Open AccessDRIFT Mapping of Organic Matter Composition at Intact Soil Aggregate Surfaces
Author(s) -
Leue Martin,
Ellerbrock Ruth H.,
Gerke Horst H.
Publication year - 2010
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2009.0101
Subject(s) - macropore , soil water , infiltration (hvac) , wetting , chemistry , earthworm , organic matter , sorption , mineralogy , soil science , materials science , environmental science , geology , composite material , adsorption , mesoporous material , paleontology , biochemistry , organic chemistry , catalysis
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.