郑州市大气PM_(2.5)中金属元素的污染特征

Pollution Characteristics of Metal Elements in PM_(2.5) in the Atmosphere of Zhengzhou

在郑州市区布设采样点，研究了郑州市PM2.5中金属元素的污染特征、季节分布规律和富集因子。在1年的监测期中， PM2.5的日平均质量浓度为87.4μg＆#183;m-3，日均质量浓度超过GB3095─2012日均值二级标准的天数占总监测天数的53%。PM2.5的日平均质量浓度季节性特征表现为冬季＆gt;秋季＆gt;夏季＆gt;春季。K、V、Mn 等10种金属平均质量浓度与 PM2.5平均质量浓度呈明显正相关，相关系数范围为0.516-0.907。Na、Cr和Ti平均质量浓度与PM2.5平均质量浓度呈明显负相关，相关系数均小于-0.6。郑州市大气PM2.5中金属元素质量浓度较高的有Ca、Na、K、Mg、Al、Fe、Zn，质量浓度较低的有Cd、Hg、Ni、V等。冬季PM2.5中Hg和Pb的平均质量浓度明显高于其他季节。金属元素总量中占比最高的是Ca、Na、K，这3种元素的比例和在4个季节中都大于65%。Cr、Cd、Pb和Hg的比例之和仅冬季超过2%。富集系数的研究表明郑州市大气PM2.5中的Ti主要来自天然的土壤，K、Ca、Mg、Fe、V的来源是自然和人为因素的结合。Cu、Zn、Pb主要来源于人为排放，富集因子远远大于其它元素，是PM2.5中主要的富集元素。Pb的富集因子在冬季最高，春季最低。对一次典型PM2.5重污染情况进行分析，结果表明PM2.5重污染时，金属元素的污染也相当严重，且其污染源相对复杂，非单一的污染来源。

Pollution characteristics, seasonal distribution rules and enrichment factor of the metal elements in PM2.5 in Zhengzhou has been studied in urban district. The daily average mass concentration of PM2.5 in the year in which the monitoring experiments conducted is 87.4μg＆#183;m-3. The number of days on which the daily average mass concentration of PM2.5 greater than the secondary standard for daily valuestipulated in GB 3095-2012 accounted for 53% of all the days monitored. Among the four seasons, the daily average mass concentration of PM2.5 of Winter is the highest with Autumn being the second highest, Summer being the third highest and Spring being the minimum. An obvious positive correlation exists between the average mass concentrations of the 10 mental elements such as K, V and Mn and the average mass concentration of PM2.5, and the correlation coefficient ranges from 0.516 to 0.907. An obvious negative correlation exists between the average mass concentrations of Na, Cr and Ti and the average mass concentration of PM2.5, and all the correlation coefficients are less than -0.6. The mass concentrations of Ca, Na, K, Mg, Al, Fe, and Zn in PM2.5 in the atmosphere of Zhengzhou are relatively high, while the mass concentrations of the metal elements, such as Cd, Hg, Ni, and V in PM2.5 are relatively low. The average mass concentration of Hg and Pb in PM2.5 in winter are much greater than that at other seasons. The percentage values of the mass concentration of Ca, Na and K in the total mass of the mental elements which are greater than 65% at all the four seasons are the top three, while only in winter, the sum of the percentage values of Cr, Cd, Pb and Hg is greater than 2%. The study on enrichment factor shows that Ti in PM2.5 in the atmosphere of Zhengzhou comes mainly from soils, and the sources of K, Ca, Mg, Fe and V are combinations of natural and human factors. Cu, Zn, and Pb, the principal enriched elements in PM2.5, are mainly from anthropogenic discharges and their enrichment factors are much greater than that of other elements. The enrichment factor of Pb in winter is the highest and the enrichment factor of Pb in spring is the lowest among the four seasons. An analysis on a typical heavy pollution case of PM2.5 has been carried out and the conclusion shows that the concentration of PM2.5 reaches heavy-pollution level, the pollution of metal elements is also fairly severe and the pollution sources are also very complicated and are of multiple sources.