16 Mar 2023
 | 16 Mar 2023
Status: this preprint is currently under review for the journal ACP.

Evolution of atmospheric age of particles and its implications for the formation of a severe haze event in eastern China

Xiaodong Xie, Jianlin Hu, Momei Qin, Song Guo, Min Hu, Dongsheng Ji, Hongli Wang, Shengrong Lou, Cheng Huang, Chong Liu, Hongliang Zhang, Qi Ying, Hong Liao, and Yuanhang Zhang

Abstract. Atmospheric age reflects how long particles have been suspended in the atmosphere, which is closely associated with the evolution of air pollutants. Severe regional haze events occur frequently in China, influencing air quality, human health, and regional climate. Previous studies have explored the characteristics of mass concentrations and compositions of fine particulate matter (PM2.5) during haze events, but the evolution of atmospheric age remains unclear. In this study, the age-resolved UCD/CIT model was developed and applied to simulate the concentration and age distribution of PM2.5 during a severe regional haze episode in eastern China. The results indicated that PM2.5 concentrations in the North China Plain (NCP) gradually accumulated due to stagnant weather conditions at the beginning stage of the haze event. Accordingly, the atmospheric age of elemental carbon (EC), primary organic aerosol (POA), sulfate (SO42−), and secondary organic aerosol (SOA) gradually increased. The subsequent PM2.5 concentration growth was driven by the local chemical formation of nitrate (NO3) under high relative humidity. The newly formed NO3 particles led to a decrease in the mean atmospheric age of the NO3 particles. During the regional transport stage, aged particles from the NCP moved to the downwind Yangtze River Delta (YRD) region, leading to a sharp increase in PM2.5 concentrations and the average age of EC, POA, SO42−, and SOA. In contrast, the average age of NO3 and ammonium remained unchanged or even slightly decreased due to continuous local formation in the YRD region. Different evolution of the atmospheric age among these components provides a unique perspective on the formation of PM2.5 components during the regional haze event. The information can also be used for designing effective control strategies for different components of PM2.5.

Xiaodong Xie et al.

Status: open (until 27 Apr 2023)

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Xiaodong Xie et al.

Xiaodong Xie et al.


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Short summary
Atmospheric age of particles reflects how long particles have been formed and suspended in the atmosphere, which is closely associated with the evolution processes of particles. Analysis atmospheric age of PM2.5 provides a unique perspective on the evolution processes of different PM2.5 components. The results also shed lights on how to design effective emission control actions under unfavorable meteorological conditions.