Abstract:

To understand the concentrations and sources of carbonaceous aerosols in Northern China, real-time, semi-online, hourly measurements of PM_2.5 compositions were conducted at an urban site in Wuqing, Tianjin from December 31, 2011 to January 11, 2012. The mean concentrations of EC and OC in Wuqing were 6.0±4.8 and 21.5±19.2 μg C/m³ respectively, which constituted 8% and 30% of the total measured PM_2.5 constituent mass. The mean concentration of WSOC was 14.3±11.8 μg C/m³, which constituted 67% of the mean OC concentration. During the observation period, the large variability of pollutant concentrations were mainly driven by synopticscale meteorological events. As a result, the diurnal patterns of EC, OC, and WSOC were relatively indistinct. The observed mass ratios of OC/EC was relatively stable throughout the observation period and averaged 3.9. Based on correlation analysis with other tracer constituents, it is found that the wintertime carbonaceous aerosols in Wuqing came mainly from biomass burning emissions and experienced significant aging. Roughly half of the OC were from biomass burning; the other half were from secondary formation processes.

Key words: organic carbon, elemental carbon, water-soluble organic carbon, secondary organic aerosol

摘要：

为了解京津冀地区冬季气溶胶含碳组分浓度及变化特征, 2011年12月至2012年1月在天津市武清区针对 PM_2.5中元素碳(EC)、有机碳(OC)、水溶性有机碳(WSOC)及水溶性离子组分进行实时半在线的逐时浓度综合观测。观测期间EC和OC的平均浓度分别为6.0±4.8和21.5±19.2 μg C/m³, 分别占PM_2.5观测组分总浓度平均值的8%和30%。WSOC平均浓度为14.3±11.8 μg C/m³, 占平均OC浓度的67%。观测期间, 污染物浓度的大幅变化主要受气象条件控制, OC, EC和WSOC日变化特征相对不显著。观测期间大部分时间OC/EC比值稳定, OC/EC平均值为3.9。通过含碳组分与其他示踪组分的相关性分析, 初步判定武清冬季的气溶胶含碳组分主要来自生物质燃烧的一次性排放, 且影响当地的气团经过明显老化过程。约一半的OC来自一次生物质燃烧排放, 另一半来自二次生成。

关键词: 有机碳, 元素碳, 水溶性有机碳, 二次有机气溶胶