39. Turekian, K. K, 1969, "The Oceans, Streams, and Atmosphere." Handbook of Geochemtstry. pp. 297-323. New York. Vol. I. kK. HR. Wedepohl, Ed. DISTRIBUTION PATTERNS AND TRANSPORT OF PLUTONIUM IN FRESHWATER Jn: Springer-Verlag, ENVIRONMENTS WITH EMPHASIS ON PRIMARY PRODUCERS Wahlgren, M. A., J. J. Alberts, D. M. Nelson, and K. A. Orlandi. 1976. Study of the Behavior of Transuranics and Possible Chemical Homo logues in Lake Michigan Water and Biota." In: Transuraniun Nuclides in the pp. 9-24, IAEA-SM-199/44. Vienna. Environment, L. Dean Eyman and John R, Trabalka Environmental Sciences Division Qak Ridge National Laboratory Oak Ridge, Tennessee ABSTRACT The major repository for transuranic elements entering aquatic ecosystems is the bed sediment. Observed Kq values for plutonium across a wide spectrum of aquatic systems are surprisingly uniform (on the order of 105). Plutonium arrives at the bed sediment as a result of association with and subsequent settling of suspended particulate matter. Consequently, the major role of phytoplankton in plutonium kinetics in aquatic systems has been postulated to be one of plutonium removal from the water column, The very high affinity of plutonium for particulate matter in aquatic systems makes it difficult to use the traditional expression of Concentration Factor (CF) as a measure of the tendency of biota to accumulate this element. A proposed term, Trophic Transfer Factor (TTF), relates concentrations observed in biota to that of the sediment. The underlying assumption is that, due to the high Kg's, accumulation in tissues of organisms at higher trophic levels will be dominated by gut absorption rather than by direct uptake from water. Plutonium in most freshwater systems is transported predominately in association with suspended particulate matter. In some organically rich systems, a fraction of the hydrologically mobile plutonium pool may be complexed or otherwise associated with naturally occurring organic acids. Although this association may result in increased environmental mobility, it does not appear to result in increased availability to aquatic biota. ee ee 38. INTRODUCTION With the exception of a few site-specific studies, historical information on the behavior of transuranics in aquatic ecosystems is related predominantly to nonpoint-source inputs of high-fired oxides to these systems from the atmosphere. Available information indicates that the