Humic Substances: Considerations of Compositions, Aspects of Structure, and Environmental Influences

Hayes, M.H.B.; Clapp, C. E.

doi:10.1097/00010694-200111000-00002

Cited by 198 publications

(126 citation statements)

References 38 publications

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“…With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indicative of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic substances in the sorption of environmental pollutants.Keywords: atomic force microscopy (AFM), dissolved humic substances, morphology, aggregation, adsorption.Humic substances (HS) are a category of naturally occurring, biogenic, heterogeneous organic materials found in or extracted from soils, sediments, and natural waters that can generally be characterized as being yellow-to-black in color, of highly variable relative molecular masses, and refractory [1,2] . Derived from a variety of organic precursors (plant biopolymers such as lignin etc.…”

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confidence: 99%

“…Humic substances (HS) are a category of naturally occurring, biogenic, heterogeneous organic materials found in or extracted from soils, sediments, and natural waters that can generally be characterized as being yellow-to-black in color, of highly variable relative molecular masses, and refractory [1,2] . Derived from a variety of organic precursors (plant biopolymers such as lignin etc.…”

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confidence: 99%

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AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Zhou

Lü

et al. 2006

SCI CHINA SER B

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Humic substances constitute the major organic fractions of soils, sediments and natural waters, and play a dominant role in the binding, mobilization, transport and ultimate fate of organic contaminants in subsurface systems. In this paper, two humic acid samples, Guanting and Tianjin, with different origin and chemical compositions have been investigated with AFM imaging for their adsorption and aggregation behaviors on mica. While the Tianjin humic sample is found to form small spheres with 250 to 330 nm in diameter at lower concentrations, irregular loop-chain assemblies of hundreds of nanometer in diameter with the chain width of about 40 nm are dominant for the Guanting humic sample, which may attribute to the more polar aliphatic fractions in the chemical composition in the latter. The heterogeneous and polydisperse nature of humic substances with multiple structural features, such as sponge-like structures, perforated sheets, aggregate of spheres, branches and chain-like assemblies etc., is apparent at higher concentrations for both humic samples, showing morphologically new evidence for the dominant view of the humic dual-mode sorption model. With naphthalene introduced, the assemblies of Guanting humic substances clearly become more compact with significantly narrowed branches and less porous the perforated sheet-like structures. It is indicative of that smaller nanometer scale rings present along the perforated assemblies could potentially represent hydrophobic domains, which may facilitate the adsorption and aggregation of naphthalene onto the natural particle surfaces and therefore lead to an important role of dissolved humic substances in the sorption of environmental pollutants.Keywords: atomic force microscopy (AFM), dissolved humic substances, morphology, aggregation, adsorption.Humic substances (HS) are a category of naturally occurring, biogenic, heterogeneous organic materials found in or extracted from soils, sediments, and natural waters that can generally be characterized as being yellow-to-black in color, of highly variable relative molecular masses, and refractory [1,2] . Derived from a variety of organic precursors (plant biopolymers such as lignin etc.), plant residues and animal debris via both transformation and synthesis processes [3] under the profound geochemical alteration, including the microbiological and chemical degradation, sedimentation and diagenesis as well, humic substances com-AFM study on the adsorption and aggregation behavior of dissolved HS on mica 257 prise highly complex composites of partially or completely degraded biomolecules, carbohydrates, lipids, and proteins etc. However, they cannot be classified into any of the normal, easily defined categories of discrete materials such as proteins, polysaccharides, and polynucleotides. As the major organic constituents of soils, sediments and waters, humic substances are ubiquitous in all terrestrial and aquatic environments. They can form molecular aggregates, dispersed in different colloidal states in solutio...

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confidence: 99%

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Zhou

Lü

et al. 2006

SCI CHINA SER B

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“…Although many artificial PGRs have been applied successfully in bulbous crops in vitro (Gerrits and de Klerk, 1992;Marinangeli and Curvetto, 1997;Kumar et al, 2005;Jásik and de Klerk, 2006), almost all reports focused only on optimization of culture conditions and work on the related bulblet growth mechanism is scarce. Among these PGRs, humic acids (HAs), complicated mixtures of biologically transformed organic debris (Hayes and Clapp, 2001), proved to be beneficial to plant growth and productivity by influencing, directly or indirectly, several plant biochemical processes (Zandonadi et al, 2007). One aspect is to promote root development to be advantageous for nutrition uptake (Canellas et al, 2002;Zandonadi et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Low humic acids promote in vitro lily bulblet enlargement by enhancing roots growth and carbohydrate metabolism

