Radioactive nuclides as tracers of environmental processes

Summary Relatively short-lived radioactive nuclides of cosmogenic origin, such as⁷Be (T_1/2=53.3 d),³²P (14.3 d),³³P (25.3 d),³⁵S (87.4 d) as well as²²Na (2.6 y) have come to be recognized as potential tools to trace environmental processes, such as precipitation, washout (precipitation scavenging), resuspension, atmospheric particle deposition and deposition patterns of airborne contaminants, aerosol deposition and aerosol trapping by above ground vegetation (air-to-vegetation transfer). Of the above radionuclides,⁷Be as well as²¹⁰Pb of terrestrial origin and¹³⁷Cs, a fission product radionuclide, are commonly used for determining the atmospheric particle deposition parameters. It was found that the deposition velocity of⁷Be-associated aerosol particles varied from 0.3 to 0.8 cm^. s^-1(average 0.5 cm^. s^-1), the washout ratio for⁷Be varied from 103 to 375 (average 144), the resuspension factor for the⁷Be-associated particles varied from 1.6^. 10^-4to 4.2^. 10^-4m^-1(average 2.3^. 10^-4m^-1) and the air-to-vegetation transfer rate for⁷Be varied from 5258 to 16180 m^3.kg^-1(average 9856 m^3.kg^-1) for grass, gramineae or poaceae the species. For the¹³⁷Cs-associated aerosol particles the deposition velocity varied from 1.3 to 6.3 cm^. s^-1(average 3.4 cm^. s^-1), the washout ratio for¹³⁷Cs varied from 284 to 3810 (average 1295), the resuspension factor for the¹³⁷Cs-associated aerosol particles varied from 0.1^. 10^-4to 1.2^. 10^-4m^-1(average 0.6^. 10^-4m^-1) and the air-to-vegetation transfer rate for¹³⁷Cs varied from 39638 to 345279 m^3.kg^-1(average 181197 m^3.kg^-1) for grass, gramineae or poaceaethe species.