Abstract |
Measurements of Al, Pb, (210)Pb, and (210)Po in precipitation and aerosol were used to estimate wet and dry components of the atmospheric flux at a semiremote site in northern Wisconsin. Wet deposition was primarily responsible for removing airborne Pb, (210)Pb, and (210)Po, while dry deposition was also important for Al. Although Pb and (210)Pb both exhibited a wet/total ratio of about 0.8, precipitation washout ratios for Pb and (210)Pb suggested that (210)Pb was washed from the atmosphere with greater efficiency than was Pb. This phenomenon was also illustrated by comparing the weighted mean annual specific activity in precipitation (976 pCi (210)Pb/mg Pb) and in aerosol (476 pCi (210)Pb/mg Pb) at this site between June 1979 and June 1980. By consideration of the apparent differential precipitation washout of Pb and (210)Pb, a reasonable estimate of the atmospheric flux of Pb was obtained by using the mean Pb/(210)Pb ratio in aerosol and the (210)Pb flux. (Copyright (c) 1983 by the American Geophysical Union.) |