Impact of Soil Microstructure Geometry on DRIFT Spectra: Comparisons with Beam Trace Modeling
Impact of Soil Microstructure Geometry on DRIFT Spectra: Comparisons with Beam Trace Modeling
复制标题
土壤微结构几何形状对 DRIFT 光谱的影响：与光束轨迹建模的比较
DOI：
10.2136/sssaj2009.0443
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发表时间：
2010
影响因子：
2.9
通讯作者：
H. Gerke
中科院分区：
文献类型：
--
作者：
M. Leue;R. Ellerbrock;D. Bänninger;H. Gerke
已经提出了漫反射模式中的傅里叶变换红外光谱（DRIFT）作为用于表征完整土壤表面处的有机质（OM）组成的工具;然而，完整结构表面的局部性质和几何形状（例如，生物孔隙和裂缝）以未知的方式影响反射。我们的目标是开发一种方法来纠正表面几何效应。其目的是分析（i）颗粒尺寸，（ii）孔隙率，和（iii）特定的表面形状上的红外信号强度的影响，通过比较测量与模拟反射率数据。中红外DRIFT光谱从不同质地的石英样品和石膏块定义的表面形状作为土壤多孔系统的模型。采用光束跟踪模型（BTM）对红外光束在该模型土壤中的传播进行了数值模拟。测量的DRIFT信号强度和模拟的双半球反射率都随着石英颗粒尺寸的增加而降低; DRIFT光谱的分辨率随着颗粒尺寸的增加而降低。微观形貌的几何效应可以通过DRIFT装置的收集镜与样品表面之间的距离的局部变化来解释。颗粒尺寸和表面形貌对信号强度的影响与BTM模拟结果一致。结果表明，辐射传输模型是有用的DRIFT数据在完整的结构表面的解释。对于由小于70 μm的颗粒组成的表面，可以使用DRIFT分析OM属性，并且具有相对较小的，即，< 1-mm，浮雕差异。
Fourier-transformed infrared spectroscopy in diffuse reflectance mode (DRIFT) has been proposed as a tool for the characterization of organic matter (OM) composition at intact soil surfaces; however, the local properties and the geometry of intact structural surfaces (e.g., biopores and cracks) affect the reflection in as yet unknown ways. Our goal was to develop an approach to correct for surface geometry effects. The objectives were to analyze the effects of (i) particle size, (ii) porosity, and (iii) specific surface shapes on the infrared signal intensity by comparing measured with simulated reflectance data. Mid-infrared DRIFT spectra were obtained from differently textured quartz samples and from gypsum blocks with defined surface shapes as models for soil porous systems. A beam tracing model (BTM) was used for the numerical description of the infrared beam propagation in such model soils. The measured DRIFT signal intensity and the simulated bihemispherical reflectance both decreased with increasing quartz particle size; the resolution of the DRIFT spectra decreased with particle size. The geometric effects of the microtopography can be explained by the local variations in the distance between the collection mirror of the DRIFT device and the sample surface. The DRIFT-measured effects of particle size and surface topography on the signal intensity agreed with the BTM simulation results. The results suggest that a radiative transfer model is useful for interpretations of DRIFT data obtained at intact structural surfaces. The OM properties can be analyzed with DRIFT for surfaces that consist of particles <70 μm and have relatively small, i.e., < 1-mm, relief differences.