Atmospheric Fallout of¹²⁹I in Japan before the Fukushima Accident: Regional and Global Contributions (1963–2005)

Abstract

Atmospheric (129)I deposition was studied in different locations of Japan (Akita, Tsukuba, Tokyo, and Ishigaki Island) with samples collected between 1963 and 2005 in order to understand the distribution and sources of this nuclide and provide a reference deposition level prior to the Fukushima accident. Over this time period, the deposition pattern of (129)I in Tsukuba and Tokyo (on the Pacific side) differed from that of Akita (on the Japan Sea side). The primary source of deposition in Tsukuba and Tokyo is related to the (129)I discharge from domestic reprocessing in Tokai-mura. In contrast, the time-series pattern of deposition in Akita seems to have been influenced by (129)I discharges from reprocessing facilities in Europe and the transport of this radionuclide by westerly winds to coastlines of the Japan Sea. The (129)I deposition in Ishigaki (one of the southernmost islands in Japan) is influenced primarily by oceanic air masses (easterly winds), and deposition was 1 order of magnitude lower than that observed in Tsukuba and Tokyo. Cumulative (129)I deposition in Tokyo before the Fukushima accident was estimated at 13 mBq/m(2). The results of this study on deposition contribute to understanding the deposition levels of (129)I prior to the accident.

Atmospheric Iodine (127I and 129I) Record in Spruce Tree Rings in the Northeast Qinghai-Tibet Plateau

“…27 The highest value of 129 I/ 127 I ratios of 20 × 10 -9 was observed in 1976 in both tree rings that matches very well with the date of the fizzled thermonuclear test with a high fission yield of 200 kt of TNT on 26 th Sep. 1976 at Lop Nor, as well as a similar peak in atmospheric fallout in Tokyo. 27 A peak value of 129 I/ 127 I ratios (15. (Fig.…”

“…The observed value in the tree rings of 1961-1962 (average: 9×10 9 ) agrees with the value recorded in atmospheric fallout samples in 1963 from Tokyo (15.5×10 ). 27 This signal was widely detected by peaks of 129 I/ 127 I ratio, 137 Cs and 239,240 Pu activities in north China. 7,44 The 1-2 years lag among these records could be attributed to the hysteresis effect of samples or/and the dating uncertainty (±1 year).…”

“…4a). 27 No 129 I data in atmospheric sample from the study region was reported. Since the 129 I level in atmosphere in the study region (36 ºN) should be similar with that in the same latitude region as Tokyo, the result might indicate that iodine uptake from atmosphere is the dominant way entering into the tree rings compared to that from soil system.…”

129I and its species in the East China Sea: level, distribution, sources and tracing water masses exchange and movement

“…A NFRP at Tokai, Japan is the nearest NFRP to the ECS (about 1500 km northeast), which was operated in 1977–2007. A constant low 129 I level observed in the precipitation collected in 1979–2003 in Ishigaki-shima (24°N, 124°E)31 located in the east edge of the ECS area indicated no significant influence of Tokai NFRP to 129 I level in the ECS. The NFRP in northwest China is far away from the ECS (>5000 km) and the catchment of the rivers (>2000 km) flowing into the ECS.…”

Temporal variation of iodine-129 in rainwater at Tsukuba before and after the Fukushima Daiichi Nuclear Power Plant accident

“…A significant amount of radioactive material was released into the atmosphere and ocean after the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) on March 11, 2011, with atmospheric emissions commencing on March 12 and peaking during March 15-16 and 20-22 (TEPCO, 2012). Anthropogenic sources such as nuclear-fuel reprocessing plants had already increased the 129 I level in the environment above its natural background ( 129 I/ 127 I = 1.5 ¥ 10 -12 ; e.g., Moran et al, 1999;Snyder et al, 2010;Toyama et al, 2013). Environmental effects of radionuclides released by the accident have been assessed by the Japanese Government, various prefectural governments, some research institutes, and universities (e.g., MEXT, 2012;Hirose, 2012).…”