Evaluation of the VOC pollution pattern and emission characteristics during the Beijing resurgence of COVID-19 in summer 2020 based on the measurement of PTR-ToF-MS

Abstract

A second wave of coronavirus disease 2019 (COVID-19) infections have emerged in summer Beijing, 2020, which provided an opportunity to explore the response of air pollution to reduced human activity. Proton-Transfer-Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) coupled with Positive Matrix Factorization (PMF) source apportionment were applied to evaluate the pollution pattern and capture the detailed dynamic emission characteristics of volatile organic compounds (VOCs) during the representative period with the occurrence of O3 pollution episodes and the Beijing resurgence of COVID-19. The level of anthropogenic VOC was lower than the same period of previous years due to the pandemic and emission reduction measures. More than two-thirds of the observation period were identified as high-O3 days and VOCs exhibited higher mixing ratios and faster consumption rates in the daytime under high-O3 days. The identified VOC emission sources and the corresponding contributions during the whole observation period included: vehicle + fuel (12.41 ± 9.43%), industrial process (9.40 ± 8.65%), solvent usage (19.58 ± 13.46%), biogenic (6.03 ± 5.40%), background + long-lived (5.62 ± 11.37%), and two groups of oxygenated VOC (OVOC) factors (primary emission and secondary formation, 26.14 ± 15.20% and 20.84 ± 14.0%, respectively). Refined dynamic source apportionment results show that the “stay at home” tendency led to decreased emission (- 34.47 ± 1.90 %) and weakened morning peak of vehicle + fuel during the Beijing resurgence. However, growing emission of primary OVOCs (+ 51.10 ± 8.28%) with similar diurnal variation was observed in the new outbreak and afterwards, which might be related to the enhanced usage of pandemic products. The present study illustrated that more stringent VOC reduction measures towards pandemic products should be carried out to achieve the balanced emission abatement of NOx and VOC when adhering to regular epidemic prevention and control measures.

Research progresses on VOCs emission investigationsviasurface and satellite observations in China

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“…Tropospheric ozone (O 3 ) and secondary organic aerosols (SOAs) cause severe atmospheric pollution in China, particularly in economically developed and densely populated regions. 1,2 Volatile organic compounds (VOCs) are important precursors of O 3 and SOAs in China. [3][4][5] Atmospheric VOCs consist of more than a thousand gaseous organic trace species including alkanes, alkenes, alkynes, aromatics, halocarbons, and oxygenated volatile organic compounds (OVOCs) that are emitted from biogenic and anthropogenic sources.…”