Abstract
The soil minerals determine essential soil properties such as the cation exchange capacity, texture, structure, and their capacity to form bonds with organic matter. Any alteration of these organo-mineral interactions due to the soil moisture variations needs attention. Visible near-infrared imaging spectroscopy is capable of assessing spectral soil constituents that are responsible for the organo-mineral interactions. In this study, we hypothesized that the alterations of the surface soil mineralogy occur due to the moisture variations. For eight weeks, under laboratory conditions, imaging spectroscopy data were collected on a 72 h basis for three Silty Loam soils varying in the organic matter (no, low and high) placed at the drying-field capacity, field capacity and waterlogging-field capacity treatments. Using the Spectral Information Divergence image classifier, the image area occupied by the Mg-clinochlore, goethite, quartz coated 50% by goethite, hematite dimorphous with maghemite was detected and quantified (percentage). Our results showed these minerals behaved differently, depending on the soil type and soil treatment. While for the soils with organic matter, the mineralogical alterations were evident at the field capacity state, for the one with no organic matter, these changes were insignificant. Using imaging spectroscopy data on the Silty Loam soil, we showed that the surface mineralogy changes over time due to the moisture conditions.
Highlights
The Soil minerals vary extensively in their composition, crystallinity and charge characteristics
Applying the United States Geological Survey (USGS) spectral library, the minerals identified in the VNIR using the Spectral Information Divergence Approach (SID) classifier belong to the phyllosilicate group to chlorite, iron oxide and hydroxide
The SID image classifier derived from the VNIR spectroscopy data was used to monitor the Soil surface mineralogical alterations under laboratory conditions
Summary
The Soil minerals vary extensively in their composition, crystallinity and charge characteristics. They determine essential Soil properties such as the cation exchange capacity (CEC), texture, structure, and their capacity to form bonds with organic matter (OM). The interactions between the mineral particles and the OM in Soil depend on the concentration of these cations [3]. Iron hydroxides such as the goethite, hematite, or maghemite can interact with both the clay minerals and organic compounds to form clay–mineral–organic associations, acting as binding and cementing agents in the soil [4,5]. The amorphous iron oxides, are more effective than the crystalline Fe oxides in stabilizing the soil, due to their large and reactive surface area [6]
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