Differences in the composition of organic aerosols between winter and summer in Beijing: a study by direct-infusion ultrahigh-resolution mass spectrometry

Sarah S Steimer,Roy M Harrison,Zoë L Fleming,Marios Panagi,Paul S Monks,Daniel J Patton,Tuan V Vu,Zongbo Shi,Markus Kalberer

doi:10.5194/acp-20-13303-2020

Abstract

Abstract. This study investigates the chemical composition of PM2.5 collected at a central location in Beijing, China, during winter 2016 and summer 2017. The samples were characterised using direct-infusion negative-nano-electrospray-ionisation ultrahigh-resolution mass spectrometry to elucidate the composition and the potential primary and secondary sources of the organic fraction. The samples from the two seasons were compared with those from a road-tunnel site and an urban background site in Birmingham, UK, analysed in the course of an earlier study using the same method. There were strong differences in aerosol particle composition between the seasons, particularly regarding (poly-)aromatic compounds, which were strongly enhanced in winter, likely due to increased fossil fuel and biomass burning for heating. In addition to the seasonal differences, compositional differences between high- and low-pollution conditions were observed, with the contribution of sulfur-containing organic compounds strongly enhanced under high-pollution conditions. There was a correlation of the number of sulfur-containing molecular formulae with the concentration of particulate sulfate, consistent with a particle-phase formation process.

Highlights

Ambient air pollution is of growing concern regarding its negative effect on public health, especially in low- and middle-income countries (Cohen et al, 2017; Hoek et al, 2013; Lelieveld et al, 2015)
While in winter almost no peaks are present with m/z > 450, a significant number of peaks up to m/z 500 are detected in the summer samples
The overall number of assigned formulae per sample ranged from 918 in the Summer low (SL) sample to 1586 in the Winter high (WH) sample. This is a lower limit on the total number of ionised compounds in the samples, as the technique cannot distinguish between structural isomers

Summary

Introduction

Ambient air pollution is of growing concern regarding its negative effect on public health, especially in low- and middle-income countries (Cohen et al, 2017; Hoek et al, 2013; Lelieveld et al, 2015) One of these countries is China, where rapid development has led to air pollution becoming a major environmental issue (Guan et al, 2016). Steimer et al.: Differences in the composition of organic aerosols in Beijing spheric Pollution and Human Health in a Chinese Megacity (APHH-Beijing) project, was launched in an effort to understand the emissions, processes and health effects of air pollution in Beijing (Shi et al, 2019) This improved scientific understanding will feed into the development of efficient mitigation measures to improve air quality and reduce health impacts. As a central part of the project, two 1-month-long coordinated field campaigns were conducted at two sites, central Beijing and rural Pinggu, in November– December 2016 and May–June 2017

Methods

Results

Conclusion