Modeling Soil Organic Carbon Content Using Mid-Infrared Absorbance Spectra and a Nonnegative MCR-ALS Analysis

• Published in: Soil & Environmental Health 2024-11, p.100123, Article 100123
• Main Authors: Borisover, Mikhail, Lado, Marcos, Levy, Guy J.
• Format: Article
• Language: English
• Subjects: carbon storage capacity; dominating SOM pools; MCR-ALS; mid-IR spectroscopy; physicochemical model; soil health; soil organic matter (SOM); SOM-mineral interactions; the Beer-Lambert law
• ISSN: 2949-9194; 2949-9194
• DOI: 10.1016/j.seh.2024.100123

A new approach based on mid-IR absorbance spectra is proposed for modeling total organic carbon (TOC) content of soils. This approach involves a first-time bilinear decomposition of soil mid-IR absorbance spectra using nonnegative multivariate curve resolution (MCR) with an alternating least squares (ALS) algorithm. An MCR-ALS-derived component signifies a chemically meaningful combination of soil constituents. A new mechanistic model has been developed to link the soil composition, expressed in terms of ratios of MCR-ALS-based concentration scores of the identified components, to soil TOC value. Nonnegative MCR-ALS decomposition, performed for 213 mid-IR absorbance spectra of soil samples collected in the north and south of Israel, yielded four components. Fitting the mechanistic model-derived TOC to the experimental TOC values exhibited a TOC content threshold that affected model performance. TOC content