浙北地区PM2.5中多环芳烃特征

为了研究浙北地区PM_2.5中多环芳烃（PAHs）的季节性变化和它们的来源，于2014年11月~2015年11月收集了杭州和宁波2个城市中4个采样点的PM_2.5样品，利用气-质联用仪测定了17种PAHs浓度.结果表明，∑PAHs年平均浓度范围为24.1~51.9ng/m³，平均值为（35.5 ±12.3） ng/m³.2~3环PAHs在PM_2.5中的浓度较低（<1ng/m³），而4~6环PAHs占总PAHs的77.0%.∑PAHs的浓度与PM_2.5呈相似的季节性变化特征，冬季浓度最高而夏季最低.惹烯作为软木燃烧的示踪物，冬季的浓度是夏季的4倍，表明在冬季软木燃烧的排放和对PM_2.5的贡献都有所增加.除了夏季的2个城区站点，其它季节和站点∑PAHs浓度和PM_2.5呈现一定的正相关性.特征PAHs比值显示，浙北地区气溶胶相关的多环芳烃主要来自燃烧和热解排放，如生物质燃烧和煤燃烧，而交通排放和石油挥发源的影响不大.

Characteristics analyses of PAHs in PM2.5 in the northern Zhejiang province

To investigate the seasonal variations and sources of polycyclic aromatic hydrocarbons (PAHs) in fine particles (PM_2.5) in the northern Zhejiang province (NZP), one year-long field PM_2.5 sampling was conducted at four representative sites in both cities of Hangzhou and Ningbo from December 2014 to November 2015 and in total 17 PAHs were analyzed by GC-MS. The results showed that the total annual averaged concentration of all these 17 PAHs ranged from 24.1 to 51.9ng/m³ with an average of (35.5±12.3) ng/m³. Basically, 2~3 rings PAHs were observed in low abundance in particle phases (<1ng/m³), while 4~6rings PAHs accounted for 77.0% of total particulate PAHs. The total concentration of 17 PAHs followed a similar seasonal trend to that of PM_2.5, showing the highest total PAHs concentration in winter while lowest in summer among four seasons. As a tracer for soft wood burning, the concentration of retene was quadruple in winter compared to that in summer, indicating the increased contribution from soft wood burning in NZP. Except at two urban sites during summer, moderate positive correlations were found between OC and PAHs. The PAHs diagnostic ratios implied that aerosols related PAHs in NZP were not significantly contributed by traffic emissions and petrogenic sources, but mainly originated from pyrogenic sources, such as biomass burning and coal combustion.