Local variance of atmospheric 14C concentrations around Fukushima Dai-ichi Nuclear Power Plant from 2010 to 2012

Abstract

Radiocarbon ( 14 C) has been measured in single tree ring samples collected from the southwest of the Fukushima Dai-ichi Nuclear Power Plant. Our data indicate south-westwards dispersion of radiocarbon and the highest 14 C activity observed so far in the local environment during the 2011 accident. The abnormally high 14 C activity in the late wood of 2011 ring may imply an unknown source of radiocarbon nearby after the accident. The influence of 14 C shrank from 30 km during normal reactor operation to 14 km for the accident in the northwest of FDNPP, but remains unclear in the southwest.

Variation of 14C in Japanese Tree Rings Related to the Fukushima Nuclear Accident

“…However, in contrast to shortlived radionuclides, 14 C needs a more complex preparation and measurement procedure and equipment like the accelerator mass spectrometry and liquid scintillation counting or gas proportional counting (Theodórsson 1991). Most of the 14 C tree ring studies examined the area close to FDNPP to the northeast and south (Xu et al 2016a(Xu et al , 2016bChen et al 2017). We have little information about the distribution of 14 C in the area west of the FDNPP.…”

“…We have little information about the distribution of 14 C in the area west of the FDNPP. Map showing the distance between the FDNPP and the sampling site in Koriyama city with locations of tree ring measurements in previous studies, Fukushima prefecture, Japan (based on Xu et al 2015Xu et al , 2016aXu et al , 2016bChen et al 2017).…”

Radiocarbon and radiocesium in litter fall at Kawamata, ~ 45 km NW from the Fukushima Dai-ichi nuclear power plant (Japan)

“…The activity of 14 C was indeed higher in the late wood than in the early wood, while the seasonal transition commonly occurs between mid-June and mid-July [7]. The 14 C activities decreased to background levels at 14 km northwest of the FDNPP in the highly contaminated region while the dispersion pattern of 14 C in the southward direction remained unclear [3][4][5]7]. A small enrichment of 14 C, linked to a 14 C release during the accident, has been noted in the late wood of the 2011 tree-ring from the Iwaki area located at 50 Km south of the FDNPP [3].…”

“…In contrast, the ßemitter 14 C has been understudied after the FDNPP accident [8], although it has provided clues on the dispersion patterns of atmospheric 14 CO2 release from nuclear fuels reprocessing plants in Japanese context [18][19][20] and on the long-term fate of Fukushima-derived 137 Cs in forest soils similar to those found in the Fukushima prefecture from the comparative analyses of bomb-produced 14 C and 137 Cs migration in soils [21]. High 14 C activities were measured from tree ring analyses of a Japanese cedar in the local environment (~2 km far from FDNPP), although revealing a reverse pattern between the early and late wood of year 2011 [4,7]. The activity of 14 C was indeed higher in the late wood than in the early wood, while the seasonal transition commonly occurs between mid-June and mid-July [7].…”

“…High 14 C activities were measured from tree ring analyses of a Japanese cedar in the local environment (~2 km far from FDNPP), although revealing a reverse pattern between the early and late wood of year 2011 [4,7]. The activity of 14 C was indeed higher in the late wood than in the early wood, while the seasonal transition commonly occurs between mid-June and mid-July [7]. The 14 C activities decreased to background levels at 14 km northwest of the FDNPP in the highly contaminated region while the dispersion pattern of 14 C in the southward direction remained unclear [3][4][5]7].…”