The Molecular Composition of Humus Carbon: Recalcitrance and Reactivity in Soils

Piccolo, Alessandro; Spaccini, Riccardo; Δρόσος, Μάριος; Vinci, Giovanni; Cozzolino, Vincenza

doi:10.1016/b978-0-12-811687-6.00004-3

Cited by 42 publications

(46 citation statements)

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“…Among bio-wastes, humic acids (HA) are the alkali-soluble fraction of natural organic matter, consisting in a multitude of heterogeneous organic molecules surviving the biological and chemical degradation of both vegetal and animal biomasses [3,4]. The associations of the amphiphilic HA components are stabilized by weak hydrophobic, hydrogen and metal-bridged electrostatic bonds in supramolecular architectures [5].…”

Section: Introductionmentioning

confidence: 99%

Tuning Functional Behavior of Humic Acids through Interactions with Stöber Silica Nanoparticles

et al. 2020

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Humic acids (HA) exhibit fascinating multifunctional features, yet degradation phenomena as well as poor stability in aqueous environments strongly limit their use. Inorganic nanoparticles are emerging as a powerful interface for the development of robust HA bio-hybrid materials with enhanced chemical stability and tunable properties. Hybrid organic-inorganic SiO 2 /HA nanostructures were synthesized via an in-situ sol-gel route, exploiting both physical entrapment and chemical coupling. The latter was achieved through amide bond formation between carboxyl groups of HA and the amino group of 3-aminopropyltriethoxysilane (APTS), as confirmed by Fourier-Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Monodisperse hybrid nanoparticles about 90 nm in diameter were obtained in both cases, yet Electron Paramagnetic Resonance (EPR) spectroscopy highlighted the different supramolecular organization of HA. The altered HA conformation was reflected in different antioxidant properties of the conjugated nanoparticles that, however, resulted in being higher than for pure HA. Our findings proved the key role of both components in defining the morphology of the final system, as well as the efficacy of the ceramic component in templating the HA supramolecular organization and consequently tuning their functional features, thus defining a green strategy for bio-waste valorization.

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Section: Introductionmentioning

confidence: 99%

Tuning Functional Behavior of Humic Acids through Interactions with Stöber Silica Nanoparticles

et al. 2020

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“…Phenolic coupling with N‐compounds and sugars is an important step in humification (Stevenson, ), which is one of the routes of aromatic C sequestration in SOM. Thus, lichen thalli contain soluble pre‐humic material, which can be leached out into the soil and may undergo further oxidative transformations to HS in biotic and abiotic heterogeneous condensation reactions (Huang & Hardie, ; Piccolo et al, ; Zavarzina, ).…”

Section: Discussionmentioning

confidence: 99%

“…These dark‐coloured aromatic molecules, formed in soil by either secondary synthesis reactions or partial oxidative transformation of organic residues, have for a long time been considered characteristic and recalcitrant components of soil humus (Orlov, ; Stevenson, ). Although this traditional view of SOM is currently criticized (Lehmann & Kleber, ) and new paradigms of SOM have been introduced (Lehmann & Kleber, ; Piccolo, Spaccini, Drosos, Vinci, & Cozzolino, ), existing experimental evidence suggests that the HS concept continues to be relevant to modern theories of SOM formation. In particular, polyphenol‐Maillard reactions catalyzed by soil minerals (Huang & Hardie, ), heterophasic polymerization reactions in the presence of clay‐bound laccase (Zavarzina, ) or oxidative and photo‐oxidative oligomerization reactions in the presence of immobilized biomimetic catalysts (Piccolo et al, ) show the importance of heterogeneous oxidative coupling reactions among phenolic monomers for aromatic carbon (C) sequestration in soils.…”

Section: Introductionmentioning

confidence: 99%

“…Although this traditional view of SOM is currently criticized (Lehmann & Kleber, ) and new paradigms of SOM have been introduced (Lehmann & Kleber, ; Piccolo, Spaccini, Drosos, Vinci, & Cozzolino, ), existing experimental evidence suggests that the HS concept continues to be relevant to modern theories of SOM formation. In particular, polyphenol‐Maillard reactions catalyzed by soil minerals (Huang & Hardie, ), heterophasic polymerization reactions in the presence of clay‐bound laccase (Zavarzina, ) or oxidative and photo‐oxidative oligomerization reactions in the presence of immobilized biomimetic catalysts (Piccolo et al, ) show the importance of heterogeneous oxidative coupling reactions among phenolic monomers for aromatic carbon (C) sequestration in soils. Self‐condensation and co‐polymerization of soluble PCs to soil components might be a quantitatively significant route for HS formation at the pre‐vascular stage in the absence of phenolic polymers (such as lignin) in the starting material (Zavarzina & Zavarzin, ).…”

Section: Introductionmentioning

confidence: 99%

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Water‐soluble phenolic metabolites in lichens and their potential role in soil organic matter formation at the pre‐vascular stage

