Study on Geochemical Change of Bioorganic Polymers in Recent Sediments

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In this study, it was aimed to analyze for 1) water-soluble proteins and their amino acids, 2) nucleic acid bases and their nucleosides, and 3) chlorophylls and chlorins in recent Tokyo Bay core sediments (depth from 0 cm to 100 cm) in order to find depth distributions of these compounds and to clear their early diagenetic changes.In the analyzes of proteins and their amino acids, we detected dipeptides, the smallest proteins. These dipeptides occur most abundantly at the surface sediment (0 cm depth), decrese their amounts drastically downward till depth 30 cm, and maintain their abundance rather constantly farther below. This abundance change with depth can be explained by that biological proteins were changed to amino acids via polypeptides due to hydrolysis during the early burial diagenesis of the sediments.In the analyzes of nucleic acid bases and their nucleosides, we identified eight kinds of nucleosides commonly present in biological matter. These nucleosides are more abundant … More at the surface sediment and decreased their amounts notably with depth. It was found that ribonucleosides were more abundant than deoxyribonucleosides, which was considered to reflect their abundances in biological matter. Furthermore, it was observed from the ratios of ribo- to deoxyribonucleosides that the former compounds were more readily decomposed than the latter ones. In addition, we found nucleosides of non-nucleic acids in origin.Chlorophylls and four kinds of chlorins from decomposition products of chlorophylls were also identified in the sediments. However, we observed that their decomposition was not proceeded notably during the early diagenesis, because their abundances are relatively unchanged with depth of the sediments.In summary, we found that the abundances of these bioorganic polymers decrease by one order of magnitude at the sediment depth 100 cm from those at the surface sediments. Particularly, their abundances decrease rapidly from surface to 30 cm depth indicating their diagenetic changes mainly occur during the first 30 years of burial diagenesis. Less