Interaction of humic acids with soil minerals: adsorption and surface aggregation induced by Ca2+

2015 ◽  
Vol 12 (6) ◽  
pp. 731 ◽  
Author(s):  
Nanci Kloster ◽  
Marcelo Avena
Keyword(s):  
Humic Acids ◽  
Adsorption Isotherms ◽  
Soil Structure ◽  
Clay Fraction ◽  
Soil Minerals ◽  
Mineral Particles ◽  
Multivalent Ions ◽  
Nucleation Centre ◽  
Soil Clay ◽  
High Concentrations

Environmental context Humic acids, important components of natural organic matter in soils, sediments and aquatic media, can interact with the surface of minerals affecting key environmental processes. In the presence of calcium, humic acids can also interact among themselves leading to molecular aggregates. We demonstrate that a solid mineral surface facilitates the formation of humic acid aggregates, and thus surface aggregation occurs under conditions where normal aggregation in solution does not occur. Abstract Humic acids (HAs) interact with the surface of mineral particles leading to the formation of clay–humic complexes that affect the transport of nutrients and contaminants in the environment, soil structure, soil erosion and carbon sequestration by soils. The interaction is influenced by the presence of multivalent ions, such as Ca2+, which enhances the uptake of HAs by the particles. This article reports the effects of Ca2+ on the interaction between a HA and a soil clay fraction, both obtained from the same soil sample. The study was performed by using zeta potential measurements, HA adsorption isotherms, Ca2+ adsorption isotherms and microscopy. The results show that at low HA concentrations and low Ca2+ concentrations HA adsorption takes place, but that at high concentrations surface aggregation and precipitation also takes place, a process that is seldom reported or analysed in the literature. HA adsorption isotherms only give the overall HA uptake by the solid but they do not allow differentiation of HA adsorption from surface aggregation. However, HA adsorption v. Ca2+ concentration plots and Ca2+ adsorption isotherms at different HA concentrations can distinguish these two processes quite clearly. In addition, surface aggregation could be undoubtedly observed with optical microscopy. Surface aggregation starts to take place at a 0.7mM Ca2+ concentration, which is lower than the Ca2+ concentration needed to start HA aggregation in solution. This indicates that the surface of soil minerals acts as a nucleation centre for HA aggregation.

scholarly journals Wien effect of Cd/Zn on soil clay fraction and their interaction

2018 ◽  
Vol 19 (1) ◽  
Author(s):  
Tingting Fan ◽  
Chengbao Li ◽  
Juan Gao ◽  
Dongmei Zhou ◽  
Marcelo Eduardo Alves ◽  
...  
Keyword(s):  
Clay Fraction ◽  
Soil Clay ◽  
Wien Effect

Initial aggregate formation: Disentangling the effects of soil texture, OM properties and microbial community using artificial model soils

2021 ◽  
Author(s):  
Franziska B. Bucka ◽  
Vincent J.M.N.L. Felde ◽  
Stephan Peth ◽  
Ingrid Kögel-Knabner
Keyword(s):  
Microbial Community ◽  
Specific Surface ◽  
Structure Formation ◽  
Surface Area ◽  
Specific Surface Area ◽  
Soil Structure ◽  
Mechanical Stability ◽  
Aggregate Formation ◽  
Water Stable Aggregates ◽  
Mineral Particles

