新疆焉耆盆地辣椒地土壤重金属污染及生态风险预警

摘要

Heavy metals have long been recognized as pollutants that are potentially harmful to human health.In recent decades,research on heavy metals in soil environments has become a hotspot in environmental research.Under normal conditions,heavy metal concentrations in soils are several orders of magnitude higher than that in the background value of soils.Thus,the concentrations and potential ecological risks of heavy metals in farmland soils are important reference indicators for evaluating farmland soil environmental quality.Human activities are known to result in heavy metal pollution of farmland soils.Recent research in this field in China has focused on the sources,distribution,pollution,and ecological risk of heavy metals in farmland soils in the eastern or central parts.However,there has been limited research on soil contamination of farmland,particularly pepper fields,in the arid regions of northwest China.Therefore,we collected a total of 105 soil samples from pepper field in the main pepper production area (Yanqi Basin) in Xinjiang,China,and determined the content of eight heavy metals (As,Cd,Cr,Cu,Mn,Ni,Pb,and Zn) by standard methods.The heavy metal pollution of pepper field soils was analyzed based on pollution load index (PLI),potential ecological risk index (RI),and ecological risk warning index (IER).The results indicated that the average content of Cd,Cr,Ni,Pb,and Zn exceeded 1.65,1.40,1.32,3.21,and 6.42 times,respectively,that of the background values for irrigation soil in Xinjiang.High levels of Pb,and Zn pollution,low levels of Cd,Cr and Ni pollution,and no As,Mn,or Cu pollution were detected in pepper field soils.The average value of PLI was 1.40,which showed a light pollution level;the average RI for each heavy metal in decreasing order was as follows:Cd,Ni,As,Cu,Pb,Cr,and Zn.The average value of RI of soil was 18.40,which indicated light ecological risk.The average value of IER of soil was-4.78,which indicated a no warning situation.The pollution level,potential ecological risk,and ecological risk warming of Bahrash county were the highest,whereas those of Hejing county were the lowest in Yanqi Basin.As,Cd,Pb,and Zn pollution in pepper field soil were mainly affected by the human activities,and Cr,Cu,Mn,and Ni pollution were mainly affected by the geochemical background of soils.Cd was the main pollutant of farmland soil with strong influence on the PLI,RI,and IER.The pollution risk of Cd should be a major concern during the process of agricultural production in Yanqi Basin.%从新疆加工辣椒主产地(焉耆盆地)采集105个辣椒地典型土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属元素的含量.采用污染负荷指数(Pollution load index,PLI)、潜在生态风险指数(Potential ecological risk index,RI)和生态风险预警指数(Ecological risk warning index,IER)对辣椒地土壤重金属污染及生态风险进行评价.结果表明:(1)焉耆盆地辣椒地土壤Cd、Cr、Ni、Pb和Zn含量的平均值分别超出新疆灌耕土背景值的1.65、1.40、1.32、3.21、6.42倍.辣椒地土壤Pb和Zn呈现重度污染,Cd、Cr和Ni轻度污染,As、Mn和Cu无污染.(2)土壤PLI平均值为1.40,呈现轻度污染.各重金属元素单项生态风险指数从大到小依次为:Cd、Ni、As、Cu、Pb、Cr、Zn.土壤RI平均值为18.40,属于轻微生态风险态势,IER平均值为-4.78,属于无警态势;博湖县辣椒地污染水平、潜在生态风险程度与生态风险预警等级最高,焉耆县污染水平、潜在生态风险程度与生态风险预警等级最低.(3)辣椒地土壤As、Cd、Pb与Zn主要受到人类活动的影响,Cr、Cu、Mn和Ni主要受到土壤地球化学作用的控制.Cd是焉耆盆地辣椒地生态风险等级最高的重金属元素,研究区农业生产过程中要防范Cd的污染风险.