Impact of HO2 aerosol uptake on radical levels and O3 production during summertime in Beijing
- 1School of Chemistry, University of Leeds, LS2 9JT, UK
- 2National Centre of Atmospheric Science, University of Leeds, LS2 9JT, UK
- 3College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
- 4Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
- 5National Centre of Atmospheric Science, University of York, Heslington, York, YO19 5DD, UK
- 6Aston Institute of Materials Research, School of Engineering and Applied Science, Aston University, Birmingham, B4 7ET, UK
- 7Turkish Accelerator and Radiation Laboratory, Ankara University Institute of Accelerator Technologies, Atmospheric and Environmental Chemistry Laboratory, Gölbaşi Campus, Ankara, Turkey
- 8Centre of Atmospheric Sciences, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
- 9National Centre for Atmospheric Sciences, University of Manchester, Manchester, M13 9PL, UK
- 10Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- 11Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YW, UK
- 12Department of Chemistry, University of Cambridge, Cambridge, UK
- 13Department of Chemistry, York University, Toronto, ON, M3J 1P3, Canada
- 14School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
- 15Department of Meteorology, University of Reading, Reading, UK
- 16Institut Pierre Simon Laplace, École Polytechnique, Palaiseau, France
- 17State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute for Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
- 18Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China
- 19Minerva Research Group, Max Planck Institute for Chemistry, 55128 Mainz, Germany
- 20State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China
- 21School of Earth and Environment, University of Leeds, LS2 9JT, UK
- anow at: The Hut Group, Unit 1 Icon Manchester, Manchester Airport, WA15 0AF
- bnow at: British Antarctic Survey, Cambridge, CB3 0ET, UK
- cChaucer, Part of Bip Group, 10 Lower Thames Street, London, EC3R 6EN
- dBeijing Hanzhou Innovation Institute Yuhang, Xixi Octagon City, Yuhang District, Hangzhou 310023, China
- ealso at: Department of Environmental Sciences, Faculty of Meteorology, Environment and Arid Land Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia
Abstract. The impact of heterogeneous uptake of HO2 onto aerosol surfaces on radical concentrations and the O3 production regime in Beijing summertime was investigated. The uptake coefficient of HO2 onto aerosol surfaces, γHO2, was calculated for the AIRPRO campaign in Beijing, Summer 2017, as a function of measured aerosol soluble copper concentration, [Cu2+]eff, aerosol liquid water content, [ALWC], and particulate matter concentration, [PM]. An average γHO2 across the entire campaign of 0.070 ± 0.035 was calculated, with values ranging from 0.002 to 0.15, and found to be significantly lower than the value of γHO2 = 0.2, commonly used in modelling studies. Using the calculated γHO2 values for the Summer AIRPRO campaign, OH, HO2 and RO2 radical concentrations were modelled using a box-model incorporating the Master Chemical Mechanism (v3.3.1), with and without the addition of γHO2, and compared to the measured radical concentrations. Rate of destruction analysis showed the dominant HO2 loss pathway to be HO2 + NO for all NO concentrations across the Summer Beijing campaign with HO2 uptake contributing < 0.3 % to the total loss of HO2 on average. This result for Beijing summertime would suggest that under most conditions encountered, HO2 uptake onto aerosol surfaces is not important to consider when investigating increasing O3 production with decreasing [PM] across the North China Plain. At low [NO], however, i.e. < 0.1 ppb, which was often encountered in the afternoons, up to 29 % of modelled HO2 loss was due to HO2 uptake on aerosols when calculated γHO2 was included, even with the much lower γHO2 values compared to γHO2 = 0.2, a results which agrees with the aerosol-inhibited O3 regime recently proposed by Ivatt et al., 2022. As such it can be concluded that in cleaner environments, away from polluted urban centres where HO2 loss chemistry is not dominated by NO but where aerosol surface area is high still, changes in PM concentration and hence aerosol surface area could still have a significant effect on both overall HO2 concentration and the O3 production regime.
Using modelled radical concentrations, the absolute O3 sensitivity to NOx and VOC showed that, on average across the summer AIRPRO campaign, the O3 production regime remained VOC-limited, with the exception of a few days in the afternoon when the NO mixing ratio dropped low enough for the O3 regime to shift towards NOx-limited. The O3 sensitivity to VOC, the dominant regime during the summer AIRPRO campaign, was observed to decrease and shift towards a NOx sensitive regime both when NO mixing ratio decreased and with the addition of aerosol uptake. This suggests that if [NOx] continues to decrease in the future, ozone reduction policies focussing solely on NOx reductions may not be as efficient as expected if [PM] and, hence, HO2 uptake to aerosol surfaces, continues to decrease. The addition of aerosol uptake into the model, for both the γHO2 calculated from measured data and when using a fixed value of γHO2 = 0.2, did not have a significant effect on the overall O3 production regime across the campaign. While not important for this campaign, aerosol uptake could be important for areas of lower NO concentration that are already in a NOx-sensitive regime.
Joanna E. Dyson et al.
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Joanna E. Dyson et al.
Joanna E. Dyson et al.
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