MOVEMENT IN SYSTEMS (Yaguchi et al,, 1974) was attributed to the predominance of diatom frustules studied by Hodge et al, (1974), It is doubtful that active absorption of a type that wouldTead to significant biomagnification could be possiole. This is borne out by available environmental data comparing CF values for algae with those for organisms at higher trophic levels (Figure 1). One would certainly expect, as suggested by Edgington et al. (1976), that surface-to-volume ratios may have some predictive value in determining expected plutonium concentrations of organisms at lower trophic levels, assuming that cross-contamination with sedimentary particulates is eliminated. The physical transport of plutonium in aquatic systems is predominately a result of its association with abiotic components of the system, (Hetherington, 1976), Nevertheless, even though biological transport accounts for a very small fraction of the plutonium pool, it must be given consideration because the potential exists for transfer to man via this fngestion pathway. => m Lit = WwW > Li - => _t czz Y =] 4! z <q uw uw) x “ s Mt a iL © WW FE x ° o Ww > or 2 <I =i ot -} _ w = i tg rw od FOOD CHAIN TRANSPORT IN AQUATIC SYSTEMS The very high affinity of plutonium for particulate matter in aquatic eco- systems (distribution coefficient ~ 10°) makes it difficult to use the traditional expression of Concentration Factor (CF) as a measure of the tendency of biota to accumulate this element in tissue, Rather, we believe the observed concentrations of plutonium in aquatic biota should 28 v = wy ow <q dq J wt} wl _J mM 4 Li <f - roa Lil = > z —-|} mt = ™ <a vv <a oO J Figure 1. In any event, that portion of the plutonium observed in phytoplankton appears to be surface-associated. This is the case for giant brown algae 4G q Tr 10° suspended particulate matter to the observed plutonium concentrations qualtfied. Wahlgren et al. (1976) reported a distribution coefficient for suspended sediment materials of ~ 3x 105. The inclusion of a small amount of those materials in the ash residue of phytoplankton samples may offer a plausible alternative interpretation of the observed correlations. a 22 104 However, in neither case was the contribution of associated inorganic = uw 40° in the samples analyzed. Wahlgren et al. (1976) reported a correlation between percent ash weight and plutonium concentrations, They also concluded that plutonium was associated with diatom frustules in the plankton samples, a x =- be related to the primary abiotic source in the system, sediment (both (> =~ suspended and bottom), In order to express this relationship, the term Trophic Transfer Factor (TTF) has been used by various researchers (Lipke, 480 481 Pu in Various Freshwater Concentration Factors (CF) for is defined as [Pu] in Organisms and Marine Environments. CF (wet weight) /[Pu] in water. 104% The major role of phytoplankton in plutonium kinetics in aquatic systems has been postulated to be one of removal of a significant fraction of plutonium from the water column (Wahlgren et al., 1976; Hetherington, 1976). However, collection techniques are such that phytoplankton cannot readily be separated from inorganic suspended particulate matter, The reported plutonium Concentration Factor (CF) values for algae (Figure 1) may, in fact, be high due to the inclusion of inorganic suspended particulate matter which would have a CF value of 10°, The correlation between percent silicon content and plutonium concentrations in phytoplankton samples