Relating microfeatures of soil organic matter to C stabilisation: optical microscopy, SEM-EDS, abiotic oxidation
Relating microfeatures of soil organic matter to C stabilisation: optical microscopy, SEM-EDS, abiotic oxidation
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DOI：
10.1007/s00374-013-0883-6
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发表时间：
2014-05
影响因子：
6.5
通讯作者：
G. Falsone;Clare Wilson;J. Cloy;Margaret C. Graham;Elenora Bonifacio
中科院分区：
文献类型：
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作者：
G. Falsone;Clare Wilson;J. Cloy;Margaret C. Graham;Elenora Bonifacio
以英国诺森伯兰郡哈伍德森林5种土壤为研究对象，采用光学显微镜、SEM-EDS分析和NaClO氧化法研究了土壤有机质（SOM）微尺度分布特征及其稳定性之间的关系。在所有样品中，通过光学显微镜观察到不同分解阶段的植物器官和无定形有机物。SOM微特征的分布、大小以及与C/N比值的关系表明，无定形特征可能是器官转化的最终产物。SEM-EDS元素分析表明，非晶物质的Si/C、Al/C和Fe/C摩尔比高于器官，这清楚地表明与土壤无机相的相互作用有助于SOM的稳定。土壤孔隙度与水分停滞的耦合似乎影响了Fe-SOM的相互作用，因为更大比例的小持水孔隙（10-50 μm）与更高丰度的富铁无定形有机特征相关。通过氧化证实了无定形特征的较高化学稳定性。NaClO处理后，器官几乎被完全去除，而无定形有机物在形态和化学上受到的影响较小。我们的研究结果表明，在受水影响的土壤中，由孔隙系统定义的局部环境会影响SOM微特征的分布，并且无定形特征的最高抗氧化性可归因于有机-无机协会的形成。建议的组合方法似乎是一个很有前途的手段，调查SOM动态相关功能的稳定性。
We investigated the relationships between microscale distribution of soil organic matter (SOM) features and their stability by combining optical microscopy, SEM-EDS analysis and NaClO oxidation of soil thin sections on five soils from Harwood Forest in Northumberland (UK) differently affected by water stagnation. Plant organs at different stages of decomposition and amorphous organic matter were observed by optical microscopy in all samples. SOM microfeature distribution, size of SOM features and the relation with the C-to-N ratio suggested that amorphous features could be the end-products of organ transformation. SEM-EDS elemental analysis showed that amorphous material had higher Si/C, Al/C and Fe/C molar ratios than organs, clearly pointing to interactions with the soil inorganic phases, which contributed to SOM stabilisation. Soil porosity coupled with water stagnation seemed to affect the Fe–SOM interactions as a greater proportion of small water retention pores (10–50 μm) was associated with higher abundance of Fe-rich amorphous organic features. The higher chemical stability of amorphous features was confirmed by oxidation. After NaClO treatment, organs were almost totally removed, while amorphous organic material was less affected both morphologically and chemically. Our results demonstrate that in water-affected soils local environment defined by the pore system affects the distribution of SOM microfeatures and that the highest resistance to oxidation of the amorphous features is attributable to the formation of organic–inorganic associations. The proposed combined approach seems to be a promising mean to investigate SOM dynamics by relating features to stability.