26 25 gravity of the Halimeda and other sediment components is 1.8 g/em? carbonate matrix and its associated transuranics in the sedimentary (km54). deposits. Activities of 2394240, assoctated with the algae are related to the activity in the surface sediment, The mean wetidry ratio of the The transuranics associated with the organic fraction released during decomposition are recycled to the benthic or pelagic Halimeda species is 2,3, and the average wet weight of the plants, environments. without holdfast, is 6.4 + 3.8 (No78a). cycling the transuranics between the sediments and aqueons environment. Therefore, the average Over the long term the algae could play a key role in 2394240, concentration associated with the live Halimeda species at Enewetak is 0.62 pCi/g wet weight. with each plant. PLUTONIUM CONCENTRATIONS IN THE LAGOON SEA WATER Approximately 4.0 pCi are associated If the number of Halimeda plants were known, the mean A considerable number of lagoon water samples have been collected Plutonium inventory associated with the living Halimeda reservoir could for plutonium analysis by this laboratory since 1972 (Ke/3, No74, ho76, be computed. No78b). Unfortunately, no estimates of Halimeda biomass at Enewetak are available. During the late 1940s, the mean sedimentation rate of Halimeda at Bikini was estimated at 3.8 mm/yr (Em54). If this Several studies are in progress at the Atoll that require data on concentrations in lagoon water so that the number of samples and the locations sampled are predicated by the current program requirements, £ 2394240 sedimentation rate is applicable toa Enewetak Atoll, approximatley 1 Ci Contours o of 2394240, is deposited annually in the sediments in association with distribution patterns (No74) Halimeda detritus. This quantity represents only 0.4% of the surface Pu concentrations in the water show complex in various regions of the lagoon, 4 The . Spatial patterns of surface and botton 23942405, concentrations in sediment inventory and yet a smaller fraction of the total inventory in solution and in association with filterable material are verv different the sediment column, as are the 2385 239240), ratios in the water mass. However, if the life span of each plant is l yr, A detailed for example, a quantity of 2394240 Pu equivalent to half the present discussion of the plutonium levels in the pelegic environment of the sediment inventory, or 125 Ci, could be recycled with the algae in lagoon is in preparation (No78b). approximately 175 yr. the analysis of lagoon water samples collected since 1972 with Spies et al. (Sp78) demonstrated that when live Instead of relating all results fron Halimeda from Enewetak were cleaned and treated with 1N acetic acid, the hydrological, seasonal, or spatial factors, we will suriarize sore of acid soluble fraction, or the carbonate material, contained 58% of the the data that is related to remobilization and redistribution of total 239240. plutonium, Pu, while 42% remained bound to the plant tissues. plant decomposes after death, As the the organic material and associated radioelements are released to the environment leaving the skeletal In 1972, 1974, and 1976 a suffictent number of water samples from JOH4240, : . the lagoon were analyscd for 23942 A Pu to permit an estinate of mean . ~" py NG6 Be r£ yw ee oe