The mechanisms of gravity-constrained aggregation in natural colloidal suspensions

Guhra, Tom; Ritschel, Thomas; Totsche, Kai Uwe

doi:10.1016/j.jcis.2021.03.153

Cited by 11 publications

(11 citation statements)

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“…Casting the principles into a mathematical framework (Ray et al, 2017; and coding the algorithms in numerical programs are the final steps ("level of bits and bytes"). Successful outcomes of this approach are presented, for example, in Rupp et al (2019), Guhra et al (2021), or Zech et al (2020 and Zech, Schweizer, et al, 2022).…”

Section: Supervised Approach For Model Development In Collaborative R...mentioning

confidence: 99%

“…Early studies (Crawford et al, 1997(Crawford et al, , 2012 already introduced the self-organization of soil its response to the chemical milieu and particle geometry (Figure 5). Guhra et al (2021) extended this approach to include gravity as a decisive mechanism that controls the settling of particles and aggregates and, therefore, their fractionation or accumulation. They further showed that gravity can accelerate as well as decelerate aggregation, depending among others on the relative settling velocity in aqueous mixtures of particles varying in density or size.…”

Section: Synoptic Modeling For Understandingmentioning

confidence: 99%

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Structure–function co‐evolution during pedogenesis—Microaggregate development and turnover in soils

Totsche,

Ray,

Kögel‐Knabner

2024

J. Plant Nutr. Soil Sci.

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Section: Supervised Approach For Model Development In Collaborative R...mentioning

confidence: 99%

Section: Synoptic Modeling For Understandingmentioning

confidence: 99%

Structure–function co‐evolution during pedogenesis—Microaggregate development and turnover in soils

Totsche,

Ray,

Kögel‐Knabner

2024

J. Plant Nutr. Soil Sci.

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“…Furthermore, the explicit aggregate structure available in three dimensions permits the estimation of functions based on morphological properties, as exemplified by Ritschel and Totsche (2019) with the derivation of the water retention characteristics from the aggregate pore size distribution. This approach was extended using sedimentation as an additional transport mechanism by Guhra et al (2021), who showed how gravity could shape the aggregation dynamics and structural features when aggregates grow and start to settle. Interestingly, gravity can accelerate as well as decelerate aggregate growth through a delicate interplay of different mechanisms (Figure 9).…”

Section: Modeling Of Explicit Aggregate Structure Dynamicsmentioning

confidence: 99%

Architecture of soil microaggregates: Advanced methodologies to explore properties and functions

Amelung,

Tang,

Siebers

et al. 2023

J. Plant Nutr. Soil Sci.

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The functions of soils are intimately linked to their three‐dimensional pore space and the associated biogeochemical interfaces, mirrored in the complex structure that developed during pedogenesis. Under stress overload, soil disintegrates into smaller compound structures, conventionally named aggregates. Microaggregates (<250 µm) are recognized as the most stable soil structural units. They are built of mineral, organic, and biotic materials, provide habitats for a vast diversity of microorganisms, and are closely involved in the cycling of matter and energy. However, exploring the architecture of soil microaggregates and their linkage to soil functions remains a challenging but demanding scientific endeavor. With the advent of complementary spectromicroscopic and tomographic techniques, we can now assess and visualize the size, composition, and porosity of microaggregates and the spatial arrangement of their interior building units. Their combinations with advanced experimental pedology, multi‐isotope labeling experiments, and computational approaches pave the way to investigate microaggregate turnover and stability, explore their role in element cycling, and unravel the intricate linkage between structure and function. However, spectromicroscopic techniques operate at different scales and resolutions, and have specific requirements for sample preparation and microaggregate isolation; hence, special attention must be paid to both the separation of microaggregates in a reproducible manner and the synopsis of the geography of information that originates from the diverse complementary instrumental techniques. The latter calls for further development of strategies for synlocation and synscaling beyond the present state of correlative analysis. Here, we present examples of recent scientific progress and review both options and challenges of the joint application of cutting‐edge techniques to achieve a sophisticated picture of the properties and functions of soil microaggregates.

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“…After the aggregation experiments, the surface charge was obtained from zeta potential measurements in 1 mM NaCl. The Hamaker constants were adopted from Guhra et al (2021).…”

Section: Aggregation Experimentsmentioning

confidence: 99%

The functional role of earthworm mucus during aggregation

Guhra,

Wonneberger,

Stolze

et al. 2023

J. Plant Nutr. Soil Sci.

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BackgroundSoil organisms influence pedogenesis on a molecular level through the production of biopolymers which interact with soil minerals depending on their molecular properties. Specifically, biopolymers impact structure formation by inhibiting aggregation as a separation agent or promoting aggregation as a bridging agent. Mucus is a biopolymer excreted by earthworms that consists mainly of proteins, polysaccharides, and, to a lesser extent, lipids. However, despite earthworms’ fundamental contribution to soil quality and structuring via bioturbation, the role of mucus in aggregation still has to be unraveled.AimsOur study explores the role of cutaneous earthworm mucus (CEM) of Lumbricus terrestris L. for the formation of organo–mineral associations and aggregates, a sub‐process of pedogenesis.MethodsWe conducted batch experiments with goethite and CEM at different pH values and varying CEM concentrations to form mucus–goethite associations. Employing the newly formed mucus–goethite associations, we explored the (homo‐/hetero‐)aggregation with quartz particles as a function of the loading of surfaces with mucus‐C and CEM concentrations in solution.ResultsOur results suggest that the molecular structure of CEM constituents (especially proteins) is sensitive to pH. We found that the adsorption of CEM to goethite depends on pH and concentration. Polysaccharides of CEM adsorbed preferentially under acidic conditions (pH 3) and at low CEM concentration (6 mg mucus‐C L–1). In contrast, stronger adsorption of proteins was observed at higher CEM concentrations (30 mg mucus‐C L–1). In subsequent aggregation experiments, the hetero‐aggregation rate of organo–mineral associations and quartz decreased at low C‐loadings. Conversely, the rate increased at high loadings compared to the CEM‐free reference. Furthermore, electrostatic/steric repulsion (separation agent) inhibited the aggregation between goethite particles at high CEM concentrations in the solution (mineral/mucus ratio of 17). However, at a low CEM supply (mineral/mucus ratio of >83), CEM took the role of a bridging agent.ConclusionsThe composition, function, and (im‐)mobilization of CEM and corresponding organo–mineral associations in earthworm‐influenced soil structures are shaped by the structure/reactivity of CEM affected by environmental parameters. Formation and aggregation of mucus–mineral associations contribute to nutrient/carbon storage and are involved in the structure formation in soil.

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The mechanisms of gravity-constrained aggregation in natural colloidal suspensions

Cited by 11 publications

References 60 publications

Structure–function co‐evolution during pedogenesis—Microaggregate development and turnover in soils

Structure–function co‐evolution during pedogenesis—Microaggregate development and turnover in soils

Architecture of soil microaggregates: Advanced methodologies to explore properties and functions

The functional role of earthworm mucus during aggregation

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