The chemical composition of measurable soil organic matter pools

被引:143
作者
Poirier, N
Sohi, SP
Gaunt, JL
Mahieu, N
Randall, EW
Powlson, DS
Evershed, RP
机构
[1] Univ Bristol, Sch Chem, Organ Geochem Unit, Bristol Biogeochem Res Ctr, Bristol BS8 1TS, Avon, England
[2] Rothamsted Res, Agr & Environm Div, Harpenden AL5 2JQ, Herts, England
[3] Queen Mary Univ London, Dept Chem, London E1 4NS, England
基金
英国生物技术与生命科学研究理事会;
关键词
D O I
10.1016/j.orggeochem.2005.03.005
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
A range of spectroscopic, `wet' chemical, gas chromatographic (GC) and mass spectrometric (MS) techniques was applied to the characterisation of three soil organic matter (SOM) fractions that have been proposed as the basis. of a new SOM turnover model based on measurable, physically defined fractions. The fractions were: the free light fraction (obtained by density separation in NaI solution at a density of 1.80 g cm(-3), without disruption of aggregates), the intra-aggregate light fraction (obtained using a second density separation after disrupting aggregates using ultrasonic dispersion) and the organomineral fraction corresponding to the residual heavy material. The techniques employed to investigate the composition of the organic constituents of each fraction were: C-13 nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) to study bulk composition. Lipid, lignin and carbohydrate fractions were assessed using GC and GC/MS with appropriate derivatisation, following oxidative and hydrolytic treatments, respectively, in the case of the latter two classes. Proteinaceous components were determined as amino acids using reversed-phase high performance liquid chromatography (HPLC) following 6 M HCl treatment and derivatisation. Each technique revealed marked differences in chemical composition between the organomineral and the two light fractions with the results being consistent with the organomineral fraction having different biological sources or having undergone a greater degree of degradation or transformation. Several techniques detected differences between the composition of the free light fraction and the intra-aggregate light fraction. With the exception of carbohydrate composition, the results were consistent with the order of reactivity previously proposed from incubation studies with isotopically labelled substrates, namely: free > intra-aggregate > organomineral. The investigation illustrates the importance of using a range of different chemical characterisation techniques in studies of complex SOM fractions as each has limitations that could, if used alone, produce ambiguous findings or fail to detect differences between them. (c) 2005 Elsevier Ltd. All rights reserved.
引用
收藏
页码:1174 / 1189
页数:16
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