Radiocesium contaminations of 20 wood species and the corresponding gamma-ray dose rates around the canopies at 5 months after the Fukushima nuclear power plant accident

Abstract

Radiocesium ((134)Cs + (137)Cs) deposition from the Fukushima nuclear power plant accident was measured in 20 woody plants (12 evergreen and 8 deciduous species) grown in Abiko (approximately 200 km SSW from the NPP). Leaves (needles) and twigs were sampled from each of three foliar positions (top, middle, and bottom) in the plant canopy in early August 2011. At the time, soils around the plants were also sampled, and gamma radiation dose rates were measured at each sampling position. The average radiocesium activity in the observed leaves of the evergreen species was 7.7 times that in the leaves of the deciduous species. Among the observed evergreen coniferous species, the activity in pre-fallout-expanded leaves was 2.4 times that in the post-fallout-expanded leaves. Notably, a distinct variation in the activity among the evergreen coniferous species could be observed for the post-fallout-expanded leaves but not for the pre-fallout-expanded leaves. Although these differences depend on whether the leaves had expanded at the time of the fallout, it is probable that a considerable amount of radiocesium was translocated to newly developed leaves at a species-specific rate. In addition, it was demonstrated that dose rates around woody plants were not consistent with the prevailing prediction that general dose rates correspondingly decrease with monitoring height from the ground. Thus, the dose rates in the top foliar layer of the deciduous species decreased more than predicted, whereas those in the top foliar layer of the coniferous species did not decrease. This may be due to differences in the balance between the attenuation resulting from a shielding effect of the plant bodies and the higher radiocesium accumulation in the leaves.

The Use of Moss Pleurozium schreberi (Brid.) Mitt. as Bioindicator of Radionuclide Contamination in Industrial Areas of Upper Silesia

“…It was proven to be a precious mean to evaluate environmental quality and its administration [9][10][11][12].…”

Development of beta ray scanner for imaging foliar uptake of radiocesium

“…After 12 h, the radiocesium had gradually spread through the plant leaf but scarcely spread over the boundary formed by the major vein. The foliar uptake of radiocesium is related to the K requirement [7]. The chemical properties of radiocesium are similar to those of K because Cs and K are in the alkali metal group.…”

“…Radioactive contamination of agricultural products (and wild plants) was reported [6][7][8] shortly after the FDNPP accident. Typical radionuclides such as 134 Cs, 137 Cs, and 131 I were measured using a gamma-ray spectrometer, an imaging plate, or both.…”

Radionuclides Behavior in Fruit Plants

“…They suggested these differences were due to the stage of the vegetative cycle, as flowering would have occurred earlier in coastal regions than in inland elevated areas, resulting in greater transfer [9]. Similarly, the radiocesium activities of the foliar parts of woody species, 5 months after the Fukushima accident, were higher in evergreen species than in deciduous species, because the foliar parts of evergreen species (leaves from previous year) were present at the time of fallout but those of the deciduous species were not [10].…”