Soil weathering behavior assessed by combined spectral ranges: Insights into aggregate analysis

Most research applying spectral sensors has focused on soil attributes quantification, with strong statistics and hundreds of data. Nevertheless, the explanation of the fundamental relationship between several spectral ranges and specific soil processes remains unclear. Soil sensing can be performed in many spectral ranges, however, the focus is usually on a specific one, which limits the knowledge of the phenomenon. Thus, this work investigated the synergistic performance of several spectral ranges (Gamma-ray; X-ray fluorescence, XRF; visible, Vis; near infrared, NIR; shortwave infrared, SWIR; and mid-infrared, MIR) on the weathering process of soils developed from magmatic material. Two soil profiles from Southeast Brazil (Sao Paulo state) were analyzed, assessing their chemical, physical and mineralogical data. The same profiles were analyzed by the indicated spectral ranges, which were related to mineralogy, weathering indices and mass balance (MB). The elements provided by Gamma-ray were related to the soil mineralogy and weathering degree of horizons. The XRF data enabled the calculation of MB and weathering indices, which were similar to those calculated by the traditional analysis. The spectra of the Vis-NIR-SWIR-MIR region presented alterations in their behavior related to the weathering degree of horizons. This synergic approach separated soil horizons by weathering degree more efficiently than a single spectral region. Single spectral measurements identified several elements and indices, which explained the weathering process. These results support further understanding of large datasets and their validation in statistical modeling.

Automated summary

This study investigated the synergistic performance of various spectral ranges on the weathering process of soils developed from magmatic material. It found that a synergic approach using multiple spectral ranges was more efficient in separating soil horizons by weathering degree compared to a single spectral region.