Radioactivity reduction experiment and the subsequent erosion in broadleaf hill forest after Fukushima ⅠNPP accident

Abstract

O horizon removal experiment was performed in broadleaf hill forest which had been extremely contaminated after Fukushima Daiichi Nuclear Power Plant accident. Soil ¹³⁷Cs decreased to 13.7 % and air radiation decreased to 47.7 % in L-F-H horizon removed plot while air radiation dose decreased to 73∼76 % in L-F horizon removed plot. After the removal treatment, 9.65 % of ¹³⁷Cs in forest floor had been washed away in L-F-H horizon removed plot during about 5 month. It was 0.64∼0.69 % in L-F horizon removed plot and 0.08 % in control plot. More than 96 % of these flown 137Cs erosion was trapped with fence at the bottom edge of plots. Concentration of dissolved ¹³⁷Cs which is taken into plants easily was 9.5 Bq/L in control plot, 3.6∼6.5 Bq/L in L-F horizon removed plot and 2.1 Bq/L in whole L-F-H horizon removed plot.