Natural radionuclides can be useful indicators of aerosol lifetimes and sources. We have performed some preliminary studies examining the interactions of 7Be, 210Pb and its daughters (210Bi and 210Po) with rainwater in laboratory and field efforts in an attempt to evaluate how strongly they are bound to carbonaceous soots. Soot samples were exposed to radionuclides in filtered rainwater with added diesel soot (NIST standard) as a function of pH to evaluate the binding strengths of these species to the soot surfaces. Aging of soot was done by exposure to ozone to examine how “aged” soot behaves with these radionuclides. Field measurements were also performed looking at 7Be in dry air events vs. precipitation events to evaluate washout of the 7Be attached to aerosol species. Simultaneous rainfall characterization was also performed. The results indicate that these species should be useful in evaluating the lifetimes of soots as they are strongly attached to the soot surfaces at most pH levels anticipated in cloud droplets and rainfall. The studies also indicate that the washout of fine aerosols containing 7Be is not a very efficient process as is currently modeled. These results and future plans for further experiments will be discussed in terms of aerosol removal and lifetimes.

One of the authors (Krzeminska-Flowers) wishes to acknowledge the support of The Kosciuszko Foundation, Inc., New York, through a fellowship. This work was supported by the Department of Energy's Atmospheric Science Program.