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  • 1
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, April 5, 2012, Vol.399, p.35(6)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.colsurfa.2012.02.021 Byline: Doreen Zirkler, Friederike Lang, Martin Kaupenjohann Keywords: Soil colloid; Vacuum filtration; Centrifugation; Particle size separation Abstract: Display Omitted Author Affiliation: TU Berlin, Department of Soil Science, Ernst-Reuter-Platz 1, 10587 Berlin, Germany Article History: Received 28 October 2011; Revised 2 February 2012; Accepted 17 February 2012
    ISSN: 0927-7757
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 05 April 2012, Vol.399, pp.35-40
    Description: ► Colloid recovery after filtration and centrifugation of soil suspensions was measured. ► Colloid recovery after filtration is 50–97% of the recovery after centrifugation. ► Cellulose nitrate filters retain colloids without losing permeability. ► Recovery of mineral colloids after filtration is less than recovery of organic colloids. ► We recommend centrifugation for soils with colloids of similar density. Soil colloid science requires the separation of the colloids from larger particles in suspensions, which is frequently achieved by filtration. However, the results of filtration may be biased due to (i) pore clogging and (ii) the formation of a filter cake. In order to quantify these effects, we filtrated different volumes of soil suspensions containing mainly mineral (M), mainly organic (O) or mineral and organic (MO) colloids through 1.2 μm membranes. Turbidity and the concentrations of colloid-bound C, Si and Al were measured in the filtrates and, as a reference, in centrifugates of the suspensions. To exclude the influence of the filter cake and examine only pore clogging effects, we conducted the same filtration experiment with suspensions which have been pre-treated by a centrifugal elimination of particles 〉3 μm. Finally, we scanned a membrane after filtration with an electron microscope for the visualisation of possible pore clogging. Turbidity and concentrations of colloid-bound Al and Si in the filtrates of the pre-treated suspensions were one order of magnitude lower than in centrifugates. This discrepancy was most pronounced for M suspensions which indicates that filters preferentially remove mineral colloids. Microscope images revealed no sign for pore clogging and smaller filtrated suspension volumes did not lead to more colloid recovery in pre-treated filtrates. We assume that the colloids are retained within the thick, multilayered structure of the filter without clogging the main pores. When filter cakes are forming (experiment without previous centrifugation), turbidity and concentrations of colloid-bound Al, Si and C decrease with increasing filtration volume. However, the retaining effect of filter cakes seems negligible compared to the retaining effect within the filter. We conclude that the composition of soil colloidal suspensions depends significantly on the technique which is used to remove larger particles. Filtration underestimates the amount of colloids in suspension and centrifugation should be preferred as separation method at least for soils with colloids of similar density, either M or O.
    Keywords: Soil Colloid ; Vacuum Filtration ; Centrifugation ; Particle Size Separation ; Engineering ; Chemistry
    ISSN: 0927-7757
    E-ISSN: 1873-4359
    Source: ScienceDirect Journals (Elsevier)
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  • 3
    Language: English
    In: Colloids and surfaces, 2012, Vol.399, pp.35-40
    Description: Soil colloid science requires the separation of the colloids from larger particles in suspensions, which is frequently achieved by filtration. However, the results of filtration may be biased due to (i) pore clogging and (ii) the formation of a filter cake. In order to quantify these effects, we filtrated different volumes of soil suspensions containing mainly mineral (M), mainly organic (O) or mineral and organic (MO) colloids through 1.2μm membranes. Turbidity and the concentrations of colloid-bound C, Si and Al were measured in the filtrates and, as a reference, in centrifugates of the suspensions. To exclude the influence of the filter cake and examine only pore clogging effects, we conducted the same filtration experiment with suspensions which have been pre-treated by a centrifugal elimination of particles 〉3μm. Finally, we scanned a membrane after filtration with an electron microscope for the visualisation of possible pore clogging. Turbidity and concentrations of colloid-bound Al and Si in the filtrates of the pre-treated suspensions were one order of magnitude lower than in centrifugates. This discrepancy was most pronounced for M suspensions which indicates that filters preferentially remove mineral colloids. Microscope images revealed no sign for pore clogging and smaller filtrated suspension volumes did not lead to more colloid recovery in pre-treated filtrates. We assume that the colloids are retained within the thick, multilayered structure of the filter without clogging the main pores. When filter cakes are forming (experiment without previous centrifugation), turbidity and concentrations of colloid-bound Al, Si and C decrease with increasing filtration volume. However, the retaining effect of filter cakes seems negligible compared to the retaining effect within the filter. We conclude that the composition of soil colloidal suspensions depends significantly on the technique which is used to remove larger particles. Filtration underestimates the amount of colloids in suspension and centrifugation should be preferred as separation method at least for soils with colloids of similar density, either M or O. ; p. 35-40.
