I a * a aid sucending series, Curves 1-% represent the radio-decay of sarpl.s co.lected 10-.1 months after March 1, 1954, while curves 4-9 pertain to sumpies so.liected s.orvtly after the Redwing series. The two ,;rouns differ in both steepness and direction of curvature. QThe first group, curves i-3, decayed with a log-log slope of -1.3 to -1.4 wiien asrees with tne slopes of the remarkably straight decay 2aurves ovir ilnost the aame period of time for the Eniwetok Atoll pazikton sesiples (UWL+S3:21). Yowever, the Rongelap Atoll plankton deciy curves differ rroin those of Eniwetok Atoll in having a down- ward flexure. In fact, curve 2 displays up to the 1350th day al- most a uniform nalf-life of about 710 days, and from days 12350 to 1740, a 430-day nalr-life. fron this pattern, Curves |] and 3 deviate only slightly being steeper in the early sections. Gamma- Spectrumetry of the sample of curve 2 on November 6 and December 3), 1957 showed cel4 of 235-day half life to be the primary con- stituer.t, which is presumable accompanied by small, amounts of longer-lived isotopes, life afser 1550 days. undetected contributing to the 450-day half The second group, curves 4-6, decayed rapidly (slopes -4.1 to -10.8) because of recent origin (Redwing), but with a distinct upward flexure. In studying tne decay rates it was evident that there was a more rapid Gecay of the radioactivity in plankton from the part of the lagson neair Rongelap Island than occurred near Kabelle Island. This is interpreted as indicating the influence of recent Redwing detona- tions probabiy within e month-preeeding-Pewa—+7-21.56} whose fallout thus al otweertst st aresumads 4 &DOSARCHIVEl ES y reee tee SetaGe re, .