Differentiating Fukushima and Nagasaki plutonium from global fallout using 241Pu/239Pu atom ratios: Pu vs. Cs uptake and dose to biota

Mathew P Johansen; Donovan Anderson; David Child; Michael A C Hotchkis; Hirofumi Tsukada; Kei Okuda; Thomas G Hinton

doi:10.1016/j.scitotenv.2020.141890

Differentiating Fukushima and Nagasaki plutonium from global fallout using ²⁴¹Pu/²³⁹Pu atom ratios: Pu vs. Cs uptake and dose to biota

Sci Total Environ. 2021 Feb 1:754:141890. doi: 10.1016/j.scitotenv.2020.141890. Epub 2020 Aug 23.

Authors

Mathew P Johansen¹, Donovan Anderson², David Child³, Michael A C Hotchkis³, Hirofumi Tsukada⁴, Kei Okuda⁵, Thomas G Hinton⁶

Affiliations

¹ Australian Nuclear Science and Technology Organisation, Sydney, Australia. Electronic address: mjo@ansto.gov.au.
² Institute of Environmental Radioactivity, Fukushima University, 960-1248, Fukushima Prefecture, Fukushima, Kanayagawa, Japan; Symbiotic Systems Science and Technology, Fukushima University, 960-1248, Fukushima Prefecture, Fukushima, Kanayagawa, Japan.
³ Australian Nuclear Science and Technology Organisation, Sydney, Australia.
⁴ Institute of Environmental Radioactivity, Fukushima University, 960-1248, Fukushima Prefecture, Fukushima, Kanayagawa, Japan.
⁵ Faculty of Human Environmental Studies, Hiroshima Shudo University, 731-3195, Hiroshima Prefecture, Asaminami-ku, Ozuka-higashi, Japan.
⁶ Institute of Environmental Radioactivity, Fukushima University, 960-1248, Fukushima Prefecture, Fukushima, Kanayagawa, Japan; CERAD CoE, Norwegian University of Life sciences, Faculty for Environmental Sciences and Nature Research Management, Aas, Norway.

PMID: 32916482
DOI: 10.1016/j.scitotenv.2020.141890

Abstract

Plutonium (Pu) has been released in Japan by two very different types of nuclear events - the 2011 Fukushima accident and the 1945 detonation of a Pu-core weapon at Nagasaki. Here we report on the use of Accelerator Mass Spectrometry (AMS) methods to distinguish the FDNPP-accident and Nagasaki-detonation Pu from worldwide fallout in soils and biota. The FDNPP-Pu was distinct in local environmental samples through the use of highly sensitive ²⁴¹Pu/²³⁹Pu atom ratios. In contrast, other typically-used Pu measures (²⁴⁰Pu/²³⁹Pu atom ratios, activity concentrations) did not distinguish the FDNPP Pu from background in most 2016 environmental samples. Results indicate the accident contributed new Pu of ~0.4%-2% in the 0-5 cm soils, ~0.3%-3% in earthworms, and ~1%-10% in wild boar near the FDNPP. The uptake of Pu in the boar appears to be relatively uninfluenced by the glassy particle forms of fallout near the FDNPP, whereas the ^134,137Cs uptake appears to be highly influenced. Near Nagasaki, the lasting legacy of Pu is greater with high percentages of Pu sourced from the 1945 detonation (~93% soils, ~88% earthworm, ~96% boar). The Pu at Nagasaki contrasts with that from the FDNPP in having proportionately higher ²³⁹Pu and was distinguished by both ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/²³⁹Pu atom ratios. However, compared with the contamination near the Chernobyl accident site, the Pu amounts at all study sites in Japan are orders of magnitude lower. The dose rates from Pu to organisms in the FDNPP and Nagasaki areas, as well as to human consumers of wild boar meat, have been only slightly elevated above background. Our data demonstrate the greater sensitivity of ²⁴¹Pu/²³⁹Pu atom ratios in tracing Pu from nuclear releases and suggest that the Nagasaki-detonation Pu will be distinguishable in the environment for much longer than the FDNPP-accident Pu.

Keywords: Atom ratios; Boar; Earthworm; Pu isotopes; Radioactive particles.

MeSH terms

Animals
Biota
Cesium Radioisotopes / analysis
Fukushima Nuclear Accident*
Japan
Plutonium* / analysis
Radiation Monitoring*
Radioactive Fallout* / analysis
Swine
Water Pollutants, Radioactive* / analysis

Substances

Cesium Radioisotopes
Radioactive Fallout
Water Pollutants, Radioactive
Plutonium