Characteristics of fine particle explosive growth events in Beijing, China: Seasonal variation, chemical evolution pattern and formation mechanism
Characteristics of fine particle explosive growth events in Beijing, China: Seasonal variation, chemical evolution pattern and formation mechanism
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北京细颗粒爆炸生长事件特征：季节变化、化学演化模式及形成机制
DOI：
10.1016/j.scitotenv.2019.06.068
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发表时间：
2019
影响因子：
9.8
通讯作者：
Wang Yuesi
中科院分区：
文献类型：
--
作者：
Liu Zirui;Hu Bo;Ji Dongsheng;Cheng Mengtian;Gao Wenkang;Shi Shuzhen;Xie Yuzhu;Yang Shuanghong;Gao Meng;Fu Hongbo;Chen Jianming;Wang Yuesi
在北京重霾天气中经常观测到细颗粒物爆炸增长（FPEG）事件，其特征和形成机制尚未完全清楚。本研究在北京进行了为期五年（2013-2017）的在线观测，分析了FPEG事件的化学演化模式，以了解其形成机制。共确定了132起FPEG事件，并从2013年的39起稳步下降至2017年的19起。超过70%的FPEG事件发生在冬季和秋季，这与不利的天气条件和增强的一次排放相吻合。有机物是PM2.5中的主要成分（约30%），但有机物作为驱动因子仅占总FPEG事件的10%左右，这是因为有机物的贡献随FPEG事件的发展而减少。与此相反，次生无机物种是主导驱动因素，硫酸盐驱动事件占50%以上。在2013-2017年期间，区域源的贡献显著下降，主要是由于区域源的排放量减少，而本地源的贡献基本保持不变，表明本地二次转化在促进FPEG事件中起主导作用。氮氧化速率（NOR）较低（0.12 ± 0.07），且随着RH的升高，NOR呈微弱的上升趋势，表明HNO 3和NH3的均相反应促进了NOR的形成。当相对湿度> 50%时，硫氧化速率（SOR）显著增加（0.50 ± 0.19），表明FPEG处理中SO2的非均相氧化作用增强。此外，我们的分析表明，在FPEG事件中的S（IV）的非均相氧化速率主要取决于气溶胶的液态水含量（ALWC），除了气溶胶的酸度。该研究为理解北京FPEG事件的形成机制提供了观测证据。
Fine particle explosive growth (FPEG) events are frequently observed in heavy haze episodes in Beijing, the characteristics and formation mechanism of which remain not fully understood. In this study, a five year (2013–2017) online observation was conducted in Beijing and the chemical evolution pattern of FPEG events was analyzed to understand its formation mechanism. A total of 132 FPEG events were identified, and steadily decreased from 39 events in 2013 to 19 events in 2017. More than 70% of the FPEG events occurred in winter and autumn, which coincides with adverse weather conditions and enhanced primary emissions. Organic matter (OM) was the dominated components (~30%) in PM2.5, but it only accounted for 10% of total FPEG events as a driven factor, because its contribution usually decreased when the FPEG events developed. In contrast, the secondary inorganic species were the dominated driven factors, and sulfate-driven events accounted >50%. During the period of 2013–2017, the contribution from regional sources decreased significantly mainly due to the reduction of emissions from regional sources, while the contribution from local sources remained largely unchanged, indicating that the local secondary transformation played a leading role in promoting the FPEG events. The low nitrogen oxidation rates (NOR, 0.12 ± 0.07) and the weak increase trend of NOR with elevated RH were observed, indicating the formation of which might be promoted by the homogenous reaction between HNO3and NH3. In contrast, a significant increase in sulfur oxidation rate (SOR, 0.50 ± 0.19) was observed when RH > 50%, suggesting enhanced heterogeneous oxidation of SO2in FPEG events. In addition, our analysis suggest the S (IV) heterogeneous oxidation rates in FPEG events depend mainly on the aerosol liquid water content (ALWC) in addition to the aerosol acidity. This study provides observational evidence for understanding the formation mechanism of FPEG events in Beijing.