泥質堆積物中の有機炭素の測定

抄録

We have examined appropriate conditions and methods for determination of organic carbon in various argillaceous sediments using a CHN elemental analyzer of dry combustion type. Usual HCl pretreatment method is not suitable for Recent sediment samples, such as ocean bottom sediments, because significant portion of organic matter may be decomposed and removed from the sediments with washings during the process of filtration. Low-temperature-conbustion method (heating at 550℃ for 15 minuites) is not suitable for samples including carbonate minerals such as siderite and magnesite, which are decomposed at relatively low temperatures. For example, siderite is decomposed completely under this condition of heating. Lowering the heating temperature may cause incomplete decomposition of organic matter in geologically old sediments. Therefore, direct HCl pretreatment method gives the most accurate value for the determination of organic carbon in Neogene sediments as well as Recent sediments. The Usual HCl pretreatment method is also useful for measuring organic carbon contents of Neogene sediments. Without examination of carbonate minerals, the low temperature combustion method is not adequate for the determination of organic carbon contents.