The 129-iodine content of subtropical Pacific waters: impact of Fukushima and other anthropogenic 129-iodine sources
Results obtained from a dedicated radiochemistry cruise approximately 100 days after the 11 March 2011 Tohoku earthquake and subsequent disaster at the Fukushima Daiichi Nuclear Power Plant show that Fukushima derived radionuclides in the nearby ocean environment had penetrated, on average, to &...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-09-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/11/4839/2014/bg-11-4839-2014.pdf |
| Summary: | Results obtained from a dedicated radiochemistry cruise approximately 100 days after
the 11 March 2011 Tohoku earthquake and subsequent disaster at
the Fukushima Daiichi Nuclear Power Plant show that Fukushima derived
radionuclides in the nearby ocean environment had penetrated, on average, to
≤250 m depth (1026.5 kg m<sup>3</sup> potential density surface). The excess
inventory of Fukushima-derived <sup>129</sup>I in the region (∼150 000 km<sup>2</sup>) sampled during the cruise is estimated to have been
between 0.89 and 1.173 billion Bq (∼136 to ∼179 grams) of <sup>129</sup>I. Based on a tight tracer–tracer relation with
<sup>134</sup>Cs (or <sup>137</sup>Cs) and estimates that most of the excess cesium is
due to direct discharge, we infer that much of the excess <sup>129</sup>I is from
direct (non-atmospheric deposition) discharge. After taking into account
oceanic transport, we estimate the direct discharge, i.e., that directly
released into the ocean, off Fukushima to have been ∼1 kg <sup>129</sup>I. Although this small pulse is dwarfed by the ~90 kg
of weapons-testing-derived <sup>129</sup>I that was released into the environment
in the late 1950s and early 1960s, it should be possible to use Fukushima-derived <sup>129</sup>I and other radionuclides (e.g., <sup>134, 137</sup>Cs) to study
transport and entrainment processes along and across the Kuroshio Current. |
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| ISSN: | 1726-4170 1726-4189 |