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  • 1
    Language: English
    In: Journal of Hydrology, June 6, 2012, Vol.442-443, p.63(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2012.03.039 Byline: Marc-O. Goebel, Susanne K. Woche, Jorg Bachmann Keywords: Aggregate stability; Contact angle; Infiltration rate; Repellency index; Soil water repellency; Surface tension Abstract: a* We investigated the effects of liquid penetration kinetics on aggregate stability. a* Stability was assessed by immersion in liquids with different surface tension. a* Penetration was related to aggregate contact angle and liquid surface tension. a* Aggregate stability was inversely related to wettability in terms of contact angle. a* Aggregate stability was controlled by solid and liquid interfacial properties. Author Affiliation: Institute of Soil Science, Leibniz Universitat Hannover, Herrenhauser Str. 2, D-30419 Hannover, Germany Article History: Received 1 June 2011; Revised 9 March 2012; Accepted 28 March 2012 Article Note: (miscellaneous) This manuscript was handled by Philippe Baveye, Editor-in-Chief, with the assistance of Hans-Jorg Vogel, Associate Editor
    Keywords: Soil Moisture -- Analysis ; Infiltration (Hydrology) -- Analysis
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Journal of Hydrology, 06 June 2012, Vol.442-443, pp.63-74
    Description: ► We investigated the effects of liquid penetration kinetics on aggregate stability. ► Stability was assessed by immersion in liquids with different surface tension. ► Penetration was related to aggregate contact angle and liquid surface tension. ► Aggregate stability was inversely related to wettability in terms of contact angle. ► Aggregate stability was controlled by solid and liquid interfacial properties. Aggregate stability is frequently shown to be enhanced by strong soil water repellency, however, there is limited systematic evidence on this effect for moderately (subcritically) water repellent soils. This study aimed to investigate the specific effects of interfacial properties on the liquid penetration kinetics in relation to the stability of subcritically water repellent aggregates (4–6.3 mm) from various arable and forest soils against breakdown by slaking. In contrast to many other studies, where aggregate stability was determined by wet sieving, we here assessed the stability by immersion of air-dry aggregates in water–ethanol solutions with surface tensions ranging from 30 to 70 mN m . This approach allowed a highly sensitive discrimination of different stability levels and the determination of breakdown kinetics also for less stable aggregates. Interfacial properties were characterized in terms of contact angle measured on crushed aggregates, , and calculated for intact aggregates, , based on infiltration measurements with water and ethanol. Aggregate stability turned out to be higher in forest soils compared to arable soils with topsoil aggregates generally found to be more stable than subsoil aggregates. For water repellent aggregates, characterized by contact angles 〉40° and low water infiltration rates (〈0.2 mm s ), the fraction of disrupted aggregates after 30 s of immersion was generally below 10%, whereas in case of the more wettable aggregates, characterized by contact angles 〈10° and higher infiltration rates (〉0.25 mm s ) more than 80% of the aggregates were disrupted. In accordance, we found a close relationship between aggregate stability and wettability with differences between and being generally small. In addition, aggregate stability turned out to be related to organic carbon content. However, correlation analysis revealed that both persistence of aggregate stability and kinetics of aggregate breakdown were more strongly affected by the contact angle, ( = 0.90 and = −0.83, respectively) and ( = 0.89 and = −0.76, respectively) than the organic carbon content ( = 0.62 and −0.52, respectively), suggesting that stability was primarily controlled by aggregate interfacial properties. Calculation of liquid penetrativity as a function of surface tension and contact angle clearly demonstrated the importance of both solid and liquid interfacial properties in determining the stability of subcritically water repellent aggregates against slaking.
