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| Titel |
Change of the Asian dust source region deduced from the composition of anthropogenic radionuclides in surface soil in Mongolia |
| VerfasserIn |
Y. Igarashi, H. Fujiwara, D. Jugder |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 14 ; Nr. 11, no. 14 (2011-07-20), S.7069-7080 |
| Datensatznummer |
250009932
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| Publikation (Nr.) |
 copernicus.org/acp-11-7069-2011.pdf |
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| Zusammenfassung |
| Recent climate change, especially during the 2000s, may be the primary
reason for the expansion of the Asian dust source region. The change in the
dust source region was investigated by examining anthropogenic radionuclides
contained in surface soil samples from Mongolia. Surface soil was globally
labeled by radioactive fallout from nuclear testing during the late 1950s
and early 1960s, but there are no current direct sources for anthropogenic
radionuclides in the air (before the Fukushima nuclear power plant accident
in 2011). Radionuclides in the atmosphere are therefore carried mainly by
wind-blown dust from surface soil, that is, aeolian dust. Asian dust carries
traces of 90Sr, 137Cs, and other anthropogenic radionuclides; the
heaviest deposition occurs in spring and has been recorded in Japan since
the early 1990s. The composition of anthropogenic radionuclides in
atmospheric depositions would be affected by a change in the dust source.
Previous studies of atmospheric deposition at long-term monitoring sites
(e.g. in Tsukuba, Japan) have detected changes in the 137Cs/90Sr
ratio and in the specific activity of the radionuclides. These changes in
the composition of observed atmospheric depositions are supposed to reflect
changes in the climatic conditions of the dust source region. To investigate
this dust source change, we conducted a field survey of radionuclides
(90Sr and 137Cs) in surface soil samples in September 2007 in the
eastern and southern regions of Mongolia, where dust storms have occurred
more frequently since 2000. The specific activities of both radionuclides as
well as the 137Cs/90Sr ratio in the surface soil were well
correlated with annual average precipitation in the Mongolian desert-steppe
zone. Higher specific activities and a higher 137Cs/90Sr ratio
were found in grassland regions that experienced greater precipitation.
These findings suggest that the increased specific activities and the
activity ratio detected in atmospheric depositions in Japan during years
with frequent Asian dust transport events in the 2000s are a sign of
grassland degradation. |
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