Analyzing organic matter composition at intact biopore and crack surfaces by combining DRIFT spectroscopy and Pyrolysis-Field Ionization Mass Spectrometry
Analyzing organic matter composition at intact biopore and crack surfaces by combining DRIFT spectroscopy and Pyrolysis-Field Ionization Mass Spectrometry
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DOI：
10.1002/jpln.201400620
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发表时间：
2016-02-01
影响因子：
2.5
通讯作者：
Leinweber, Peter
中科院分区：
文献类型：
--
作者：
Leue, Martin;Eckhardt, Kai-Uwe;Leinweber, Peter
在淋溶土的粘土-淀积层（Bt）中，相对于土壤基质的大部分，生物孔隙和团聚体的表面可以富集粘土和有机质（OM）。这些涂层的OM组成决定了它们的生物物理化学性质，并与运输和转化过程有关，但在分子尺度上基本上是未知的。本研究的目的是提高光谱的解释傅里叶变换红外光谱在漫反射模式（DRIFT）通过使用热谱图和释放的离子强度与热解场电离质谱（Py-FIMS）获得的mm尺度的空间分布OM组件在完整的结构表面的更详细的分析。样品被分离出的Bt层淋溶土的洞穴壁，裂纹涂层，未涂覆的裂缝，根通道，和针孔填充物。来自Py-FI质谱的信息使得OM官能团也能够从重叠DRIFT信号强度的光谱区域分配到特定的OM化合物类别。特别是，在1，641和1，605 cm（-1）之间的红外波数范围内的C=O和C=C键的谱带与杂环N-化合物、苯甲腈和萘有关。的OM在crossborrow墙壁是由化学不稳定的脂肪族C-丰富的和相当稳定的木质素和烷基芳烃化合物，而厚裂纹涂层和针孔的OM占主导地位的杂环N和腈类和高分子化合物，可能来自燃烧残留物。结合Py-FIMS，DRIFT应用程序完整的样品似乎有希望产生一个更详细的毫米级空间分布的OM相关的吸附和润湿性的裂纹和生物孔表面，可以作为优先的流动路径结构化土壤的性能。
In the clay-illuvial horizons (Bt) of Luvisols, surfaces of biopores and aggregates can be enriched in clay and organic matter (OM) relative to the bulk of the soil matrix. The OM composition of these coatings determines their bio-physico-chemical properties and is relevant for transport and transformation processes but is largely unknown at the molecular scale. The objective of this study was to improve the interpretation of spectra from Fourier transform infrared spectroscopy in diffuse reflectance mode (DRIFT) by using thermograms and released ion intensities obtained with pyrolysis-field ionization mass spectrometry (Py-FIMS) for a more detailed analysis of the mm-scale spatial distribution of OM components at intact structural surfaces. Samples were separated from earthworm burrow walls, crack coatings, uncoated cracks, root channels, and pinhole fillings of the Bt-horizons of Luvisols. The information from Py-FI mass spectra enabled the assignment of OM functional groups also from spectral regions of overlapping DRIFT signal intensities to specific OM compound classes. In particular, bands from C=O and C=C bonds in the infrared range of wave numbers between 1,641 and 1,605 cm(-1) were related to heterocyclic N-compounds, benzonitrile, and naphthalene. The OM at earthworm burrow walls was composed of chemically labile aliphatic C-rich and rather stable lignin and alkylaromatic compounds whereas the OM of thick crack coatings and pinholes was dominated by heterocyclic N and nitriles and high-molecular compounds, likely originating from combustion residues. In combination with Py-FIMS, DRIFT applications to intact samples seem promising for generating a more detailed mm-scale spatial distribution of OM-related sorption and wettability properties of crack and biopore surfaces that may serve as preferential flow paths in structured soils.