天津秋冬季PM2.5碳组分化学特征与来源分析

为研究天津大气PM2.5中有机碳和元素碳的特征,于2009年9月4日到2010年2月25日在天津3个监测点位采集PM2.5样品,分析了PM2.5颗粒中元素碳和有机碳的含量特征、与气象条件的相互关系、以及碳组分的来源.结果表明3个监测点位PM2.5的平均质量浓度为123.85μg/m3;TC的平均浓度为18.76μg/m3,其中OC的平均浓度为14.48μg/m3,EC的平均浓度为4.27μg/m3,日均OC和EC浓度分别占PM2.5的11.7%和3.5%.秋季SOC的估算值为5.1μg/m3, 占OC的40.7%、PM2.5的4.3%;冬季SOC的估算值为6.5μg/m3, 占OC的35.7%,PM2.5的4.9%.观测期间EC与温度呈比较好的负相关关系; OC、EC、TC的浓度与风速有较好的负相关性.48h后推气流轨迹结果显示局地盘旋的气流(L)和来自天津北方或西北方区域气流(N/NW)有较高的碳组分浓度;天津大气PM2.5中碳组分受包括生物质燃烧、汽车排放、燃煤和道路扬尘混合来源影响.

Character and source analysis of carbonaceous aerosol in PM2.5 during autumn-winter period, Tianjin.

Concentrations of organic carbon (OC) and element carbon (EC) in PM2.5 were measured at three sites including urban and suburban areas in Tianjin, from September 4 2009 to February 25 2010. Average PM2.5 levels was 123.85μg/m3. The average OC and EC concentrations in PM2.5 were 14.48 and 4.27μg/m3, accounting for 11.7% and 3.5% of particulate mass, respectively. Secondary organic carbon calculated based on minimum OC/EC ratio method was 5.1μg/m3 for autumn and 6.5μg/m3 for winter, accounting for 40.7% and 35.7% of the total organic carbon, or 4.3% and 4.9% of particulate mass, respectively. EC concentrations had good negative correlations with temperature, while OC, EC and TC concentrations had significant negative correlations with wind speed during the observational period. Air masses looped around observation site (L) and from the north and northwest of China (N/NW) were featured with higher OC and EC concentrations contrast to other categories. Multi-sources (including biomass burning, vehicle emission, coal combustion and road dust) contributed to OC and EC burden in Tianjin during observation period.