SEQUENTIAL EXTRACTION PROCEDURE FOR MARINE SEDIMENTS AND APPLICATION TO THE MIDDLE OKINAWA TROUGH

In marine sediments,elements may occur as different speciations, i.e. they are combined with various fractions under different sedimentary environments and settling mechanisms. So the sequential extraction procedure, which partitions the elements in sediments among various forms, is an important tool for studying the sedimentary environments and material sources. In this study, based on the procedure established by Tessier et al in 1979,five elements (Fe,Mn,Co,Cu and V) in the deep sea sediment reference material GBW07315 are determined. The accuracy and repeatability of the method are also evaluated. The results show that the recovery rates vary between 94% and 126% for all the five elements, with an average of 106%. For Fe-Mn oxides fraction, organic fraction, and residual fraction, the relative standard devia-tions of four or five paralleling samples are lower than 15% for all elements, except for V in the Fe-Mn ox-ides fraction. However, for carbonate fraction and exchangeable fraction, a little higher deviations are found and should be attributed to the low concentrations of analyzed elements in these fractions. There-fore, this method is steady and dependable for the deep sea sediments, especially for the extraction of Fe-Mn oxides fraction, organic fraction, and residual fraction. This sequential extraction procedure is also applied to the hydrothermal influenced sediments from the middle Okinawa Trough, getting an effective extraction and separation of hydrothermal signatures.