Abstract
Radiocarbon (14C) 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 14C activity observed so far in the local environment during the 2011 accident. The abnormally high 14C activity in the late wood of 2011 ring may imply an unknown source of radiocarbon nearby after the accident. The influence of 14C 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.
Highlights
The 2011 Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident resulted in the release of a huge amount of radioactive materials to the atmosphere
Radiocarbon (14C) has been measured in single tree ring samples collected from the southwest of the Fukushima Dai-ichi Nuclear Power Plant
The results of radiocarbon and stable carbon isotope measurements on the samples are listed in Table 1 together with the published data for the 2010–2012 tree-ring samples from OKU [16]
Summary
The 2011 Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident resulted in the release of a huge amount of radioactive materials to the atmosphere. A previous study of 14C released from the Fukushima accident has revealed that the 14C excess was likely distributed along a northwest direction from FDNPP, and declined quickly with increasing distance [14] This pattern is consistent with that of the short half-life radionuclides (131I, 134Cs, etc.) that mainly dispersed north-westwards [6, 15]. The results are expressed as per mil deviations from the Vienna Pee Dee Belemnite (VPDB) standard and have an uncertainty of ±0.1% Another aliquot of CO2 was catalytically reduced to pure graphite by reacting with Zn and Fe. The graphite was pressed into 1 mm internal-diameter aluminium sample holders and loaded into a 5 MV accelerator mass spectrometer (AMS) for 14C/13C measurements [19]. The D14C is expressed as per mil derivations from the primary standard sample (0.7459 times activity of NBS oxalic acid II (SRM-4990C))
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