Radioactive nuclides as tracers of environmental processes
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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 m3 .kg-1(average 9856 m3 .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 m3 .kg-1(average 181197 m3 .kg-1) for grass, gramineae or poaceaethe species.
KeywordsRadionuclide Transfer Rate Aerosol Particle Fission Product Deposition Velocity
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