Abstract
Organic-metal compound are enriched in the euphotic and bottom layers, relative to the intermediate layer. It has been suggested that these compounds within the euphotic layer are supplied by biological activities such as excretion from plankton. However, these compounds in the bottom layer may be supplied by means of not only plankton excretion but also dissolution from sediments under the anoxic conditions. Then the dissolution of organic-metal compounds from sediments is investgated. Distilled water was added to sediment sample and repeat leaching operation by means of the irradiation of ultrasonic waves was carried out. Organic-metal compounds was divided into amino acid, organic acid, carbohydrate and marine humus fractions, respectively. The greater part of organic-metal compounds was removed from sediment to the aqueous phase by the first leaching operation. Then, copper was detected in organic acid fraction, manganese in amino acid fraction and selenium in all fractions. In addition, the dissolution experiment for reducing sediment under the aerated condition was carried out. Organic copper, manganese and selenium compounds were leached in the same fractions as well as the ultrasonic irradiation experiment. However, the amount of dissolution account for only 5 to 10% of the case for the ultrasonic irradiation.
