AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Highly Time-resolved Urban Aerosol Characteristics during Springtime in Yangtze River Delta, China: Insights from Soot Particle Aerosol Mass Spectrometry
JUNFENG WANG, Xinlei Ge, Yanfang Chen, Yafei Shen, Qi Zhang, Yele Sun, Jianzhong Xu, Yu Huan, Mindong Chen, Nanjing University of Information Science and Technology
Abstract Number: 125 Working Group: Urban Aerosols
Abstract In this work, a soot particle – aerosol mass spectrometer was deployed during the spring of 2015 in urban Nanjing, to characterize the submicron aerosols (PM1). The SP-AMS enables real-time and fast quantification of refractory black carbon simultaneously with other non-refractory particles. The average PM1 concentration was found to be 28.2 micro-gram per cubic-meter (~54 % of the PM2.5 mass), with organics (45 %) as the most abundant component, following by sulfate (19.3 %), nitrate (13.6 %), ammonium (11.1 %), rBC (9.7 %) and chloride (1.3 %). These PM1 species together can reconstruct ~44 % of the light extinction based on the IMPROVE method. Chemically-resolved mass-based size distributions revealed that small particles especially ultrafine ones (<100 nm vacuum aerodynamic diameter) were dominated by organics and rBC, while large particles had significant contributions from secondary inorganic species. PMF analysis of organic aerosols (OA) yielded four OA subcomponents, including hydrocarbon-like OA (HOA), cooking-related OA (COA), semi-volatile oxygenated OA (SV-OOA), and low-volatility oxygenated OA (LV-OOA). Overall, secondary organic aerosol (SOA) dominated the total OA mass (55.5 %), but primary organic aerosol (POA) can outweigh SOA in early morning and evening due to enhanced human activities. High OA concentrations were often associated with high mass fractions of POA and rBC, indicating the important role of anthropogenic emissions during heavy pollution events. The diurnal cycles of nitrate, chloride and SV-OOA both showed good anti-correlations with air temperatures, suggesting their variations were likely driven by thermodynamic equilibria and gas-to-particle partitioning, meanwhile sulfate and LV-OOA concentrations increased during afternoon, showed no positive correlations with relative humidity, indicating the significant role of photochemical processing rather than aqueous-phase processing for their formations. The bivariate polar-plots show that the SV-OOA was formed locally; the variations of hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios further suggest an evolution pathway of SV-OOA to LV-OOA.