Aerosol chemistry and particle growth events at an urban downwind site in the North China Plain

Abstract

Abstract. The North China Plain (NCP) has experienced frequent severe haze pollution events in recent years. While 25 extensive measurements have been made in megacities, aerosol sources, processes, and particle growth at urban downwind sites remain less understood. Here, an Aerosol Chemical Speciation Monitor and a Scanning Mobility Particle Sizer, along with a suite of collocated instruments, were deployed at the downwind site of Xingtai, a highly polluted city in the NCP, for real-time measurements of submicron aerosol (PM 1 ) species and particle number size distributions during May and June 2016. The average mass concentration of PM 1 was 30.5 (± 19.4) μg m -3 , which is significantly lower than that during 30Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-889 Manuscript under review for journal Atmos. Chem. Phys. Discussion started: 9 January 2018 c Author(s) 2018. CC BY 4.0 License. 2 wintertime. Organic aerosols (OA) constituted the major fraction of PM 1 (38%) followed by sulfate (25%) and nitrate (14%).Positive matrix factorization with the Multilinear Engine version 2 showed that oxygenated OA (OOA) was the dominant species in OA throughout the study, on average accounting for 78% of OA, while traffic and cooking emissions both accounted for 11% of OA. Our results highlight that aerosol particles at the urban downwind site were highly aged and mainly from secondary formation. However, the diurnal cycle also illustrated the substantial influence of urban emissions on downwind 35 sites, which are characterized by similar pronounced early morning peaks for most aerosol species. New particle formation and growth events were also frequently observed (58% of the time) on both clean and polluted days. Particle growth rates varying from 1.2 to 4.9 nm h -1 were positively related to the condensation sink during periods with high OOA contributions and also to sulfate concentrations during relatively clean periods. Our results showed that sulfate and OOA played important roles in particle growth during clean periods, while OOA was more important than sulfate during polluted events. Further analyses 40showed that particle growth rates have no clear dependence on air mass trajectories.

Characterization of aerosol hygroscopicity, mixing state, and CCN activity at a suburban site in the central North China Plain

“…Figure 1b shows the mean distribution of SO 2 concentrations from May 2012 to 2016, which confirms that the measurement site is located in one of the pollution centers in this region. A detailed analysis of gas precursors and aerosol chemical species shows that this station is a representative site in this region (Zhang et al, 2018).…”

“…Trace-gas analyzers (manufactured by Ecotech) were used to measure the gaseous species of ozone, SO 2 , NO x , NO, and carbon monoxide. More detailed descriptions of the analyzers are given by Zhu et al (2016).…”

“…This is why aerosol hygroscopicity and the occurrence of NPF events increased. Zhang et al (2018) characterized the aerosol chemistry during NPF events in this field campaign. The diurnal pattern in κ gf for 80-200 nm particles differs from that of 40 nm particles.…”

Characteristics of atmospheric fungi in particle growth events along with new particle formation in the central North China Plain

“…These are considered clean air masses. However, Direction A air masses flow across many relatively polluted urbanized and industrialized regions (Zhang et al, 2018). Integrated with SMPS data, we find that 18% of the HYSPLIT back trajectories from the direction A occur the clearly PGE-NPF, and for the direction B is 33%.…”