135 com ls .) - ooserved . (slope) (mass)], aff, ton 7 Ei = [9 (1) corrected where: _ mass = mg/cm 2 slope = .1591 (From Appendix figure 1.) efficiency = .47 An attempt was made to evaluate the fractionation effects of pipetting only the smaller sized particles for the total alpha measurement, compared to the activity of the entire sample. For this, aliqucts of the whole and pipetted fractions of the Bravo Crater "standard" samole and fcur lagoon samples were analyzea chemically for plutonium. The results are shown in Appendix Table 1. Similar fractionation was found between the four different lagoon samples reflecting homogenization yet constant fractionation from ‘anual grinding. These particular samples were selected because they represented the extremes and means of both the concentrations and the actual physical size ranges encountered in lagoon sediments. The surprising difference shown between lagoon samples and the Bravo “standard” sample is probably due to the very fine and well sorted sizes of the Bravo Crater material, which was close to the limits of grinding in the undisturbed state. These average fraction factors, when multiplied by the constant 459.45 and by the corrected activities obtained from equation 1, gave the activity of whole coralline sediments in pCi/g as shown in Appendix Table 2, column A.