Radiocarbon dating of loess-paleosoil is notoriously problematic due to its heterogeneous mix of multiple organic fractions, each of which may have a different radiocarbon age. Thus, the results yielded by 14C dating of total SOM are often inconsistent with the stratigraphic succession: too young, too old, or even reversed. The onerous chemical extractions for TOM (total soil organic matter) fractions do not always produce satisfactory 14C dates. Thus, IEECAS aims at confirming the very fraction that can be applied to decide the real age of loess-paleosoil.
A temperature-stepped-pyrolysis approach is introduced in which pyrolysis-combustion is carried out to partition SOM into pyrolytic volatile (Py-V) and pyrolytic residue (Py-R) fractions at different pyrolytic temperatures. The known age palesoil samples are used to get the appropriate pyrolytic temperature condition at 200℃, 400℃, 600℃, and 800℃. The preliminary results show that the reliable fraction can be obtained from the Py-V at 800℃.
This work has been published on Radiocarbon. (Peng Cheng, Weijian Zhou, Hong Wang, Xuefeng Lu, Hua Du. 14C Dating of Soil Organic Carbon (SOC) In Loess-Paleosol Using Sequential Pyrolysis and Accelerator Mass Spectrometry (AMS), Radiocarbon, Vol 55, No 3–4 (2013), in press.)
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