Geochemical studies on amino acids (AAs) in hydrothermal system and laboratory are reviewed to examine the reliability and applicability of AAs as indicator of bioactivity under sub-seafloor extreme environment. AA analyses of the sediment cores revealed the presence of AAs and the change of AA compositions by microbial mediated decarboxylation in sub-seafloor around the hydrothermal vents. Isomer (D/L) ratios indicated the AAs were biologically formed in the hydrothermal fluids and sediments, although the allochthonous AAs are possibly supplied from ambient sediment through pore water. The AAs were decomposed in water solution and sediment with increasing temperature higher than 100℃. However, laboratory experiment showed that the AAs could be inorganically synthesized under present hydrothermal condition, and were continuously dehydrated to form peptide at temperatures between 100 and 200℃. The AAs were well preserved in the conditions containing silica and clay minerals, presumably due to restriction for dissolution and decomposition of AAs at high temperature, although its mechanism is not clear.

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Various information on the geochemical characteristics of seawater is recorded in reef-building coral skeletons, which have been widely utilized for the high temporal resolution (one or two weeks) analysis of paleoenvironment in the tropical ocean. The stable oxygen/carbon isotopic ratios and trace element contents in coral skeletons are generally applied to the paleoenvironmental reconstruction. The paleoenvironmental analysis based on organic matter in coral skeletons, however, has rarely been performed. Organic analysis of coral skeletons has been conducted mainly for the understanding of coral biomineralization. Coral organic matter, which is much less reactive than sedimentary organic matter, can be a useful paleoenvironmental proxy. Combination of organic and inorganic geochemical analyses for coral skeletons will be a powerful tool to provide more information on the paleoenvironment.

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We studied the diurnal variation of atmospheric peroxides from August 2005 to December 2006 at the southern part of Okinawa Island, Japan. A stripping coil technique was used to capture gaseous peroxides in a phosphoric acid solution with its pH adjusted to 3.5. The concentrations of peroxides were determined using the p-hydroxyphenyl acetic acid (POHPAA) dimer technique. For many of the samples studied, the diurnal variation in the hydrogen peroxide (HOOH) mixing ratio did not follow a consistent pattern during the study period. In some cases, the HOOH mixing ratios were higher in the early morning than in the mid afternoon, while in other cases, the HOOH mixing ratios were relatively stable during the daytime. The HOOH mixing ratios ranged from 0.2 to 12.1 ppbv, with a mean of 4.8 ppbv. The HOOH mixing ratios showed seasonal variation with the highest observed in October and the lowest in August. Statistical analyses showed that the HOOH mixing ratios were correlated with the ozone mixing ratios (r=0.44), while other on-site meteorological parameters, such as wind direction, wind speed, and temperature, did not show any correlation for the samples studied. Moreover, backward trajectory analyses showed that the HOOH mixing ratios were higher when northern and northwestern winds prevailed.

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