乌鲁木齐市大气颗粒物中重金属浓度的分布特征

Distribution Characteristics of Heavy Metals Concentration in Atmospheric Particles of Urumqi

从2009年7月-2010年4月，在乌鲁木齐市新疆大学设置采样点采集大气PM25-30和PM25。采用双道原子荧光光谱法分析了样品中的7种重金属元素，对采样期间可吸人颗粒物及重金属的浓度进行了分析，并对重金属的污染水平进行了评价。结果表明：PM25质量浓度的日平均值为222μg／m3，超过美国EPA997年颁布的PM25日平均值35μg／m3的6．4倍；PM25-30和PM25中7种金属元素的浓度从高到低的顺序为Cr〉Pb〉Mn〉Cu〉Ni〉As〉Hg；PM2Ⅻ和PM25中Mn的污染指数岳≤1为无污染，Cu污染指数：3≤Igeo≤4为重污染，Ni、Cr、As污染指数：4≤Igeo≤5为重污染至严重污染，Pb、Hg的污染指数：k≥5为严重污染。以Fe作为参考元素计算重金属的富集因子表明，自然来源的Mn具有较小的富集因子，而受工业活动影响的Cr、Pb、Ni、Cu、Hg、As具有较大的富集因子，可以认为大气可吸入颗粒物中重金属的主要来源于工业活动。

PM25 and PM25-10 samples were collected from July 2009 to April 2010 at the location of Xinjiang University in Urumqi, Xinjiang. Total concentration and chemical speciation of 7 heavy metals in PM25-10 and PM25 were quantified by atomic fluorescence spectrometry. During the sampling period inhalable particulate matters and heavy metal concentrations were analyzed, and heavy metal pollution levels were evaluated. Results showed that daily average concentration of PM2z was 222 g/μm3, which was 6.4 times higher than outdoor PM25 standard of 35 g/μm3 recommended by US EPA. Concentrations of heavy metals in PM25-10 and PM25 in the order from high to low was ranked as Cr, Pb, Mn, Cu, Ni, As and Hg. According to the results of mull indexes evaluating, mull index of Mn was indicated as uncontaminated, Cu as heavily contaminated, Cr, Ni and As as heavily to extremely contaminated, and Pb, Hg as extremely contaminated. Fe as the reference element to calculate heavy metal enrichment factors （EFs）indicated that naturally derived Mn showed the lowest enrichment relative to the background values, while anthropogenically enhanced Cr, Pb, Ni, Cu, Hg and As showed the maximum enrichment, which indicated that inhalable particles of heavy metals are mainly from industrial activities.