Spatial variations of ²²⁶Ra, ²²⁸Ra, and ²²⁸Th activities in seawater from the eastern East China Sea Spatial variations of ^<226>Ra, ^<228>Ra, and ^<228>Th activities in seawater from the eastern East China Sea

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Abstract

A total of 74 surface and subsurface water samples at depths shallower than 200 m were collected in the eastern East China Sea (ECS), and spatial and seasonal variations in <sup>226</sup>Ra, <sup>228</sup>Ra, and <sup>228</sup>Th activities were examined by low-background γ-spectrometry. The <sup>228</sup>Ra and <sup>228</sup>Th activities (as well as <sup>228</sup>Ra/<sup>226</sup>Ra and <sup>228</sup>Th/<sup>228</sup>Ra activity ratios) on the surface exhibited notable seasonal and lateral variations (<sup>228</sup>Ra/<sup>226</sup>Ra = 0.2-3.4; <sup>228</sup>Th/<sup>228</sup>Ra = 0.1-0.4). From the <sup>228</sup>Ra activity (0.2-6 mBq/L) and salinity (27.2-34.5), fractions of the Kuroshio, shelf, and Yangtze River waters on the surface of the ECS were estimated to be 50-95%, 3-50%, and 2-8% in July, and 95-100%, 1-5%, and 0-1% in April, respectively, exhibiting a lower fraction of shelf water in winter-spring and on the Japan side of the ECS. While the surface waters had high <sup>228</sup>Th activity (~0.1-0.6 mBq/L) in July, resulting from the high activity of the parent <sup>228</sup>Ra, their <sup>228</sup>Th/<sup>228</sup>Ra ratio (~0.1) was lower compared with that of waters in February-April (0.15-0.35). <sup>228</sup>Th is considered to be preferentially removed from the surface in summer, reflecting a high flux of biogenic particles.

Journal

  • GEOCHEMICAL JOURNAL

    GEOCHEMICAL JOURNAL 46(5), 429-441, 2012-10-01

    GEOCHEMICAL SOCIETY OF JAPAN

References:  31

Codes

  • NII Article ID (NAID)
    10031137505
  • NII NACSIS-CAT ID (NCID)
    AA00654975
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    00167002
  • NDL Article ID
    024025619
  • NDL Call No.
    Z53-R488
  • Data Source
    CJP  NDL  J-STAGE 
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