Radiocesium in the Taiwan Strait and the Kuroshio east of Taiwan from 2018 to 2019
Huang, W.-J.; Lee, M.-T.; Huang, K.-C.; Kao, K.-J.; Lee, M.-A.; Yang, Y.J.; Jan, S.; Chen, C.-T.A. (2021). Radiocesium in the Taiwan Strait and the Kuroshio east of Taiwan from 2018 to 2019. NPG Scientific Reports 11(1): 22467. https://dx.doi.org/10.1038/s41598-021-01895-y
In: Scientific Reports (Nature Publishing Group). Nature Publishing Group: London. ISSN 2045-2322; e-ISSN 2045-2322, more
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| Authors | | Top |
- Huang, W.-J.
- Lee, M.-T.
- Huang, K.-C.
- Kao, K.-J.
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- Lee, M.-A.
- Yang, Y.J.
- Jan, S.
- Chen, C.-T.A.
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| Abstract |
The release of anthropogenic radiocesium to the North Pacific Ocean (NPO) has occurred in the past 60 years. Factors controlling 137Cs (half-life, 30.2 year) and 134Cs (half-life, 2.06 year) activity concentrations in the Kuroshio east of Taiwan and the Taiwan Strait (latitude 20° N–27° N, longitude 116° E–123° E) remain unclear. This study collected seawater samples throughout this region and analyzed 134Cs and 137Cs activity concentrations between 2018 and 2019. A principal component analysis (PCA) was performed to analyze the controlling factors of radiocesium. Results of all 134Cs activity concentrations were below the detection limit (0.5 Bq m−3). Analyses of water column 137Cs profiles revealed a primary concentration peak (2.1–2.2 Bq m−3) at a depth range of 200–400 m (potential density σθ: 25.3 to 26.1 kg m−3). The PCA result suggests that this primary peak was related to density layers in the water column. A secondary 137Cs peak (1.90 Bq m−3) was observed in the near-surface waters (σθ = 18.8 to 21.4 kg m−3) and was possibly related to upwelling and river-to-sea mixing on the shelf. In the Taiwan Strait, 137Cs activity concentrations in the near-surface waters were higher in the summer than in the winter. We suggest that upwelling facilitates the vertical transport of 137Cs at the shelf break of the western NPO. |
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