Aggregated transfer factor of 137Cs in edible wild plants and its time dependence after the Fukushima Dai-ichi nuclear accident

Abstract

We obtained the aggregated transfer factor (Tag) for 10 common edible wild plant species (four perennial spermatophytes, bamboo shoot, two tree species, and three perennial pteridophytes) in northeastern Japan. Measurement of Tag was carried out in 2012–2019 and we also used publicly available data for 2012–2019: food monitoring data and total deposition data from an airborne survey. The Tag obtained from actual measurements agreed well with Tag values calculated from the publicly available data. The sampling locations were only identified at the municipal level and uncertainty of the deposition for the publicly available data, and thus Tag values showed substantial variation. The Tag of the perennial spermatophytes, including bamboo shoot, and perennial pteridophytes showed single exponential decline with effective half-lives of approximately 2 years, whereas those of tree species did not show distinct temporal change. These results imply that data since 2014 are applicable for Tag estimation for long-term potential ingestion dose in the future to the public because of the slow decline. The calculated Tag values of all species for 2014–2019 ranged from 6.1 × 10−5 to 5.2 × 10−3 m2/kg-fresh mass. The maximum Tag value was observed for the tree koshiabura (Chengiopanax sciadophylloides) and the minimum value was observed for the perennial spermatophyte giant butterbur (Petasites japonica). Tree species showed higher Tag than spermatophyte and pteridophyte perennials.

Simple ways to avoid collecting highly137Cs-contaminatedAralia elatabuds

“…The GM and GSD of the Tag for A. elata buds were 3.7 × 10 -4 m 2 /kg and 1.3 for 2022-2023, respectively. The GM and GSD values were smaller than those reported previously for A. elata buds (1.1 × 10 -3 m 2 /kg and 3.1 for 2016-2018 [22] and 4.3 × 10 -4 m 2 /kg and 4.0 for 2014-2019 [21]). The smaller GM value suggests a gradual reduction in the transfer of 137 Cs from the soil to A. elata buds [27].…”

“…In addition, the remarkably smaller GSD value suggests that such a migration may induce a steady-like state of 137 Cs dynamics in the soil, showing the clear positive relationship between the dose rate at the soil surface and 137 Cs activity concentrations in A. elata buds. Although T ag is generally rather variable (and thus often represented with GM and GSD) [8, 21, 22], the positive relationship may become observable under the current soil conditions more than 10 years after the contamination event.…”

Exploring simple ways to avoid collecting highly 137Cs-contaminated Aralia elata buds for the revival of local wild vegetable cultures

“…The GM and GSD values were smaller than those reported previously for A . elata buds (1.1 × 10 −3 m 2 /kg and 3.1 for 2016–2018 [ 22 ] and 4.3 × 10 −4 m 2 /kg and 4.0 for 2014–2019 [ 21 ]). The smaller GM value suggests a gradual reduction in the transfer of 137 Cs from the soil to A .…”

“…elata buds. Although T ag is generally rather variable (and thus often represented with GM and GSD) [ 8 , 21 , 22 ], the positive relationship may become observable under the current soil conditions more than 10 years after the contamination event.…”

“…Estimating the potential internal radiation exposure after consuming contaminated wild vegetables is important for radiation protection [ 20 ]. This is particularly important to improve the quality of life of local people who wish to enjoy collecting and consuming wild vegetables [ 21 ]. In this regard, the aggregated transfer factor (T ag ) is widely used to indicate the relationship between radionuclide concentration in wild vegetables and the soil.…”