Radiocesium in the Taiwan Strait and the Kuroshio east of Taiwan from 2018 to 2019

The release of anthropogenic radiocesium to the North Pacific Ocean (NPO) has occurred in the past 60 years. Factors controlling 137 Cs (half-life, 30.2 year) and 134 Cs (half-life, 2.06 year) activity concentrations in the Kuroshio east of Taiwan and the Taiwan Strait (latitude 20° N–27° N, longitu...

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Bibliographic Details
Published in:Scientific reports 2021-11, Vol.11 (1), p.22467-22467, Article 22467
Main Authors: Huang, Wei-Jen, Lee, Ming-Ta, Huang, Kuei-Chen, Kao, Kai-Jung, Lee, Ming-An, Yang, Yiing-Jang, Jan, Sen, Chen, Chen-Tung Arthur
Format: Article
Language:English
Subjects:
704/829
704/829/827
Anthropogenic factors
Cesium radioisotopes
Chemical analysis
Datasets
Humanities and Social Sciences
multidisciplinary
Nuclear power plants
Oceanography
Principal components analysis
Salinity
Science
Science (multidisciplinary)
Seawater
Straits
Surface water
Upwelling
Water analysis
Water column
Wind
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Summary:The release of anthropogenic radiocesium to the North Pacific Ocean (NPO) has occurred in the past 60 years. Factors controlling 137 Cs (half-life, 30.2 year) and 134 Cs (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 134 Cs and 137 Cs activity concentrations between 2018 and 2019. A principal component analysis (PCA) was performed to analyze the controlling factors of radiocesium. Results of all 134 Cs activity concentrations were below the detection limit (0.5 Bq m −3 ). Analyses of water column 137 Cs profiles revealed a primary concentration peak (2.1–2.2 Bq m −3 ) at a depth range of 200–400 m (potential density σ θ: 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 137 Cs peak (1.90 Bq m −3 ) was observed in the near-surface waters (σ θ  = 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, 137 Cs 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 137 Cs at the shelf break of the western NPO.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-021-01895-y