南京市春节前后大气PM2.5中重金属来源及健康风险评价

Sources and risk assessment of heavy metals in PM_(2.5) around 2014 Spring Festival in Nanjing

选择南京某居民区采样点,于2014年春节前后,采集大气PM_(2.5)样品,分析其中的V、Cr、Mn、Co、Ni、Cu、Zn、As、Cd、Ba、Sb和Pb等12种金属元素,结合富集因子、聚类分析和主成分分析对其来源进行了探讨,并采用健康风险评价模型对其危害进行评估.结果表明:春节期间大气PM2.5的平均浓度相比春节前上升11.4%,春节后相比春节期间下降31.1%.V、Cr、Mn、Ni、Cu、Zn、As、Cd、Sb和Pb的平均浓度相比春节前下降了5.5%(V)~56.7%(Zn).PM_(2.5)及其载带元素浓度的变化反应了节日前后工厂、机动车排放及烟花燃放等污染源的变化.春节期间Ba平均浓度相比节前增加了16.2倍,而在节后下降了94%,表明节日期间的烟花燃放是Ba的一个重要来源.富集因子和地累积指数分析显示,Cd、Sb、Pb、Cu、Zn、As、Ni和Ba属于重度富集元素,其富集因子范围为21~2259.主成分分析和聚类分析表明,金属冶炼和燃煤、烟花燃放和机动车尾气、工业过程是采样期间重金属的主要来源,贡献率分别为57.5%、12.4%和9.9%.风险评价结果表明致癌性元素(Cr、Co、Ni、As和Cd)的风险指数分别为2.0×10^(-6),8.9×10^(-9),1.3×10^(-8),1.9×10^(-7)和7.7×10^(-9).除Cr外,其它值均低于致癌风险阈值范围(10^(-6)~10^(-4)),处于可接受水平.

Daily PM2.5 samples were collected around the 2014 Spring Festival （SF） at a suburban site of Nanjing and twelve kinds of heavy elements were analyzed. Sources were identified by enrichment factor （EF）, cluster analysis and principal component analysis. Human health risks of heavy metals were assessed. Results showed that during SF, the average mass concentration of PM2.5 was 11.4% higher than that for pre-SF period. After the SF, PM2.5 concentrations decreased by 31.1%. The mass concentrations of V, Cr, Mn, Ni, Cu, Zn, As, Cd, Sb and Pb decreased by 5.5% （V） ~56.7% （Zn）, when compared with those for pre-SF period. The variation of PM2.5 and associated elements reflected the sources variation of industrial plants, vehicle emission and fireworks burning. The concentration of Ba during SF period was 16.2times of that for pre-SF period, and then decreased by 94%, indicating firework burning was an important source of it. EF and geoaccumulation index showed that Cd, Sb, Pb, Cu, As, Ni, Ba and Zn are heavily enriched, with the EFs values ranging in 21~2259. Principal component analysis and cluster analysis showed that industrial emissions and coal combustion, fireworks burning and vehicle exhaust, industrial process are the main sources of heavy metals, contributing by 57.5%, 12.4% and 9.9%, respectively. Health risk assessment results indicated that during SF, the risk levels of carcinogenic elements-Cr, Co, Ni, As and Cd were 2.0×;10-6, 8.9×;10-9, 1.3×;10-8, 1.9×;10-7 and 7.7×;10-9, respectively. Except for Cr, the values were below the carcinogenic risk threshold range （10-6~10-4）, at an acceptable level.