In this short review, the abnormal embryogenesis, and the changes in hatchability of eggs and in gonads of fish kept in contaminated water with radionuclides are dealt with. Many reports on the effects of radionuclides on the hatchability of fish eggs have been published. However, there is a marked divergence among these results. In our experiments, the process of embryogenesis was rather radioresistant, when eggs were irradiated with internal radiation from radionuclides incorporated into the eggs. It has been shown from estimation of absorbed dose that insufficient size of dose to produce low hatchability was given to the embryos during their embryogenesis. The damage of the gonads of fish was observed when fish was kept in water containing such low concentration of radionuclides that normal embryogenesis proceeded. It seems that the gonad of fish is a critical organ for the assessment of the effect of radionuclides on the fish population.
The sorption of some inorganic anions to Toyoura fine sand were examined by using single column experiments. Adsorption of Cl- was weak but SO42- and PO43- were adsorbed extremely. The breakthrough curve of SO42- for Ca2+ saturated sand was similar to that of cation, though SO42- was leached with deionized water. This means that the sorption phenomenon is based on not an ion exchange but a chemical reaction on solid phase. The adsorbed ion of PO43- on a fine sand was not leached with 10-3N CaCl2 solution and distilled water. This irreversible phenomenon stems from that the ion pairs of PO43- as Ca3(PO4)2 or CaHPO4 are formed in solution and these colloidal particles or precipitates are filtered on fine sand. Iodine in solution consists of two soluble forms, one is nonreactive forms to fine sand, and another is tightly sorbed on the quartz sand. Thus, the behavior of anions is affected by various types of reaction, though it was not based on the ion exchange.
The experiment was performed in order to investigate the intestinal retention and absorption of radiocerium in juvenile beagles and the result was compared with that obtained previously in the rat. 141Ce given orally was retained in the whole-body for more prolonged time by suckling than by weanlings or adults. Distribution study showed that the 141Ce was associated with the intestinal tract and a little was transferred to the organs other than the intestine. The present result was in accord with that in rats qualitatively. However, there are important differences of the 141Ce metabolism between beagles and rats which affects the intestinal dose calculation. The retention curve of 141Ce for beagle sucklings can be described exponentially and the levelling off of whole-body 141Ce retention occurs before the time of weaning, while the curve for rat sucklings has a so-called shoulder and the levelling off takes place at about weaning.
A theoretical explanation and the experimental results of the volume reduction ratio in incineration and compression are presented for low level solid waste treatments. The volume reduction ratio of the combustibles by incineration can be expressed as the product of the weight reduction ratio and the reverse ratio of bulk densities before and after treatment. The weight reduction ratio is the most important factor in the process. The volume reduction ratio by compression is represented only by the reverse ratio of the two bulk densities, because the weight reduction is not involved. The bulk density of a compressed waste decreases due to its elasticity when the mechanical compression is removed. The preventive measures against volume restoration should be taken to retain the effect of volume reduction.