ABSTRACT ~~ Background radioactivity and oceanograpnic conditions in the Pacific Proving Ground are of significance; in evaluating Thus, as a part of Project 2.62, a month- long study has been made of radioactivity in water, organisms, and bottom sediments, and of currents and physical character of the water over a 140,000 square mile area around Bikini Atoll. The waters are slightly radioactive, with values of 150 to 1500 gamma counts per minute per liter (cpm/1), whereas the natural radioactive background, due to potassium-bO, is about 94 epn/l.t A field of maxinun activity (8CO to 1500 cpm/1)} r exists at 806 to 1260 meters depth at locations to the west of Bikini Atoll, within 150 miles of it, and between 103° and 133° N. Radioactivity is associated with particulate matter (possibly organic) at the surface only; at all other depths it is mostly in solution, Organisms collected from the upper lay- ers and deep sea fauna captured in a trawl as deep as 2500 meters depth are about equally radioactive; the level of acti- vity in these marine creatures is about 30 to 50 times as much per unit weight as that in equivalent weight of water. Lagoon waters and surface waters in the open sea around the lagoons are slightly more radioactive than other areas cpm/l). _~— eee 1. y 1 co te eee oe eee All values of radioactivity given in this report are vamma rays emitted per minute. coriedl® Of CANE RG ~ t-- (1100 to 2100 —_ 3 ‘ fallout patterns. +) atoneenema ing of the fallout problem at sea and extrapolation to land Nn Pena Sm the contaminating effects of REDWING events, in the understanc-