Accumulation of americium 243 in selected brackish and marine invertebrates

Abstract

As an initial step in a programme designed to investigate factors which are of importance in affecting the behaviour of actinides towards certain invertebrates found in estuarine and marine environments, laboratory procedures have been developed to study the accumulation of americium in three species: the polychaete wormNereis diversicolor, the brackish-water amphipodGammarus duebeni and the harpacticoid copepodTisbe holothuriae. The species chosen are considered representative of groups having wide ecological importance. It was found that large differences in concentration factors occurred for the same organisms, depending upon aging of the contaminated medium; much higher and more variable values being found when uptake was from freshly contaminated solutions than from those aged up to a week. The interaction of specimens with physico-chemical reactions of americium which appear to take place within the first few days after its introduction into water are considered to be responsible for these differences. Uptake from contaminated water that had been allowed to age in the absence of organisms appears to be unaffected by subsequent conditioning by specimens. Americium concentration factors show a strong tendency to increase with decreasing size of the species, varying from over 1000 forT. holothuriae to about 3 forN. diversicolor. The possibility that the mechanisms regulating the uptake of actinides in different species may depend upon pH is briefly discussed.