Birnessite-Induced Binding of Phenolic Monomers to Soil Humic Substances and Nature of the Bound Residues

Abstract

The nature of the abiotic birnessite (δ-MnO(2))-catalyzed transformation products of phenolic compounds in the presence of soil organic matter is crucial for understanding the fate and stability of ubiquitous phenolic carbon in the environment. (14)C-radioactive and (13)C-stable-isotope tracers were used to study the mineralization and transformation by δ-MnO(2) of two typical humus and lignin phenolic monomers--catechol and p-coumaric acid--in the presence and absence of agricultural and forest soil humic acids (HAs) at pH 5-8. Mineralization decreased with increasing solution pH, and catechol was markedly more mineralized than p-coumaric acid. In the presence of HAs, the mineralization was strongly reduced, and considerable amounts of phenolic residues were bound to the HAs, independent of the solution pH. The HA-bound residues were homogeneously distributed within the humic molecules, and most still contained the unchanged aromatic ring as revealed by (13)C NMR analysis, indicating that the residues were probably bound via ester or ether bonds. The study provides important information on δ-MnO(2) stimulation of phenolic carbon binding to humic substances and the molecular distribution and chemical structure of the bound residues, which is essential for understanding the environmental fates of both naturally occurring and anthropogenic phenolic compounds.

Influence of vegetation on phenolic acid contents in soil

“…Considerable amounts of phenolic residues bound to humic acids still contained the unchanged aromatic ring as revealed by C -13 NMR analysis, indicating that the residues were probably bound via ester or ether bonds (Li et al 2012).…”

Recent advances in allelopathy for weed control: from knowledge to applications

“…Despite recent techniques providing facile analyses and quantification, flavonoids do not seem to show notable properties that make them relevant allelochemicals in recent research. Furthermore, application for weed control implies soil release and related interactions, which may substantially modify phenolic structures by oxidation, reduction, hydrolysis, acetylation and nitration …”

“…Furthermore, application for weed control implies soil release and related interactions, which may substantially modify phenolic structures by oxidation, reduction, hydrolysis, acetylation and nitration. [33][34][35] Furanocoumarins have recently become the most relevant coumarins in allelopathy. These compounds have a furan ring fused to a chromen-2-one ring.…”

Role of ferric oxide in abiotic humification enhancement of organic matter

“…Natural minerals, such as birnessite, allophane and nontronite can enhance abiotic humification of organic matter, which has been validated by numerous studies [8][9][10]. Manganese oxides typically exhibit highly enhancing performance in humification, which can stimulate combination of phenolic carbon to humic-like substances (HLS) [11][12][13][14][15][16]. Moreover, Fe-loaded zeolites as catalysts can also promote humification, and the yield of HLS increases with the addition of Fe into zeolite [17].…”