Study on transport of terrestrial organic matter into marginal sea inferred from biomarker and stable isotope analysis of sedimentary organic matter.

为了揭示北太平洋及其邻近海域海洋生物生产与陆地有机质通量相互关系的历史变化，采集了北太平洋沙茨基隆起、阿巴什里湖、长江口等不同盆地的沉积岩芯样品，分析了沉积有机质中碳、氮稳定同位素、正构烷烃、烯酮和甾醇等地球化学指标，重建了海洋生物生产力和大气降水陆地生物标志物的时间变化。我们使用烯酮作为浮游分子标志物来估算海洋浮游组分沉积通量的历史变化。结果表明，末次冰期陆源有机质的积累速率是冰期的10倍，表明冰期风尘通量可能有所增加。我们还研究了位于北海道东部的阿巴什里湖的钻孔岩心样品，发现了近10k年来沉积有机质的时间变化，表明沉积有机质中氮同位素比值的独特漂移。结果表明，δ^&lt；15&gt；N可能是揭示近20 k年来沿海环境气候变化的有用工具。泰国沿海南部沉积物样品的同位素结果表明，有机碳和氮的同位素组成已经记录了近期人类活动、城市化和流域富营养化的证据。来自长江口的钻孔岩芯表明，现代土壤中的氮可能是由于人类种群增长过程中氮的积累而富集的。这项工作成功地表明，沉积有机质对研究末次冰期以来海洋和湖泊环境的时间变化是有用的。

The purpose of this project is to reveal historical changes of an interrelation between marine biological production and terrestrial organic matter flux in the North Pacific ocean and its adjacent seas.Sediment core samples were collected from various basins such as Shatsky rise in the North Pacific, Lake Abashiri, and the estuary of Changjiang river etc. Geochemical proxies in sedimentary organic matter, such as carbon and nitrogen stable isotopes, n-alkane, alkenone and sterol were analyzed to reconstruct the temporal change of marine biological productivity and atmospheric precipitation of terrestrial biomarkers. We estimated the historical variation of sedimentary flux of marine planktonic components using alkenone as a planktonic molecular markers. The result showed ten times greater accumulation rate of terrestrial organic matter in the last glacial period, suggesting that aeolian dust flux might be increased in the ice age. We studied also a boring core sample from Lake Abashiri that located in east Hokkaido, and found temporal change of sedimentary organic matter in the last 10 k years, indicating that a unique excursion of nitrogen isotope ratio in sedimentary organic matter. The result indicates that δ^<15>N may be useful tool to figure out the climatic change of coastal environment in last 20 k years. The isotopic results of sediment samples from the sourth of Thailand coast indicated that organic carbon and nitrogen isotopic composition have already recorded evidence of recent anthropological activities, urbanization and eutrophication in watershed. A boring core from Changjian river mouth represented that ^<15>N might be enriched in recent soil perhaps due to nitrogen accumulation in the growth of human population. This work successfully indicated that sedimentary organic matters are useful to study temporal change of marine and lacustrine environment since the last glacial period.