<p>The interaction between mineral particles and organic matter (OM) is an important and complex process in the course of soil structure formation. For a better understanding it is necessary to disentangle the texture-dependent interplay of individual OM types and mineral particles. We developed an experimental set-up to study early aggregate formation within a controlled lab environment. Artificial soil microcosms with a mineral mixture resembling arable soils of three different textures (clay loam, loam and sandy loam) were used in a short-term, 30-day incubation experiment under constant water-tension. OM was added individually either as plant litter (POM) of two different sizes (0.63-2 mm and < 63 µm, respectively) or bacterial necromass (Bacillus subtilis). The mechanisms of soil structure formation were investigated by isolating water-stable aggregates after the incubation, analyzing their mechanical stability and organic carbon allocation, and measuring the specific surface area and OM covers of the mineral surface, microbial activity, and community structure.</p><p>The dry mixing process and incubation of the mineral mixtures led to particle-particle interactions and fine particle coatings of the sand grains as shown by a reduction of the specific surface area. The OM input of all types caused between 3 to 17% of the mineral surfaces to be covered by OM, with larger covered areas in the clay-rich mixtures. The added OM was quickly accessed and degraded by microbes, as shown by the peak in CO<sub>2</sub>-release within the first 10 days of the incubation. The POM of both sizes induced the predominant formation of water-stable macroaggregates (0.63-30 mm) with a mass contribution of 72 to 91% (irrespective of texture) and fostered the development of a microbial community with a high relative abundance of fungi. The bacterial necromass induced the formation of macroaggregates, but also microaggregates (63-200 µm), while the microbial community was dominated by bacteria. The mechanical stability analysis showed that very small forces < 4 N were sufficient for aggregate failure and breakdown to 80% of the original aggregate size.</p><p>We propose that the microbial degradation of all OM types leads to small, distinct OM clusters consisting of OM substrate, microbes, and extracellular polymeric substances. These interact with mineral particles, resulting in the cross-linking of particles and formation of water-stable aggregates in all textures. The OM can thereby act both as microbial substrate and as structural building block. The initially formed aggregates are a loosely connected scaffold with a very low mechanical stability. Differences in the developed microbial community may lead to additional stabilization mechanisms, like fungal hyphae enmeshing and stabilizing larger aggregates also in sandy texture.</p>

Physicochemical properties of protein-smectite and protein-Al(OH)x-smectite complexes

Clay Minerals ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 325-336 ◽  
Author(s):  
A. Violante ◽  
A. de Cristofaro ◽  
M.A. Rao ◽  
L. Gianfreda
Keyword(s):  
Physicochemical Properties ◽  
Clay Minerals ◽  
Adsorption Isotherms ◽  
Electrostatic Interactions ◽  
Clay Fraction ◽  
Electrostatic Forces ◽  
Molecular Weights ◽  
Protein Molecules ◽  
Isoelectric Points ◽  
Heating Treatment

AbstractProteins (catalase, albumin, pepsin and lysozyme with different molecular weights and isoelectric points) were differently adsorbed at pH 7.0 on the clay fraction of three raw Na-saturated smectites (Crook and Uri montmorillonites and one hectorite). The adsorption isotherms of proteins on clay minerals showed typical Langmuir characteristics. Lysozyme was adsorbed under the effect of electrostatic interactions between the opposite charges of clay surfaces and protein molecules, whereas catalase and albumin were adsorbed under the effect of non-electrostatic forces. Pepsin was held in relatively high amounts only on the surfaces of hectorite. Proteins were intercalated in the interlayers spaces of smectites, usually undergoing extensive unfolding. Protein-smectite complexes showed different behaviour to heating treatment. Some complexes remained practically unchanged after heating at 200°C. Presence of ‘wrecks’ of interlayered materials was found after heating at 500°C for two hours. The amounts of proteins adsorbed on the external and interlamellar surfaces of clay minerals, partially coated with OH-Al species, were much lower than those fixed on the clean clays. Only lysozyme was intercalated in chlorite-like complexes.

Colloidal dynamics of soil clay under the effect of fine-sized biochars: Implication for biochar amendment towards preventing clay loss and soil erosion

2020 ◽  
Author(s):  
Nga T. Mai ◽  
Nga T. T. Pham ◽  
Anh T. Q. Nguyen ◽  
Anh T. N. Nguyen ◽  
Anh M. Nguyen ◽  
...  
Keyword(s):  
Soil Erosion ◽  
Surface Charge ◽  
Clay Fraction ◽  
Test Tube ◽  
Soil Clays ◽  
Soil Clay ◽  
Ph Range ◽  
Polyelectrolyte Titration ◽  
Repulsive Forces ◽  
Biochar Amendment

