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 (Aleachable, 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