provides good decontamination. Anion-exchanae resin. AG? 1-X8. 100 290 mesh. Bio-Rad Lab. Richmond, Calif. Counting apparatus connected to a vacuum system. a detector bias supply (ORTEC Mod. No. 428), a FET preamplifier (ORTEC No. 109A). a power supply (ORTEC No. 115), a linear ot amplifier (Canberra No. 1416) and a 512-channe! pulse-height analyzer (Nuclear Data No. 120) connected to a typewriter readout. With a scale expander (Canberra No. 1461). a 128-channel analyzer (Nuclear Data No. 110} mayalso be used. de teh TPP LT OKA URLT ae The x-spectrometer system consisted of an ORTEC 300 mm-, 100-um depletion-depth. lithitum-drifted silicon surface-barnier detector mounted in a chamber Procedure for sea water | i} Sea-water samples of 56-60 1 collected at depths of 0-700 m from the North Atlantic Ocean (1967-1969} contained sufficient -*°Pu activity for convenient deter- i mination: however, much lower activity was observed for deeper samples'?. h Clean thoroughly the sample barre! (top. side. handles. caps. etc.) of all dust, dirt and loose material. Weigh the sample in the original barrel and transfer the sea water to a polyethylene container of the appropriate size (100-300 1 capacity). Weigh the empty barrel to determine the weignt of the sample. Observe any unusual appearancein the sample (e.g. color, particulate matter, etc.}. This information maybe useful to establish contamination,if any. of the sample. Add ca. 500 mi of 3 M hydro- chloric acid to the empty barrel. recap. rotate the barrel on its side a few times. and oat art ble ab citeela Ki Eire leave for at least 2-3 h. Combine the acid rinse with the sample. Rinse the empty barrel twice with about | | of deionized water and combine with the sample. Add 10 ml of iron carrier and | ml of standardized plutonium-236 (2-3 d.p.m.) tracer. Stir the sample with tank nitrogen for about | h. Add 100 mi of 2 M sodium hydrogensulfite and stir with tank nitrogen for about 30 min. Add a second 100 mlof the sulfite solution and sufficient 15 44 ammonia solution (300-400 ml) to make the solution basic: mix well. Cover the sample securely and allow the precipitate to settle overnight. Carefully siphon off the main fraction of the supernate and transfer the hydroxide slurry to a 3-l beaker. Cover the beaker with aluminum foil or plastic wrap and let the hydroxide settle. Decant and centrifuge the remaining supernate. Dissolve the hydroxide with a minimal amount of 16 M nitric acid. Estimate the volume of the solution and add an equal volumeof 16 M nitric acid. Transfer the solution to a 400-ml beaker and dilute the solution to ca. 100 ml with 8 M nitric acid. Add 5 ml of 30% hydrogen peroxide, cover the beaker with a watch glass, and heat on a hotplate at 90-100° until the peroxide has decomposed. Cool the sample to room temperature, add 1 g of solid sodium nitrite. mix. Jeave for 30 min and then proceed with the plutonium purification. Procedure for sediments Usually 50-100 g of dried shallow water sediments give sufficient fall-out °3°Pu activity for convenient counting. Samples from the lower sections of cores (below 10 cm) or of oceanic sediments may require a Jarger aliquot; the *7°Pu Anal. Chim. Acta, 56 (197%) 355-364 pooen, KM. WONG 356