    Keywords: Colloids ; Filtrates ; Centrifugation ; Filtration ; Aluminum ; Turbidity ; Soil Colloids ; Silicon ; Filter Cake ; Soil
    ISSN: 0927-7757
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 4
    Language: English
    In: Nutrient Cycling in Agroecosystems, 2012, Vol.93(1), pp.75-88
    Description: Topsoil constituents are eroded from agricultural sites and leached towards drainage channels. This transfer can affect aquatic ecosystems and deteriorate the efficiency of drainage systems and fertilisers. As long as erosion cannot be completely avoided, the recycling of sediments and associated nutrients may offer a sustainable solution to these problems. The aim of our case study at the island Sant Erasmo, lagoon of Venice (Italy) was to assess the ecological problems and potentials of sediment recycling. With our assessment we concentrated on (1) the origin of channel sediments, (2) the benefit of sediment application for increasing the nutrient stocks of the soils, and (3) the risk of heavy metal (HM) contamination of arable soils by sediment application. Samples from soils of horticultural sites, sediments, and waters from adjacent drainage channels and lagoon sediments were analyzed for the concentrations of nutrients (P and K) and HM (Cu, Pb, and Zn). Potentially available channel sediment masses and element stocks were calculated for the soil fertility classes of Sant Erasmo based on local measurements of sediment depths and analyses of aerial photographs by a geographic information system. In a column experiment, leaching of both nutrients and Cu from recently dredged sediments was analyzed. Heavy metal concentrations of soils and channel sediments were much higher than of lagoon sediments. The similarity of the chemical properties of the channel sediments and of top soil samples implies that topsoil material is eroded into the channels. The amount of sediments accumulated in the channels corresponded to soil erosion rates between 2 and 23 t ha −1  a −1 . Channel sediments contained higher concentrations of nutrients and organic carbon but slightly lower concentrations of HM than the soils of adjacent horticultural sites. Sediment P and K yields would be sufficient to replace fertiliser application at the horticultural sites for up to 51 and 35 years, respectively. The column experiment indicated that Cu mobilization induced by oxidation processes is restricted to the first years after sediments are applied to the soils. Our study emphasizes that for a comprehensive assessment of sediment recycling in agricultural systems the available sediment stocks as well as the contents of nutrients and pollutants of the sediment in relation to soils have to be considered.
    Keywords: Phosphorus ; Heavy metals ; Nutrient cycling ; Leaching experiment
    ISSN: 1385-1314
    E-ISSN: 1573-0867
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  • 5
    Language: English
    In: Environmental Chemistry, 2012, Vol.9(5), p.462-473
    Description:  The size of soil colloids is – among other characteristics – crucial for the mobility of associated contaminants. We analysed the effect of liming on the size of colloids mobilised from strongly contaminated shooting-range soils using multi-stage tangential ultrafiltration (MTUF) for the size fractionation of dispersed soil colloids. Our results indicate the high analytical potential of MTUF and show that liming induces the aggregation of colloids, thereby decreasing the mobilisation of colloid-bound Sb and As, but increasing colloidal Pb.
