Source and distribution characteristics of 239, 240, 241Pu, 237Np and 134, 137Cs in sediments in the Northwest and Central Equatorial Pacific after the Fukushima nuclear accident

Fenfen Wang; Jian Zheng; Tatsuo Aono; Shaoming Pan; Wu Men

doi:10.1016/j.envpol.2022.119214

Source and distribution characteristics of ^{239, 240, 241}Pu, ²³⁷Np and ^{134, 137}Cs in sediments in the Northwest and Central Equatorial Pacific after the Fukushima nuclear accident

Environ Pollut. 2022 Jul 1:304:119214. doi: 10.1016/j.envpol.2022.119214. Epub 2022 Mar 28.

Authors

Fenfen Wang¹, Jian Zheng², Tatsuo Aono³, Shaoming Pan⁴, Wu Men⁵

Affiliations

¹ The Key Laboratory of Coastal and Island Development of the Ministry of Education, School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing, 210023, China; Department of Radioecology and Fukushima Project, National Institutes for Quantum and Radiological Science and Technology, 491 Anagawa, Inage, Chiba, 263-8555, Japan; The Laboratory of Marine Ecological Environment Early Warning and Monitoring, Third Institute of Oceanography, Ministry of Natural Resources, P.R.C, Xiamen, 361005, China.
² Department of Radioecology and Fukushima Project, National Institutes for Quantum and Radiological Science and Technology, 491 Anagawa, Inage, Chiba, 263-8555, Japan. Electronic address: zheng.jian@qst.go.jp.
³ Department of Radioecology and Fukushima Project, National Institutes for Quantum and Radiological Science and Technology, 491 Anagawa, Inage, Chiba, 263-8555, Japan.
⁴ The Key Laboratory of Coastal and Island Development of the Ministry of Education, School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing, 210023, China.
⁵ The Laboratory of Marine Ecological Environment Early Warning and Monitoring, Third Institute of Oceanography, Ministry of Natural Resources, P.R.C, Xiamen, 361005, China.

PMID: 35358631
DOI: 10.1016/j.envpol.2022.119214

Abstract

To understand the possible influence of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on the deep sea, as well as the geochemical behavior and transport of radionuclides, ¹³⁴Cs, ¹³⁷Cs, ^{239, 240}Pu, ²⁴¹Pu, and ²³⁷Np were measured in the abyssal sediments of the Northwest Pacific (NWP) and Central Equatorial Pacific (CEP) Ocean. Data on the characteristics of these sediments obtained after the FDNPP accident are extremely rare, especially in the NWP subtropical gyre (NPSG) region. FDNPP-derived radio-Cs (¹³⁴Cs, ¹³⁷Cs) arrived at the open sea floor of the NWP before 2018 but was only found in the Kuroshio-Oyashio Extension (KOE) region. No FDNPP-derived Pu was detected in the abyssal sediments of the NWP or CEP. Pu in the NWP mainly originated from global fallout and the Pacific Proving Ground (PPG) close-in fallout, except for at station WP1 (39°N in the KOE region), where an abnormal but non-FDNPP-derived Pu signal was detected. Pu in the eastern CEP sediment was less affected by the PPG close-in fallout from the Marshall Islands and was mainly derived from global fallout, with some close-in fallout from the Johnston Atoll test. The KOE region was the area most affected by PPG close-in fallout Pu via Kuroshio transport, while the lowest inventories of ^239+240Pu and ²³⁷Np were found in the NPSG region due to its oligotrophic environment. The ²³⁷Np originated from the same source as Pu, and the latitudinal pattern of ²³⁷Np was consistent with that of Pu. Station SS (in the marginal sea of the NWP) contained high ²³⁷Np/²³⁹Pu atom ratios in the deeper layers of sediment and had a ²³⁷Np depth profile opposite that of the ^239+240Pu profile, compared to other stations; these differences are mainly attributed to differences in the behaviors of ²³⁷Np and ²³⁹Pu.

Keywords: Behavior; Characteristic; FDNPP accident; Inventory; Source identification.

MeSH terms

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

Substances

Cesium Radioisotopes
Water Pollutants, Radioactive
Cesium-137
Plutonium