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| Titel |
Temporal change in the size distribution of airborne Radiocesium derived from the Fukushima accident |
| VerfasserIn |
Naoki Kaneyasu, Hideo Ohashi, Fumie Suzuki, Tomoaki Okuda, Fumikazu Ikemori, Naofumi Akata |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250071790
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| Zusammenfassung |
| The accident of Fukushima Dai-ichi nuclear power plant discharged a large amount of
radioactive materials into the environment. After 40 days of the accident, we started to collect
the size-segregated aerosol at Tsukuba City, Japan, located 170 km south of the
plant, by use of a low-pressure cascade impactor. The sampling continued from
April 28, through October 26, 2011. The number of sample sets collected in total
was 8. The radioactivity of 134Cs and 137Cs in aerosols collected at each stage
were determined by gamma-ray with a high sensitivity Germanic detector. After
the gamma-ray spectrometry analysis, the chemical species in the aerosols were
analyzed.
The analyses of first (April 28-May 12) and second (May 12-26) samples showed that the
activity size distributions of 134Cs and 137Cs in aerosols reside mostly in the accumulation
mode size range. These activity size distributions almost overlapped with the mass size
distribution of non-sea-salt sulfate aerosol. From the results, we regarded that sulfate is the
main transport medium of these radionuclides, and re-suspended soil particles that attached
radionuclides were not the major airborne radioactive substances by the end of May, 2011
(Kaneyasu et al., 2012).
We further conducted the successive extraction experiment of radiocesium from the
aerosol deposits on the aluminum sheet substrate (8th stage of the first aerosol sample,
0.5-0.7 μm in aerodynamic diameter) with water and 0.1M HCl. In contrast to the relatively
insoluble property of Chernobyl radionuclides, those in aerosols collected at Tsukuba in fine
mode are completely water-soluble (100%).
From the third aerosol sample, the activity size distributions started to change, i.e.,
the major peak in the accumulation mode size range seen in the first and second
aerosol samples became smaller and an additional peak appeared in the coarse
mode size range. The comparison of the activity size distributions of radiocesium
and the mass size distributions of major aerosol components collected by the end
of August, 2011, (i.e., sample No.5) and its implication will be discussed in the
presentation.
Reference Kaneyasu et al., Environ. Sci. Technol. 46, 5720-5726 (2012). |
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