Impacts of freeze-thaw processes and subsequent runoff on 137Cs washoff from bare land in Fukushima

The deposited 137Cs is one of the long-lived radionuclides, that was released following Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, has been hydrologically transported as particulates in terrestrial environment region. impact freeze-thaw processes and subsequent runoff affecting flux concentration sediment discharge were revealed bare land erosion plot FDNPP accident by detailed monitoring laser scanner measurement on soil surface. We found surface topographic changes due to frost-heaving during winter-spring period, rill formation summer. also evident seasonal concentration; high early spring gradually decreased thereafter, then from frequently occurred autumn when rainfall reached a maximum From these results, higher caused mixture unstable spring, but amount not significant because less event. with lower concentration, which supplied its expansion, wash-offed summer, contributing most In case, heavy occurs caution required concentrations cesium may flow down into river.