High molecular weight organic compounds (HMW-OCs) in severe winter haze: Direct observation and insights on the formation mechanism
High molecular weight organic compounds (HMW-OCs) in severe winter haze: Direct observation and insights on the formation mechanism
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DOI：
10.1016/j.envpol.2016.07.004
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发表时间：
2016-11-01
影响因子：
8.9
通讯作者：
Toyoda, M.
中科院分区：
文献类型：
--
作者：
Duan, F. K.;He, K. B.;Toyoda, M.
高分子量有机化合物（HMW-OCs），形成二次有机气溶胶（SOA），已在许多实验室研究报告。然而，HMW-OCs形成的证据很少，特别是在冬季在真实的大气中，已经报道。2013年1月，北京遭遇历史性严重雾霾污染，PM2.5小时浓度高达974 μ g m（-3）。确定了四个典型的灰霾事件（HE 1至HE 4），HE 2（1月9日至16日）是其中最严重的。基于PM2. 5的逐时化学成分观测和基质辅助激光解吸电离飞行时间质谱（MALDI-TOF-MS）分析的逐日有机成分，我们发现，在重霾天出现了丰富的m/z 200-850的离子峰，而在晴天这些离子峰可以忽略不计，表明冬季霾中存在HMW-OCs。HMW-OCs和O3之间的负非线性相关性表明，气体氧化不太可能是HMW-OCs形成的主导机制。在重度灰霾天气过程中，大气相对湿度和H2O/PM2.5质量比分别高达80%和0.2。高含水量及其与高分子量有机碳的良好正相关性表明，水相过程可能是冬季的一个重要途径。HE 2期间的酸度（0.37 μ g m（-3））比其他日子高得多，以及其与HMW-OCs的强相关性的证据表明，酸催化反应可能导致北京冬季重度雾霾期间HMW-OCs的形成。(C)2016爱思唯尔有限公司版权所有。
High molecular weight organic compounds (HMW-OCs), formed as secondary organic aerosols (SOA), have been reported in many laboratory studies. However, little evidence of HMW-OCs formation, in particular during winter season in the real atmosphere, has been reported. In January 2013, Beijing faced historically severe haze pollution, in which the hourly PM2.5 concentration reached as high as 974 mu g m(-3). Four typical haze events (HE1 to HE4) were identified, and HE2 (Jan. 9-16) was the most serious of these. Based on the hourly observed chemical composition of PM2.5 and the daily organic composition analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), we found that abundant ion peaks in m/z 200-850 appeared on heavy haze days, whereas these were negligible on a clear day, indicating the existence of HMW-OCs in the wintertime haze. A negative nonlinear correlation between HMW-OCs and 03 suggested that gas oxidation was not likely to be the dominant mechanism for HMW-OCs formation. During the heavy haze events, the relative humidity and mass ratio of H2O/PM2.5 reached as high as 80% and 0.2, respectively. The high water content and its good positive correlation with HMW-OCs indicated that an aqueous-phase process may be a significant pathway in wintertime. The evidence that acidity was much higher during HE2 (0.37 mu g m(-3)) than on other days, as well as its strong correlation with HMW-OCs, indicated that acid catalyzed reactions likely resulted in HMW-OCs formation during the heavy winter haze in Beijing. (C) 2016 Elsevier Ltd. All rights reserved.