te em es albaahhoe el, nn 304 TRANSURANIUM ELEMENTS IN SAMPLES COLLECTED NEAR BIKINI ATOLL Table |. Sampling data on manne sediment sumples Sample Patitude Cangitude 73104 TA1O8 FAH) VV 1341.6" 1156.07 Poe 1149.0" beax44 Y Loa*-44 4° LAA LO4° 2) a Wailer depth {mn} Topography of sea bottom XXX 1420 1600 etd) then dissolved with hydrochloric acid and the coprecipitation was repealed by adding a sodium hydroxide solution. Afler removing iron by the solvent extraction with di-isobutylketone, plutontum was extracted with lO% (viv) tri-n-octylamine (TOA) xylene solution from 8M nitric acid solution. The organic phase was washed successively with 8m nitric acid lo remove the uranium, and with [Om hydrochloric acid to remove the thorium. Plutonium was stripped with 6M hydrochlori¢ acid containing 0.2 M hydrofluaric acid (Sa7 1). The aqueous phase of the TOA extraction, containing anericium and gadolinium, was evaporated to dryness. The americium was then extracted, together with “Gd, into 50% (viv) di(2-ethylhexyl) phosphoric acid (HDEHP) toluene solution from the hydrochloric acid solution adjusted to pH 1.2, and stripped with 8M hydrochloric acid. For alpha spectrometry, americtum and plutaniumfractions were subjected, respectively, to electrodeposition on 18-8 stainless steel disks having diameters of 2.7 cm. The eleetrolytic solution containing 0.5 ml of O.1M hydrochloric acid, 0.5 mi of 0.5 M oxalic acid, O.75 ml of 2M ammonium formate, 5 ml of sodium chloride and 3 ml of distted water. The eleclrodeposition was carried out for 2hr at SO) mA, using a platinum wire as an anode. Americium and plutonium were determined by alpha-spectrometry using a Si(Au) surface barrier detector and a 200-channel pulse height analyzer. The top of Guyot The top of Guyot The shoulder of Guy ot Oocan faar Characteristics af sample Globiyerina sand Globigenina sand Globigerina sand Red cley RESULTS AND DISCUSSION The alpha-spectra of plutonium and amiericiumfractions of all samples are shown in Figs. 4a and b, respectively. In the alphaspectra of the americium fraction of the sample 73113, the contamination with *7Ac, the daughter nuclide of **U, is shown by the existance of the alpha-emitting daughter nuclides of *7Ac. Since actinium in a 3+ oxidation state is the most stable in an aqueous solution and the chemical properties of actinium resemble americium and lanthanides, actinium may behave as similarly as americium and lanthanide in the present analytical procedure for americium. As the energies of alpha rays from the daughters of 7Ac are higher than that from “Am, the peaks due to these nuclides did not interfere with the determination of “'Am in samples which had no high *’Ac content. The contents of ??°"’Pu and *“'Am are shown in Table 2 and Fig. 3, The overall chemical yields of ’*Pu and '"Gd varied from 12 to 42%. The “'Am in the “Bikini Ash" sample was found to be 12.9 + 0.9 dis/min/mg. The “'Am/??'**°pu ratios for the ‘Bikint Ash" sample and the sediment samples were found to be nearly the same, within the statistical counting error of the samples. 239 MOTD There are a few reports on the contamination of deep sea sediments due to the worldwide fallout. Noshkin and Bowen analyzed six sediment profiles collected from the Atlantic Ocean and the Medilerrancan Sea tn 1969~ 1971 (No73). Among. these samples three had been collected im the northern hemisphere. The contents of Concurrent with these analyses, the intercalibration sample, plutontum standard soll No. 3, prepared by the US Energy Research 2)in ocean floor sediment samples, Service Laboratory in Idaho was also analyzed by the above-mentioned method, bulk sediment, respectively. Livingston ef al, and Development Administrations Health The validity of our calibration of Pu tracer was confiemed by the agreement of our data with those from the Health Service LaboraLory. collected from about 1000 and $000 m depths, were around 0.02 and 0.005 dis/minfem’ of reported the value of 0.16dis/min/g for the top-of-core samples collected from the 1000- m depth in the Atlantic Ocean in 1972 (L175). The present values for samples 73108 and ope peteh Gs ‘8 or heer SENS