Determination of 129I/127I in environmental water before and after the 2011 Fukushima Daiichi nuclear power plant accident with a solid extraction disk

A method that combines solid extraction with accelerator mass spectrometry was applied to determine 129I in terrestrial environmental water samples. To validate the method, water samples were spiked with diluted NIST SRM 3231 129I isotopic standard (high level). Then 129I/127I ratios in river and pond waters in Fukushima and Ibaraki prefectures were measured in samples obtained both before and after the Fukushima Daiichi nuclear power plant accident caused by the great earthquake and tsunami of 11 March 2011. Before the accident, 129I/127I was 1.1–3.5 × 10−9 in the river waters and 6.0–6.6 × 10−9 in the pond waters, and afterwards it was 3.3–8.4 × 10−9 in the river waters and 3.7–6.5 × 10−8 in the pond waters, reflecting the large amounts of radionuclides that were released into the environment by the accident. In the samples collected in April 2011, 129I/127I ratios were about one order of magnitude larger in pond water, and several times higher in river water, compared with the samples collected before the accident.