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| Titel |
Analysis of actinides in an ombrotrophic peat core - evidence of post-depositional migration of fallout radionuclides |
| VerfasserIn |
Francesca Quinto, Erich Hrnecek, Michael Krachler, William Shotyk, Peter Steier, Stephan R. Winkler |
| 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 |
250072813
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| Zusammenfassung |
| Plutonium (239Pu, 240Pu, 241Pu, 242Pu) and uranium (236U, 238U) isotopes were analyzed in
an ombrotrophic peat core from the Black Forest, Germany, representing the last 80 years of
atmospheric deposition. The reliable determination of these isotopes at ultra-trace
levels was possible using ultra-clean laboratory procedures and accelerator mass
spectrometry.
The 240Pu/239Pu isotopic ratios are constant along the core with a mean value of 0.19
±0.02 (NÂ = 32). This result is consistent with the acknowledged average 240Pu/239Pu
isotopic ratio from global fallout in the Northern Hemisphere. The global fallout origin of Pu
is confirmed by the corresponding 241Pu/239Pu (0.0012 ±0.0005) and 242Pu/239Pu
(0.004 ±Â 0.001) isotopic ratios. The identification of the Pu isotopic composition
characteristic for global fallout in peat layers pre-dating the period of atmospheric atom bomb
testing (ADÂ 1956 - AD 1980) is a clear evidence of the migration of Pu downwards the peat
profile.
The maximum of global fallout derived 236U is detected in correspondence to the
age/depth layer of maximum stratospheric fallout (AD 1963). This finding demonstrates that
the 236U bomb peak can be successfully used as an independent chronological marker
complementing the 210Pb dating of peat cores.
The profiles of the global fallout derived 236U and 239Pu are compared with those of
137Cs and 241Am. As typical of ombrothrophic peat, the temporal fallout pattern
of 137Cs is poorly retained. Similarly like for Pu, post-depositional migration of
241Am in peat layers preceding the era of atmospheric nuclear tests is observed. |
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