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Extraneous Carbon Assessments in Radiocarbon Measurements of Black Carbon in Environmental Matrices

Published online by Cambridge University Press:  09 February 2016

Alysha I Coppola*
Affiliation:
Department of Earth System Science, University of California, Irvine, Irvine, California 92697-3100, USA
Lori A Ziolkowski
Affiliation:
Geography and Earth Science, McMaster University, Hamilton ON L8S 2S4, Canada
Ellen R M Druffel
Affiliation:
Department of Earth System Science, University of California, Irvine, Irvine, California 92697-3100, USA
*
2 Corresponding author. Email: acoppola@uci.edu.

Abstract

Extraneous carbon (Cex) added during chemical processing and isolation of black carbon (BC) in environmental matrices was quantified to assess its impact on compound specific radiocarbon analysis (CSRA). Extraneous carbon is added during the multiple steps of BC extraction, such as incomplete removal of solvents, and carbon bleed from the gas chromatographic and cation columns. We use 2 methods to evaluate the size and Δ14C values of Cex in BC in ocean sediments that require additional pretreatment using a cation column with the benzene polycarboxylic acid (BPCA) method. First, the direct method evaluates the size and Δ14C value of Cex directly from the process blank, generated by processing initially empty vials through the entire method identically to the treatment of a sample. Second, the indirect method quantifies Cex as the difference between processed and unprocessed (bulk) Δ14C values in a variety of modern and 14C-free or “dead” BC standards. Considering a suite of hypothetical marine sedimentary samples of various sizes and Δ14C values and BC Ring Trial standards, we compare both methods of corrections and find agreement between samples that are >50 μg C. Because Cex can profoundly influence the measured Δ14C value of compound specific samples, we strongly advocate the use of multiple types of process standards that match the sample size to assess Cex and investigate corrections throughout extensive sample processing.

Information

Type
Oceanic Carbon Cycle
Copyright
Copyright © 2013 by the Arizona Board of Regents on behalf of the University of Arizona 

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