from the river, ponds and canal have been reported (Wayman et al., 1974; 1975). This paper studies in more detail the plutonium activities in aquatic plants from these sites with emphasis on macrophytes. Possible modes of plutonium accumulation and distribution within certain plants will be discussed, There is a brief comparison of plutonium activities in the same species of Cladophora present in two adjacent dissimilar sites, the Great Miami River and the adjacent canal. MATERIALS AND METHODS The aquatic plants investigated in this report are the green alga, Cladophora, and the macrophytes, Lemna (duckweed), Typha (cattail), Potamogeton (pondweed), Myriophyllum (water milfoil). Lemna is a small floating plant consisting of fronds and roots which hang down from the underside of the leaves. Suspended in the water, the roots extract nutrients and are never in contact with consolidated sediment. The plants prefer hard water and grow abundantly to form interwoven masses in still waters of lakes, ponds and quiet areas of large rivers (Fassett, 1957). Lemna was found flourishing in the canal and small patches were observed in the ponds; however, it was not found in any quantity in the river. Also growing in the canal and ponds was the emergent macrophyte, Typha, which has complex rhizoid root systems extending away from the primary plant and penetrating deeply into the sediment, Some waterfowl! and mammals are known to feed on these emergent plants (Reid, 1961). The only aquatic macrophytes found in the Great Miami River were Potamogeton and Myriophyllum. These plants are submergent species which are rooted into the river bed. Both species have long stems with fine feathery leaves, The plants prefer flowing water which allows the stems and leaves to be continually extended in the water column for maximum gas exchange and nutrient uptake. The submergents are food for waterfowl, Miamisburg), ponds and canal are lMsted in Tables 1 and 2. Mean concentrations of plutonium in the water corresponding to the above sites have also been determined (Table 3). The activity of 238pu in sediment and water collected downstream of the Mound Laboratory is one to three orders of magnitude higher than it is in upstream background samples, while the water and sediment in the canal and ponds havethree to six orders of magnitude greater 238pyu activities than background. Aquatic plants (Tables 4 and 6) whether rooted in sedi- ment, attached to substrata or free-floating generally exhibit high plutonium activity in plant tissues when there are high concentrations in the water and sediment. There are two to three orders of magnitude higher 238py activities in aquatic piants from sites below the Mound Laboratory effluent pipe than in those collected upstream, Plants from Chautauqua site (1.6 miles below pipe) have two to ten times more 238pu than samples collected at Franklin (6 miles below pipe). 238pu activity in sediment, water and biota diminishes with distance from the source, while the 239,240py activity in aquatic plants from upstream and downstream of Mound Laboratory shows no apparent trend, Concentration factors for aquatic plants were determined for plutonium activities in both sediment, C.F.seq, and water, C.F -H20- All C.F .sed for aquatic plants are low (Tables 5 and 6). The lowest values were calculated for aquatic plants from the ponds and canal. The C.F.y,9 for pond and canal plants are also lower than the values for river plants’ (Tables 5 and 6). In the river, Cladophora accumulates 5—10 times more plutonium than the macrophytes, Potamogeton and Myriophylium, In Lake Michigan, Cladophora mammals and fish and provide substrata for periphyton. contains four times more plutonium than Potamogeton (Yaguchi et al., 1973b). The concentration factors (C.F.435Q) for ' Pu tn the river for All plants were collected by hand and rinsed to remove excess sediment and etal., 1973a). The C.Pewy0 for algae in the river is an order of magnitude detritus. Roots were detached from Typha (except one sample), Potamogeton and Myriophyllum. Samples were immediately frozen and stored until the time of analysis. Just prior to analysis samples were thawed and wet weights determined, the excess water having been eliminated in the field. Next, the samples were dried to a constant weight at 105°C and ashed at 500°C. Radiochemical analysis was performed on aliquots of ashed samples following the procedures described by Nelson et al, (1973). Cladophora are in general agreement with values for Lake Michigan (Yaguchi higher than the C.F .H50 fot algae in the canal (Table 5). This may indicate that the Cladophora growing in elevated plutonium levels of the canal water have all the surface sites occupted by 2 Bpy and therefore the apparent C.F.4350 is lower than in the river where active sites still exist. High saturation favors surface adsorption of plutonium rather than active uptake. For example, brown algae are known to concentrate activity on their outer surfaces (Hodge et al., 1973). The 238py C.F 10 for Cladophora in the RESULTS AND DISCUSSION canal are comparable to the values for Cladophora in the Hanford waste pond which has a similar concentration of *?5Pu in water (Emery and Klopfer, 1976). The concentration of plutonium in sediment from the Great Miami River, Mad River (a tributary of the Great Miami River located upstream of The activities of 238pu in the aquatic plants from the canal and ponds (Table 6) are much higher than the activities in plants from the river due to elevated 506