Abstract Number: 373 Working Group: Haze in China: Sources, Formation Mechanisms, and Current Challenges
Abstract Shanghai, located on the east coast of China, with a population of over 23 million, is one of the megacities of the world with high economic growth and rapid industrialization. During the recent years, air quality in Shanghai has markedly deteriorated. Among the key air pollutants, high levels of airborne particulate matter (PM), emitted by anthropogenic sources and formed by gas-to-particle conversion, are of major concern as they contribute to atmospheric visibility reduction (haze) and its related impacts. The severe winter haze episode that occurred in Shanghai from December 2013 to January 2014, characterized by elevated levels of particulate matter (PM), received considerable international attention because of its impacts on public health and disruption of day-to-day activities. To examine the characteristics of PM during this haze episode and to assess the chemistry behind formation of secondary inorganic aerosols (SIA) and associated health impacts, we characterized eight water soluble inorganic (WSI) ions and twenty four trace elements in twelve size-fractionated PM (10 nm to 9.9 µm). The in-situ pH (pHIS), as predicted by the Aerosol Inorganic Model (AIM-IV) in all sizes of PM, was observed to be lower during hazy days than that during non-hazy days; there was an increased acidity in haze aerosols. Based on the measured concentrations of particulate-bound toxic elements, health risk assessment was conducted, which revealed that the excess lifetime carcinogenic risk to individuals exposed to fine particles under haze events increased significantly (P < 0.05). The qualitative source attribution analysis suggested that the haze events during the measurement campaign could be due to a combination of increased emissions of PM from multiple anthropogenic sources followed by its accumulation under unfavorable meteorological conditions with lower mixing heights and less wind speeds and the formation of secondary aerosols.