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

Abstract

Anthropogenic radionuclides were released into the environment in large quantities by the Fukushima Daiichi Nuclear Power Plant (1FNPP) accident. To evaluate accident-derived ¹²⁹I, the ¹²⁹I concentrations in seawater before and after the accident were compared. <br><br> Before the accident (2008–2009), the ¹²⁹I concentrations in the western margin of the North Pacific between 32&deg; N and 44&deg; N showed a latitudinal gradient that was expressed as a linear function of latitude. The highest and average ¹²⁹I concentrations after the accident were 73 times and approximately 8 times, respectively, higher than those before the accident in this study area. Considering the distribution of ¹²⁹I in surface seawater, the accident-derived ¹²⁹I in the southern and northern stations of the 1FNPP was predominantly supplied by seawater advection and atmospheric deposition (including microbial volatilization), respectively. <br><br> As of October 2011, depth profiles of ¹²⁹I revealed that ¹²⁹I originating from the 1FNPP existed mainly in the upper 100 m depth. From the depth profiles, the cumulative inventories of accident-derived ¹²⁹I were estimated to be (1.6–9.6) × 10¹² atoms m⁻² in this study area. <br><br> On the basis of the ¹²⁹I data in the seawater near Fukushima, the effective dose of ¹²⁹I from seafood ingestion was much smaller than the annual dose limit

The 129-Iodine content of subtropical Pacific waters: impact of Fukushima and other anthropogenic &lt;sup&gt;129&lt;/sup&gt;I sources

“…We compare our results with data from the IAEA-97 radiochemistry cruise (Povinec et al, 2003) and individual profiles to the northeast of Japan (Suzuki et al, 2010(Suzuki et al, , 2013. One of the IAEA-97 stations is from within the climatological mean of the Kuroshio near the northwest edge of the North Pacific subtropical gyre (NPSG), one station from just within the western NPSG, and two near the Marshall Islands from within the North Equatorial Current.…”

“…Vectors are mean monthly sea surface currents (http://www.oscar.noaa.gov/). Stations plotted include the pre/post-Fukushima stations presented in Suzuki et al (2013) and the profiles from the IAEA-97 cruise (Povinec et al, 2000(Povinec et al, , 2010. The pre-event profiles are demarked.…”

“…One of the IAEA-97 stations is from within the climatological mean of the Kuroshio near the northwest edge of the North Pacific subtropical gyre (NPSG), one station from just within the western NPSG, and two near the Marshall Islands from within the North Equatorial Current. The pre-Fukushima profiles of Suzuki et al (2010Suzuki et al ( , 2013 include a subarctic site (OS8) and several within the confluence zone, where seasonally to interannually the site may be more or less influenced by subtropical surface water versus subarctic (Fig. 3).…”

An approach for measuring the 129I/127I ratio in fish samples

“…This anthropogenic 129 I, released into the sea directly or indirectly (transported by the atmosphere), has dramatically increased the concentration of 129 I in surface seawater. In particular, the concentration has risen to 10 10 atoms/L in the Irish Sea and the North Sea owing to the direct discharge of 129 I from nearby nuclear reprocessing plants, Sellafield and La Hague [1,2], while in the far field such as the Pacific and Indian Oceans, the rise had been rather mild, up to 10 6 -10 7 atoms/L [3][4][5]. In the Pacific Ocean, 129 I and several anthropogenic nuclides are known to transfer from the atmosphere and slowly diffuse into deeper layers such that there is a steep gradient of the concentration [see, e.g.…”

“…In this study the "carrier method" was adopted to overcome this difficulty. This method has been successfully employed for a minimal amount of solid and liquid samples [4,9,10]. The iodine carrier increases the total iodine amount so that it can be treated easily.…”