<p>In soils clay loss by leaching and surface runoff is one of the initial steps increasing the risk of erosion. Here we set out to determine the effect of fine-sized biochar amendment on colloidal dynamics of soil clay, with the aim of answering whether biochar addition enhances or curbs soil erosion. Fine-sized biochar samples were prepared from fern Dicranopteris linearis’s biomass under non-biochar-oriented pyrolysis (open heating) and biochar-oriented pyrolysis (N<sub>2</sub>-supported heating) over a temperature range from 400 to 900°C. The clay fraction (< 2 µm) separated from a clay-rich soil in a hilly area of the Red River basin containing relatively high amounts of kaolinite was tested for its dispersion properties under the presence of the prepared biochars. Surface charge of biochar-soil clay mixtures was determined by polyelectrolyte titration using a particle charge detector, while corresponding colloidal properties of the mixtures were examined by the test tube method. Both, the soil clay fraction and biochar samples showed strongly negative surface charge and their surface charge was variable depending on pH. In a pH range from 3 to 10 and at an electrolyte background of 0.01 M NaCl, surface charge of the clay fraction decreased from -1.68 to -44.75 mmol<sub>c</sub> Kg<sup>-1</sup>, while the biochars surface charge varied from -0.6 to -48.8 mmol<sub>c</sub> Kg<sup>-1</sup>. Soil clays were more strongly dispersed in the presence of biochars by increasing electrostatic repulsive forces. The biochar preparation method had a crucial role for surface charge properties of biochars and in consequence colloidal dynamics of biochar-clay mixtures. The N<sub>2</sub>-supported pyrolysis at lower temperatures does not increase charge density but creates a more porous structure, thereby increasing the total negative net charges. As a result, the N<sub>2</sub>-supported biochars favor clay dispersion more effectively, while the open-pyrolysis biochars showed lesser effects. Our results indicate that fine-sized biochar amendments generally enhance the risk of clay loss, however, such techniques for creating low-charged biochars can help to decrease clay dispersibility when applying biochar for soil.</p>

Humus Substances and Soil Structure

2012 ◽  
Vol 63 (3) ◽  
pp. 31-36
Author(s):  
Erika Tobiašová ◽  
Juraj Miškolczi
Keyword(s):  
Humic Acids ◽  
Soil Structure ◽  
Size Fraction ◽  
Fulvic Acids ◽  
Optical Parameters ◽  
Humus Substances ◽  
Haplic Chernozems ◽  
Positive Correlations ◽  
The Stability

Abstract In this study, the soil structure of two soil types (Haplic Chernozems and Eutric Fluvisols) in four ecosystems (forest, meadow, urban and agro-ecosystem) with dependence on humus substances were compared. The stability of dry-sieved and waterresistant macro-aggregates and micro-aggregates with a dependence on the proportion of humus substance fractions was determined. Quantity of humus substances influenced mainly water-resistant aggregates. A positive correlation was recorded between size fraction of 2.3 mm and contents of humus substances (P < 0.01; r = +0.710) and fulvic acids (P < 0.05; r = +0.634), and negative correlation between size fraction of 0.5.1 mm and contents of humus substances (P < 0.05; r = -0.613) and fulvic acids (P < 0.01; r = -0.711). Humic acids influenced mainly the formation of dry-sieved aggregates and fulvic acids played an important role in micro-aggregate formation. The quality of humus substances influenced more intensively the formation of dry-sieved aggregates. There were positive correlations between optical parameters of humus substances and humic acids and larger dry-sieved aggregates (3.7 mm) and negative correlations with smaller (0.5.3 mm). The highest proportions of larger size of water-resistant aggregates (1. 20 mm) were in forest ecosystem, but smaller (0.25.1 mm) agreggates were dominated in agro-ecosystem.

scholarly journals ORGANIC GEOCHEMISTRY OF HUMIC ACIDS FROM A NEOGENE LIGNITE SAMPLE, BULGARIA

2017 ◽  
Vol 43 (5) ◽  
pp. 2398
Author(s):  
M. Stefanova ◽  
S.P. Marinov
Keyword(s):  
Humic Acids ◽  
Organic Geochemistry ◽  
Distribution Patterns ◽  
Bacterial Activity ◽  
Long Chain Fatty Acids ◽  
Plant Origin ◽  
Higher Plant ◽  
Acidic Fraction ◽  
High Concentrations ◽  
Very High

