18 in” 65 peak. The presence of zn°* is corroborated by the 0.5-mev — peak, Fig. 8 also shows the gamma-ray spectrum of noddy tern guano coilected in this area, The 1.12-mev peak predominates over the 1.17 peak of coe? and the 0.51 peak of gne> is evident. The foliar contribution to the litter contains only es'37 from among the gamma-—emitters. In undisturbed areas Cs 137 and Sr” 90 are being deposited with the litter and are thus replacing at the surface some of the csi37 and sy 7? lost by leaching. There is not sufficient # data from the field work to determine whether there eventually ‘ will be a loss of these radionuclides from the soil-plant system, or a steady state (excluding physical decay of the radionuclides). Long-term experiments, under simulated field conditions, with monolith lysimeters and controlled and uniform addition of the radionuclides would define this point. Young Soil Fig. 9 gives the spectra of the 0 to l-inch, 1 to 2-inch, and 9 to 10-inch increments of a young soil. 20°? , gn®>, cet44. pri44 and Eut35 were detected only in the surface layers, and with increasing depth the 0.60 to 0,66-mev photopeak region of 2 the spectra shifts toward the 0.60-mev peak of spt 5 The spec- trum of the 9 to 10-inch increment is compared with that of an 5b 125 spike in Fig. 10, showing that the photopeaks of the soil and spike gamma spectra are identical. ‘2lo