~12- about 660 d/m/1 (beta), re:aains in the filtrate by this method. Radiocesium also remainsin the filtrate; however, it accounts for less than (3) one per cent of the total disintegration rate at the time of collection. Gamma.radiation surveyof surface water The gamma radiation measurements of the surface water immediately following the Wahoo test were obtained with U. 5. Navy survey meters (AN/PDR-27C and AN/PDR-43(XN-2)) by three-man teams stationed on the bow of the ship. bridge by telephone The readings were relayed to the at frequent intervals and plotted with the posi- tions of the ship during the survey. The ship was maneuvered to fol- low a 10 mr/hr surface radiation field (Fig. 4). Radiochemical analyses of the samples Radiochemical analyses by ion-exchange techniques were made of sixteen samples including plankton, fish, shrimp, and squid. The samples were wet-ashed with concentrated HNOg and superoxol and dissolved in 0.2N HCL. The samples were then passed through 0. 28 em? x 10-cm columns containing Dowex-50* (100 -200 mesh), and the radioisotopes were eluted with 50 ml of the following reagents: 0.5 per cent ox- © alic acid and 5 per cent ammonium citrate at pH 3, pH 4, and pH 6. 5°) Aliquots of the collected fractions were counted for total gamma activity, and the fractions with significant amounts of gamma radioactivity were ; Available from Dow Chemical Co., Midland, Michigan, ancHives POR