Rapid degradation of pyrogenic carbon

Zimmermann, Michael, Bird, Michael I., Wurster, Chrisopher, Saiz, Gustavo, Goodrick, Iain, Barta, Jiri, Capek, Petr, Santruckova, Hana, and Smernik, Ronald (2012) Rapid degradation of pyrogenic carbon. Global Change Biology, 18 (11). pp. 3306-3316.

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Abstract

Pyrogenic carbon (PC- charcoal, biochar or black carbon) represents a poorly understood component of the global carbon (C) cycle, but one that has considerable potential to mitigate climate change through provision of long-term soil C sequestration. Mass balance calculations suggest global PC production and stocks are not in balance, indicating a major gap in our understanding of the processes by which PC is re-mineralized. We collected PC samples derived from the same wood material and exposed to natural environmental conditions for 1 and 11 similar to years. We subjected these materials to repeated laboratory incubation studies at temperatures of up to 60°C, as ground surface temperatures above 30°C and up to 60°C occur regularly over a significant area of the tropics and sub-tropics. Mineralization rates were not different for the two samples and followed an exponential Arrhenius function that suggest an average turnover time of 67 similar to years for conditions typical of a tropical savannah environment. Microbial biomass as measured by chloroform fumigation and DNA extractions was the same for the two samples, but abiotic CO₂ production was lower for the fresh PC sample than that for the aged sample. Nuclear magnetic resonance spectroscopy, hydrogen pyrolysis and scanning electron microscopy demonstrate that the measured CO₂ production originates dominantly from polycyclic aromatic compounds rather than any minor labile components. Therefore, rapid, sub-centennial rates of re-mineralization of PC on the soil surface in tropical and sub-tropical environments may represent a major and hitherto unidentified mechanism for balancing the PC production at the global scale.

Item ID: 23928
Item Type: Article (Research - C1)
ISSN: 1354-1013
Keywords: biochar, carbon sequestration, mineralization, pyrogenic carbon, soil surface temperatures
Date Deposited: 14 Nov 2012 05:33
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0503 Soil Sciences > 050301 Carbon Sequestration Science @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 100%
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