Petroleum migration is one of the key processes for the formation of oil fields. To understand the process, it is necessary to find the tools to assess the direction and distance of petroleum migration (secondary migration) and the degree of the fractionation of oil compositions during the migration. Recently nitrogen compounds became a useful tool to indicate the degree of the fractionation. This tool was proposed, and was first applied to the Sarukawa Oil Field, Japan, by Yamamoto (1992).

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Measurements of the stable carbon isotopic compositions (δ¹³C) of individual hydrocarbons extracted from the Japan Sea sediments are reviewed. It was demonstrated that the compound-specific δ¹³C, when combined with organic molecular geochemistry, is quite useful not only for identifying detailed sources of sedimentary hydrocarbons but also for assessing the paleo-biogeochemical conditions of the Japan Sea.

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Insoluble organic matter isolated from five Antarctic carbonaceous chondrites was heated and compounds released were examined by GC and GU/MS. Over 120 compounds, mainly aromatic compounds and sulfur-containing heterocycles, were identified in pyrolyzates of the Yamato-791198 sample. Yamato-791198 and Yamato-74662 released a relatively large amount of organic compounds over the temperature range of 300-600℃, while the other three samples (Yamato-793321, Belgica-7904, and Yamato-86720) released almost no compounds. The results indicate that insoluble organic matter in Yamato-791198 and Yamato-74662 have a thermally labile fraction, whereas the other three do not and insoluble organic matter are graphitic. The difference may be related to thermal history on their parent bodies. Also insoluble organic matter from the Murchison carbonaceous chondrite was analyzed by the same method and the results are generally similar to those of the Yamato-791198 sample.

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Size-segregated aerosol samples were collected in Singapore and Indonesia during forest fire event and afterward in 1997. They were analyzed for dicarboxylic acids, ketoacids and dicarbonyls using a capillary GC and GC/MS. Molecular composition of the dicarboxylic acids and the related compounds showed that oxalic (C2) acid was the most abundant species followed by malonic (C3) and succinic (C4) acids. Concentrations of dicarboxylic acids in fine aerosol particles (diameter<2.1μm) collected in Singapore during intensive forest fires were formed to be more than 3 times higher than those collected afterward. This suggests that the dicarboxylic acids associated with forest fire are more concentrated in fine particles. During the forest fire, volatile organic compounds are likely generated by the combustion process of trees and are oxidized to dicarboxylic acids by photochemical reactions. The diacids are probably condensed in fine particle size. However, it is not easy to distinguish between the diacids directly produced by biomass burning and secondary produced by photooxidation. Dicarboxylic acids such as C3, C4 and azelaic (C9) acid that were most abundant in the coarse particles (diameter2.1-11μm) are suggested to be formed by atmospheric heterogeneous reaction on aerosol surfaces.

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Photochemical reactions of oleic acid (C18:1ω9) that is ubiquitous atmospheric constituents have been conducted in the quartz vessel with ozone and OH radical under UV irradiation. The reaction products were derived to dibuthyl esters and determined using a capillary gas chromatography (GC) and GC/mass spectrometry (GC/MS). During a laboratory oxidation, we observed the production of homologous series of low molecular weight dicarboxylic acids (C₂-C₉) with azelaic acid (C₉) as a dominant species. Azelaic acid is produced by the oxidation of the double bond at C-9 position. Other dicarboxylic acids (C₂-C₈) were thought to be produced by the oxidation of azelaic acid with OH radical. Dicarboxylic acids except for oxalic (C₂) and malonic (C₃) acids showed an increase in the amounts with irradiation time, but they decreased after 20 hours, suggesting that not only production but also degradation of dicarboxylic acids occur. This experiments have clearly showed that biogenic unsaturated fatty acids, widely present in the atmosphere, are oxidized by ozone and OH radical, and produce low molecular weight dicarboxylic acids. These results are generally consistent with the distributions of dicarboxylic acids that have been reported in marine and urban aerosols and rain samples. However, oxalic acid is much more abundant than azelaic acid in the natural atmospheric samples. This suggests that short chain dicarboxylic acids, such as oxalic acid, have sources other than unsaturated fatty acids.

