title: Simultaneous presence of diverse molecular patterns in humic substances in solution.
abstract: The chemical and structural nature of humic substances (HS) is the object of an intense debate in the literature involving two main theoretical positions: the classical view defending the macromolecular pattern, and the new, more recent, view proposing a supramolecular pattern. In this study, we observe that both molecular patterns are present in different whole humic systems in solution. We also identify these molecular patterns with a specific fraction of HS. Thus, the HS family formed by the gray humic acids studied presented a clear macromolecular pattern, whereas the HS family formed by the fulvic acids studied presented the coexistence of supramolecular assemblies and individual molecules. The third HS family studied, the brown humic acids, presented both the macromolecular pattern and the supramolecular pattern. We also find that molecular aggregation-disaggregation has a strong influence in the fluorescence pattern of HS, thus indicating that the current concepts of HS structure derived from fluorescence studies need revision.
authors: R&D-AFI Department, Inabonos-Roullier Group, Polígono Arazuri-Orcoyen, 31160 Orcoyen, Spain.
authors: Roberto
authors: R
authors: Baigorri
authors: Marta
authors: M
authors: Fuentes
authors: Gustavo
authors: G
authors: Gonzalez-Gaitano
authors: Jose Ma
authors: JM
authors: García-Mina
mesh_terms: D019342:Acetic Acid / Q000737:chemistry; D001578:Benzopyrans / Q000032:analysis / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D012996:Solutions; D013050:Spectrometry, Fluorescence; D014462:Ultrafiltration
chemical_list: D001578:Benzopyrans; D006812:Humic Substances; D012996:Solutions; D019342:Acetic Acid; C005023:fulvic acid