quarterly isotopic depositions during 1958 and 1959. These contributions are summed to give the total dose that would be delivered if this debris were undisturbed until 1989. These levels are in turn compared with lifetime or 70-year doses and infinity doses. In relation to ionization-chamber measurements of dose rates from cosmic and natural terrestrial sources made by Solon and his associates (27). the Infinite-plane dose rates from fallout in New York City reached as high as 50 percent of total background rates. Suggested correction factors for absorption produced by vertical displacement of fallout activity, Compton scattering of gamma radiation, and partial shielding by topological and architectural structures range from onefifth to one-tenth of the uncorrected calculated doses (3, 5). Even with the maximum correction, however, dose rates for Zr"—Nb”™ fallout alone were between 0.2 and 0.4 microrad per hour for most of the 2-year observation period. Moreover, both the instantaneous and the long-term doses produced by the shorter-lived nuclides were of at least the same order of magnitude as those produced by the long-lived Cs'"-Ba’™ chain. to Discussion As is well known, the use of measured nuctide ratios to study meteorological factors controlling fallout is subject to serious error. In addition, the effects of rapidly changing factors, such as the air mass trajectories and the Ba concentrations which Martell (6) has studied, are largely obscured in monthly sampling. Nevertheless, the calculations for Hardtack Soviet contributions to total New York City are in fair with Martell’s observations England rains, with Gustafson’s Cs'" analyses in Chicago (/), and with Lockhart’s earlier measurements of Sr™ concentrations in air over Washington, D.C. (7). The extension of isotopic data to total fallout is admittedly limited by such unknown factors as fractionation of volatile fission products in the fission process, resuspension of deposited debris, variation of actual yields from theoretical values, and the assignment of single apparent production dates to series of tests. These. difficulties are illustrated by the anomalous Sr*/Sr* ratios shown for -the August and September 1958 samples in Fig. 1! and the uniform + ise s z< Fr JJ r - 3 r a 4 a x - 4 r “NO 1 r a z 2 <= g d cies 10% ' a C 7 £ 1 PF = L = z3 GT Sascotion 4 b — eo OF q F j4 OUT 7 . 3 - 3 OCT ~ re < 4 10 more diffuse fallout from the equa- torial tests as compared with the polar seties appears to be established. Generalization of these findings to future testing 1s limited because the peak depositions of Soviet debris are attributable to seasonal effects as well as to latitudinal considerations. Absolute assay of either factor could only be achieved if one factor were held constant—that is, :f Hardtack and the Soviet series had both occurred near the poles but at different times, or if they had been conducted simultaneously at different latitudes. The significance of the data in terms of radiation dose levels is more clearly discernible. The calculated contributions of the fallout that accumulated on the ground in New York City during 1958 and 1959 to external-gammaradiation dose rates and to long-term doses are illustrated in Fig. 3 and Table 3, respectively. The values are in agreement with the results of gammaradiation spectrometric analyses of soils T od ™~. : 1-0) E E NE i- F\.f = ba Z - ; = 10" ge =“ | = —_ 1 4 — z and for fallout in agreement on New divergence of Ce“/Sr* and Zr" Sr* ratio curves calculated for 1959 from those obtained from theoretical decay constants. Precise knowledge undoubtedly awaits more exhaustive study, but that there is more sustained and q PLL ee - °a @z 01 ° . . 1 -~ €£C L 4 ar) 200 200 4090 500 0.01 1939 DAYS AFTER MEAN DETONATION TIME Fig. 2 (left). Comparison of the arrival patterns in New York City of debris from polar (Soviet) and from equatorial (Hard- tack) test series conducted during 1958. Fig. 3 (right). Calculated infiaite-plane dose rates from cumulative levels of gamma activities measured in fallout in New York City during 1958 and 1959. 56