Humic substances naturally occur in Miocene/Pliocene-aged lignite at very high concentrations. Here biomarkers in the bitumen-free extract of humic acids from Thracian lignite, Bulgaria, are studied. Applying methods of organic geochemistry a broad range of compounds are isolated and characterised. Species are classified according to abundance, possible source input and diagenetic transformation. A feature of humic acids derived from Thracian coal is the extremely high content of 16α(H)Phyllocladane, ~60% of aliphatic fraction, or 1.6 wt.% of initial lignite. The high diterpenoids content, especially with abietane skeleton, proved the conifer contribution to the peat-forming helophytes, i.e. Cupressaceae s. str., Podocarpaceae, Araucariaceae, Taxodiaceae, Phyllocladus, Piceae. Tightly-trapped, linear long-chain fatty acids (FAs) are the main constituents of the acidic fraction of humic acids. Their distribution patterns indicate a dominant higher plant origin. The presence of αOH-FAs and hopanoid acids assumes bacterial activity in the plant material reworked. A hint for the input of plant biopolymers, i.e. cutin, suberin, is the relative high content of “even” carbon numbered ωΟΗFAs and α,ω-alkanedioic FAs. “Even” numbered short-chain ωΟΗFAs could originate from cutin-derived constituents of the needles of numerous species of gymnospermous families.

Adsorption of DL-alanine by allophane: effect of pH and unit particle aggregation

Clay Minerals ◽  
1999 ◽  
Vol 34 (2) ◽  
pp. 233-238 ◽  
Author(s):  
H. Hashizume ◽  
B. K. G. Theng
Keyword(s):  
Adsorption Isotherms ◽  
Linear Increase ◽  
Particle Aggregation ◽  
Published Data ◽  
Effect Of Ph ◽  
Linear Rise ◽  
Equilibrium Concentrations ◽  
Ph Dependent ◽  
High Concentrations

AbstractThe adsorption of DL-alanine at pH 4, 6 and 8 by a soil allophane has been determined. Two sets of experiments were carried out: (1) in which the allophane had been kept in a moist state throughout; and (2) in which the mineral had previously been dried at 50°C. In both instances, the adsorption isotherms showed three distinct regions as the concentration of alanine in solution was increased: (1) an initial, nearly linear, rise at low equilibrium concentrations; (2) a levelling off to a plateau at intermediate concentrations; and (3) a steep linear increase at high concentrations. For comparable concentrations of alanine in solution, adsorption decreased in the order pH 6 > pH 8 > pH 4. Irrespective of pH, however, more alanine was adsorbed by the ‘wet’ allophane than by its ‘dry’ counterpart. These observations are interpreted in terms of the morphology and aggregation of allophane unit particles together with the pH-dependent charge characteristics of allophane and alanine. The results are compared with published data on the adsorption of alanine by montmorillonite.

Predicting natural regeneration of white spruce in boreal mixedwood understories

2001 ◽  
Vol 77 (6) ◽  
pp. 1006-1013 ◽  
Author(s):  
James D. Stewart ◽  
Simon M. Landhäusser ◽  
Kenneth J. Stadt ◽  
Victor J. Lieffers
Keyword(s):  
Picea Glauca ◽  
Mineral Soil ◽  
Clay Fraction ◽  
Basal Area ◽  
White Spruce ◽  
Height Growth ◽  
Feather Moss ◽  
Moss Cover ◽  
Rotten Wood ◽  
Soil Clay

Successful mixedwood management in the boreal forest of Alberta requires better knowledge of the occurrence and success of natural white spruce regeneration. In this study we developed statistical models to predict the natural establishment and height growth of understory white spruce (Picea glauca (Moench) Voss) in the boreal mixedwood forest in Alberta using data from 148 provincial permanent sample plots, supplemented by measurements of the amount and height growth of regenerating white spruce, and the amount and type of available substrate. A discriminant model correctly classified 73% of the sites as to presence or absence of a white spruce understory based on the amount of spruce basal area, rotten wood, ecological nutrient regime, soil clay fraction and elevation, although it explained only 30% of the variation in the data. On sites with a white spruce understory, a regression model related the abundance of regeneration to rotten wood cover, spruce basal area, pine basal area, soil clay fraction, and grass cover (R2 = 0.36). About half of the seedlings surveyed grew on rotten wood, and only 3% on mineral soil, and seedlings were 10 times more likely to have established on these substrates than on litter. Exposed mineral soil was rare, covering only 0.3% of the observed transect area, rotten wood covered 4.5%, and litter/undisturbed forest floor covered the remainder. The regression models developed for average relative height growth rate included feather moss cover, stand age and birch basal area for seedlings ≤ 1 m (R2 = 0.23), and feather moss cover, elevation, other moss cover and soil clay fraction for seedlings between 1 m and 3 m (R2 = 0.27). Key words: Picea glauca, seedling establishment, seedbeds, site factors, coarse woody debris, predictive models, mixedwood management

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