bias in the determination of 261 standard carrier dissolution was used Although the number of samples to process these samples. compared is a relatively small frac- were primarily for 706). and Pu. tion of the total analyzed, it appears Americium-241 was determined in three that the standard vegetation aliquots of (3 g) may underestimate the 239,240), are compared in Table 8. concentrations by 7 percent and the 241 ; Am concentrations by as much as of A to B samples is presented for 16 percent. isotopic concentrations. the samples. Analyses Measurement results The ratio each of the measured atom ratios and Since the compared OQOuoted samples were either litter or roots, statistics are derived from the pro- sample inhomogeneity is the likely pagation of errors. source of these apparent biases. geneity is evidenced by the excellent However, it is also possible that agreement in the 239, 240, and 90... these biases may be indicative of an concentrations from both Bikini and error resulting from surface con- Eneu. tamination of vegetation so that some spread among the individual the results may not be a true data points but are reproducible to measure of the isotopic uptake by within 11 percent at a mean of unity. the plant. This spread is but another example of Results for Sample homo- Alo exhibit the inherent difficulty of minor isotopic measurement by mass spectroSAMPLE HOMOGENEITY metry. MCL received duplicate samples Th e 241 iy comparison, Limited to three points, though also shows from 17 large-volume soil specimens. no significant bias. The question to be answered was these samples indicates that separate whether separate samples from a large aliquots of soil can be expected to specimen of finely divided soil could show reproducible results give reproducible results. the errors presented in Table 8. The Comparison of to within Data Comparison MEASUREMENT OF 244 CONCENTRATION — metry were selected for ALPHA VS GAMMA DETECTION chemistry analysis. 241 wet— In each of the 624 samples of soil, vegetation, and animal tissue, Approximately 13 percent of the through either a positive gamma 624 samples assayed by gamma spectro-~15L | 9010051. tam was quantified