AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Recent Declines in Water Uptake and Acidity of Inorganic Aerosols during Beijing Winter Haze Events
SHAOJIE SONG, Harvard University
Abstract Number: 548 Working Group: Aerosol Chemistry
Abstract In recent years, aggressive air pollution mitigation measures in China have resulted in considerable changes in gas and aerosol chemical compositions. However, the responses of aerosol water uptake and acidity, two parameters pivotal to the formation of severe northern China winter haze events, to such changes remain uninvestigated. Here, we performed thermodynamic equilibrium modeling using gas and aerosol composition and meteorological data observed during three winter seasons in urban Beijing, and quantified the changes in the mass growth factor and pH of inorganic aerosols. We found, from the winter haze condition in 2014/2015 to that in 2017/2018, that the mass growth factor decreased by about 10% due to changes in aerosol chemical compositions (more nitrate and less sulfate and chloride) and that pH increased by about 0.2 unit owing to rising excess ammonia. The buffer equation for the gas-particle system was derived for the first time and was very helpful to conceptually understand the sensitivity of aerosol pH to meteorological variables and chemical compositions. These new insights had implications for evaluating the potential chemical feedbacks in secondary aerosol production and the role ammonia played in haze formation.