Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, Japan
The long-lived U isotopes, 233U and 236U, have been used increasingly in recent years as marine circulation tracers and for identifying sources of uranium contamination in the environment. The sedimentation histories of these two U isotopes in combination with natural 238U were reconstructed for an...
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| Format: | Article |
| Language: | English |
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Elsevier
2023-04-01
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| Series: | Heliyon |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2405844023013609 |
| _version_ | 1827957498459455488 |
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| author | Hodaka Takahashi Aya Sakaguchi Karin Hain Andreas Wiederin Michinobu Kuwae Peter Steier Yuichi Takaku Shinya Yamasaki Keisuke Sueki |
| author_facet | Hodaka Takahashi Aya Sakaguchi Karin Hain Andreas Wiederin Michinobu Kuwae Peter Steier Yuichi Takaku Shinya Yamasaki Keisuke Sueki |
| author_sort | Hodaka Takahashi |
| collection | DOAJ |
| description | The long-lived U isotopes, 233U and 236U, have been used increasingly in recent years as marine circulation tracers and for identifying sources of uranium contamination in the environment. The sedimentation histories of these two U isotopes in combination with natural 238U were reconstructed for an anoxic sediment core collected from Beppu Bay, Japan, in the western North Pacific Ocean showing good time resolution (less than 2.6 y/sample). The 233U/236U atom ratio showed a prominent peak of (3.20 ± 0.30) × 10−2 around 1957 which can be attributed to the input from atmospheric nuclear weapons tests including thermonuclear tests conducting in the Equatorial Pacific. The integrated 233U/236U ratio of (1.64 ± 0.08) × 10−2 for the sediment was found to be in relatively good agreement with the representative ratio published for global fallout (∼1.4 × 10−2). A prominent increase in the authigenic ratio of 233U/238Ua,s in the leached fraction (1.39 ± 0.11 × 10−11) and the bulk digestion (1.36 ± 0.10 × 10−11) was also observed around 1957. This reflects the input supply of 233U to the seawater which is known to have a relatively constant 238U content. The authigenic 236U/238Ua,s ratio (0.18 ± 0.02 × 10−9) obtained for 1921 increased from the early 1950's to a maximum of (6.59 ± 0.60) × 10−9 around 1962. The variation in this ratio represents well the introduction history of U into the surface environment without site-specific U contamination and the time profile is also consistent with the 137Cs signature. This work thus provides a benchmark for the long-term use of the isotopic U composition as an input parameter for seawater circulation tracers and as a chronological marker for anoxic sediments and sedimentary rocks. Especially the 233U/236U ratio may serve as a key-marker for the new geological age Anthropocene. |
| first_indexed | 2024-04-09T15:19:55Z |
| format | Article |
| id | doaj.art-f8cb5713e1a24f65b265f6d5b99c8aac |
| institution | Directory Open Access Journal |
| issn | 2405-8440 |
| language | English |
| last_indexed | 2024-04-09T15:19:55Z |
| publishDate | 2023-04-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Heliyon |
| spelling | doaj.art-f8cb5713e1a24f65b265f6d5b99c8aac2023-04-29T14:50:14ZengElsevierHeliyon2405-84402023-04-0194e14153Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, JapanHodaka Takahashi0Aya Sakaguchi1Karin Hain2Andreas Wiederin3Michinobu Kuwae4Peter Steier5Yuichi Takaku6Shinya Yamasaki7Keisuke Sueki8Graduate School of Science and Technology, University of Tsukuba, JapanInstitute of Pure and Applied Sciences, University of Tsukuba, Japan; Corresponding author.University of Vienna, Faculty of Physics, Isotope Physics, AustriaUniversity of Vienna, Faculty of Physics, Isotope Physics, AustriaCenter for Marine Environmental Studies, Ehime University, JapanUniversity of Vienna, Faculty of Physics, Isotope Physics, AustriaInstitute of Pure and Applied Sciences, University of Tsukuba, JapanInstitute of Pure and Applied Sciences, University of Tsukuba, JapanInstitute of Pure and Applied Sciences, University of Tsukuba, JapanThe long-lived U isotopes, 233U and 236U, have been used increasingly in recent years as marine circulation tracers and for identifying sources of uranium contamination in the environment. The sedimentation histories of these two U isotopes in combination with natural 238U were reconstructed for an anoxic sediment core collected from Beppu Bay, Japan, in the western North Pacific Ocean showing good time resolution (less than 2.6 y/sample). The 233U/236U atom ratio showed a prominent peak of (3.20 ± 0.30) × 10−2 around 1957 which can be attributed to the input from atmospheric nuclear weapons tests including thermonuclear tests conducting in the Equatorial Pacific. The integrated 233U/236U ratio of (1.64 ± 0.08) × 10−2 for the sediment was found to be in relatively good agreement with the representative ratio published for global fallout (∼1.4 × 10−2). A prominent increase in the authigenic ratio of 233U/238Ua,s in the leached fraction (1.39 ± 0.11 × 10−11) and the bulk digestion (1.36 ± 0.10 × 10−11) was also observed around 1957. This reflects the input supply of 233U to the seawater which is known to have a relatively constant 238U content. The authigenic 236U/238Ua,s ratio (0.18 ± 0.02 × 10−9) obtained for 1921 increased from the early 1950's to a maximum of (6.59 ± 0.60) × 10−9 around 1962. The variation in this ratio represents well the introduction history of U into the surface environment without site-specific U contamination and the time profile is also consistent with the 137Cs signature. This work thus provides a benchmark for the long-term use of the isotopic U composition as an input parameter for seawater circulation tracers and as a chronological marker for anoxic sediments and sedimentary rocks. Especially the 233U/236U ratio may serve as a key-marker for the new geological age Anthropocene.http://www.sciencedirect.com/science/article/pii/S2405844023013609Anthropogenic uranium (233U and 236U)Beppu Bay (Japan)Northwest Pacific OceanAnthropoceneChronological marker |
| spellingShingle | Hodaka Takahashi Aya Sakaguchi Karin Hain Andreas Wiederin Michinobu Kuwae Peter Steier Yuichi Takaku Shinya Yamasaki Keisuke Sueki Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, Japan Heliyon Anthropogenic uranium (233U and 236U) Beppu Bay (Japan) Northwest Pacific Ocean Anthropocene Chronological marker |
| title | Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, Japan |
| title_full | Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, Japan |
| title_fullStr | Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, Japan |
| title_full_unstemmed | Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, Japan |
| title_short | Reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from Beppu Bay, Japan |
| title_sort | reconstructing the chronology of the natural and anthropogenic uranium isotopic signals in a marine sediment core from beppu bay japan |
| topic | Anthropogenic uranium (233U and 236U) Beppu Bay (Japan) Northwest Pacific Ocean Anthropocene Chronological marker |
| url | http://www.sciencedirect.com/science/article/pii/S2405844023013609 |
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