Characterization of Soil Organic Matter Individual Fractions (Fulvic Acids, Humic Acids, and Humins) by Spectroscopic and Electrochemical Techniques in Agricultural Soils

The objective of this paper was to investigate the molecular characterization soil organic matter fractions (humic substances (HS): fulvic acids-FAs, humic acids-HAs, and humins-HNs), which are most reactive components. A wide spectrum spectroscopic (UV–VIS VIS–nearIR), as well electrochemical (zeta potential, particle size diameter, polydispersity index), methods were applied find relevant differences in behavior, formation, composition, sorption properties HS derived from various soils. Soil material (n = 30) used for study sampled surface layer (0–30 cm) agricultural FAs HAs isolated by sequential extraction alkaline acidic solutions, according International Humic Substances Society method, while HNs determined residue (after extraction) mineral fraction digestion using a 0.1M HCL/0.3M HF mixture DMSO. Our showed that significant structures FAs, Has, occurred. Optical analysis confirmed lower weight with high amount lignin-like compounds higher weighted aliphatic–aromatic structure HAs. characterized very pronounced strong condensed associated highest weight. molecules exhibited an abundance acidic, phenolic, amine functional groups at aromatic ring aliphatic chains, mainly presence methyl, methylene, ethenyl, carboxyl groups. related their structure. ellipsoidal shape being long revealed smaller diameter more spherical caused intermolecular forcing between particles. observed trends directly indicate individual differ properties, reflects binding potential other depending on resulting type. presented averaged characteristics over examined soils different physico-chemical properties.