Abstracts of Annual Meeting of the Geochemical Society of Japan

Chemical compositions of about one hundred spherules separated from deep sea sediment dredged off Hawaii island were determined by INAA (Instrumental Neutron Activation Analysis) using KUR (Kyoto University Reactor). Some spherules were identified to be extraterrestrial in origin and are named as cosmic spherules here. In this study, we report the formation mechanism of such cosmic spherule samples in terms of two types of elemental fractionations; fractionations between metal and silicate and between solid metal and liquid metal. From chemical characteristics of the cosmic spherules analyzed, chondrites are assigned as precursor matters for them. Such two fractionations occur when chondrites are heated, melted, and re-solidified into spherules in atmospheric entry.

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Developing mass spectrometric techniques, dataing methods using extinct nuclides have been applied to many meteorites to understand cosmochemical processes. In the dating, a half life is a very important value for obtaining an accurate age. Almost half lives values of extinct radionuclides were detemined by 1960s, since then it was a few case that their half lives were examined. Recently we measured a half life of 53Mn. We will review half lives of extinct radionuclides and present our half life value of ⁵³Mn.

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Five years long-term trends of air pollutants such as PM10, PM2.5, polycyclic aromatic hydrocarbons (PAHs), trace metals and ionic constituents at Beijing, China were discussed.

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Organic aerosols were studied at molecular level in 14 coastal and inland mega-cities in China during 2003 winter and summer. They are characterized by the abundant presence of n-alkanes (annul average, 340 ng m^-3), fatty acids (769 ng m-3), sugars (412 ng m^-3), and phthalates (387 ng m^-3). In contrast, fatty alcohols, polyols/polyacids, lignin and resin products, sterols, polycyclic aromatic hydrocarbons (PAHs) and hopanes were detected as relatively minor components. n-Alkanes show a weak odd/even carbon predominance (CPI = 1.1) and PAHs do the predominance of benzo(b)fluoranthene, suggesting a serious contribution from fossil fuel (mainly coal) combustion. Their concentrations (except for phthalates and polyols/polyacids) were 2-15 times higher in winter than summer due to a significant usage of coal burning and an enhanced atmospheric inversion layers. Phthalates were found to be more abundant in summer than winter, probably due to enhanced vaporization from plastics followed by adsorptive deposition on the pre-existing particles. Concentrations of total quantified compounds are extremely high (∼10 μg m^-3) in the mid-west (Chongqing and Xi'an), where active industrialization/urbanization is going on. This study shows that concentrations of the compounds detected are 1-3 orders of magnitude higher than those reported from developed countries.

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