Equation to predict the 137Cs leaching dynamic from evergreen canopies after a radio-cesium deposit

​Journal of Environmental Radioactivity / Volume 147, pages 100-107, septembre 2015

The Fukushima Daiishi nuclear power plant (FDNPP) accident led to a massive radionuclide deposition mainly onto Japanese forest canopies. In our previous study, an improved double exponential (IDE) equation including rainfall intensity was proposed to estimate the ¹³⁷Cs hydrological transport from evergreen canopies to the ground. This equation used two types of parameters, kinetic (k₁ and k₂) and leachable stock (A₁ and A₂). Those parameters have been estimated by adjusting them in the IDE equation in order to accurately describe the measured cumulative leached ¹³⁷Cs from canopies (k₁ = 4.2E-04–5.0E-04 d⁻¹, k₂ = 1.2E-02–1.7E-02 d⁻¹, A₁ = 62–99 kBq/m², A₂ = 25–61 kBq/m²).

In this study, we linked the total leachable stock (A_leachable, a parameter of the IDE equation corresponding to A₁ + A₂) to a physiological criteria (the canopy closure CC, which can be measured with a simple camera equipped with a fish-eye objective). Furthermore, the kinetic parameters measured for Japanese cedar (k₁ = 5.0E-04 d⁻¹, k₂ = 1.2E-02 d⁻¹, and r₁₂ = 0.22 (r₁₂ = A₁/A₂) could also be used for two other coniferous species: Japanese cypress and spruce. This suggests that these parameters could be constants for coniferous forests.