Residence time of tropospheric aerosols in association with radioactive nuclides

The residence time of atmospheric aerosol particles is a function of various removal processes, such as dry deposition by impaction, diffusion, sedimentation and resuspension as well as wet deposition by rain drops (precipitation scavenging). Estimation of the mean-residence time of atmospheric aerosols could be based on measurements of the activities and ratios of activities of cosmic-ray produced radionuclides, such as 7Be and the radioactive decay products of radon-222 emanated from soil into the atmosphere, such as 210Pb, 210Bi and 210Po. It was found that a mean value of about 8 days could be applied to aerosol particles in the lower atmosphere below precipitation cloud levels as resulted by the application of two different methods, i.e. the 7Be-associated atmospheric aerosols and the radon decay product aerosols at two different locations, i.e. at Thessaloniki, Greece 40°38′N 22°58′E with dry (precipitation free) climate and at Oak Ridge, Tennessee, USA 35°58′N 84°17′W with high precipitation (wet climate), roughly at similar temperate latitudes, but the first one at East longitude and the other at West longitude, respectively.