In this study, we measured aerosol particles along the 140°E line at Rishiri, Hachijo, and Chichi-jima simultaneously during the spring (March to May) in 2001 as a part of the collaborative experiment, ACE-Asia. Duirng the Asian dust events, the concentrations of crustal elements, e.g. Al, Ca, were high and the enrichment factors of anthropogenic elements, e.g. Pb, Zn, were low. The source regions of crustal elements were estimated by a backward trajectory analysis. The enrichment factor of non sea salt Ca in the coarse mode was a better indicator of source regions of the dust than of crustal total particles. The Ca enrichment factors in the coarse mode were about twice when the air masses originated in Gobi desert and to the north of it. Lead mostly occurred in the fine mode. However, substantial fraction of Pb was transported in the coarse mode during the Asian dust event, which indicates that anthropogenic metals can significantly be transported by paticles of both sizes, during the dust season.

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Methane-derived carbonated rocks in Lower Pleistocene Koshiba Formation, Kazusa Group crop out in Sakae-ku, Yokohama City, are among the first described examples of carbonate rocks produced at fossil cold-seeps in Japan. The methane-related origin of these carbonates have been inferred from the occurrence of chemosymbiotic fossil community such as Lucinoma, Conchocele, Acharax and from the depletion of carbonate in ¹³C. The present work is focused on the distribution and δ¹³C values of biomarkers for Archaea associated with anaerobic methane oxidation. This carbonate rock contained ¹³C depleted PME (pentamethyleicosane), but was lacking in crocetane. Acyclic and cyclic C₄₀-isoprenoid (biphytanes) released upon the cleavage of ether bonds in polar compounds from the carbonate were not depleted in ¹³C. Carbon isotope variability among Archaeal biomarkers in this cold-seep carbonate suggests that Archaeal species were multiple and that only some were related to anaerobic methane oxidation.

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In order to understand various magma processes occurring in the terrestrial body, highly precise isotope analyses of U, Th and Ra have been developed. In the first, an effective silicate rock decomposing method was established. Conventional acid digestion of mafic silicate rocks resulted in the precipitation of insoluble fluorides and very poor recovery yields of some trace elements. In contrast, almost 100% of the trace elements were recovered using larger amounts of HClO₄ than was conventionally used and evaporating the sample to dryness in a step-wise fashion. Then, new chemical separation methods of U, Th, and Ra were developed by employing some novel extraction chromatographic resins. For U isotope analysis by TIMS, a new activator, silisic-acid and phosphoric acid mix solution was very effective to produce stable and strong UO₂⁺ beam, resulted in excellent improvement for both precision and reproducibility. For Ra isotope analysis, a new, precise and accurate analytical method was developed by employing total evaporation TIMS technique. These new methods have been applied for Miyakejima volcano, Izu arc, Japan. ²³⁸U-²³⁰Th-²²⁶Ra disequilibria observed in lavas with large ²³⁸U and ²²⁶Ra excesses imply metasomatism of depleted mantle by fluid related processes. In the equiline diagram, the trends for two magmatic stages (Stage 1 and 2) are regarded as two different isochrons with a common initial (²³⁰Th/²³²Th) ratio, although the trend for Stages 3 and 4 is a mixing line. The age difference in the equiline diagram corresponds to the interval of individual fluid-release events. Thus, fluid release from the slab and subsequent magma generation occur as episodic events on a several-kyr timescale. The model calculations show a very rapid ascent time of the slab components in the mantle wedge (<7 kyr), which can be explained by nearly instantaneous material transport in the mantle wedge.

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The world ocean is a key component of the global climate system, because the oceans hold very large amounts of both heat and carbon compared to other surface reservoirs. Therefore, it is likely that large, geologically documented changes in atmospheric CO₂ content and global climate during the latter half of the Pleistocene are strongly associated with some changes in the oceanic carbon budget. This likelihood and a growing recognition that the presently rising atmospheric CO₂ content may induce dangerous levels of global warming in the near future heighten our drive to better understand the oceanic carbon cycle. Yet there is sizable gap in our knowledge of this very important and challenging field. Given the opportunity to introduce my work here, I provide a perspective on the state of our knowledge in three aspects of the ocean carbon cycle in which I have done some research. My perspective is not meant to be comprehensive, as the enormously diverse body of knowledge in this field has benefited from many and only marginally from my work. The three aspects are: (1) oceanic role in accounting for the low atmospheric CO₂ content during the last glacial maximum; (2) oceanic uptake of anthropogenic carbon since the preindustrial period; and (3) oceanic sequestration of anthropogenic carbon by direct injection. In each, I present the state of our knowledge (including gaps) as I see it, touch on my contribution, and lay out possible future directions. In order to give some sense of coherency, I limit the introduction of my work to those involving numerical ocean biogeochemistry models of various levels of complexity.

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