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We established a separation procedure of sedimentary straight-chain and cyclic fatty acids by urea adduction to facilitate GC/C/IRMS analysis. The procedure involves a mixing of the monocarboxylic methyl ester fraction with 15% (w/v) urea in MeOH (200μl), ethyl acetate (300μl) and n-pentane (500μl) at room temperature. After drying the solvents under N₂ flow, the non-adduct fraction (cyclic compounds) is washed with n-hexane (3×1.5ml) (mean recovery: 91%). The residue is dissolved in water (4ml) and the adduct fraction (straight-chain compounds) is subsequently extracted with n-hexane/ether (9:1v/v; 3×1.5ml) (mean recovery: 87%). The separation we apply here was confirmed not to affect the isotopic composition of the straight-chain and the cyclic fatty acids.

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Eocene coals and coaly mudstones of Yubari, Bibai, and Ikushunbetsu Formations are obtained from three outcrops exposed in western Yubari Mountains, Hokkaido. Microscopic observations under reflected light show that the samples consist of vitrinite group macerals and degradinite as major macerals. Thin degradinite bands are embedded in vitrinite group macerals, and are characterized by non-continuous laminations, which fluoresce visible light under ultraviolet light. Scanning electron microscopy revealed that degradinite is much porous compared to vitrinite group macerals. Bacteria-like textures are often observed in degradinite pores.
Vitrinite reflectance and 20S/(20S+20R) of C₂₉ regular steranes are in the ranges of 0.44 to 0.59 Ro% and 0.20 to 0.35, respectively, showing that almost all the samples are immature for hydrocarbon generation. However, T_max is variable, ranging from 425 to 445℃. Hydrogen index (HI) increases with increasing TOC and decreases with increasing T_max. The samples characterized by high HI are generally rich in degradinite.
Degradinite and vitrinite group macerals isolated from the sample were analyzed by pyrolysis gas chromatography and open system pyrolysis. Phenols, which are typical pyrolysis products of lignin, are major compounds of pyrolysates of vitrinite group macerals. Pyrolysates of degradinite are rich in aliphatic compounds and poor in phenols, being similar to those of plant cuticles. HI of degradinite is estimated to be more than 800mgHC/gTOC, showing strongly oil-prone characteristics like Type I kerogen. Degradinite is characterized by lower T_max compared to vitrinite group macerals. Considering the micro-textures and pyrolysates of degradinite, biodegradation and selective preservation of resistant biomacromolecular substances such as plant cuticles can be an essential process for the formation of degradinite.

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Optical anisotropy appears from low volatile bituminous to anthracite coal ranks. We conducted heating experiments to understand factors which might be controlling the anisotropy under various load pressures. Results of the experiments were applied to vitrinites separated from Miocene mudstones of the Bessho and Aoki Formations, northern Fossa Magna region, central Japan to understand the burial depth. These mudstones are known to have been affected by hydrothermal alteration during the Pliocene. Estimated burial depths of the formations obtained from the experimental anisotropy data are consistent with the stratigraphcal information of this district. Thus, optical anisotropy of vitrinite is a possible parameter for basin analysis in geology.

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Hydrocarbons, extracted from microbial mats inhabiting some hot springs in central Japan, were analyzed in order to find out possible biomarkers of microbes indicating the terrestrial hydrothermal habitats. Marked are the occurrences of C₁₈ and C₁₉ mono-, di-methyl alkanes and C₁₇-C₂₁ alkenes associated with the mats forming under high temperature (>50℃) conditions. The structure of the branched alkanes were determined by purification with an argentous silica gel column followed by a normal resolution GC-MS analysis. Those hydrocarbon profiles except for alkenes, principally accorded with the previous report by Robinson and Eglinton (1990) for Icelandic hot spring algal mats. Nevertheless, the isomeric composition varied significantly from sample to sample, suggesting a differentiation of the habitant micro-organisms presumably depending on the water temperature.

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