DRIFT Mapping of Organic Matter Composition at Intact Soil Aggregate Surfaces
DRIFT Mapping of Organic Matter Composition at Intact Soil Aggregate Surfaces
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DOI：
10.2136/vzj2009.0101
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发表时间：
2010-05-01
影响因子：
2.8
通讯作者：
Gerke, Horst H.
中科院分区：
文献类型：
--
作者：
Leue, Martin;Ellerbrock, Ruth H.;Gerke, Horst H.
在结构性土壤中，渗透水和活性溶质与土壤基质的相互作用通常局限于优先流道的外表面。这些土壤团聚体和生物孔的表面大多被有机质（OM）覆盖，有机质最终控制着流动路径的润湿性、吸附性和转移性。然而，由于涂层相对较薄且脆弱，迄今为止，这些表面的局部OM特性在很大程度上是未知的。本研究的目的是确定和比较作为优先流动路径的完整骨料表面土壤OM组成的局部二维分布。漫反射模式下的傅里叶变换红外光谱（漫反射红外傅里叶变换，DRIFT）被应用于确定土壤团聚体样品未受干扰和完整表面上OM官能团数据（即CH/CO比率）的横截面和网格，使用DRIFT作图程序，步骤为1 mm。在蚯蚓洞、根通道和骨料涂层等区域，可以通过DRIFT测绘来区分骨料样品表面。这些结构表面的水滴入渗时间与未包覆裂缝表面的CH/CO比值一致，而与蚯蚓洞的CH/CO比值不一致。结果表明，优先流道表面的涂层在局部OM组成、分布以及润湿性方面存在差异，这表明了水和活性溶质优先运动的未知含义。
In structured soils, interaction of percolating water and reactive solutes with the soil matrix is often restricted to the outer surfaces of the preferential flow paths. Such surfaces of soil aggregates and biopores are mostly covered by organic matter (OM) that finally controls wettability, sorption, and transfer properties of the flow pathways. However, the local OM properties along such surfaces are largely unknown to date because the coatings are relatively thin and vulnerable. The objective of this study was to determine and compare the local two-dimensional distribution of soil OM composition at intact aggregate surfaces that serve as preferential flow paths. The Fourier transformed infrared spectroscopy in diffuse reflectance mode (diffuse reflectance infrared Fourier transform, DRIFT) was applied to determine transects and grids of OM functional group data (i.e., CH/CO ratios) on undisturbed and intact surfaces of soil aggregate samples using a DRIFT mapping procedure in 1-mm steps. The aggregate sample surfaces could be distinguished by DRIFT mapping in areas from earthworm burrows, root channels, and aggregate coatings. The water drop infiltration time of these structural surfaces appeared to correspond with CH/CO ratios for uncoated crack surfaces but less so for earthworm burrows. The results show that coatings at preferential flow-path surfaces differed locally in terms of OM composition, distribution, and possibly also in wettability, indicating yet unknown implications for preferential movement of water and reactive solutes.