Xia

Zhang

et al. 2016

J. Zhejiang Univ. Sci. B

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Bulblet development is a problem in global lily bulb production and carbohydrate metabolism is a crucial factor. Micropropagation acts as an efficient substitute for faster propagation and can provide a controllable condition to explore bulb growth. The present study was conducted to investigate the effects of humic acid (HA) on bulblet swelling and the carbohydrate metabolic pathway in Lilium Oriental Hybrids 'Sorbonne' under in vitro conditions. HA greatly promoted bulblet growth at 0.2, 2.0, and 20.0 mg/L, and pronounced increases in bulblet sucrose, total soluble sugar, and starch content were observed for higher HA concentrations (≥2.0 mg/L) within 45 d after transplanting (DAT). The activities of three major starch synthetic enzymes (including adenosine 5'-diphosphate glucose pyrophosphorylase, granule-bound starch synthase, and soluble starch synthase) were enhanced dramatically after HA application especially low concentration HA (LHA), indicating a quick response of starch metabolism. However, higher doses of HA also caused excessive aboveground biomass accumulation and inhibited root growth. Accordingly, an earlier carbon starvation emerged by observing evident starch degradation. Relative bulblet weight gradually decreased with increased HA doses and thereby broke the balance between the source and sink. A low HA concentration at 0.2 mg/L performed best in both root and bulblet growth. The number of roots and root length peaked at 14.5 and 5.75 cm, respectively. The fresh bulblet weight and diameter reached 468 mg (2.9 times that under the control treatment) and 11.68 mm, respectively. Further, sucrose/starch utilization and conversion were accelerated and carbon famine was delayed as a result with an average relative bulblet weight of 80.09%. To our knowledge, this is the first HA application and mechanism research into starch metabolism in both in vitro and in vivo condition in bulbous crops.

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“…Hydromorphic soils cover 3 % of the terrestrial surface and 1 % of the Brazilian territory (Valladares, 2003). These soils have a greater capacity to store carbon (C) than freely drained soils (Raich & Potter, 1995;Alongi et al, 2001;Whiting & Chanton, 2001), but on the other hand can be significant CH 4 sources to the atmosphere (Hayes & Clapp, 2001;Whalen, 2005).…”

Section: Introductionmentioning

confidence: 99%

Methane fluxes from waterlogged and drained Histosols of highland areas

Rachwal

Zanatta

Dieckow

et al. 2014

Rev. Bras. Ciênc. Solo

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SUMMARYSoil can be either source or sink of methane (CH 4 ), depending on the balance between methanogenesis and methanotrophy, which are determined by pedological, climatic and management factors. The objective of this study was to assess the impact of drainage of a highland Haplic Histosol on CH 4 fluxes. Field research was carried out in Ponta Grossa (Paraná, Brazil) based on the measurement of CH 4 fluxes by the static chamber method in natural and drained Histosol, over one year (17 sampling events). The natural Histosol showed net CH 4 eflux, with rates varying from 238 µg m -2 h -1 CH 4 , in cool/cold periods, to 2,850 µg m -2 h -1 CH 4 , in warm/hot periods, resulting a cumulative emission of 116 kg ha -1 yr -1 CH 4 . In the opposite, the drained Histosol showed net influx of CH 4 (-39 to -146 µg m -2 h -1 ), which resulted in a net consumption of 9 kg ha -1 yr -1 CH 4 . The main driving factors of CH 4 consumption in the drained soil were the lowering of the water-table (on average -57 cm, vs -7 cm in natural soil) and the lower water content in the 0-10 cm layer (average of 5.5 kg kg -1 , vs 9.9 kg kg -1 in natural soil). Although waterlogged Histosols of highland areas are regarded as CH 4 sources, they fulfill fundamental functions in the ecosystem, such as the accumulation of organic carbon (581 Mg ha -1 C to a depth of 1 m) and water (8.6 million L ha -1 = 860 mm to a depth of 1 m). For this reason, these soils must not be drained as an alternative to mitigate CH 4 emission, but effectively preserved.Index terms: greenhouse gas, water sources, water-table, gravimetric moisture, air temperature, rainfall.(1) Part of the thesis submitted by the first author to obtain a doctorate in Forestry Science, sub-area Nature Conservation. RESUMO: FLUXOS DE METANO EM ORGANOSSOLO NATURAL E APÓS DRENAGEMO solo pode atuar como fonte ou sumidouro de metano (CH 4 ), dependendo do balanço entre metanogênese e metanotrofia, definido por fatores pedológicos, climáticos e de manejo. O objetivo deste estudo foi avaliar as implicações da drenagem do Organossolo Háplico hêmico, típico em campo hidrófilo de altitude sobre os fluxos de CH 4 . A pesquisa de campo foi conduzida no município de Ponta Grossa, PR, e envolveu avaliações de fluxos de CH 4 pelo método da câmara estática em Organossolo natural e Organossolo drenado, por um período de um ano (17 coletas). No Organossolo natural, ocorreu efluxo líquido de CH 4 , com taxas variando entre 238 µg m -2 h -1 de CH 4 , em épocas mais frias, e 2.850 µg m -2 h -1 de CH 4 , em épocas mais quentes, totalizando emissão acumulada de 116 kg ha -1 ano -1 de CH 4 . Na área drenada, ocorreu influxo líquido (-39 a -146 µg m -2 h -1 de CH 4 ), que totalizou em consumo de 9 kg ha -1 ano -1 de CH 4 . O rebaixamento do nível freático (em média -57 cm, contra -7 cm no solo natural) e a menor umidade gravimétrica na camada de 0-10 cm (média de 5,5 kg kg -1 , contra 9,9 kg kg -1 do solo natural) foram os principais fatores determinantes do consumo de CH 4, na área drenada. Apesar de os Organ...

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Humic Substances: Considerations of Compositions, Aspects of Structure, and Environmental Influences

Cited by 198 publications

References 38 publications

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

AFM study on the adsorption and aggregation behavior of dissolved humic substances on mica

Low humic acids promote in vitro lily bulblet enlargement by enhancing roots growth and carbohydrate metabolism

Methane fluxes from waterlogged and drained Histosols of highland areas

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