EXPERIMENTAL METHODS AND RESULTS Three specific experiments are described below which illustrate the usefulness of plutonium-237 as an environmental research tool. We conducted an experiment whereby channel catfish received a dose of plutonium-237 incorporated in a diatomaceous earth slurry and administered by intragastric injection (gavage) (Eyman et al,,1976). The purpose of this experiment was to examine the effect of chemical form on the gastrointestinal uptake of olutonium by a fresh-water fish. The choice of fish a 2,44 x 104 y 8.3 Xx 107 86 ¥ Qa 1225 10.85 p 100 complex 237, 246, 238p 239p, 2th, 45.6 D (MeV) | A LOW SPECIFIC ACTIVITY DUE To CONTAMINATION witH 244p,, 1 1,77 X 10 7-2 0,06 17,48 0,274 1.1 x 104 (C1/4) SPECIFIC Activity PHOTON ENERGY a HALF-LIFE Isotope TaBLE 1. COMPARATIVE PHYSICAL CHARACTERISTICS 0 F Gamma EMITTING AND ALPHA EMITTING ISOTOPES oF PLUTONIUM Gavage Study species was determined by three factors: (1) Its importance as a food species for man; (2) its propensity to ingest significant quantities of sediment along with its diet; and (3} its prevalence in the southeastern U.S. where significant facilities associated with the Breeder Reactor technology are to be Jocated. The choice of chemical forms to be incorporated in the diatomaceous earth slurry was such that we had a representative sedimentary form (fulvate} and two reference forms (citrate and hydroxide} for comparison both with mammalian results and with our previous data. Doses contained approximately 20 nCi of plutonium237/fish (represents a mass equivalent to approximately 1 pCi of plutonium- 239). The average weight of specimens tagged was 57 g. Fish were wholebody counted un to 90 days at time intervals which gradually increased from 1 day to 30 days. Retention of plutonium was expressed as a percentage of the initially measured whole-body burden. Elimination coefficients were calculated by separating different compo- nents of the whole-body retention curve (Richmond, 1958). The initial rapid loss compenent (Kb]) represents that portion of the ingested dose that passed through the animal and was not assimilated. The half-time for gut clearance ranged from 0.51 to 1.17 days (Fig. 1). Elimination of the fraction of the ingested dose that was absorbed and/or associated with the gut wall was separated into two components. The calculated elimination coefficients for the second component were comparable for Pu-fulvate and Pu-hydroxide while citrate (0.0238 day-') was significantly different (p < 0.05) from the other two forms (Table 2}. The biological half-lives of this component for the three treatments ranged from 13.4 to 30.2 days. Extrapolation of the second component to day zero was used to estimate the percent uptake of the ingested dose. Untake ranged from 1.62% for Pu-fulvate to 10.5% for Pu-citrate (Table 2). Catculated uptake of Pu-fulvate was significantly lower (po < 0.05) than either of the remaining treatments. Between 50 and 70 days postingestion, elimination was dominated by a third, long-term component with a calculated half-life of 534 days. The chserved retention of ingested dose on day 90 was 3.8% and 0.5%, respectively, for Pu-citrate and Pufulvate. These values are significantly greater than observed in studies with mammals (0.09-0.30%, Pu(1IV} citrate; 0.001-0.01%, Pu(IV¥)}) nitrate) (Baxter and Sullivan, 1972; Carritt et al,, 1947; Weeks et al, ,1956). 493