Iodine-129 concentration in seawater near Fukushima before and after the accident at the Fukushima Daiichi Nuclear Power Plant

[摘要] Anthropogenic radionuclides were released into the environment in largequantities by the Fukushima Daiichi Nuclear Power Plant (1FNPP) accident. Toevaluate accident-derived ¹²⁹I, the ¹²⁹I concentrations inseawater before and after the accident were compared.

Before the accident (2008–2009), the ¹²⁹I concentrations in thewestern margin of the North Pacific between 32° N and 44° Nshowed a latitudinal gradient that was expressed as a linearfunction of latitude. The highest and average ¹²⁹I concentrations afterthe accident were 73 times and approximately 8 times, respectively, higherthan those before the accident in this study area. Considering thedistribution of ¹²⁹I in surface seawater, the accident-derived¹²⁹I in the southern and northern stations of the 1FNPP waspredominantly supplied by seawater advection and atmospheric deposition(including microbial volatilization), respectively.

As of October 2011, depth profiles of ¹²⁹I revealed that ¹²⁹Ioriginating from the 1FNPP existed mainly in the upper 100 m depth. From thedepth profiles, the cumulative inventories of accident-derived ¹²⁹Iwere estimated to be (1.6–9.6) × 10¹² atoms m⁻² in thisstudy area.

On the basis of the ¹²⁹I data in the seawater near Fukushima, theeffective dose of ¹²⁹I from seafood ingestion was much smaller than theannual dose limit.

[学科分类] 地球化学与岩石