Phytoremediation of radiocesium in different soils using cultivated plants

A huge amount of radionuclides were released into the environment after the Fukushima Daiichi nuclear power plant accident. Radiocesium, which is one of the more prevalent radionuclides, was deposited in the soil. It is well known that radiocesium is adsorbed into the soil and binds strongly to clay. As a result, it is difficult to reduce the contamination level in the soil. We examine the possibility of decontamination by means of phytoremediation. Four species of plants (sunflower, sorghum, amaranth, and buckwheat) were sown in light-colored Andosol and gray lowland soil. When the plants matured, they were harvested and separated into their different parts, i.e., flower, leaf, stem, and root. The removal percentage of ¹³⁷Cs for the aboveground parts, which is defined as the ratio of the total content of ¹³⁷Cs in the aboveground biomass of plants to that in the cultivated soil of 0-15 cm depth, was 0.013-0.93% for the light-colored Andosol and 0.0072-0.038% for the gray lowland soil. The plants exhibiting the highest value cultivated in the light-colored Andosol and gray lowland soil were amaranth (0.093%) and sunflower (0.038%), respectively. This indicates that it is difficult to remove radiocesium from contaminated soil by means of phytoremediation. (author)