We found a match
Your institution may have rights to this item. Sign in to continue.
- Title
Impact of HO2 aerosol uptake on radical levels and O3 production during summertime in Beijing.
- Authors
Dyson, Joanna E.; Whalley, Lisa K.; Slater, Eloise J.; Woodward-Massey, Robert; Ye, Chunxiang; Lee, James D.; Squires, Freya; Hopkins, James R.; Dunmore, Rachel E.; Shaw, Marvin; Hamilton, Jacqueline F.; Lewis, Alastair C.; Worrall, Stephen D.; Bacak, Asan; Mehra, Archit; Bannan, Thomas J.; Coe, Hugh; Percival, Carl J.; Ouyang, Bin; Hewitt, C. Nicholas
- Abstract
The impact of heterogeneous uptake of HO 2 on aerosol surfaces on radical concentrations and the O 3 production regime in Beijing in summertime was investigated. The uptake coefficient of HO 2 onto aerosol surfaces, γHO2 , was calculated for the AIRPRO campaign in Beijing, in summer 2017, as a function of measured aerosol soluble copper concentration, [Cu 2+ ] 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, HO 2 and RO 2 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. The rate of destruction analysis showed the dominant HO 2 loss pathway to be HO 2 + NO for all NO concentrations across the summer Beijing campaign, with HO 2 uptake contributing <0.3 % to the total loss of HO 2 on average. This result for Beijing summertime would suggest that under most conditions encountered, HO 2 uptake onto aerosol surfaces is not important to consider when investigating increasing O 3 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 HO 2 loss was due to HO 2 uptake on aerosols when calculated γHO2 was included, even with the much lower γHO2 values compared to γHO2= 0.2, a result which agrees with the aerosol-inhibited O 3 regime recently proposed by Ivatt et al. (2022). As such it can be concluded that in cleaner environments, away from polluted urban centres where HO 2 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 HO 2 concentration and the O 3 production regime. Using modelled radical concentrations, the absolute O 3 sensitivity to NO x and volatile organic compounds (VOCs) showed that, on average across the summer AIRPRO campaign, the O 3 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 O 3 regime to shift towards being NO x -limited. The O 3 sensitivity to VOCs, the dominant regime during the summer AIRPRO campaign, was observed to decrease and shift towards a NO x -sensitive regime both when NO mixing ratio decreased and with the addition of aerosol uptake. This suggests that if [NO x ] continues to decrease in the future, ozone reduction policies focussing solely on NO x reductions may not be as efficient as expected if [PM] and, hence, HO 2 uptake to aerosol surfaces continue 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 O 3 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 NO x -sensitive regime.
- Subjects
BEIJING (China); RADICALS (Chemistry); AEROSOLS; MICROBIOLOGICAL aerosols; SUMMER; PARTICULATE matter; VOLATILE organic compounds; CARBONACEOUS aerosols
- Publication
Atmospheric Chemistry & Physics, 2023, Vol 23, Issue 10, p5679
- ISSN
1680-7316
- Publication type
Article
- DOI
10.5194/acp-23-5679-2023