Remediation of Radiocesium-137 Affected Soil Using Napiergrass Under Different Planting Density and Cutting Frequency Regimes

Abstract

This study investigated the use of napiergrass (Pennisetum purpureum Schum.) to remediate soils highly contaminated with radiocesium-137 (137Cs) in the town of Namie, Fukushima Prefecture, which is located around 9 km northwest of the Fukushima Daiichi Nuclear Power Plant, Japan. Field experiments were performed to investigate the remediation effects using two sites (paddy or upland grassland) as replicates, three planting densities (low, medium, and high density), and two different cutting frequencies (cut once or twice a year) over 2 consecutive years. Napiergrass can be more efficient than sorghum for 137Cs remediation. The maximum 137Cs removal ratio (CR, %) in napiergrass achieved with high-density planting (11 plants m−2) was between 0.32 and 0.57%. However, cutting frequency did not affect the CR. Higher biomass leads to a dilution of 137Cs in cutting frequency. Therefore, we suggest that the greatest CR could be achieved through a high above ground biomass (high-density planting).