Real‐Time Characterization of Aerosol Compositions, Sources, and Aging Processes in Guangzhou During PRIDE‐GBA 2018 Campaign

Abstract

AbstractTo investigate the chemical compositions, sources, and aging processes of submicron particles (PM1), a comprehensive field campaign was conducted in Guangzhou urban area of China during the autumn (October–November) of 2018. The average mass concentration of PM1 was 35.6 ± 20.8 µg m−3, which was mainly contributed by organic aerosols (OA, 42%), then followed by sulfate (25%) and inorganic nitrate (11%). The inorganic nitrate was found to be the main driving component (up to ∼50%) to account for the fast increase of PM1 during the polluted periods of Guangzhou autumn. The promotion effects of sulfate, aerosol liquid water content, and particles acidity on nitrate formation were systematically discussed. Source apportionment results showed 72% of OA in Guangzhou autumn was contributed by secondary OA (SOA), and 28% of primary OA (POA), including vehicle emission related hydrocarbon‐like OA (HOA, 16%), nitrogen‐containing OA (NOA, 3%) and cooking OA (COA, 8%). To explore the aging processes of OA, the dynamic variations of OA and its oxidation level as a function of ambient photochemical age are shown. Using an in situ field‐deployed oxidation flow reactor, the heterogeneous reaction rate coefficients of ambient POA with OH radicals () were estimated to be 4.0–5.4 × 10−13 cm3 molecules−1 s−1, which is equivalent to a lifetime of POA >2 weeks. The long heterogeneous lifetime of POA supports gas phase oxidation was the major pathway for ambient OA aging. The OH uptake coefficient () was estimated to be 0.76–0.84, underlining that OH radicals can be taken up efficiently on ambient aerosols.