Nitrogen isotope ratio of nitrate ion in precipitation at Toyama was traced from June 2003 to December 2005 to investigate the behavior of nitrate ion inassociation with precipitation. δ¹⁵N value varied from -7.8 to + 1.6%o and showed seasonal variation; i.e., it was higher in winter than in summer. δ¹⁵N value negatively correlated to solar radiation. Negative correlation was also observed between δ¹⁵N value and concentration of atmospheric oxidant, which converted NO₂ to HNO₃. Such correlations suggest that the δ¹⁵N value of nitrate ion decreases with increasing conversion rate from atmospheric NO₂ to HNO₃. Based on an equation obtained from the relationship between the conversion rate and δ¹⁵N value according to the Rayleigh distillation model, 78-98% (av. ±1σ, 90±5%) NO₂ exhausted into the atmosphere were estimated to be converted into HNO₃. The similar seasonal variation was also observed at Nagoya, although the δ¹⁵N values are systematically higher than those of Toyama. The NO₂ concentration at Nagoya istwice as high as the concentration at Toyama, suggesting that the conversion rate from NO₂ to HNO₃ is lower in Nagoya (av. ±1σ, 86±6%) than in Toyama.

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Chemical compositions and sulfur isotopic ratios of sulfate of deep groundwater in Hakodate Plane, Japan, were analyzed in order to characterize a deep groundwater system in this area. Most samples are classified into two groups: non-carbonate alkali and carbonate alkali waters. Based on the principle components analysis, one of multivariate analysis, the groundwaters in this study can be described by mixing with at least three end-member components of waters, i.e., seawater, deep groundwater containing volcanic material, and dilute shallow groundwater. The seawater component contributed more than the other components. Sulfur isotopic ratios (δ³⁴S) are in the range from +7.2 to +24.7%o. The δ³⁴S values higher than that of seawater (+20.3‰) would be attributed to the effect of bacterial sulfate reduction. The δ³⁴S values lower than that of seawater in two samples may result from the contribution of sulfur derived from volcanic material. These sample locations aligned along the northwest-southeast line in the Hakodate plane. Since the crater of Zenikamezawa, a submarine volcano erupted about 33,000-45,000 years ago, is located on the extension of the line, the volcanic material from this volcano may affect the deep groundwater chemistry and sulfur isotopic composition.

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In this review article, stereo chemical investigation of biogenic and abiogenic organic compounds regarding organic cosmochemical and geochemical approaches were summarized. Representative results are as follows. At first, endo- and exogenous abiotic formation of bio-organic compounds were experimentally verified. Among these, high-molecular-weight complex organics synthesized from mixtures of simple inorganic gases similar to those found in the interstellar medium were irradiated with a particle beam. Molecular weight of complex organics were ranging from several hundred to 3,000 Da. A wide variety of organic compounds, not only a number of amide compounds, but also heterocyclic and polycyclic aromatic hydrocarbons (PAHs), were detected by Curie point pyrolysis combined with gas chromatograph and mass spectrometer (Pyr/GC/MS). Secondary, emergence of enantiomeric excess of chiral amino acids in meteorite were experimentally verified. Before acid-hydrolysis, the synthesized high-molecular-weight complex organics containing amino acid precursors were irradiated with right (R-) or left (L-) continuous ultraviolet circularly polarized light (UV-CPL) obtained from a synchrotron radiation (SR). Enantiomeric excesses (% D-% L) were obtained by UV-R-CPL and UV-L-CPL, respectively: R-CPL preferentially produced D-alanine, and L-CPL yielded more L-alanine. Thirdly, the author described molecular chirality in extreme environment and sub-surface biosphere. Deep-sea hydrothermal systems are natural laboratories for the study of organic geochemistry related to molecular chirality and microbial habitats on extreme environments. A high-temperature deep-sea hydrothermal system was drilled using the benthic multi-coring system (BMS) employed for direct sampling of microorganisms, rocks and fluids beneath hydrothermal vents as a part of the Archaean Park Project (International research project on interaction between sub-vent biosphere and geo-environment). Based on the distribution of organic compounds derived from this vigorous hydrothermal environment, a description of deep-sea subterranean chemistry and biology was investigated with optimal microbial activities.

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