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    Structural Characterization of Charcoal Exposed to High and Low pH: Implications for 14C Sample Preparation and Charcoal Preservation

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    Author
    Rebollo, N. R.
    Cohen-Ofri, I.
    Popovitz-Biro, R.
    Bar-Yosef, O.
    Meignen, L.
    Goldberg, P.
    Weiner, S.
    Boaretto, E.
    Issue Date
    2008-01-01
    
    Metadata
    Show full item record
    Citation
    Rebollo, N. R., Cohen-Ofri, I., Popovitz-Biro, R., Bar-Yosef, O., Meignen, L., Goldberg, P., ... & Boaretto, E. (2008). Structural characterization of charcoal exposed to high and low pH: Implications for 14C sample preparation and charcoal preservation. Radiocarbon, 50(2), 289-307.
    Publisher
    Department of Geosciences, The University of Arizona
    Journal
    Radiocarbon
    URI
    http://hdl.handle.net/10150/654331
    DOI
    10.1017/S0033822200033592
    Additional Links
    http://radiocarbon.webhost.uits.arizona.edu/
    Abstract
    Chemical and structural similarities between poorly preserved charcoal and its contaminants, as well as low radiocarbon concentrations in old samples, complicate 14C age determinations. Here, we characterize 4 fossil charcoal samples from the late Middle Paleolithic and early Upper Paleolithic strata of Kebara Cave, Israel, with respect to the structural and chemical changes that occur when they are subjected to the acid-base-acid (ABA) treatment. Differential thermal analysis and TEM show that acid treatment disrupts the structure, whereas alkali treatment results in the reformation of molecular aggregates. The major changes are ascribed to the formation of salt bridges at high pH and the disruption of the graphite-like crystallites at low pH. Weight losses during the treatments are consistently greater for older samples, implying that they are less well preserved. Based on the changes observed in vitro due to pH fluctuations, various methods for removing contamination, as well as a mechanism for preferential preservation of charcoal in nature, are proposed.
    Type
    Article
    text
    Language
    en
    ISSN
    0033-8222
    ae974a485f413a2113503eed53cd6c53
    10.1017/S0033822200033592
    Scopus Count
    Collections
    Radiocarbon, Volume 50, Number 2 (2008)

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