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On the Distribution of Radioactivity in the Sea around Bikini Atoll in June, 19!54. “1. NII The )hser+’aflon of the actua, sure of the radioact)vi!y around until 4 th July aboard the survey }x)a: the Shclnkotsu-maru “ belonging to the bomb testg hac bee-I done by L. S Aron;:c znergy Commission, to make clear the against the serious damage fell on the Jap:!ne. e pelaglc fisher]es due to the radioactivity carelessly scattered In th19 sea dre ZS since the unfortunate affair of the bt this exped)t]on the present authors took charge of making a p}an and observations on tbz radioactive contaminatjcr. of sea water and the air. Two of The fairly strong radloactl~ity was clete (k in wide area around Bikini Atoll, radloactivty In the area was negllg::)ie ~ In this pa~r the authcrs intend to repvrt the resu~:s of obwrvatlons ari(: s~,n e octanographlc dlscusslsns regarding 2. TIM method of measurement of radioac-tiv ity in SWI water Wxlw adopted, After .dd]ng z gr of solid ammon urn chloride, 1 ml of the aqueous solution of sea water water is heated to 60- To’(_’stirring well. A few drops of an alcoholic
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To obtain the ~ounting efficiency .4 small brass case :(J {Y,)IG !r. e folding of the surface of a filterpper. standard RaE was treated rherni~ally as l]ent]oned above, and its radioactivity waa measured under the same geometr]~’al conditions. Thus, the efficie~y of the measurement was found to be T ~~~, that is, 1000 counts per minute is muivalent to about 59 m~’. The maximum actlv!ty in sea water obtained aboard by this method was 7025 cpm / which was found At the depth of 75 m, at 450 km west of The second was 6050 cpm 1 found al the depth of 20 m at 150 km west of the atoII on 12 th June. It was confirmed that most parts of the radioactive materials were (iispersed )n water as :nle solutions, Ionic or eucolloidal, since more than
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!)9 ‘~ of the radiuactlvlty passed through a hlt’r paper pore size 0.5 p, No. 4 Filter it IS rather surprising that the acrivlty JrI sea water near Bikini and Eniwwtok Af(I1l.a was often stronger than, or at Ieast con~parable to, that of White Oak Lake . s{I,)wa the horizontal dlsrri burlon If the act~. ity in the surface water’ the auaes If changes cated, and the (’or rectiw were almost tribution was drawn by using directly the without gi~ Ing my the radioactive water extended un the ing near Bikini Atoll while a branch spread out to WSW. The ing is not clear But, as explalned below, it seems that there was a weak ary along the Iine pasaing Bikini and on the nort hem side of this !ine had on an average the Fig 3 The horizontal i:+trbution of the radic)activity of the surface wdler Xu:r.ber expresses the radioact]vlty in ----”--3‘:-”--;”75Fig. 4, The crrur.e linen of observation, the watef W~t~~C and the current speed and its direction.
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19 2~M and u,, 22.51 at 50 m depth. On the jernls :nat there was a siight hut defin]te L~it”r systems, which might be one of the
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Fig. 10. The /ertlcal distribution of the radiact;vlt} of sea water in the section perpendicular to the North Equatora[ L-.rrent along the iine at 13CQkm west
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been found that [y IS In the original tis - to pH of sea water,
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