Sulfate Formation Enhanced by a Cocktail of High NOx, SO2, Particulate Matter, and Droplet pH during Haze-Fog Events in Megacities in China: An Observation-Based Modeling Investigation

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Title:	Sulfate Formation Enhanced by a Cocktail of High NOx, SO2, Particulate Matter, and Droplet pH during Haze-Fog Events in Megacities in China: An Observation-Based Modeling Investigation
Authors:	谷邁世;Xue, Jian;Yuan, Zibing;Griffith, Stephen M;Yu, Xin;Lau, Alexis K H;Yu, Jian Zhen
Contributors:	地球科學學院大氣科學學系
Keywords:	aerosols;Air Pollutants;calcium;China;Cities;droplets;dust;emissions;Environmental Monitoring;fossil fuels;fuel combustion;gases;Hydrogen Peroxide;Hydrogen-Ion Concentration;mixing;nitrogen dioxide;Particulate Matter;particulates;pollution;sulfates;Sulfates - chemistry;sulfur dioxide
Date:	2016-07-19
Issue Date:	2026-04-21 14:15:18 (UTC+8)
Publisher:	American Chemical Society;United States
Abstract:	摘要： In recent years in a few Chinese megacities, fog events lasting one to a few days have been frequently associated with high levels of aerosol loading characterized by high sulfate (as high as 30 μg m(-3)), therefore termed as haze-fog events. The concomitant pollution characteristics include high gas-phase mixing ratios of SO2 (up to 71 ppbv) and NO2 (up to 69 ppbv), high aqueous phase pH (5-6), and smaller fog droplets (as low as 2 μm), resulting from intense emissions from fossil fuel combustion and construction activities supplying abundant Ca(2+). In this work, we use an observation-based model for secondary inorganic aerosols (OBM-SIA) to simulate sulfate formation pathways under conditions of haze-fog events encountered in Chinese megacities. The OBM analysis has identified, at a typical haze-fogwater pH of 5.6, the most important pathway to be oxidation of S(IV) by dissolved NO2, followed by the heterogeneous reaction of SO2 on the aerosol surface. The aqueous phase oxidation of S(IV) by H2O2 is a very minor formation pathway as a result of the high NOx conditions suppressing H2O2 formation. The model results indicate that the unique cocktail of high fogwater pH, high concentrations of NO2, SO2, and PM, and small fog droplets are capable of greatly enhancing sulfate formation. Such haze-fog conditions could lead to rapid sulfate production at night and subsequently high PM2.5 in the morning when the fog evaporates. Sulfate formation is simulated to be highly sensitive to fogwater pH, PM, and precursor gases NO2 and SO2. Such insights on major contributing factors imply that reduction of road dust and NOx emissions could lessen PM2.5 loadings in Chinese megacities during fog events. 其他題名： Environ Sci Technol 出版者： United States 出版日期： 2016-07-19 出處： Environmental science & technology, 2016-07, Vol.50 (14), p.7325-7334 資源來源： American Chemical Society Journals 識別號： ISSN: 1520-5851 識別號： EISSN: 1520-5851 識別號： DOI: 10.1021/acs.est.6b00768 識別號： PMID: 27331615
Appears in Collections:	[Department of Atmospheric Sciences] journal & Dissertation

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