A Trophic Transfer Factor equals the concentration in an organism expressed as a percent of the mean sediment concentration. This was related to gut loading of sediments and/or surface contamination (Table 3). [n general, snails exhibited highest concentrations in shells and lost 50% of their plutonium burden when held for 48 hours. The importance of the gut contribution is best shown in the goldfish data. Plutonium concen- trations are nearly an order of magnitude less when the gut is isolated. The uptake by rooted macrophytes not exposed to surface contamination was quite small: < 0.03 to 0.1%. The comparison between emergent plants sampled above the waterline, and submerged plants was very instructive in this regard. Concentrations were many orders of magnitude higher in submerged piants; sorption to surfaces is strongly indicated. CONCLUSIONS ili We believe our results have shown the utility of ??7Pu as a laboratory i tool to shed light on some of the fundamental processes occurring in : natural aquatic systems. It is equally obvious that it cannot be used to answer questions relative to long-term time-dependent phenomena. Specific plutonium-contaminated aquatic ecosystems must be preserved as research sites to answer those important questions. Environmenta? : be required studies carried out in a natural ecosystem will ultimately to validate results of laboratory studies. Our results suggest that surface phenomena at plant surfaces, on gut walls, and on exoskeletons appear to dominate in submerged components of aquatic systems. This is a partial explanation for the higher plutonium levels found in biota from aquatic versus terrestrial environments as reported in reviews on the subject. We also note that trophic transfer factors for sediment-associated animals in the microcosm study are comparable to the percentage uptake of plutonium in our gavage work with channel catfish. Conmon name i | Emergent plants | Gi { 1 ! ! { | mes Panicum a Spikes Stem and leaves nN 3] «0.11 «0,045 Cateail ° aes Typha Stem and leaves Stem and leaves 1 1 <0.029 Watercress Nasturtium Stem and leaves ? <0.089 Algae Oedogeonium Clumps Moss Hygrohypnum Branches Stonewort Pondweed Chara , Potamogeton Branches a1 Stem and teaves gnats Physa whole body | i | | «0,040 Submerged plants Gyraulus Gonfobas{s terrestrial systems where significant surface contamination occurs either by atmospheric processes or as a result of periodic inmersion of floodplains, for example. A major question not addressed by our studies tim longer time biologically available form of plutonium could occur over a longer nphipod ayatela ACKNOWLEDGMENTS Goldfish carasstus We would like to thank J. W. Gooch and C. P. Allen for technical support Whole body 60 75 0 27.0 . 0.19 + 0.078" 05 . 30 2.42 0.46 63 6421.4 1.52 0.28 13 0-3 30 % whole body” Shell ; 9,1 7 Invertebrates ae Our results also suqgest that surface phenomena also may predominate in to date would appear to be whether biochemical transformation to a more Trophic transfer factors Sample size Body Part Genus b 14 ; Wele body, ; 99 16 75 Whole body snore poe : ie note body 130 carcasses? Vertebrate Carcass-gut 4 Gut Whole body 4 5.0 sb 36°09) 0.47 (0.16, 0.54 30 (18-91) 2.3 (1.2-8.1 } ‘ 4 in gavage studies. We would particularly like to single out M. L. Frank for work involving plasma protein separation and identification. Finally, : of blood-transport proteins and assistance in tissue preparation for banimals held for 48 hr {n uncontaminated spring water before sacrifice. H. L. Bergman provided significant input regarding physiological behavior raeionssey- 500 | if les 95% C.1. (counting error). Not shown f “geometric means and ranges. Significant values only. Table 3. Tess than than 10% of mean. 9 Mean for carcasses based on statistically Trophic Transfer Factors for Plutonium-237 in Biota of an Aquatic Microcosm. 50]