Highly time resolved chemical characterization of submicron organic aerosols at a polluted urban location

Abstract

Non-refractory submicron (NR-PM1) aerosols were measured during the late winter period (February-March) via an Aerodyne High Resolution Time of Flight Aerosols Mass Spectrometer (HR-ToF-AMS) along with Black Carbon (BC) and trace gasses in an industrial city, Kanpur, situated in the Gangetic Plain (GP) of India. The composition of NR-PM1 aerosols was dominated by organics (54%), followed by inorganics (36%), and BC (10%). Source apportionment via Positive Matrix Factorization (PMF) of AMS measured organic aerosols (OAs) revealed 6 factors. Factors are identified as 2 types of oxidized organic aerosols (OOAs), 2 types of biomass burning organic aerosols (BBOAs), freshly emitted hydrocarbon-like organic aerosols (HOAs) and oxygenated primary organic aerosols (OPOAs). A substantial increase in relative OOA contributions (200%) and O/C ratio (26%) has been observed from the high loading events (HLE) to the low loading events (LLE). Back trajectory analysis indicated that the study location received contributions from regional and long-range transported aerosols. OA composition and evolution during this study period were also very different from those observed during a fog influenced peak winter period of December-January. This is the first study to present detailed aerosol composition during the late winter period in India highlighting the changes in OA composition and chemistry within the same winter season.