    Keywords: Aggregate Stability ; Contact Angle ; Infiltration Rate ; Repellency Index ; Soil Water Repellency ; Surface Tension ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 3
    Language: English
    In: Journal of hydrology, 2012, Vol.442, pp.63-74
    Description: Aggregate stability is frequently shown to be enhanced by strong soil water repellency, however, there is limited systematic evidence on this effect for moderately (subcritically) water repellent soils. This study aimed to investigate the specific effects of interfacial properties on the liquid penetration kinetics in relation to the stability of subcritically water repellent aggregates (4–6.3mm) from various arable and forest soils against breakdown by slaking. In contrast to many other studies, where aggregate stability was determined by wet sieving, we here assessed the stability by immersion of air-dry aggregates in water–ethanol solutions with surface tensions ranging from 30 to 70mNm⁻¹. This approach allowed a highly sensitive discrimination of different stability levels and the determination of breakdown kinetics also for less stable aggregates. Interfacial properties were characterized in terms of contact angle measured on crushed aggregates, θc, and calculated for intact aggregates, θᵢ, based on infiltration measurements with water and ethanol. Aggregate stability turned out to be higher in forest soils compared to arable soils with topsoil aggregates generally found to be more stable than subsoil aggregates. For water repellent aggregates, characterized by contact angles 〉40° and low water infiltration rates (0.25mm³s⁻⁰.⁵) more than 80% of the aggregates were disrupted. In accordance, we found a close relationship between aggregate stability and wettability with differences between θc and θᵢ being generally small. In addition, aggregate stability turned out to be related to organic carbon content. However, correlation analysis revealed that both persistence of aggregate stability and kinetics of aggregate breakdown were more strongly affected by the contact angle, θc (r=0.90 and r=−0.83, respectively) and θᵢ (r=0.89 and r=−0.76, respectively) than the organic carbon content (r=0.62 and −0.52, respectively), suggesting that stability was primarily controlled by aggregate interfacial properties. Calculation of liquid penetrativity as a function of surface tension and contact angle clearly demonstrated the importance of both solid and liquid interfacial properties in determining the stability of subcritically water repellent aggregates against slaking. ; p. 63-74.
    Keywords: Forest Soils ; Soil Water ; Water Repellent Soils ; Quantitative Analysis ; Aggregate Stability ; Surface Tension ; Soil Aggregates ; Arable Soils ; Pharmacokinetics ; Contact Angle
    ISSN: 0022-1694
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 4
    Language: English
    In: Journal of Hydrology, March 25, 2013, Vol.484, p.45(10)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2013.01.009 Byline: Christina Ganz (a), Jorg Bachmann (a), Axel Lamparter (b), Susanne K. Woche (a), Wilhelmus H.M. Duijnisveld (b), Marc-O. Gobel (a) Keywords: Stable contact angles; Ponded infiltration; Unstable flow; Macro-finger; Water repellency Abstract: a* In a sandy soil the persistence of water repellency increases with depth. a* Stable contact angles in the subsoil were determined in the laboratory. a* Ponded infiltration showed slight saturation overshoot indicating unstable flow. a* The excavated tracer pattern was conical shaped. a* The persistent water repellency triggered the non-ideal dye pattern. Author Affiliation: (a) Institute of Soil Science, Leibniz University of Hannover, Herrenhauser Str. 2, 30419 Hannover, Germany (b) Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655 Hannover, Germany Article History: Received 30 July 2012; Revised 9 December 2012; Accepted 10 January 2013 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of Ty Ferre, Associate Editor
    Keywords: Infiltration (Hydrology) ; Tracers (Biology)
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 5
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, August 20, 2013, Vol.431, p.150(11)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.colsurfa.2013.04.038 Byline: Marc-O. Goebel, Susanne K. Woche, Priya M. Abraham, Gabriele E. Schaumann, Jorg Bachmann Abstract: Author Affiliation: (a) Institute of Soil Science, Leibniz Universitat Hannover, Herrenhauser Str. 2, D-30419 Hannover, Germany (b) Department of Environmental and Soil Chemistry, Institute for Environmental Sciences, Universitat Koblenz-Landau, Fortstr. 7, D-76829 Landau, Germany Article History: Received 14 December 2012; Revised 16 March 2013; Accepted 10 April 2013
    ISSN: 0927-7757
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Industrial & Engineering Chemistry Research, 03/15/2017, Vol.56(10), pp.2824-2833
    Description: The development of new adsorbent materials is a key factor for applying sorption-based technologies designed to clean effluents. Clay biomass complexes (BMMT) from fungal biomass grown on a raw montmorillonite (MMT) were generated in a previous work and used in a wet state. These samples were examined previously as a material to retain metals and improve separation after adsorption processes. The objective of this study was to characterize the uranium(VI) adsorption of previously dried BMMT, to determine differences from wet BMMT samples, and to understand some of the processes responsible for those differences. The differences between dried and wet BMMT adsorption capacities were verified. Proton exchange of dried BMMT samples was analyzed. Furthermore, X-ray diffraction and ζ-potential measurements of the samples after uranium(VI) uptake were performed. The hydration degree during the adsorption contact time was evaluated. Contact-angle measurement and diffusion experiments by Fourier transform infrared spectroscopy were also conducted. Dried BMMT samples presented a higher uranium(VI) uptake capacity than wet BMMT samples. Biomass played an important role in the behavior of samples evaluated, and the results indicated the importance to specify the hydration degree of adsorbents.
