ik rs 3 a) fay ‘oo B PLUTONIUMIN SI. WATERS. LTC RK. M. wong E concentration in the 10-12 cm section of the core + usually about | 10 the concentra- ual ab.. Richmond, 34 tion of the surface section. cy a It was found that the addition of hvdrochloric acid in the leaching step 1s one B necessary only for sediment samples of lowsalinity. Most marine sediments contain ates mm”, 100-ym - sufficient chloride for complete leaching of plutonium from the sample using only ‘nitric acid. Weigh out a 100-g aliquot of dried sediment. transfer it to a 3-] beaker, wet the t sample with water. and add 1 ml of standardized plutonium-236 tracer. Carefully = add 200 ml of 16 M nitric acid and 100 ml of 12 M hydrochloric acid. slowly stir the -ed in a chamber od. No. 428), a. o. 115), a linear alyzer (Nuclear inder (Canberra . & sample and allow the mixture to react at room temperature. If foaming becomes . appreciable, controlit with the addition ofa few drops of n-octanol. Whenthe reaction : subsides, cover the beaker witha watchglass, heat gently, then to near boiling (90-100°) . and digest the sample for about 2 h with occasionalstirring. be used. Add 300 ml of 1 M nitric acid and 25 ml of 30°hvdrogen peroxide and continue from the North ynvenient deter- heating (90-100°) until the peroxide has decomposed. Cool the sample, filter through = a glass fiber filter paper and wash the residue with ca. 50 ml of hot | M nitric acid. transfer the sea rinses and evaporate (90-100°) unul salts begin to form. Estimate the volume of the so'ution, add an equal volume of 1 M nitric acid, dilute to 1 | with 8 M nitric acid. and cool to room temperature. Add ca. 10 ¢ of solid sodium nitrite. mix and leave for 30 min before proceeding with the plutonium purification. imples??, etc.) of all dust, * Transfer the residue back to the 3-1 beaker and repeat the entire process from the ; addition of concentrated nitric and hydrochloric acids. Combinethefiltrate and acid ‘cipitate to settle Lay ee Rigeet ent Tve any unusual mation may be . ul of 3 M hydro1 few times, and tinse the empty 1¢ sample. -236 (2-3 d.p.m.} of 2 M sodium second 100 miof ml) to make the a 300 | capacity). Procedure for marine organisms The concentration of fall-out plutonium in marine organisms1s quite variable: a range from 0.004 d.p.m.kg in fish tissue to more than 10 d.p.m. kg7’ in certain seaweeds has been observed'*. For optimal sample counting rate, the activity should .. be about 0.5-5 d.p.m. Lower activity would require too long counting whereas higher activity could unnecessarily increase the chance of cross-contamination between * samples. Table I, which may be used as a guidefor the selection of the proper sample size, lists the average °7°Pu concentrations in some marine organismsof the Atlantic Ocean collected in 1970'*. Similar ranges of 77°Pu concentration have also been found in some Pacific organisms'*. -nsfer the hydro- jlastic wrap and ate. Dissolve the -e volume of the ition to a 400-ml TABLE | AVERAGE PLUTONIUM-239 CONCENTRATION OF MARINE ORGANISMS IN THE ATLANTIC OCEAN!+ .dd 5 mi of 30% Oruanisms on a hot plate at om temperature, ‘roceed with the . Sargasso weed Mixed Zooplankton Starfish, Asterias forbesi Mussels and clams. shell 13 3 2 0.6 meat 0.3 Milena, Saiiearea er eS eee PE quot: the 77°Pu 2 Fish, guts ufficient fall-out sections of cores *39 Py (dpm. per ky wet wt.) 90084282 bone liver meat 0.9 0.3 0.1 0.004 Anal. Chim. Acta, 56 (1971) 355-364