Abstract
This paper describes the vertical profiles of selenite, selenate and organic selenide in pore water, and the vertical profi1es of selenium, iron, and manganese in sediment cores in the marginal seas.
Selenium speciation was investigated for the pore water. Organic selenide was the predominant species in the pore waters at the surface (46.5-54.7% of total dissolved selenium). The vertical profi1es of dissolved selenium species in the South China Sea showed spechic distribution patterns such as surface-enrichment of organic selenide and selenite. Significant high and negative correlations were recognised between the concentrations of organic selenide and selenate in pore water and those of manganese and iron in sedimentsat the South China Sea. The relatively highconcentration of dissolved organic selenide at the surface layer indicated that the rateoftransfbrmation of particulate selenide to dissolved organic selenide was extremely highinthev olcanic ash sediment in the South China Sea. The vertical profiles of selenium species in pore water and sediment at the Celebes and Sulu Seas were complex.
