南宁市冬季大气PM_(2.5)中有毒重金属污染特征及健康风险评价

Pollution characteristics and health risk assessment of heavy metals in PM_(2.5)during winter in Nanning

目的探讨南宁市冬季大气细颗粒物(Particulate matter 2.5,PM_(2.5))中有毒重金属污染特征和人群健康风险。方法于2019年1—2月在南宁市城区连续采集大气PM_(2.5)样品,采用X射线荧光光谱法分析PM_(2.5)中镉(Cd)、砷(As)、铬(Cr)、铅(Pb)、镍(Ni)、汞(Hg)和锰(Mn)等7种有毒重金属元素浓度。运用地累积指数法和富集因子法分析重金属元素的污染特征,并采用美国环境保护署的健康风险评价模型评估其对儿童和成人的健康风险。结果南宁市2019年冬季大气PM_(2.5)质量浓度为(44±29)μg/m3,总体处于较低水平。PM_(2.5)中Hg、Cd、As、Cr、Pb均存在不同程度的污染,其中Hg和Cd的污染较重。PM_(2.5)中的Hg和Cd高度富集,Pb中度富集,这3种元素主要来自人为污染。PM_(2.5)中的As、Cr和Ni为轻度富集,同时受自然源和人为源影响。非致癌风险As>Pb>Hg>Cr>Cd>Mn>Ni。3种人群的总非致癌风险均小于1,在可接受范围。致癌风险Cr>As>Cd>Ni,Cr、As和Cd对儿童和成人的致癌风险均在1×10^(-6)~1×10^(-4),儿童总致癌风险(Cr、As、Cd和Ni)>1×10^(-4),具有潜在的致癌风险。结论南宁市2019年冬季大气PM_(2.5)质量浓度及重金属元素处于较低水平,但重金属污染仍然存在,重金属非致癌风险在可接受范围,但在儿童群体中具有潜在致癌风险。

Objective To explore the characteristics of toxic heavy metal pollution in atmospheric PM_(2.5)(Particulate matter 2.5)during winter in Nanning City and to evaluate the health risks for the population.Methods Atmospheric PM_(2.5)samples were continuously collected in the urban areas of Nanning from January to February 2019.The concentrations of seven toxic heavy metals,including cadmium(Cd),arsenic(As),chromium(Cr),lead(Pb),nickel(Ni),mercury(Hg),and manganese(Mn)in atmospheric PM_(2.5)were analyzed by X-ray fluorescence spectrometry.The pollution characteristics of toxic heavy metals were studied by geo-accumulation index and enrichment factor methods,and their health risks to children and adults were assessed using the health risk assessment model of the United States Environmental Protection Agency.Results The mass concentration of atmospheric PM_(2.5)in Nanning in winter 2019 was(44±29)μg/m3,which was generally at a low level.Different degrees of pollution were found for Hg,Cd,As,Cr,and Pb in PM_(2.5),with Hg and Cd being more seriously polluted.Hg and Cd were highly enriched in PM_(2.5),followed by Pb with moderate enrichment.These three elements mainly originated from manmade pollution.As,Cr and Ni were mildly enriched and affected by both natural and anthropogenic sources.The non-carcinogenic risks were in the order of As>Pb>Hg>Cr>Cd>Mn>Ni.The total non-carcinogenic risks for the three populations were all less than 1,which is within acceptable limits.The carcinogenic risks were ranked as Cr>As>Cd>Ni,with Cr,As,and Cd posing carcinogenic risks to children and adults ranging from 1×10^(-6)to 1×10^(-4).Moreover,the total carcinogenic risks of heavy metals(Cr,As,Cd,and Ni)were higher than 1×10^(-4)for children,indicating a potential carcinogenic risk.Conclusions The mass concentration of PM_(2.5)and heavy metal elements in Nanning City during the winter of 2019 was relatively low,but the pollution of heavy metals still exists.The non-carcinogenic risk of heavy metals is within an acceptable range,but the carcinogenic risk poses a potential danger to children.