Concentration and Distribution of the Transuranium Radionuclides 239 + 240Pu, 238Pu and 241Am in Mytilus edulis, Fucus vesiculosus and Surface Sediment of Esk Estuary

Abstract

Concentrations and distributions are reported for 239 + 240h, 2 3 8 P~ and 2 4 1~m in Mytilus edulisL., Fucus vesiculosus L. and surface sediment from the Esk estuary Cumbria UK, which is subjected to effluents from the British Nuclear Fuel Ltd uranium reprocessing plant at Windscale, Cumbria. For M. edulis, data was obtained on total soft tissues, shell and for 11 organs and tissues. The distribution of alpha particle activity for thin sections of the mussels was obtained by autoradiography using a new thermoset dielectric detector CR-39. Evidence is presented which indicates that uptake of transuranium radionuclides is probably from seawater rather than from ingested sediment. Pu und Am retained within the intestinal tract is excreted in faeces; that which enters the systemic circulation gives rise to a diffuse distribution. No significant enr~chment of Pu and Am occurs in kidney granules, but in the pericardial gland as a result of ultrafiltration processes localised enhanced levels of alpha radioactivity were observed. Highest enrichment of Pu and Am occurs in byssal threads and periostracum, lowest in the shell when the periostracum has been removed. Alpha particle distribution for byssal threads and periostracum is diffuse, hot-spots are absent and hence uptake is probably direct form conservative species present in the seawater. In situ dialysis studies in surface silty sediments of the area provide evidence of conservative species for both Pu and Am. Differences in concentration of Pu and Am for 1977in 1979 there was an increase in levels of h in the mussel and sediment. F. vesiculosus contained more h than Am. However, the Am/Pu ratio for F. vesiculosus is similar to that in byssal threads of M. edulis.

Histo-autoradiographic localisation of americium (241Am) in tissues of European lobster Homarus gammarus and edible crab Cancer pagurus after uptake from labelled sea water

“…But histo-autoradiography indicated that in lobster, americium was localised in the mucus between the gill lamellae, and In crab, on the chitinous external surface of the gills. The mucus and chitin contain polysaccharides which are known to bind transuranic elements, as has been shown in polychaetes, bivalve molluscs and other crustaceans (Hamilton & Clifton 1980, Grillo et al 1981, Carvalho & Fowler 1984, Miramand et al 1987). This localisation indicates that the marked binding of americium in the gills of decapod crustaceans is essentially due to simple adsorption on the large surface area of these tissues, as in the exoskeleton.…”

Concentration and depuration of some radionuclides present in a chronically exposed population of mussels (Mytilus edulis)

“…M a n y radioisotopes are also strongly associated with t h e shell (Gaury and particularly t h e periostracum (Hamilton a n d Clifton, 1980), a n d this is t h e subject of further study.…”

“…Guary and Fowler (1981), however, have identified a 3-compartment system for the loss of ^'Am and ^PU from Mytilus galloprovincialis. A variety of factors, apart from the choice of indicator species, may be responsible for the observed differences between both sets of data: Guary and Fowler's data includes radionuclides associated with the shell in the calculation of biological half-lives, and their mussels were exposed to tracers for 28 d in the laboratory; in our study the mussels have been chronically exposed under environmental conditions for the whole of their life-span of 7-10 yr Hamilton (1980). Van Weers (1973) suggests that the biological half-life of an isotope is a function of its uptake time.…”

“…The data on mussels, chronically exposed to radioactive isotopes, are generally limited to monitoring surveys which report the concentrations of selected radioisotopes originating from either nuclear weapon test fallout (Pillai et al, 1964;Noshkin, 1972;Bowen et al, 1976;Murray and Fukai, 1978;Goldberg et al, 1978) or from nuclear fuel reprocessing plants (Hetherington et al, 1976;Pillai and Mathew, 1976;Guary and Frazier, 1977;Hamilton and Clifton, 1980). 1 Inter-Research/Printed in F. R. Germany…”

Accumulation of metal radiotracers by Mytilus edulis

“…1976, Phillips 1976a, b, 1980, Goldberg et al 1983. Soft tissues, shells, and even byssal threads have been proposed as indicators (Hamilton & Clifton 1980, Koide et al 1982, Goldberg et al 1983. The use of bioindicators and problems associated with their application in aquatic monitoring programmes have been discussed by many authors, notably Philhps (1980).…”