Dados do Trabalho

Título

CHARACTERIZING THE VIS-NIR SPECTRAL PATTERNS OF PETRIC PLINTHOSOLS REMOTELY SENSED AT TERRESTRIAL AND ORBITAL LEVELS

Resumo

Petric Plinthosols (PT.pt) are soils with a high concentration of petroplinthite, which confers unique properties perceptible via remote sensing. Therefore, we aimed to compare PT.pt spectral patterns obtained by sensors at terrestrial and orbital levels, relating them with the physical-chemical attributes of soils. For that, in the laboratory, we analyzed 32 points of PT.pt occurrence in Central Brazil in June 2022 at the soil fractions finer than 2 mm and at two depths. The Fieldspec Pro spectroradiometer provided hyperspectral soil readings in the 0.35 to 2.5 µm range, which were interpreted and resampled for the 10 Vis-NIR bands of Sentinel-2 (S-2) to compare them visually and statistically with spectra extracted from a synthetic soil image (SySI) from S-2 soils at the sampling sites. The Morphological Interpretation of the Reflectance Spectrum allowed the observation of the average curve of the A horizons. This spectrum exhibited an ascending form from 0.35 to 1.4 µm; flattened between 1.4 and 1.8 µm and descending from 1.8 to 2.5 µm, with reflectance peaks around 3.2. We observed the obliterating action of organic matter, added to the clayey texture, responsible for the low albedo. The predominance of goethite over hematite in the visible range expresses the yellowish-red colors (10YR 6/8). We also observed kaolinite features at 1.4 µm and 2.205 µm; water and hydroxyl groups at 1.4 µm and 1.9 µm and gibbsite at 2.265 µm, characteristic of highly weathered soils. Petroplinthite spectral patterns demonstrated low albedo with absorption peaks at 0.95 µm caused by the high residual concentration of Fe and Al oxyhydroxides. Thus, we illustrate the gradual influence of petroplinthite on the spectral response of PT.pt. Finally, the average spectral patterns of both sensors did not differ statistically, highlighting the potential of spectral data in modeling attributes for digital soil mapping soils, reducing costs, time and waste generation in analyses and surveys.

Palavras-chave

soil spectroscopy; spectral behavior; oxides; ferruginous concretion

Instituição financiadora

The State of São Paulo Research Foundation (FAPESP) #2021/05129-8

Agradecimentos

We thank GeoPed and GeoCiS Research Group for sampling and analyses.