HTO transport and OBT formation after nighttime wet deposition of atmospheric HTO onto land surface

Ota, Masakazu  ; Nagai, Haruyasu  

A simulation study was carried out, to evaluate formation of organically-bound tritium (OBT) after wet deposition of atmospheric HTO onto soil, a process which would be important for an accidental HTO release. To evaluate tritium transfers in atmosphere-vegetation-soil system, we adopted a sophisticated numerical-model SOLVEG-II which calculates diffusion of HTO in atmosphere, diffusion and advection of HTO in soil, and, tritium exchange and OBT assimilation in leaves, in conjunction with transport of heat and water, and CO exchange. Evaporation and condensation between atmospheric HTO and rainwater are newly modeled, to calculate wet deposition of atmospheric HTO. Then a simulation was carried out, assuming an acute release of atmospheric HTO in nighttime at which a rainfall event exists. Successive TFWT variation and OBT formation were calculated, and, importance of wet deposition and re-emission of HTO for the OBT formation was discussed.