黄石市夏季昼间大气PM_(10)与PM_(2.5)中有机碳、元素碳污染特征

Pollution characteristics of organic carbon and elemental carbon in atmospheric particles during the summer day in Huangshi City

2012年7月,对黄石市城区夏季昼间大气颗粒物PM10与PM2.5样品进行采集,并用热/光反射法(TOR)分析其中的有机碳(OC)、元素碳(EC).结果显示,新老城区PM10中OC平均含量分别为14.60μg·m-3和18.70μg·m-3,EC平均含量分别为4.70μg·m-3和11.02μg·m-3;PM2.5中OC平均含量分别为11.89μg·m-3和13.66μg·m-3,EC平均含量分别为2.28μg·m-3和4.96μg·m-3.研究结果表明,夏季昼间黄石市新老城区大气PM10与PM2.5中碳组分浓度变化趋势相同,且老城区大气PM10、PM2.5中的OC和EC含量普遍要比新城区高,且PM10中OC、EC在总碳(TC)的质量分数均高于在PM2.5中,说明黄石市老城区碳污染状况较新城区要严重,其夏季昼间大气粗颗粒物中碳的含量更高.通过对OC/EC及8个碳组分进行探讨,发现黄石市大气颗粒物中OC易形成二次污染,而EC排放以烟炱为主,夏季燃煤和机动车尾气是黄石碳污染的重要污染源,生物质燃烧也具有一定影响.

The atmospheric particle samples from the old and new towns of a typical mining city, Huangshi, were collected by miniVol （5 L·min^-1, 12 h, Airmetrics USA） during the summer day in July 2012. The carbonaceous components were quantified with the thermal/optical reflectance （TOR） method, which produced five organic carbon （OC） fractions, OC1, OC2, OC3, OC4, and pyrolyzed organic carbon （OP）, and three elemental carbon （EC） fractions, EC1, EC2, and EC3. The results indicated that OC in PM10 from the new and the old town were 14.60 μg·m^-3 and 18.70 μg·m^-3, respectively, and the EC were 4.70 μg·m^-3 and 11.02 μg·m^-3, respectively. OC in PM2.5 from the new and the old town were 11.89 μg·m^-3 and 13.66 μg·m^-3, respectively, and the EC were 2.28 μg·m^-3 and 4.96 μg·m^-3, respectively. OC and EC in the old town were significantly higher, but sharing the same trend of variability with that in the new town. OC and EC in PM10 mass fraction were higher than in PM2.5. This suggested that carbon pollution in the old town was more serious, and carbon contents in big size particles of the summer day were higher. Based on the ratios of OC/EC and char-EC/soot-EC, we found that OC was largely secondary, while EC was usually soot-EC based. Coal combustion and motor vehicle tail gas are the important pollution sources in the summer day, with certain contribution from biomass combustion.