Multi-stable isotope systematics of individual organic compounds in cosmogeochemical samples

对碳质陨石等宇宙化学样品和海洋、湖泊沉积物等环境样品中的单个有机化合物进行了化合物特有的多同位素(特别是碳、氢同位素)测定，以了解其来源、来源以及形成和降解机理。陨石大分子有机质(MOM)的水合热解生成的乙酸相对于水溶性醋酸更贫化。δ^&lt；13&gt；C-δD图解表明，CM球粒陨石的7个MoM分成3组，其同位素变化可能与陨石母体的蚀变过程有关。沉积生物标志物的δ^&lt；13&gt；C-δD变化对区分其来源和运移过程非常有用。我们进一步测定了有机小分子如醋酸、甲醇和苯在紫外光照射下的碳、氢同位素分馏，以了解其在自然环境中的同位素变化。随着紫外光降解的进行，分子的δ^&lt；13&gt；C和OD值都增大。动力学过程和同位素交换反应可能是控制同位素变化的因素，由于主要研究人员在本次研究期间从东京市立大学搬到冈山大学，一些研究计划无法在拟议的研究期限内完成。然而，通过21篇同行评议的英文论文和40篇在国际和国内科学会议上的报告，大多数研究计划已经成功完成。

Compound-specific multi-isotope (especially carbon and hydrogen isotopes) measurement has been carried out for individual organic compounds in cosmochemical samples such as carbonaceous meteorites and in environmental samples such as marine and lacustrine sediments in order to understand their origins and sources as well as formation and degradation mechanisms.Acetic acid generated by hydrous pyrolysis of meteoritic macromolecular organic matter (MOM) is more depleted in ^<13>C relative to the water-soluble acetic acid. A δ^<13>C-δD plot indicates that seven MOMs of CM chondrites are divided into 3 groups, where the isotope variation could relate to alteration processes of the meteorite parent bodies. The δ^<13>C-δD variation of sedimentary biomarkers is very useful to discriminate their origins as well as transport processes.We further determined carbon and hydrogen isotope fractionations of small organic molecules such as acetic acid, methanol and benzene during the UV light irradiation to understand their isotope variations in natural environment. As the UV degradation proceeds, both δ^<13>C and OD values of the molecules increase. Kinetic process and isotope exchange reaction may be factors to control the isotope variations.Because the principal investigator move from Tokyo Metropolitan University to Okayama University during this research project, a few research plan could not be completed within the proposed research period. However, most research plans have been successfully accomplished with the 21 peer-reviewed English papers and 40 presentations at international and domestic scientific meetings.