Anthropogenic Radioactivity in Aerosol

Abstract

Large-scale injection of huge amounts of any pollutant into the atmosphere has health and environmental impacts, but also provides an opportunity for understanding associated bio-geochemical cycles. Radiologically important, long-lived radionuclides emitted by atmospheric nuclear tests, such as 90 Sr, 137 Cs, and plutonium isotopes, are good examples. These radionuclides remain in the biosphere, although dilution and radioactive decay have mitigated their radiation impact, which is at present negligible compared with natural radiation. Nevertheless, the study of their redistribution over the Earth , s surface can enhance understanding of various environmental processes. In this review, available up-to-date information on the source, transport, and deposition of these radionuclides in the atmosphere is collected and these aspects of radionuclides in various global regions are reviewed. In regions adjacent to arid or semi-arid lands, aeolian dust is likely the dominant source of these radionuclides, whereas in northern regions adjacent to contaminated boreal forests, forest res are a more important source, especially of 137 Cs in air. Understanding of the atmospheric processes responsible for the redistribution of these radionuclides can improve forecast models in various environmental research elds. Future tasks include continued long-term monitoring and data integration with global data consistency and data analysis with modern chemical transport models. YASUHITO IGARASHIYasuhito IGARASHI is a Senior Researcher at Atmospheric Environment and Applied M e t e o r o l o g y R e s e a r c h D e p a r t m e n t , Meteorological Research Institute, Japan Meteorological Agency. He obtained his Ph.D. degree in chemistry from University of Tsukuba in 1987. Although he has worked on various research elds so far, radioactivity has constantly been the most important element of his concerns. His current interests are atmospheric aerosols and the precursors, and their possible influences on climate as well as general environmental change, etc.

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

“…It is useful to look at our 129 I deposition results in the context of the deposition of other anthropogenic radioisotopes over the same time period. Figure S3 (Supporting Information) compares the monthly 129 I deposition in Tsukuba in 1986 with 90 Sr and 137 Cs deposition during the same period . On April 26, 1986, the Chernobyl accident released various radionuclides into the atmosphere.…”

“…Atmospheric fallout samples (precipitation containing airborne particulate dust) have been collected monthly by MRI since the 1960s at their different research stations in Japan. , The samples have already been analyzed for radiocesium and radiostrontium within a framework organized by the MRI . In this study, we selected a subset of samples from four different sites: Akita, located on the Japan Sea side; Tsukuba, located between Tokai reprocessing plant (TRP) and Tokyo; Tokyo, located on the Pacific Ocean side; and Ishigaki, a small island west of Okinawa in Japan’s southernmost prefecture (Figure ).…”

Fungal spore involvement in the resuspension of radiocaesium in summer

“…We measured radiocaesium resuspension 6 in the atmosphere at Kawamata and Namie, Fukushima Prefecture, after the accident 7,8 . In this area, which is 30 to 35 km northwest of the FDNPP and surrounded by heavily contaminated forest, as defined above, the effects of the primary emission of radiocaesium from the FDNPP likely ceased in fall 2011 9,10 ; then, from 2012–2015, the radiocaesium activity concentration in the air slowly decreased, although seasonal fluctuations were observed, with increases during the warm season and decreases during the cold season (Supplementary Fig.…”

Rain-induced bioecological resuspension of radiocaesium in a polluted forest in Japan

“…Although the initial primary emission surge from the F1NPP site by the accident decreased circa the fall of 2011 17,18 , radiocaesium has been detected continuously in the atmosphere since 2011. The source of these continuous atmospheric radiocaesium levels is considered to be resuspension (i.e., secondary emissions from polluted surfaces 19 ); notably, the measured radiocaesium concentrations in the range of 10 -1 to 10 -5 Bq m −3 (Supplementary Information Figure S1) have not reached a level with certain health impacts (see Annex in Igarashi et al 13 ). In a typical mountainous village area in Fukushima (see Fig.…”