Distribution and mean residence time of natural radionuclides in the forest ecosystem

Activity concentrations of radionuclides, Be-7, Pb-210 and Po-210, in preci pitation train, throughfall and stemflow), wood and soil were determined by using gamma-ray and alpha-ray spectrometry to estimate the migration behav ior of these radionuclides in the forest canopy. The activity ratios betwee n output and input precipitations for the forest canopy were 0.53 of Be-7, 0.79 of Pb-210 and 1.5 of Po-210 for Pasania edulis forest. A dynamic model of the transport and fate of radionuclides in the forest ecosystem was con structed. Mean residence times of radionuclides were 56 days for Be-7, 765 days for Pb-210 and 653 days for Po-210 for Pasania edulis forest.