148 The concentration of 2385 reported in Appendix Tabie 5 is in a few cases the resuit of swltiple determinations. PBecausa these concentrations era also determined somewhat differently from the procedure outlined in section 4.2-4, the procedure used to calculate the concentration in these samples is discussed selcw. Early in the analytical work it was found that several samples had 239+240, unusually high ratios of mized for the 239+240 238 Pu/-~-Pu. Because the sample size was opti- Pu concentration, as estimated from the total alpha measurements, the low chemical yields resulting at tnis early time resulted . in 23 . . . . woe Boy concentrations in sone final samples at or below tne limits of detection. After modification of the separation prececdures so that larger samples could be run with better chemical yields, aliquots of these relatively very low 238 Pu concentration sediments, and others previously analyzed, were rerun without the addition of a radiochemical tracer. This provided én accurate means of determining the 233 Pu concentrations in the samples where the 2385 concentration was originally below the detectior limit, | and provided for an additional verification of the 2394240 pu/??8pu ratios measured in samples for which this ratio had previously been determined with a 236 Pu tracer added for yield determinations. The results of these comparisons are shown in Appendix table 4. Inspection of the plutonium raticos obtained from the analysis of spiked and unsnit.ed alisuots of tha same dissolved sediments shows that with the exception of sample lo. C~4, the two ratios obtainea fer each sample agree within a 1 S.D. deviation about the mean, based on counting 1 2385, 2394240), ( Pu Ist aliquot)+ S9+2405, 238 /-~~Pu (2nd aliquot).