In order to understand the aging and processing of organic aerosols (OA), anintensive field campaign (ampaign of irollution at ypical oastalreas Eastern China, CAPTAIN) was conductedMarch–April at a receptor site (a Changdao island) in central eastern China.Multiple fast aerosol and gas measurement instruments were used during thecampaign, including a high resolution time-of-flight aerosol massspectrometer (HR-ToF-AMS) that was applied to measure mass concentrations andnon-refractory chemical components of submicron particles (PM).The average mass concentration of PM(PM+blackcarbon) was 47 ± 36 μg m during the campaign and showeddistinct variation, depending on back trajectories and their overlap withsource regions. Organic aerosol (OA) is the largest component of PM(30%), followed by nitrate (28%), sulfate (19%), ammonium (15%),black carbon (6%), and chloride (3%). Four OA components were resolvedby positive matrix factorization (PMF) of the high-resolution spectra,including low-volatility oxygenated organic aerosol (LV-OOA), semi-volatileoxygenated OA (SV-OOA), hydrocarbon-like OA (HOA) and a coal combustion OA(CCOA). The mass spectrum of CCOA had high abundance of fragments frompolycyclic aromatic hydrocarbons (PAHs) ( 128, 152, 178, etc.). The averageatomic ratio of oxygen to carbon in OA (O / C) at Changdao was 0.59, which iscomparable to other field studies reported at locations downwind of largepollution sources, indicating the oxidized nature of most OA during thecampaign. The evolution of OA elemental composition in the van Krevelendiagram (H / C vs. O / C) showed a slope of −0.63; however, the OA influenced bycoal combustion exhibits a completely different evolution that appearsdominated by physical mixing. The aging of organic aerosols vs.photochemical age was investigated. It was shown that OA / ΔCO, as wellas LV-OOA / ΔCO and SV-OOA / ΔCO, positively correlated withphotochemical age. LV-OOA accounted for 73% of the OA secondary formation(SOA) in the oldest plumes (photochemical age of 25 h). The atChangdao, by assuming SOA formation and aging as a first-order processproportional to OH, was calculated to be 5.2 × 10 cm molec. s, which is similar to those determinedin recent studies of polluted air in other continents.
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