Variability in oxidative degradation of charcoal: influence of production variables and environmental exposure

Ascough, P. , Bird, M.I., Francis, S.M., Thornton, B., Midwood, A., Scott, A.C. and Apperley, D. (2011) Variability in oxidative degradation of charcoal: influence of production variables and environmental exposure. Geochimica et Cosmochimica Acta, 75(9), pp. 2361-2378. (doi:10.1016/j.gca.2011.02.002)

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Abstract

Charcoal is a key component of the Black Carbon (BC) continuum, where BC is characterized as a recalcitrant, fire-derived, polyaromatic material. Charcoal is an important source of palaeoenvironmental data, and of great interest as a potential carbon sink, due to its high apparent environmental stability. However, at least some forms of charcoal are clearly susceptible to environmental alteration and degradation over relatively short timescales. Although these processes have importance for the role of charcoal in global biogeochemistry, they remain poorly understood.

Here we present results of an investigation into the susceptibility of a range of charcoal samples to oxidative degradation in acidified potassium dichromate. The study examines both freshly-produced charcoal, and charcoal exposed to environmental conditions for up to 50,000 years. We compare the proportion of carbon present in different forms between the samples, specifically with respect to the relative chemical resistance of these forms. This was undertaken in order to improve understanding of the post-depositional diagenetic changes affecting charcoal within environmental deposits.

A wide range in chemical compositions are apparent both within and between the sample groups. In freshly-produced charcoal, material produced at 300 °C contains carbon with more labile forms than charcoal produced at ≥400 °C, signifying a key chemical change over the 300–400 °C temperature range. Charcoal exposed to environmental depositional conditions is frequently composed of a highly carboxylated aromatic structure and contains a range of carbon fractions of varying oxidative resistance. These findings suggest that a significant number of the environmental charcoals have undergone post-depositional diagenetic alteration. Further, the data highlight the potential for the use of controlled progressive oxidative degradation as a method to characterize chemical differences between individual charcoal samples.

Item Type:Articles
Additional Information:This is the author’s version of a work that was accepted for publication in Geochimica et Cosmochimica Acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms, may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Geochimica et Cosmochimica Acta, 75, 9, 1 May 2011, 10.1016/j.gca.2011.02.002.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Ascough, Dr Philippa
Authors: Ascough, P., Bird, M.I., Francis, S.M., Thornton, B., Midwood, A., Scott, A.C., and Apperley, D.
Subjects:G Geography. Anthropology. Recreation > GE Environmental Sciences
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Geochimica et Cosmochimica Acta
Publisher:Elsevier
ISSN:0016-7037
ISSN (Online):1872-9533
Published Online:01 January 2011
Copyright Holders:Copyright © 2011 Elsevier
First Published:First published in Geochimica et Cosmochimica Acta 75(9):2361-2378
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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