Year-round variations in the fluvial transport load of particulate 137Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident

Particulate 137Cs was collected from stream water for 2 years to assess the long-term trend of 137Cs discharge from a forest after the Fukushima Nuclear Power Plant accident. A seasonal increase in the fluvial transport load of particulate 137Cs in suspended solids (SS) was observed in July–October when rainfall was abundant. The 137Cs load was controlled by the SS load. This control was attributed to cesium affinity for phyllosilicate clay minerals as verified by the low extractability of particulate 137Cs. These findings indicate the fluvial particulate 137Cs load is significantly related to the climate and geomorphological features of Japan.