Abstract
A total of 215 marine sediments collected from the eastern part of the Japan Sea were analyzed for selenium (Se) by continuous hydride generation and atomic absorption spectrometry. The average Se content of surface samples (0.60±0.45 ppm, n=81) and core samples (1.88±2.19 ppm,n=134) is clearly higher than that of the crustal abundance (0.12 ppm). In the case of surface samples,the Se is generally enriched in the fine sediment fraction than coarse one and positively correlated with the water depth of the sampling station and organic carbon and total sulfur contents. It is considered that major Se forms are organic Se and elemental Se for the surface samples and organic Se for the core samples. The recent anthropogenic inputs to the Se content of the studied sample are estimated to be negligible. The considerable enrichment of Se in the dark layers of D1 and D2, which exist in the core samples collected at approximately 600 m water depth or deeper in the Japan Sea, is assumed mainly due to the reduction of Se (IV) and Se (VI) in seawater under reduced environments. It has been concluded that the geochemical behavior of Se in marine sediments is controlled mainly by the mode of occurrence, supply of Se to the seawater, redox conditions of environments, biological productivity and formation with migration of volatile Se compounds. The vertical profiles of Se in the core samples should be suitable as a geochemical indicator of the past sedimentary environments.
