Variation of size-segregated particle number concentrations in wintertime Beijing

Ying Zhou,Tuukka Petäjä,Juha Kangasluoma,Chao Yan,Federico Bianchi,Lubna Dada,Yueyun Fu,Kaspar R Daellenbach,Markku Kulmala,Jingkun Jiang,Biwu Chu,Yiliang Liu,Tom V Kokkonen,Veli-Matti Kerminen,Lin Wang,Yongchun Liu,Joni Kujansuu,Tommy Chan

doi:10.5194/acp-20-1201-2020

Abstract

Abstract. The spatial and temporal variability of the number size distribution of aerosol particles is an indicator of the dynamic behavior of Beijing's atmospheric pollution cocktail. This variation reflects the strength of different primary and secondary sources, such as traffic and new particle formation, as well as the main processes affecting the particle population. In this paper, we report size-segregated particle number concentrations observed at a newly developed Beijing station during the winter of 2018. Our measurements covered particle number size distributions over the diameter range of 1.5 nm–1 µm (cluster mode, nucleation mode, Aitken mode and accumulation mode), thus being descriptive of a major fraction of the processes taking place in the atmosphere of Beijing. Here we focus on explaining the concentration variations in the observed particle modes, by relating them to the potential aerosol sources and sinks, and on understanding the connections between these modes. We considered haze days and new particle formation event days separately. Our results show that during the new particle formation (NPF) event days increases in cluster mode particle number concentration were observed, whereas during the haze days high concentrations of accumulation mode particles were present. There was a tight connection between the cluster mode and nucleation mode on both NPF event and haze days. In addition, we correlated the particle number concentrations in different modes with concentrations of trace gases and other parameters measured at our station. Our results show that the particle number concentration in all the modes correlated with NOx, which reflects the contribution of traffic to the whole submicron size range. We also estimated the contribution of ion-induced nucleation in Beijing, and we found this contribution to be negligible.

Highlights

Atmospheric aerosols are the main ingredient of China’s pollution cocktail (Kulmala, 2015)
We observed that the cluster and nucleation mode particle concentrations were the highest on the new particle formation (NPF) event days
Aitken and accumulation mode particles contributed to 52 % of the total particle number concentration on the haze days, as compared to 4 % on the NPF event days

Summary

Introduction

Atmospheric aerosols are the main ingredient of China’s pollution cocktail (Kulmala, 2015). Aerosols have gained increasing attention due to their effects on human heath, climate and visibility (Lelieveld et al, 2015; IPCC, 2007). Y. Zhou et al.: Variation of size-segregated particle number concentrations cles, which contribute to a negligible fraction of the mass concentration, dominate the total number concentration in urban areas (von Bismarck-Osten et al, 2013; Wehner et al, 2004; Wu et al, 2008). Zhou et al.: Variation of size-segregated particle number concentrations cles, which contribute to a negligible fraction of the mass concentration, dominate the total number concentration in urban areas (von Bismarck-Osten et al, 2013; Wehner et al, 2004; Wu et al, 2008) Due to their high concentrations, ultrafine particles’ toxicological effects are enhanced by their large total surface area (Kreyling et al, 2004)

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