A Comparative Numerical Study of Aerosols during Dust and Haze Events in Beijing Springtime

A regional air quality model system driven by the weather research and forecasting model is applied to investigate the distribution and evolution of aerosol components in Beijing during the springs of 2014. The synoptic conditions, meteorological variables, and characteristics of aerosol chemical components are comparatively analyzed. Moreover, the effects of heterogeneous reactions on dust and anthropogenic aerosol surface on chemical compositions during the dust (17 Mar and 29 Mar 2014) and haze (25–27 Mar 2014) periods are quantified and compared. The comparison with the observations indicates that the model is capable of reproducing the meteorological variables, PM2.5, and PM10, and their chemical component concentrations during the study period. Moreover, the inclusion of heterogeneous reactions apparently improves the prediction accuracy of PM2.5 and chemical component concentration. In dust days, dust is the dominant component of PM10 mass (50.7%), and its percentage contribution to PM2.5 is comparable to that of organic material (OM) and primary particulate matter (PPM). In hazy days, nitrate (25.6%) and OM (23.6%) contribute the most to PM2.5 mass. Meanwhile, the fractions of nitrate, PPM, and OM in PM10 are comparable. The fraction of coarse particle considerably increases during dusty days, with the mean fraction of 45.5% in PM10. In hazy days, fine particle dominates the PM10 mass, with a fraction of 85.6%. The heterogeneous reactions increase sulfate and nitrate concentrations by 16.9% and 83.8% in dusty days and by 14.5% and 45.0% in hazy days, respectively. On an average, the heterogeneous reactions lead to changes in near-surface SO₂, NO₂, O₃, sulfate, ammonium, and nitrate concentrations by −2.5%, −5.7%, −3.4%, 11.7%, 18.6%, and 58.5%, respectively, in Beijing during March 2014 thereby highlighting the important role of heterogeneous reactions in secondary aerosol formation.