A086-0010
Impact of HO2 Heterogeneous Aerosol Uptake on Ozone Formation During Haze Events in Central Beijing
Thursday, 10 December 2020
Poster
Dwayne E Heard1, Eloise Slater2, Lisa Whalley1, Robert Woodward-Massey3, Chunxiang Ye4, James D Lee5, Freya Anne Squires5, James R Hopkins5, Rachel Dunmore5, Marvin Shaw6, Jacqueline Hamilton5, Alastair C Lewis6, Leigh Crilley7, Louisa J Kramer8, William Bloss8, Tuan Vu9, Yele Sun10, Weiqi Xu11, Pingqing Fu12, Siyao Yue10, Lujie Ren12, W. Joe F. Acton13, C Nick Hewitt13 and Xinming Wang14, (1)University of Leeds, School of Chemistry, Leeds, LS2, United Kingdom, (2)University of Leeds, School of Chemistry, Leeds, United Kingdom, (3)Peking University, College of Environmental Sciences and Engineering, Beijing, China, (4)Peking University, Beijing, China, (5)University of York, Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, York, United Kingdom, (6)Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, United Kingdom, (7)York University, Chemistry, Toronto, ON, Canada, (8)University of Birmingham, School of Geography, Earth and Environmental Sciences, Birmingham, United Kingdom, (9)University of Birmingham, Birmingham, United Kingdom, (10)Institute of Atmospheric Physics, Chinese Academy of Sciences, State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Beijing, China, (11)Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, (12)Institute of Surface-Earth System Science, Tianjin University, Tianjin, China, (13)University of Lancaster, Lancaster Environment Centre, Lancaster, United Kingdom, (14)Chinese Academy Of Sciences, Guangzhou, China
Abstract:
O
3 levels in Beijing and throughout China have been increasing in recent years whilst other pollutants (SO
2, NO
x, CO and PM) have been decreasing. Recent work by Li et al. (2019) proposed that the reduction in PM across China is leading to a decreasing rate of heterogeneous uptake of HO
2 onto aerosol and hence higher O
3 formation rates. In this work, field measurements of OH, HO
2 and RO
2 radicals were made in central Beijing during the Air Pollution and Human Health (APHH) campaigns that took place in winter (November/December 2016) and summer (May/June 2017). The radical concentrations were calculated with a box model using the detailed Master Chemical Mechanism (MCM) and constrained with concentrations of co-measured chemical species, as well as aerosol and radiative parameters. We explore the impact of heterogeneous uptake of HO
2 onto aerosols on the rate of O
3 formation during haze events.
The results showed that in winter, heterogeneous HO2 uptake onto aerosols does not compete with the loss of HO2 via its reaction with NO, despite the very high loadings of aerosol experienced during heavy haze events. The haze events are driven by anthropogenic processes and coincide with high NO concentrations, and therefore aerosol uptake does not influence O3 formation rates. However, in summer, PM and NO are only weakly correlated, and on some haze days the inclusion of HO2 aerosol uptake in the model decreased the HO2 concentration by as much as 70%, and led to significant improvements with measured levels of HO2. Aerosol HO2 uptake is only competitive with reaction with NO during the non-anthropogenic haze events in summer, which are characterised by high aerosol surface areas and low mixing ratios of NO (< 2 ppbv). The decrease in O3 formation rate driven by the reduction in HO2 concentration owing to aerosol HO2 uptake reaches up to ~5 ppbv hr-1 in the haze events during summer.
Li, K., Jacob, D. J., Liao, H., Zhu, J., Shah, V., Shen, L., Bates, K. H., Zhang, Q. and Zhai, S., A two-pollutant strategy for improving ozone and particulate air quality in China, Nature Geoscience, 12 (11), 906-910, 2019.
