Rapid mass growth and enhanced light extinction of atmospheric aerosols during the heating season haze episodes in Beijing revealed by aerosol–chemistry–radiation–boundary layer interaction

Zongkai Lin ,Chang Li,Putian Zhou,Jing Cai,Simo Hakala,Lubna Dada,Markku Kulmala,Federico Bianchi,Zemin Feng,Tommy Chan,Lili Wang,Feixue Zheng,Wei Du,Juha Kangasluoma,Lei Yao,Yusheng Zhang,Ying Zhou,Kaspar R Daellenbach,Yonghong Wang,Yongchun Liu,Yishuo Guo,Runlong Cai,Chao Yan,Biwu Chu,Xiaolong Fan,Tuukka Petäj̈ä ,Tom Kokkonen ,Veli‐Matti Kerminen

doi:10.5194/acp-21-12173-2021

Abstract

Abstract. Despite the numerous studies investigating haze formation mechanism in China, it is still puzzling that intensive haze episodes could form within hours directly following relatively clean periods. Haze has been suggested to be initiated by the variation of meteorological parameters and then to be substantially enhanced by aerosol–radiation–boundary layer feedback. However, knowledge on the detailed chemical processes and the driving factors for extensive aerosol mass accumulation during the feedback is still scarce. Here, the dependency of the aerosol number size distribution, mass concentration and chemical composition on the daytime mixing layer height (MLH) in urban Beijing is investigated. The size distribution and chemical composition-resolved dry aerosol light extinction is also explored. The results indicate that the aerosol mass concentration and fraction of nitrate increased dramatically when the MLH decreased from high to low conditions, corresponding to relatively clean and polluted conditions, respectively. Particles having their dry diameters in the size of ∼400–700 nm, and especially particle-phase ammonium nitrate and liquid water, contributed greatly to visibility degradation during the winter haze periods. The dependency of aerosol composition on the MLH revealed that ammonium nitrate and aerosol water content increased the most during low MLH conditions, which may have further triggered enhanced formation of sulfate and organic aerosol via heterogeneous reactions. As a result, more sulfate, nitrate and water-soluble organics were formed, leading to an enhanced water uptake ability and increased light extinction by the aerosols. The results of this study contribute towards a more detailed understanding of the aerosol–chemistry–radiation–boundary layer feedback that is likely to be responsible for explosive aerosol mass growth events in urban Beijing.

Highlights

Despite the recent reduction of air pollutants and their precursors in China between 2013 and 2017, the current emission and air pollution levels are still substantially high
To further study which particle size possesses the highest light extinction efficiency during the haze events, and to what extent nitrates contribute to light extinction with the variation of mixing layer height (MLH), a case of rapid aerosol mass growth event is selected for further study
We investigated the synergetic variations of aerosol chemical composition and mixing layer height during the daytime in urban Beijing

Summary

Introduction

Despite the recent reduction of air pollutants and their precursors in China between 2013 and 2017, the current emission and air pollution levels are still substantially high Z. Lin et al.: Rapid mass growth and enhanced light extinction of atmospheric aerosols et al, 2020b; Zheng et al, 2018). Lin et al.: Rapid mass growth and enhanced light extinction of atmospheric aerosols et al, 2020b; Zheng et al, 2018) Such high emissions, combined with specific meteorological conditions, frequently lead to severe haze episodes (An et al, 2019; Wang et al, 2019). Particulate matter, a major air pollutant, has considerable effects on climate, human health and visibility degradation (Che et al, 2007; Lelieveld et al, 2015; Spracklen et al, 2008; Wang et al, 2015)

Objectives

Methods

Results

Conclusion