Impact of contamination and pre-treatment on stable carbon and nitrogen isotopic composition of charred plant remains.
Bottom Line: Pre-treatment protocols have been adapted in distinct forms from radiocarbon dating, but insufficient research has been carried out on evaluating their effectiveness and necessity for stable carbon and nitrogen isotope analysis.The results show a ca 1‰ decrease in the δ(15)N values of archaeological charred plant material caused by harsh acid treatments and ultra-sonication.This study fills an important gap in plant stable isotope research that will enable future researchers to evaluate potential sources of isotopic change and pre-treat their samples with methods that have been demonstrated to be effective.
Affiliation: Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford, OX1 3QY, UK.Show MeSH
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Mentions: The FTIR results (Fig.4) show that the presence of carbonates in an archaeological sample causes the appearance of peaks at 720 and 870cm–1 (which increase with higher percentage contamination) and that these peaks are successfully removed by 0.5 M HCl (aq.). The removal of contamination by treatment is confirmed by the δ13C values (Table4): the contaminated samples show progressively less negative values with higher calcite content (–22.5‰, –22.2‰, –16.6‰) and the acid-treated samples have δ13C values within 0.1‰ of the uncontaminated value (treated: –22.9‰ and –23.0‰; uncontaminated: –22.9‰). The FTIR measurements confirm the observation made by Styring et al.: acid treatment causes the COO– peak (at 1400 cm–1) to shift to COOH (at 1650 cm–1).
Affiliation: Research Laboratory for Archaeology and the History of Art, University of Oxford, Dyson Perrins Building, South Parks Road, Oxford, OX1 3QY, UK.