    Keywords: Fourier-Transform-Infrared-Spectra ; Hydration ; Uranium ; Adsorbent ; Biomass ; Sectioning ; Adsorption-Process ; Exchange ; X-Ray-Diffraction ; Diffusion ; Effluent ; Montmorillonite ; Wet-State ; Contact-Time ; Ftir-Spektroskopie ; Hydratation ; Uran ; Adsorptionsmittel ; Biomasse ; Separation ; Adsorptionsverfahren ; Austausch ; Röntgendiffraktion ; Diffusion ; Abwasser ; Montmorillonit ; Nasszustand ; Kontaktzeit ; Engineering;
    ISSN: 0888-5885
    E-ISSN: 1520-5045
    Source: American Chemical Society (via CrossRef)
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  • 7
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 05 October 2018, Vol.554, pp.156-168
    Description: In order to assess the mobility and function of Fe oxihydroxides in terrestrial and aquatic environments, knowledge of the parameters and conditions determining aggregation and the size of formed aggregates is crucial. Here we study the impact of different organic matter (OM) types on the aggregation of goethite (α-FeOOH) with particular focus on the relevance of surface charge (SC). Synthetic goethite was reacted with galacturonic acid (GA), polygalacturonic acid (PGA), and tannic acid (TA) as model substances as well as with natural dissolved OM (DOM) from a litter (Oi-DOM) and a humified horizon (Oa-DOM). The SC of goethite was adjusted at pH 4 and 6 by the adsorption of organic acids and DOM to equal positive and negative SC as well as point of zero charge ( ). Aggregation was traced by laser light scattering and sedimentation experiments. Aggregation of all goethite-OM associations depended on OM type and could well be explained by SC. Associations of goethite with OM rich in acidic groups (PGA, Oi-DOM, and Oa-DOM) followed the aggregation behavior of pure goethite. Largest aggregates with diameters up to 7 μm formed at , whereas smaller ones (∼0.4 μm) developed at positive or negative SC. Organic substances rich in acidic functional groups interacted strongly with goethite at high additions, thus favoring charge reversal and limiting aggregate growth. For OM with low acidity (TA and GA), adsorption on goethite was incomplete even at high additions. These associations remained close to and, hence, were susceptible to aggregation with maximum diameters at 6 μm. Aggregation was possibly also promoted by the exposure of less polar moieties exposed at the goethite-OM interface. Our data suggest that aggregation in environmental systems such as soils is driven by the nature and acidity of ubiquitous OM, which determines SC by the extent of adsorption to mineral surfaces.
