10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Effect of Aqueous-Phase Processing on Formation and Evaluation of the Organic Aerosol during Fog Processing in Kanpur, India
ANIL KUMAR MANDARIYA, Tarun Gupta, S.N. Tripathi, Indian Institute of Technology Kanpur
Abstract Number: 1380 Working Group: Aerosol Chemistry
Abstract Kanpur is a polluted urban location in India, situated at the center of Indo-Gangetic Plain which witnesses several fog episodes every year during winter time and these fog episodes are linked to the enhanced in the production of secondary organic aerosol (SOA) via aqueous-phase processing. This study highlights the aqueous-phase processing of organic aerosol (OA) and relative importance of OA factors during the processing periods of fog in heavily polluted site affected by biomass emissions in the winter time. Our results show that loading of OA and inorganic species (NO3-, SO42-, NH4+, and Cl-) changes drastically from period of Pre-Fog-Haze to Fog and Fog to Post-Fog-Haze as compare to period of Pre-Fog to Pre-Fog-Haze and Post-Fog-Haze to Post-Fog during fog processing while mass fractions remain approximately steady, indicating the wet removal through fog droplets. Vankrevelen slopes vary throughout the periods of fog processing indicating different aging mechanism during different stages of fog processing. In contrast of aqueous phase processing mass of more oxidized oxygenated organic aerosol (MO-OOA) slightly varies throughout the fog processing periods which indicate that aqueous-phase processing plays a minor role in the formation of it as it shows poor correlation (R=0.23) with aerosol liquid water content (ALWC). In addition, fog processing has dominant impact on the formation of Low oxidized OOA (LO-OOA), oxidized biomass burning OA (O-BBOA) and biomass burning OA (BBOA) and their contribution to OA varies substantially as a function of fog periods as indicated by good significant (p<0.05) correlation (R=0.66, 0.66 & 0.59 respectively) with ALWC and typical fragments ions i.e. C2H2O2+, C2O2+, CH2O2+ (typical fragment ions of methylglyoxal and glyoxal) and CH3SO+, CH2SO2+, CH3SO2+ (fragment ions of methanesulfonic acid (MSA)). These results also highlighting the wet scavenging of LO-OOA, O-BBOA, and BBOA more efficiently through fog droplets as these OA components decrease significantly during the period of fog through the fog processing as compare to MO-OOA. In addition, oxygen to carbon ratio (O/C) of OA and secondary organic aerosol (SOA) also varies during the periods of fog with the maximum during Pre-Fog and Post-Fog periods as compare to rest of periods while O/C is higher during a period of Fog as compare to Pre-Fog-Haze and Post-Fog-Haze.