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Abstract. The present study reports on long-term trends of carbonaceous aerosols in total suspended particulate (TSP) samples collected at Chichijima in the western North Pacific during [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010][2011][2012]. Seasonal variations of elemental carbon (EC), organic carbon (OC), and water-soluble organic carbon (WSOC) concentrations showed maxima in winter to spring and minima in summer. These seasonal differences in the concentrations of carbonaceous aerosols were associated with the outflows of polluted air masses from East Asia, which are clearly distinguishable from pristine air masses from the central Pacific. The higher concentrations of carbonaceous aerosols during winter to spring are associated with long-range atmospheric transport of East Asian continental polluted air masses, whereas lower concentrations may be due to pristine air masses from the central Pacific in summer. The annual trends of OC / EC (+0.46 % yr −1 ), WSOC (+0.18 % yr −1 ) and WSOC / OC (+0.08 % yr −1 ) showed significant (p < 0.05) increases during the period of 2001-2012, suggesting that photochemical formation of WSOC and its contributions to secondary organic aerosols (SOAs) have increased over the western North Pacific via long-range atmospheric transport. We found a significant increase (+0.33 % yr −1 ) in nss-K + / EC ratios, demonstrating that concentrations of biomass-burning-derived carbonaceous aerosols have increased, while those of primary fossilfuel-derived aerosols have decreased over the western North Pacific. Further, secondary biogenic emissions are also important over the western North Pacific as inferred from a significant increase (+0.14 % yr −1 ) in the concentrations of methanesulfonate (MSA − , a tracer for biogenic sources). This point was further supported by a moderate correlation (r = 0.40) between WSOC and MSA − . We also found a significant increase in OC / TC (total carbon) and WSOC / TC ratios, further suggesting that photochemical formation of WSOC and its contributions to SOAs have increased over the western North Pacific during 2001-2012 via long-range atmospheric transport from East Asia.

Abstract. PM2.5 aerosol samples were collected from the Chinese megacity of Nanjing (32.21∘ N, 118.73∘ E) during winter and analyzed for a total of 127 compounds from 12 organic compound classes. The most abundant classes of compounds were n-alkanes (mean concentration of 205 ng m−3), followed by fatty acids (76.3 ng m−3), polycyclic aromatic hydrocarbons (PAHs; 64.3 ng m−3), anhydrosugars (56.3 ng m−3), fatty alcohols (40.5 ng m−3) and phthalate esters (15.2 ng m−3), whereas hydroxy-/polyacids (8.33 ng m−3), aromatic acids (7.35 ng m−3), hopanes (4.19 ng m−3), primary sugars and sugar alcohols (4.15 ng m−3), lignin and resin products (2.94 ng m−3), and steranes (2.46 ng m−3) were less abundant. The carbon preference index of n-alkanes (0.83–1.38) indicated that they had a strong fossil fuel combustion origin. Diagnostic concentration ratios of organic tracers suggested that PAHs and hopanes originated mostly from coal burning and traffic emissions, respectively, in the Nanjing urban area. Positive matrix factorization analysis demonstrated that fossil fuel combustion was the major pollution source (28.7 %), followed by emissions from biomass burning (17.1 %), soil dust (14.5 %) and plastic burning (6.83 %) for Nanjing winter aerosols, although the contribution of secondary oxidation products (32.9 %) was the most abundant. Most of the compounds generally showed higher concentrations at nighttime compared with daytime; this was due to the accumulation process associated with inversion layers and the enhancement of emissions from heavy trucks at night. We conclude that fossil fuel combustion largely influences the winter organic aerosols in urban Nanjing. Based on the comparison of this study's results with previous research, we found that pollution levels in organic aerosols have decreased in the urban Nanjing atmosphere over the last decade.