Заварзина

Nikolaeva

Демин

et al. 2019

European J Soil Science

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Soil organic matter (SOM) is the largest reservoir of organic carbon in the biosphere. However, little is known about the processes of its formation at the pre‐vascular stage. Lichens are among the pioneer colonizers on mineral substrates and are possible early land flora. This study is the first report on the identification and quantification of water‐soluble phenolic compounds (PCs), potential precursors of humic substances, in epigeyic lichens from two systematic groups. Results show (Folin–Denis assay) that cyanobiont‐containing lichens (order Peltigerales) possess three to five times more total soluble PCs than Lecanoralean lichens (Cladonia, Cetraria spp.) and mosses. Soluble PCs in lichens occur in the conjugated form. Alkali‐hydrolysable compounds (esters) predominate over acid‐hydrolysable compounds (glycosides). Phenolic complexes with N‐containing compounds or reducing sugars, or both, have been identified by thin layer chromatography (TLC). Benzoic acid derivatives were most common among PCs, detected in lichens by reversed‐phase high‐pressure liquid chromatography (RP‐HPLC). Phenolic acids occur in the order (μg 100 g−1): p‐hydroxybenzoic acid (327–1,007) > syringic acid (87–361) > salycilic acid (135–210) > vanillic acid (12–19) (Peltigeralean lichens); salicylic acid (53–102) > p‐hydroxybenzoic acid (45–54) > caffeic acid (29) > syringic acid (18) > vanillic acid (9–13) (Lecanoralean lichens). Protocatechuic, caffeic and p‐coumaric acids were rare; ferulic acid was not detected. Syringyl and vanillyl aldehydes and ketones occur in much larger amounts than acids. Methoxy‐substituted and ortho‐substituted phenols, detected in lichens, are known for their high reactivity in soils under lignified vegetation, suggesting their important roles in SOM formation under a cryptogam cover. Highlights Phenolic composition of SOM and humification processes at pre‐vascular stage are largely overlooked Soluble phenolic acids, aldehydes and ketones are quantified in lichens for the first time Lichens are depleted in phenylpropanoids and enriched in syringyl structures and monophenols Lichen‐derived phenolic compounds are potential precursors of humic substances under cryptogam cover

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“…41 A baixa acessibilidade dos microrganismos a determinados componentes da fração orgânica do solo se deve às características químicas da MOS que permitem a exclusão do meio aquoso mediante forças de repulsão hidrofóbicas e interações químicas com óxidos, dificultando assim o acesso microbiano para a decomposição. 42 A capacidade da MO em aumentar a capacidade de troca de cátions e ânions no solo responde à presença de grupamentos ionizáveis de diferente natureza química presentes na estrutura das SH (aryl-OH, alkyl-OH, -NH2, -OH, -COOH, -SH). A presença de um padrão estrutural nas SH do solo independente das características destes, assim como a organização e arranjo destas moléculas em uma supraestrutura húmica estável e termodinamicamente provável, fazem possível despejar as dúvidas sobre a inexistência de uma identidade estrutural húmica no solo, recentemente expostos por grupos de pesquisa que advertem contra a existência de um processo de humificação onde colocam as características estruturais da MO como um aspecto secundário para explicar suas funções, inclusive a estabilidade do carbono orgânico.…”

Section: Padrão Estrutural Das Substâncias Húmicasunclassified

Critical Review About Structure-Property-Functions Relationship for Humic Substances Interactions with Plant Oxidative Metabolism

et al. 2019

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The understanding of humic substances (HS) chemistry in soil science faces new challenges at present. Theories alternative to humification (HS formation process) have been presented to scientific community propagating uncertainty about the existence of these compounds as a structural entity located in the soil. In this review, we aim to show in a compressible manner that HS have a structural pattern independent of its origin, which allows us the characterization by means of techniques common to other groups of compounds ( 13 C NMR CP/MAS). These characteristics (C-aliphatic, Caromatic, carboxyl, carbonyl) allow the obtaining and quantification of HS properties (aromaticity, aliphaticity, hydrophobicity, recalcitrance) that define different functions in the soil (plant bioactivity). The preservation of the structureproperty-function relationship of HS qualifies them as a chemical compounds groups that are formed in the soil and are widely distributed in nature. The relevance of the supramolecularity concept to explain chemical and organizational characteristics of the humic structure, as well as, the use of spectroscopic techniques combined with chemometrics to understand the complex behavior of HS and its various functions is highlighted in this review. ResumoO entendimento da química das substâncias húmicas (SHs) na ciência do solo enfrenta hoje novos desafios. Teorias alternativas à humificação (processo de formação das SH) têm sido apresentadas à comunidade científica gerando questionamentos sobre a existência destes compostos como uma entidade estrutural presente no solo. Esta revisão tem como objetivo mostrar de forma compreensível que as SHs possuem um padrão estrutural independente da fonte de origem, que permite a caracterização por meio de técnicas comuns a outros grupos de compostos ( 13 C NMR CP/MAS). As características que as SHs apresentam (C-alifáticos, C-aromáticos, carboxilas, carbonilas) permitem a obtenção e quantificação de propriedades (aromaticidade, alifaticidade, hidrofobicidade, recalcitrância) que definem as diferentes funções que as mesmas exercem no solo (bioatividade em plantas). A preservação da relação estrutura-propriedade-função das SHs as qualifica como compostos químicos que são formados no solo e que estão amplamente distribuídos na natureza. Destaca-se nesta revisão a importância do conceito de supramolecularidade para explicar as características químicas e organizacionais da estrutura húmica e o uso de técnicas espectroscópicas aliadas à quimiometria para entender o comportamento complexo das SHs e suas diversas funções.Palavras-chave: Ácidos húmicos; espectroscopia; quimiometria; estresse oxidativo.

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The Molecular Composition of Humus Carbon: Recalcitrance and Reactivity in Soils

Cited by 42 publications

References 123 publications

Tuning Functional Behavior of Humic Acids through Interactions with Stöber Silica Nanoparticles

Tuning Functional Behavior of Humic Acids through Interactions with Stöber Silica Nanoparticles

Water‐soluble phenolic metabolites in lichens and their potential role in soil organic matter formation at the pre‐vascular stage

Critical Review About Structure-Property-Functions Relationship for Humic Substances Interactions with Plant Oxidative Metabolism

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