cd and Pb.Pb showed the moderate pollution,Cd,Cr,Cu,Ni and Zn showed the low pollution,As and Mn showed the no-pollution level.The average value of the pollution load index is 1.08,showed a low pollution level.The pollution degree of heavy metals in 0～20 cm and 20～40 cm soil layers were similar;In different types of farmland soil,the pollution levels of pepper and tomatoes field soil were higher than that of the wheat field soil.(3)Results of potential ecological risks assessment and warning indicated that,the individual potential ecological risk index of each heavy metal in farmland soils in the research area showed a low ecological risk.The comprehensive ecological risk index was 19.22,which showed a low ecological risk.The average of ecological risks warning index was 2.06,which indicated a low warning situation.(4)The non-carcinogenic risk quotient and non-carcinogenic risk index,single carcinogenic risk index and total non-carcinogenic risk index calculated by three exposure ways for As、Cd、Cr、Cu、Ni、Pb、Zn belonged to the acceptable risk level.(5)Results of source analysis indicated that,As,Cd,Pb and Zn in farmland soils in the study area mainly originated from human factors,while Cr,Cu,Mn and Ni sources mainly originated from natural factors.