Measurements of 7Be and 210Pb in Rain, Snow, and Hail

Abstract

Measurements of the levels of 7Be and 210Pb are reported for rain, snow, and hail samples taken at Argonne, Illinois, and Socorro, New Mexico. 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 7Be is enriched in the precipitation samples with respect to 210Pb, as compared to the ratios of these radioisotopes found in aerosol samples. Use of the 210Po/210Pb activity ratios as an internal clock indicated that the aerosols contributing to the precipitation ranged in age from 10 to 47 days. Levels of 7Be ranged from 11 to 55 pCi L?1 for the samples, with the highest levels in a stratus precipitation event and in a thunderstorm with the lowest wet deposition rate. These results are discussed with regard to the potential for use of these radioisotopes in the determination of stratospheric-tropospheric mixing and in their geochemical usage as indicators of sedimentation rates.