Radioecological Studies of ⁹⁰ Sr in Limnological Ecosystems

—Accumulation and Excretion of ⁸⁵Sr in Goldfish, Carassius auratus auratus, Rearing in the Radioactive Freshwater—

Abstract

Accumulation and excretion of ⁸⁵Sr in goldfish, Carassius auratus auratus, rearing in the radioactive freshwater were investigated in order to elucidate the accumulation mechanism of ⁹⁰Sr in naturally living fishes.
The accumulation of ⁸⁵Sr, expressed in concentration ratio (CR) between fish and water, in whole body of the fish showed a increasing tendency with the rearing time, and the CR value reached 5.4±0.4 (mean±standard error) at 7th day. On the other hand, the excretion of ⁸⁵Sr, expressed in retention rate, in whole body rearing in non-radioactive freshwater following the accumulation above for 7 days demonstrated a rapid decreasing at first few days, and then a gradual decreasing tendency indicating the biological half lives about 4 days and 205 days, respectively. The retention rate resulted in nearly 75% of initial radioactivity, i. e. 25% of excretion, at 25th day.
As for the tissues and organs, the CR values of ⁸⁵Sr reared in the radioactive freshwater for 7 days were 62.3 (vertebra : bone), 31.1 (scale), 12.5 (gill), 0.6 (viscera) and 0.4 (muscle) . On the other hand, higher excretion was found in the viscera and the muscle than that in the bone, the scale and the gill. It is so suggested that the metabolic turnover rate of this radionuclide is different among these tissues and organs particularly characterizing higher accumulation and lower excretion in the vertebra (bone) and scale.