Mass, inverse of mass, uncertainty in inverse of mass, F14C value and uncertainty in F14C value of standard compounds used for 14C blank assessment in compound-specific radiocarbon analysis of lipid biomarkers and lignin phenols

  • Shuwen Sun (Contributor)
  • Vera D. Meyer (Contributor)
  • Andrew M. Dolman (Contributor)
  • Maria Winterfeld (Contributor)
  • Jens Hefter (Contributor)
  • Wolf Dummann (Contributor)
  • Cameron P. McIntyre (Contributor)
  • Daniel B. Montluçon (Contributor)
  • Negar Haghipour (Contributor)
  • Lukas Wacker (Contributor)
  • Torben Gentz (Contributor)
  • Tessa van der Voort (Contributor)
  • Timothy I. Eglinton (Contributor)
  • Gesine Mollenhauer (Contributor)

Dataset

Description

Abstract: Compound-specific radiocarbon dating often requires working with small samples of < 100 µg carbon (µgC). This makes the radiocarbon dates of biomarker compounds very sensitive to biases caused by extraneous carbon of unknown composition, a procedural blank, which is introduced to the samples during the steps necessary to prepare a sample for radiocarbon analysis by accelerator mass spectrometry (i.e., isolating single compounds from a heterogeneous mixture, combustion, gas purification and graphitization). Reporting accurate radiocarbon dates thus requires a correction for the procedural blank. We present our approach to assess the fraction modern carbon (F14C) and the mass of the procedural blanks introduced during the preparation procedures of lipid biomarkers (i.e. n-alkanoic acids) and lignin phenols. We isolated differently sized aliquots (6-151 µgC) of n-alkanoic acids and lignin phenols obtained from standard materials with known F14C values. Each compound class was extracted from two standard materials (one fossil, one modern) and purified using the same procedures as for natural samples of unknown F14C. There was an inverse linear relationship between the measured F14C values of the processed aliquots and their mass, which suggests constant contamination during processing of individual samples. We used Bayesian methods to fit linear regression lines between F14C and 1/mass for the fossil and modern standards. The intersection points of these lines were used to infer F14Cblank and mblank and their associated uncertainties. We estimated 4.88±0.69 μgC of procedural blank with F14C of 0.714±0.077 for n-alkanoic acids, and 0.90±0.23 μgC of procedural blank with F14C of 0.813±0.155 for lignin phenols. These F14Cblank and mblank can be used to correct AMS results of lipid and lignin samples by isotopic mass balance. This method may serve as a standardized procedure for blank assessment in small-scale radiocarbon analysis.

Category: geoscientificInformation

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Datum van beschikbaarheid22-apr-2020
UitgeverUniversity of Groningen

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