Evolution of humic substances in polymerization of polyphenol and amino acid based on non-destructive characterization

• Published in: Frontiers of environmental science & engineering 2021-02, Vol.15 (1), p.5, Article 5
• Main Authors: Zou, Jianmei, Huang, Jianzhi, Zhang, Huichun, Yue, Dongbei
• Format: Article
• Language: English
• Subjects: Amino acids; Earth and Environmental Science; Environment; Evolution; Fulvic acids; Humic acids; Humic substances; Humic substances (HSs); Humification; Manganese dioxide; Measurement methods; Metal oxides; NMR; Nondestructive testing; Nuclear magnetic resonance; Organic matter; Organic soils; Polymerization; Polyphenol; Research Article; Soil organic matter; Spectroscopy; Spectrum analysis; Synergistic effect; Two-dimensional correlation spectroscopy (2D-COS)
• ISSN: 2095-2201; 2095-221X
• DOI: 10.1007/s11783-020-1297-y

* Humification evolution was identified with non-destructive characterization method. * Humification process from precursors to fulvic and humic acid was confirmed. * MnO 2 alone had limited oxidation ability to form HA. * MnO 2 played a key role as a catalyst to transform FA to HA in the presence of O 2. * MnO 2 could affect the structure of the humification products. Abiotic humification is important in the formation and evolution of organic matter in soil and compost maturing processes. However, the roles of metal oxides in abiotic humification reactions under micro-aerobic remain ambiguous. The aim of this study was to use non-destructive measurement methods to investigate the role of MnO 2 in the evolution of humic substances (HSs) during oxidative polymerization of polyphenol-amino acid. Our results suggested a synergistic effect between MnO 2 and O 2 in promoting the polymerization reaction and identified that MnO 2 alone had a limited ability in accelerating the transformation of fulvic acid (FA) to humic acid (HA), whereas O 2 was the key factor in the process. Two-dimensional correlation spectroscopy (2D-COS) showed that the evolution in the UV-vis spectra followed the order of 475-525 nm>300-400 nm>240-280 nm in the humification process, indicating the formation of simple organic matter followed by FA and then HA. 13C nuclear magnetic resonance ( 13C NMR) analysis revealed that the products under both air and N 2 conditions in the presence of MnO 2 had greater amounts of aromatic-C than in the absence of MnO 2, demonstrating that MnO 2 affected the structure of the humification products. The results of this study provided new insights into the theory of abiotic humification.