Radiocesium concentrations in soil and leaf after decontamination practices in a forest plantation highly polluted by the Fukushima accident

Abstract

Owing to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident a vast amount of radiocesium was released polluting the land. Afterwards, a variety of decontamination practices has been done, reducing the ambient dose rates. In this study we evaluated the effectiveness of eight forest decontamination practices by means of monitoring the radiocesium (Cs) concentration in soil and leaf samples, and the daily discharge rates in ten plots during 27 months (May 2013-July 2015). A forest plantation located 16 km southwest to the FDNPP and within the exclusion area was selected. Radiocesium concentrations were analysed using a germanium gamma ray detector. The differences in radiocesium activities between the different plots were statistically significant (p < 0.05) and four homogeneous groups were distinguished. Tree thinning and litter removal greatly reduced the radioactivity and the two plots devoted to these practices presented the highest discharge rates of Cs (Th + LR; 350-380 Bq/m day), followed by the two Th plots (163-174 Bq/m day). The clearcutting with LR and the LR plots (104 and 92 Bq/m day) also had higher rates than those rates in the control plots (51 Bq/m day). We only observed low rates in the two plots with matting (19-25 Bq/m day). The temporal variability was explained by (i) the different rainfall depths registered during the measurement intervals (accumulated precipitation from 14 to 361 mm); and (ii) the fluctuations of the total surface coverage. The decrease trend in radiocesium concentration was high in 2013, moderate in 2014 and low in 2015 owing to the vegetation recovery after the countermeasures, thus reducing the possibility of the second pollution of the neighbouring areas. The average proportions of contribution of Cs discharge by soil and leaf fraction were 96.6% and 3.4%.

Effectiveness of landscape decontamination following the Fukushima nuclear accident: a review

“…In general, owing to the strong and nearly irreversible bond of radiocesium to fine soil particles, the majority of FDNPPderived 137 Cs is stored within the topsoil (i.e. the top 5 cm) in undisturbed soils (Lepage et al, 2014;Matsuda et al, 2013Matsuda et al, , 2015Takahashi et al, 2015;Mishra et al, 2015). Mishra et al (2015) reported that for these undisturbed soils, the vertical migration of radiocesium down the soil profile was slower in forest soils compared to grassland soils.…”

Strategies and effectiveness of land decontamination in the region affected by radioactive fallout from the Fukushima nuclear accident: A review

“…CC BY 4.0 License. (Lepage et al, 2015;Matsunaga et al, 2013). For example, Lepage et al (2015) illustrated that 90% of the FDNPP derived radiocesium was homogeneous throughout the tilled soil layer in cultivated soils.…”

“…(Lepage et al, 2015;Matsunaga et al, 2013). For example, Lepage et al (2015) illustrated that 90% of the FDNPP derived radiocesium was homogeneous throughout the tilled soil layer in cultivated soils. Endo et al (2013) reported that radiocesium concentrations were not depth dependent in cultivated soils (i.e.…”

Detailed Inspection of γ-ray, Fast and Thermal Neutrons Shielding Competence of Calcium Oxide or Strontium Oxide Comprising Bismuth Borate Glasses

“…exposure, appropriate shielding materials are compulsory. For instance, as a fission product of 235 U, 137 Cs radioactive isotope, which emits high energy β -particles and γ -rays (charge = 0, rest mass = 0), highly contaminates the surrounding environment (water, soil, air) once any nuclear reactor accident occurs (e.g., Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, Japan, 2011) [ 1 ]. In humans, external exposure to 137 Cs (in greater amounts) can cause radiation burns, acute radiation sickness (ARS), coma, and even death, while internal exposure through inhalation/ingestion increases cancer (abnormal growth in cells) risk.…”