Dramatic changes in aerosol composition during the 2016–2020 heating seasons in Beijing–Tianjin–Hebei region and its surrounding areas: The role of primary pollutants and secondary aerosol formation

Distinct Seasonality in Aerosol Responses to Emission Control Over Northern China

“…The seasonal difference in trends of OA concentrations is close to that of organic carbon emissions, implying a straightforward response to emission reductions. This finding agrees with observational studies that indicate a dominant contribution of reductions in primary OA to the decreasing trend of OA concentrations in the BTH region (Wang, Gao, et al., 2022). The declining trend of nitrate concentrations in winter is second to OA, and is 1.6 times larger than that in summer, thus further enhancing the contrast in PM 2.5 trends between the two seasons.…”

“…In fact, some observational studies have illustrated the hygroscopic capacity of the aged secondary OA (Hong et al., 2018; Kuang et al., 2020; Xu et al., 2020). Unlike the strong reduction of primary aerosols, there is evidence suggesting the enhancement of secondary aerosol formation in winter due to the rising atmospheric oxidizing capacity (Wang, Gao, et al., 2022; Wang, Parrish, et al., 2022). If this is the case for secondary OA, a consideration of its hygroscopicity would imply an additional offset on the AOD decline effect from PM 2.5 reduction in winter.…”

Factors Affecting Recent Pm2.5 Concentrations in China and South Korea from 2016 to 2020

“…For example, Zheng et al (2018) reported that the emission amounts of NO 2 and SO 2 in China had been reduced by approximately −2 % and − 11 % annually in 2017 compared with that in 2016, respectively; whereas, in our study, the emissions changed from −9 % to +15 % (NO 2 ) and − 11 % to −23 % (SO 2 ) for January to March 2017, respectively. Considering a long-term change, it is also reported that SO 2 decreased by approximately −56 % to −78 %, and NO 2 decreased by −22 % to −51 % in 2020 compared with that in 2016 (Wang et al, 2022), respectively; whereas this study shows a − 58 % to −86 % and − 27 % to −48 % reduction in SO 2 and NO 2 from January to March 2020, respectively.…”

Seasonal Changes of Brown Carbon in an Industrial City of Central China: Importance of Water-Insoluble Brc

“…Since EC is mainly considered as a tracer of primary combustion emissions, the ratio of secondary substances such as SOC, SO4 2-, NO3 -and NH4 + to EC indicates the information of secondary aerosol formation (Chow et al, 2004;Huang et al, 2021;Wang et al, 2022). According to the different degrees of secondary component occupancy (SIA/EC, SOC/EC) and aerosol oxidation (WSOC/OC), the relationship between SOC and SIA and babs, BrC, 405 nm was analyzed to illustrate the mechanism for the evolution of BrC light absorption in autumn and winter (Fig.…”