MEASUREMENTS OF BE-7 AND PB-210 IN RAIN, SNOW, AND HAIL

Measurements of the levels of Be-7 and Pb-210 are reported for rain, s now, and hail samples taken at Argonne, Illinois, and Socorro, New Mex ico. These natural radioisotopes are indicators of the sources of the aerosols contributing materials to the precipitation samples. The data presented indicate that the more soluble Be-7 is enriched in the prec ipitation samples with respect to Pb-210, as compared to the ratios of these radioisotopes found in aerosol samples. Use of the Pb-210/Pb-21 0 activity ratios as an internal clock indicated that the aerosols con tributing to the precipitation ranged in age from 10 to 47 days. Level s of Be-7 ranged from 11 to 55 pCi L-1 for the samples, with the highe st levels in a stratus precipitation event and in a thunderstorm with the lowest wet deposition rate. These results are discussed with regar d to the potential for use of these radioisotopes in the determination of stratospheric-tropospheric mixing and in their geochemical usage a s indicators of sedimentation rates.