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Stable isotopic analysis of pyrogenic organic matter in soils by liquid chromatography-isotope-ratio mass spectrometry of benzene polycarboxylic acids


Yarnes, C; Santos, F; Singh, N; Abiven, S; Schmidt, M W I; Bird, J A (2011). Stable isotopic analysis of pyrogenic organic matter in soils by liquid chromatography-isotope-ratio mass spectrometry of benzene polycarboxylic acids. Rapid Communications in Mass Spectrometry, 25(24):3723-3731.

Abstract

Pyrogenic organic matter (PyOM), the incomplete combustion product of organic materials, is considered stable in soils and represents a potentially important terrestrial sink for atmospheric carbon dioxide. One well- established method of measuring PyOM in the environment is as benzene polycarboxylic acids (BPCAs), a compound-speci␣c method, which allows both qualitative and quantitative estimation of PyOM. Until now, stable isotope measurement of PyOM carbon involved measurement of the trimethylsilyl (TMS) or methyl (Me) polycarboxylic acid derivatives by gas chromatography–combustion–isotope ratio mass spectrometry (GC-C-IRMS). However, BPCA derivatives can contain as much as 150% derivative carbon, necessitating post-analysis correction for the accurate measurement of d13 C values, leading to increased measurement error. Here, we describe a method for d13 C isotope ratio measurement and quanti␣cation of BPCAs from soil-derived PyOM, based on ion-exchange chromatography (IEC-IRMS). The reproducibility of the d13 C measurement of individual BPCAs by IEC-IRMS was better than 0.35% (1s). The d13 C-BPCA analysis of PyOM in soils, including at natural and arti␣cially enriched 13 C-abundance, produced accurate and precise d13 C measurements. Analysis of samples that differed in d13 C by as much as 900% revealed carryover of <1% between samples. The weighted sum of individual d13 C-BPCA measurements was correlated with previous isotopic measurements of whole PyOM, providing complementary information for bulk isotopic measurements. We discuss potential applications of d13 C-BPCA measurements, including the study of turn- over rates of PyOM in soils and the partitioning of PyOM sources based on photosynthetic pathways.

Pyrogenic organic matter (PyOM), the incomplete combustion product of organic materials, is considered stable in soils and represents a potentially important terrestrial sink for atmospheric carbon dioxide. One well- established method of measuring PyOM in the environment is as benzene polycarboxylic acids (BPCAs), a compound-speci␣c method, which allows both qualitative and quantitative estimation of PyOM. Until now, stable isotope measurement of PyOM carbon involved measurement of the trimethylsilyl (TMS) or methyl (Me) polycarboxylic acid derivatives by gas chromatography–combustion–isotope ratio mass spectrometry (GC-C-IRMS). However, BPCA derivatives can contain as much as 150% derivative carbon, necessitating post-analysis correction for the accurate measurement of d13 C values, leading to increased measurement error. Here, we describe a method for d13 C isotope ratio measurement and quanti␣cation of BPCAs from soil-derived PyOM, based on ion-exchange chromatography (IEC-IRMS). The reproducibility of the d13 C measurement of individual BPCAs by IEC-IRMS was better than 0.35% (1s). The d13 C-BPCA analysis of PyOM in soils, including at natural and arti␣cially enriched 13 C-abundance, produced accurate and precise d13 C measurements. Analysis of samples that differed in d13 C by as much as 900% revealed carryover of <1% between samples. The weighted sum of individual d13 C-BPCA measurements was correlated with previous isotopic measurements of whole PyOM, providing complementary information for bulk isotopic measurements. We discuss potential applications of d13 C-BPCA measurements, including the study of turn- over rates of PyOM in soils and the partitioning of PyOM sources based on photosynthetic pathways.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Language:English
Date:2011
Deposited On:24 Nov 2011 15:18
Last Modified:05 Apr 2016 15:07
Publisher:Wiley-Blackwell
ISSN:0951-4198
Publisher DOI:10.1002/rcm.5272
Permanent URL: http://doi.org/10.5167/uzh-51251

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