Outflow patterns of air pollutants, and mechanisms associated with a "monsoon" condition that is peculiar to the East Asian region in winter, have been studied. To capture the continental outflow, airborne and shipboard measurements of aerosols and trace gases were conducted over the northern part of the East China Sea and the western part of the Sea of Japan on January 17-26, 1991 (airborne), January 28-29, 1992 (airborne), January 22-31, 1993 (shipboard), and January 29-30, 1993 (airborne). At least two types of highly polluted air masses were found at different times of the monsoon. Type 1 polluted air mass, which contained more than 10 •tg m -3 of non-sea-salt SO42-and more than 5 •tgC m -3 of black carbon aerosols, typically appeared over the East China Sea at the beginning of the monsoon period. Chemical and microphysical characteristics suggest that the type 1 polluted air mass is chemically aged. Type 2 air mass appeared in the later half of the monsoon period and had characteristics of freshly emitted pollutants. It consisted of several high concentrations of SO: (>10 ppbv) confined in narrow horizontal width (10 to 30 km wide). Analyses using an Eulerian chemical transport model and detailed backward trajectories indicate that the type 1 polluted air mass was subcontinental in extent and its formation and the transport were dominated by a synoptic-scale weather cycle; it was formed over the Asian continent under anticyclonic conditions that persisted for 3-4 days, and transported intermittently to the east over the Pacific Ocean by the passage and the development of traveling cyclones. This study suggests that aerosols that flow out from East Asia are enriched with carbonaceous materials and consequently have low single-scattering albedo, which may affect the direct radiative forcing by aerosols over the North Pacific.
This study aims to reveal spatial distribution of hydrogen sulfide and sulfur species in marine sediments in Hiroshima Bay, Japan, by direct analyses using a combination of detection tubes and X-ray absorption fine structure spectroscopy. In summer and autumn, the hydrogen sulfide concentration ranged from <0.1 to 4 mg-S L. In this study, only hydrogen sulfide was observed in autumn and at two stations in summer. In contrast, some earlier studies reported in all seasons in Hiroshima Bay the presence of acid volatile sulfide, which is used as a proxy of sulfide content. The sulfur species in sediments were mainly identified as sulfate, thiosulfate, elemental sulfur, and pyrite. Thiosulfate was a minor component compared to the other sulfur species. The formation of pyrite and sulfur derived from hydrogen sulfide oxidation played an important role in the scavenging of hydrogen sulfide.
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