Changes of Chemical Structure and Composition of Charcoal by Radiocarbon Pretreatments

Decontamination by ABA and ABOx Treatments

Bibliographic Data

ID9246181
AuthorsShinji Tomiyama, Masayo Minami (0000-0002-9374-6842), Toshio Nakamura, Koichi Mimura (0000-0001-9195-1861), Hiroyuki Kagi
Year2016
Volume58
Issue3
Pages565-581
Publication date2016-09-01
Open AccessYes
TypeARTICLE
VenueRadiocarbon (JOURNAL)
Journal identifiersISSN: 0033-8222 • E-ISSN: 1945-5755
PublisherCambridge University Press (CUP) (PUBLISHER)
DOI10.1017/rdc.2016.29
OpenAlexW2361781967
LanguageEN
Citations received1
References cited29

Charcoal is widely used for radiocarbon dating in archaeological and paleoenvironmental studies. Reliable 14 C dating requires appropriate chemical treatment to remove postdeposition contamination from the charcoal samples. This study assesses two pretreatments: acid-base-acid (ABA) and acid-base-oxidation with stepped combustion (ABOx-SC). In addition to 14 C, the effects of the treatments on the chemical structure and composition of charcoal were studied using Fourier transform infrared spectroscopy (FTIR) and C/H/O elemental analysis. Samples of pine wood charred in the laboratory at 270, 300, 400, 500, and 600°C, and environmental samples of charred pine wood from pyroclastic flow deposits in southern Kyushu, Japan, were tested. The laboratory-charred samples showed that NaOH treatment removed highly hydrophilic organic components derived from endogenous and exogenous organic materials in the samples and that oxidation treatment caused the oxidative degradation of molecules in samples starting from its edges. The ABA-treated environmental charcoal yielded younger 14 C dates than the ABOx-treated samples, probably owing to the effects of remaining organic contaminants bound to the edges of the aromatic molecular structures produced by the original pyrolysis. Meanwhile, it was found that ABA-SC treatment can reduce contaminants as effectively as ABOx-SC treatment. This implies that the stepped combustion (SC), not the chemical oxidation, is the key to reduce contaminant residue left after ABA and ABOx treatments. The results in this study indicate that the investigation of the structural and compositional changes of charcoal during its pretreatment is useful for assessment of the reliability of the 14 C ages

Charcoal · Chemical composition · Contamination · Pyrolysis · Archaeology and ancient environmental studies · Chemistry · Cultural Heritage Materials Analysis · Pacific and Southeast Asian Studies · Environmental Chemistry · Organic Chemistry

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