    Keywords: Goethite ; Organic Acids ; Dissolved Organic Matter ; Surface Charge ; Aggregation Kinetics ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
    Source: ScienceDirect Journals (Elsevier)
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  • 8
    Language: English
    In: Journal of Hydrology, 25 March 2013, Vol.484, pp.45-54
    Description: ► In a sandy soil the persistence of water repellency increases with depth. ► Stable contact angles in the subsoil were determined in the laboratory. ► Ponded infiltration showed slight saturation overshoot indicating unstable flow. ► The excavated tracer pattern was conical shaped. ► The persistent water repellency triggered the non-ideal dye pattern. Despite growing knowledge about water repellent soils it is not well investigated how soil water repellency (SWR) of a lower level influences the in situ water infiltration into soils. Hence, we investigated a sandy soil where we found subcritical water repellency and unexpected stable (persistent) contact angles (CAs) in the subsoil characterized by CA measurements in the laboratory. To characterize the influence of this persistence on in situ water infiltration, a ponded tracer infiltration experiment was carried out. During the infiltration, hydraulic sensors revealed a slight saturation at the wetting front which is a sign for unstable flow. The excavated dye-stained infiltration zone was conical and its lateral extent decreased with increasing depth, showing characteristics of a macro-finger. We suggest the subsoil to exhibit a strong hysteretic water retention characteristic governing the infiltration process, but we could not verify this by standard laboratory measurements, as strongly persistent SWR prevented the fast wetting of the soil samples. Close to saturation the persistence of SWR led to a wetting period of soil samples of at least 56 days to overcome SWR and reaching an equilibrium state. There are three major conclusions of this study: 1. In contrast to many other studies we found persistent SWR also in the subsoil and not only in the humic topsoil, 2. The shape of the wetting front is contrary to common expectations for homogeneous sandy soils and 3. The wettability characteristics found might also be relevant for assessing infiltration dynamics at other sites regarding the fact that those observations are not obvious.
    Keywords: Stable Contact Angles ; Ponded Infiltration ; Unstable Flow ; Macro-Finger ; Water Repellency ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 9
    Language: English
    In: Journal of Plant Nutrition and Soil Science, June 2014, Vol.177(3), pp.449-458
    Description: To investigate the effect of plants on soil water repellency (SWR), two column experiments with wheat () and alfalfa () with a growing period of three months had been carried out under constant and near‐natural climatic conditions. Model soils with defined wettability were created by mixing a natural sandy loam subsoil with different proportions of a wettable and a hydrophobized pure quartz sand, resulting in a wettable model soil and three model soils with increasing level of subcritical SWR (initial contact angle CA 〉 0° and 〈 90°). Results showed a significant decrease of the mean CA after the experiments compared to the initial CA while the mean CA was constant for plant free columns used as a reference. CA as a function of depth in some cases showed a depth dependent variation with decreased CA at the bottom or as well at top and bottom. The deviation from the initial CA was most pronounced for wheat under constant climatic conditions. Changes in CA could be related to changes in pH, , CA was decreased and pH increased. Subcritical WR at the beginning of the growth period affected significantly the moisture content profiles during the entire growing season as well as plant dry mass production. We expect that plant root exudates of plants widely used for foot production cause directly or indirectly pH‐related modifications of the WR level in the root zone dependent on plant species and the ambient climatic conditions.
    Keywords: Contact Angle Ca ; Subcritical Water Repellency ; Wettability Of Root Zone ; Dimethyldichlorosilane Dmdcs
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 10
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 20 August 2013, Vol.431, pp.150-160
    Description: The effect of grain water repellency on transport and deposition of hydrophilic colloids was studied by analyzing the breakthrough behavior of carboxylate-modified microspheres in water-saturated wettable and hydrophobic sand columns at different ionic strengths. Interaction free energies calculated from zeta ( )-potential and contact angle data were used to explain the specific colloid breakthrough behavior. Experimental breakthrough data could be well described with the finite-element code HYDRUS-1D using a one kinetic site model with attachment and detachment kinetics. Higher colloid deposition rates found for the hydrophobic sand could primarily be explained by its small electron-donor component of surface free energy ( = 1.6 × 10 mJ m , compared to = 64.1 mJ m for the wettable sand), leading to strongly attractive acid–base interactions at separation distances 〈 5 nm. Increasing ionic strength reduced the repulsive electrostatic interactions and generally increased colloid deposition with the effect being more pronounced in the hydrophobic sand. It can be concluded that grain water repellency tends to increase the deposition of negatively charged hydrophilic colloids, which can be ascribed to specific acid–base interactions. However, our results further revealed that the calculated interaction free energy profiles should be considered only as an approximation showing general trends because surface chemical heterogeneity as detected by atomic forces microscopy impeded the determination of the actual interaction energy conditions, resulting in an overestimation of electrostatic repulsion.
    Keywords: Acid–Base Interaction ; Carboxylate-Modified Microspheres ; Colloid Breakthrough ; Interaction Free Energy ; Surface Free Energy Components ; Wettability ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
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