Data on atmospheric 129 I concentrations and 129 I/ 137 Cs ratios for suspended air particulate matter dispersed in eastern Japan just after the 2011 nuclear accident in Fukushima, Japan

Data of the atmospheric activity concentrations (in Bq/m 3 ) of 129 I dispersed into the environment as aerosol immediately after the nuclear accident at Fukushima Daiichi Nuclear Power Plant in 2011 are presented. The radioactivity of 129 I was determined in suspended particulate matter (SPM) collected on filter tapes at 41 SPM monitoring sites in Fukushima and other prefectures in eastern Japan including the metropolitan area. For quantitative determination of 129 I in SPM samples by accelerator mass spectrometry (AMS), 129 I was chemically separated. Prior to the 129 I measurement, the 137 Cs activity was determined for the same SPM sample by gamma-ray spectrometry using Ge-semiconductor detectors. Combining activity concentrations of the two nuclides, an activity ratio of 129 I/ 137 Cs (in Bq/Bq) was calculated for each SPM sample. In our research project, atmospheric activity concentrations of 129 I and 137Cs, and their activity ratios were obtained for 920 SPM samples. Scientific dis-cussion related to those data was described in the research article entitled "Time-series variations of atmospheric 129 I concentrations and 129I/137Cs ratios in eastern Japan just af-ter the 2011 nuclear accident in Fukushima, Japan" (Ebi-hara et al. 2022), where 363 data sets were presented. The remaining 557 data sets are presented in this article, so this data article makes up for the original research arti-cle (Ebihara et al. 2022). Blank values were obtained for whole analytical procedure. In addition, those for reagents and filters (both bland-new and used filters) were ana-lyzed for assessing the contribution of the 129 I activity from these samples. Those data also are presented in this article.(c) 2022 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )