Chemical and Spectroscopic Characteristics of Anthrosol (Amazonian Dark Earth) and Surrounding Soil from the Brazilian Amazon Forest: Evaluation of Mineral and Organic Matter Content by Depth

Abstract

The chemical and spectroscopic characteristics of soil organic matter (SOM) isolated from Amazonian dark earth (ADE) and surrounding soil (SR) were evaluated according to the soil depth. The results showed opposite trends for the soils. While ADE featured SOM with a greater aromatic condensation degree and greater hydrophobicity in the top layer, the SR showed more aliphatic and polar SOM. The SOM arrangement from ADE was less hydrophobic, aromatic, and more polar in depth. In contrast, the SOM from SR showed an increase in molecular weight and hydrophobicity. Besides the aromatic protection in the SOM from ADE, there was organo-mineral protection through binding to soil minerals. This suggested that the SOM from ADE was protected by its hydrophobicity and interaction with minerals compared with that from the SR, thereby showing that the combination of both characteristics is important to create new technologies for soil carbon storage.

Assessing extracted organic matter quality from river sediments by elemental and molecular characterization: Application to the Tietê and Piracicaba Rivers (São Paulo, Brazil)

“…C2 resembles humic acids from the soil due to the red-shifted component, which is attributed to a more complex structural arrangement mainly composed of aromatic moieties (Soares da Silva et al, 2020). Furthermore, the shift in the wavelength concerns the aggregation of humic structures in solution; a red-shifted humic structure can show a molecular arrangement with higher molecular aggregation, while a shorter wavelength suggests smaller molecules (Bento et al, 2020;Sokołowska, 2020, 2016). Component 3 (C3) demonstrated two excitation maxima at 250 nm and 315 nm, and an emission maximum at 395 nm.…”