    Keywords: cation effect; colloid; remediation.
    ISSN: 1448-2517
    E-ISSN: 1449-8979
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  • 6
    Language: English
    In: Journal of Soils and Sediments, 2012, Vol.12(8), pp.1209-1210
    Description: Issue Title: Special issue: Coevolution of organic substances and soils
    Keywords: Environment ; Environmental Physics ; Soil Science & Conservation ; Environment, General ; Agriculture;
    ISSN: 1439-0108
    E-ISSN: 1614-7480
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  • 7
    Language: English
    Description: Benetzungshemmung ist eine zentrale Steuergröße für den bevorzugten Wasser- und Stofftransport im Boden. Die vorliegende Arbeit untersucht den Einfluss der Benetzungshemmung auf die Stoff- und Wasserflüsse in einem schadstoffbelasteten ehemaligen Rieselfeld. Des Weiteren untersucht diese Arbeit den Einfluss der Benetzungshemmung auf das Mobilisierungspotential von Schwermetallen und PAHs im Dispergierungsversuch. Wir überprüften, ob der bevorzugte Fluss das Risiko einer Grundwasserbelastung senkt, da benetzungsgehemmte Bodenpartien umflossen werden, oder erhöht, da hydraulische Scherkräfte in präferentiellen Fließwegen eine Mobilisierung von kolloid-gebundenen Schadstoffen bewirken können (1). Darüber hinaus gehen wir davon aus, dass benetzungsgehemmte Bodenpartien reaktionsträge sind und daher weniger als Schadstoffquelle fungieren als benetzbare Bereiche (2). Des Weiteren nehmen wir an, dass die Ausbildung einer zeitlich stabiler Benetzungshemmung die Bildung und Stabilität der Fließwege (3) und damit die Sammeleffizienz von Platten-Lysimetern beeinflusst (4) Die erste Hypothese wurde getestet, indem der langfristige und räumliche Verlauf der Stoffflüsse im Sickerwasser mittels freidränenden Lysimetern und Dochtlysimetern analysiert wurde und physikalisch-chemische Faktoren identifiziert wurden, die die Mobilität von gelösten und kolloid-gebundenen Schadstoffen im Boden kontrollieren (1). Die zweite Hypothese wurde getestet, indem die Auswirkungen der Boden-Hydrophobizität auf das Mobilisierungspotenzial von Schadstoffen im Labor-Dispergierungsversuch ermittelt wurden (2). Der Einfluss der Bodenfeuchte auf die Bildung und Stabilität der Fließwege wurde... ; Water repellency has been found to be a crucial parameter in controlling preferential transport of water and solutes in the soil. This thesis investigates the impact of water repellency on solute and water fluxes in a contaminated former sewage site. Moreover this thesis examines the impact of water repellency on the mobilisation potential of heavy metals and PAHs by dispersion experiments. We tested the hypothesis whether preferential flow decreases the risk of groundwater contamination, since water repellent soil parts are bypassed, or if it increases, since hydraulic shear forces may cause a rapid downward transport of colloid-bound contaminants through the vadose zone (1). Moreover we assume that hydrophobic compounds are chemically inert and therefore act to a lesser extend as a source for contaminants than hydrophilic compounds (2). Furthermore we suppose that the moisture-related temporal and spatial extend and severity of water repellency influences the formation and stability of preferential flow paths (3) and hence the collection performance of plate lysimeters (4). To address the first hypothesis the long-term spatial and temporal course of solute fluxes sampled by zero-tension and tension lysimeters are analysed and physico-chemical factors which control the mobility of dissolved and colloid-bound contaminants in the soil are...
    Keywords: Naturwissenschaften Und Mathematik ; Hydrophobizität ; Lysimeter ; Preferentieller Fluß ; Schadstoffmobilität ; Schwermetalle ; Contaminant Mobility ; Heavy Metals ; Lysimeter ; Preferential Flow ; Water Repellency
    Source: DataCite
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