Characteristics of fine particle explosive growth events in Beijing, China: Seasonal variation, chemical evolution pattern and formation mechanism

• Published in: The Science of the total environment Vol. 687; pp. 1073 - 1086
• Main Authors: Liu, Zirui, Hu, Bo, Ji, Dongsheng, Cheng, Mengtian, Gao, Wenkang, Shi, Shuzhen, Xie, Yuzhu, Yang, Shuanghong, Gao, Meng, Fu, Hongbo, Chen, Jianming, Wang, Yuesi
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.10.2019
• Subjects: Chemical evolution pattern; Formation mechanism; FPEG events; Local/regional contribution; Chemical evolution pattern; FPEG events; Formation mechanism; Local/regional contribution
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2019.06.068

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 HNO3 and 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 SO2 in 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. [Display omitted] •Typical evolution patterns of fine particle explosive growth (FPEG) events were analyzed.•Secondary inorganic aerosols (SIA) dominated the evolution of FPEG events.•SIA in FPEG events was mainly formed from local secondary transformation.•Enhanced heterogeneous oxidation of SO2 primarily depend on aerosol liquid water content.