MEASUREMENTSOF AIRBORNE RADIONUCLIDES 213 of the various radionuclides in these samples to their '*"Cs content are plotted as a function of latitude. It is interesting that these ratios are essentially constant with changing latitude for all the radionuclides except ®8y, ‘sb, and Zr. These three radionuclides have short half- lives compared with the others, and it might be expected that their concentration would decrease with decreasing latitude since the most recent high-yield nuclear shots were made at a high latitude, This is generally true for *Zr—*Nb since it does decrease with decreasing latitude. However, both **y and '4Sb show peak concentrations at about 41 and 63°N, and a definite lack of mixing relative to "Cs. DEPOSITION AND PROPERTIES OF AIRBORNE RADIONUCLIDES It has been pointed out that a definite correlation exists between the air concentrations of radionuclides and the seasonal precipitation rate.'* This correlation appears to exist at our sampling location in Richland, Wash., as shown in Fig, 11. Here the monthly precipitation rate shows the typical inverse relation to the '*Cs content of the air. PTTT TT TTT TrTy ft tttrtttrry dt tr ttt oe | < - z 2% : OS lok — | ES sp — — = g< — V - Us w =y — Zz = = — 1.0 Omo” _ oO — a — = : iN ° : A ea | =~3/ a \8 ° 4 = 2.05 ° \ — a Y ay \/ 0 0 /\ ole “3 \= on — S ound Lib ttupyr pe teppei "EN 505 4 oe 10O- — We, pro _— ¢ > _ 4 \ Lt “ an “\ oo” , \ / * one of PRECIPITATION 97° ‘\ e \‘ oe ‘ / e — q ° 4 \ “4 4 6 = ]) *— ZopLttitiriritit sip tt ire srie tir piri JSFMAMJIJASONDSFMAMJJASONDJFMAMJ JAS 1962 1963 1964 Fig. 11—Comparison of airborne '¥’Cs concentration with annual precipitation.