The measurements of atmospheric aerosol and associated species have been carried out on the ground observation network over the western North Pacific as part of the Variability of Marine Aerosol Properties (VMAP) project. The network consists of four Japanese islands (Rishiri, Sado, Hachijo, and Chichi‐jima), ranging widely in latitudes from 25°N to 45°N along with the line of 140°E. In this paper, we report on simultaneous measurements of particulate elemental carbon (EC) on the four islands from March to May 2001, which cooperated with the Asia‐Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) campaign, in order to characterize the outflow patterns of continental polluted air masses to the North Pacific. The mean concentrations of particulate EC in the four islands during this period ranged from 0.18 to 0.60 μg m−3. It is interesting to note that the temporal variations in the concentrations of particulate EC in Rishiri and Sado, which are located in the northern region of Japan (35°N–45°N), synchronized with each other. The EC concentrations in Hachijo and Chichi‐jima, located in the southern region of Japan (25°N–35°N), also showed similar temporal variations with each other but did not synchronize with those in Rishiri and Sado. These results demonstrate that the transport patterns of the polluted air masses from the east Asian continent to the northern regions of the northwestern Pacific are often different from those to the southern regions. It was also found that continental air masses are usually accompanied by pollutants over the southern regions but not over the northern regions of the northwestern Pacific.

[1] To characterize the transport and chemical transformation of anthropogenic and mineral aerosols in the marine boundary layer over the western North Pacific, intensive observations of aerosol chemistry were conducted in the period from March to May of 2001 simultaneously on two remote islands, Hachijo and Chichi-jima, located about 300 km and 1000 km south of Japan's main island, respectively. On the other hand, in the remote marine environment, NO 3 À was mainly associated with sea-salt particles. Thus sea-salt particles act as important sinks for NO 3 À over the remote ocean. Elemental carbon (EC) in fine particles exhibited mean concentrations of 0.27 and 0.18 mg m À3 at Hachijo and Chichi-jima, respectively, with higher concentrations at Hachijo due to the influence of anthropogenic sources. On the other hand, mean concentrations of organic carbon (OC) in fine particles were estimated to be 0.35 and 0.41 mg m À3 at Hachijo and Chichi-jima, respectively. The higher concentration of OC in the remote marine atmosphere of Chichi-jima was attributed to carbonaceous substances evolved at lower temperatures (<200°C), which are probably derived from en route production and/or oceanic emissions.

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A year‐round observation of atmospheric aerosols and their associated species was conducted from March 2001 to May 2002 on Rishiri Island in the northern area of the east Asian Pacific rim region. Asian outflows brought continental air masses to this area during the period from the autumn to the spring although marine air masses from the high‐latitudinal ocean often broke into this area during the midwinter. In contrast, marine air masses were predominant over this area in the summer. Particulate elemental carbon (EC) would be mainly transported with biomass smoke particles, and seasonal variation in its concentrations was well correlated with the air mass alternation, showing higher concentrations during the period from the autumn to the spring with some decreases in the midwinter. The concentrations of particulate organic carbon (OC) showed a similar seasonal trend with those of the particulate EC, but relatively high concentrations were found in the summer due to photochemical secondary productions. The particulate OC that is vaporized by heating at higher temperatures (OCHT) would be mainly carried with the biomass smoke, and the particulate OC that is vaporized at lower temperatures (OCLT) would be mainly caused by secondary production processes. Summer enhancements of the secondary species, such as OC and nss‐SO42–, caused decreases in the ratio of EC/PM2.5, which would contribute to the high single scattering albedo of fine aerosols in the summer. Aerosols in the Asian outflows in this area are relatively “black” in the winter, although the aerosol mass loading increases in the spring.