Long-term black carbon dynamics in cultivated soil

来自 EBSCO

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225

作者：

BT Nguyen，J Lehmann，J Kinyangi，R Smernik，Susan J. Riha and Mark H. Engelhard

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摘要：

Black carbon (BC) is a quantitatively important C pool in the global C cycle due to its relative recalcitrance compared with other C pools. However, mechanisms of BC oxidation and accompanying molecular changes are largely unknown. In this study, the long-term dynamics in quality and quantity of BC were investigated in cultivated soil using X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared ( FTIR ) and nuclear magnetic resonance (NMR) techniques. BC particles and changes in BC stocks were obtained from soil collected in fields that were cleared from forest by fire at 8 different times in the past (2, 3, 5, 20, 30, 50, 80 and 100years before sampling) in western Kenya. BC contents rapidly decreased from 12.7 to 3.8mgCg 1 soil during the first 30years following deposition, after which they slowly decreased to a steady state at 3.5mgCg 1 soil. BC-derived C losses from the top 0.1m over 100years were estimated at 6,000kgCha 1 . The initial rapid changes in BC stocks resulted in a mean residence time of only around 8.3years, which was likely a function of both decomposition as well as transport processes. The molecular properties of BC changed more rapidly on surfaces than in the interior of BC particles and more rapidly during the first 30years than during the following 70years. The Oc/C ratios (Oc is O bound to C) and carbonyl groups (C=O) increased over the first 10 and 30years by 133 and 192%, respectively, indicating oxidation was an important process controlling BC quality. Al, Si, polysaccharides, and to a lesser extent Fe were found on BC particle surfaces within the first few years after BC deposition to soil. The protection by physical and chemical stabilization was apparently sufficient to not only minimize decomposition below detection between 30 and 100years after deposition, but also physical export by erosion and vertical transport below 0.1m.

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关键词：

Biochar Black carbon Charcoal FTIR Long term agriculture XPS

DOI：

10.1007/s10533-008-9248-x

被引量：

575

年份：

2009