A three-dimensional stochastic model of the behavior of radionuclides in forests III. Cs-137 uptake and release by vegetation

Using a three-dimensional stochastic model of radionuclide behavior in forests described in Part I, this work simulates the long-term behavior of Cs-137 in forest vegetation. The stochastic model assumes the behavior of Cs-137 in forest vegetation to follow a Markov process with state transitions driven by the processes and mechanisms affecting radiocesium uptake, translocation, and release. To develop this random walk model, the primary processes and mechanisms driving the uptake, translocation and release by vascular plants, saprophytic fungi, symbiotic fungi, lichen, and moss are described. It is assumed that the driving force behind the uptake of Cs-137 by vegetation is the demand of the plant for potassium (i.e., a biological analogue of radiocesium). The model is then tested using the base line scenario presented in Part I in which Cs-137 is deposited into a coniferous forest ecosystem.