Aerosol pH and regime transition of sulfate formation in aerosol water during winter haze events in northern China
- 1Max Planck Institute for Chemistry, Multiphase Chemistry Department, Mainz, Germany
- 2Department of Earth System Science, Tsinghua University, Beijing, China
Understanding the formation mechanism of severe haze is crucial for the development of efficient pollution control strategy. Recently, multiphase reactions in aerosol water has been suggested as an important source of sulfate aerosol during severe haze (Zheng et al., 2015;Cheng et al., 2016). Though several oxidation mechanisms have been recognized, the dominant oxidation pathway is still under debate reflecting a missing consensus. Based on a model survey with Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), we have investigated the variability of aerosol pH and regimes of sulfate formation through multiphase oxidation during the haze episodes in January of 2013. Our results show a large spatial and temporal variability in the aerosol pH and sulfate formation regimes. Surface aerosol pH shows a clear diurnal variation with low pH during daytime and high pH during night-time for most cases. Aerosol pH tends to decrease with increasing altitude in the lower atmosphere. For the scenario best reproduces the observations in Beijing, NO2, TMI+O2, O3 and H2O2 pathways can all dominate the production of sulfate in specific areas of the Beijing-Tianjin-Hebei (BTH) region. With the increasing height, O3 pathway and gas phase oxidation by OH radicals become more important. Moreover, sensitivity tests also suggest that, emissions of crustal particles, NH3 and soluble iron/manganese have great impacts on aqueous phase chemistry, and should be better constrained in future studies.
References:
Zheng, G. J., Duan, F. K., Su, H., Ma, Y. L., Cheng, Y., Zheng, B., Zhang, Q., Huang, T., Kimoto, T., Chang, D., Poschl, U., Cheng, Y. F., and He, K. B.: Exploring the severe winter haze in Beijing: the impact of synoptic weather, regional transport and heterogeneous reactions, Atmos. Chem. Phys., 15, 2969-2983, 10.5194/acp-15-2969-2015, 2015.
Cheng, Y. F., Zheng, G. J., Wei, C., Mu, Q., Zheng, B., Wang, Z. B., Gao, M., Zhang, Q., He, K. B., Carmichael, G., Poschl, U., and Su, H.: Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China, Sci Adv, 2, e1601530, UNSP e1601530,10.1126/sciadv.1601530, 2016.
How to cite: Tao, W., Su, H., Zheng, G., Wang, J., Liu, L., Wei, C., Li, M., Zhang, Q., Poschl, U., and Cheng, Y.: Aerosol pH and regime transition of sulfate formation in aerosol water during winter haze events in northern China, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14982, https://doi.org/10.5194/egusphere-egu2020-14982, 2020
