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Berlin Brandenburg

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  • Kaupenjohann, Martin  (11)
  • Lang, F
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  • 1
    In: Canadian Journal of Forest Research (Revue canadienne de recherche forestière), 2000, Vol.30(7), pp.1034-1040
    Description: Molybdenum plays an important role in the nitrogen turnover of ecosystems. However, very little is known about Mo availability in forest soils. We measured the oxalate-extractable Mo concentrations of acid forest soils, the Mo, nitrate, phosphate, and sulfate fluxes from the organic forest floor into the mineral soil using resin tubes and the Mo concentrations of the tree needles at 28 different Norway spruce ( Picea abies (L.) Karst.) sites in southern Germany. The supply of oxalate-extractable Mo varied from 51 to 3400 gha -1 , with the lowest values occurring in sandstone-derived soils (370 212 gha -1 ; mean SD). Molybdenum concentrations of current-year needles were in the range of 5 to 48 ngg -1 . The Mo needle concentrations and oxalate-extractable Mo of soils did not correlate. However, Mo fluxes (6-60 gha -1 a -1 ) from the organic forest floor into the mineral soils were correlated to needle concentrations and to the NO 3 fluxes. We conclude that Mo turnover within forest ecosystems is governed by Mo plant availability of mineral soils as well as by plant Mo uptake. In addition, Mo cycling strongly affects Mo distribution within soil profiles and Mo fluxes out of the organic layer.
    Description: Le molybdne joue un rle important dans le renouvellement de l'azote des cosystmes. Toutefois, on connat peu de choses au sujet de la disponibilit de Mo dans les sols forestiers. Nous avons mesur la concentration de Mo extractible l'oxalate dans des sols forestiers acides, les flux de Mo, de nitrate, de phosphate et de sulfate, de la couverture morte organique vers le sol minral, l'aide de tubes de rsines ainsi que la concentration de Mo dans les aiguilles d'pica commun ( Picea abies (L.) Karst.) dans 28 sites diffrents du sud de l'Allemagne. L'apport de Mo extractible l'oxalate variait de 51 3400 gha -1 avec les plus faibles valeurs provenant des sols drivs de grs (370 212 gha -1 ; moyenne ET). La concentration de Mo dans les aiguilles de l'anne courante variait de 5 48 ngg -1 . La concentration de Mo dans les aiguilles et le Mo extractible l'oxalate dans les sols n'taient pas corrls. Toutefois, les flux de Mo (6-60 gha -1 a -1 ) de la couverture morte organique vers le sol minral taient corrls aux concentrations foliaires et aux flux de NO 3 . Nous en concluons que le renouvellement de Mo dans les cosystmes forestiers est gouvern par le Mo des sols minraux disponible pour la plante autant que par le prlvement de Mo par la plante. De plus, le recyclage de Mo affecte fortement la distribution de Mo dans les profils de sol et le flux de Mo hors de la couche organique.[Traduit par la Rdaction]
    Keywords: Forest Floor ; Soils (Acid) ; Mobility ; Soil Profiles ; Molybdenum ; Minerals ; Nitrogen ; Sulfate ; Picea Abies ; Management and Conservation;
    ISSN: 0045-5067
    E-ISSN: 1208-6037
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  • 2
    Language: English
    In: Science of the Total Environment, 15 December 2018, Vol.645, pp.192-204
    Description: Riverbank filtration systems are important structures that ensure the cleaning of infiltrating surface water for drinking water production. In our study, we investigated the potential risk for a breakthrough of environmentally aged silver nanoparticles (Ag NP) through these systems. Additionally, we identified factors leading to the remobilization of Ag NP accumulated in surficial sediment layers in order to gain insights into remobilization mechanisms. We conducted column experiments with Ag NP in an outdoor pilot plant consisting of water-saturated sediment columns mimicking a riverbank filtration system. The NP had previously been aged in river water, soil extract, and ultrapure water, respectively. We investigated the depth-dependent breakthrough and retention of NP. In subsequent batch experiments, we studied the processes responsible for a remobilization of Ag NP retained in the upper 10 cm of the sediments, induced by ionic strength reduction, natural organic matter (NOM), and mechanical forces. We determined the amount of remobilized Ag by ICP-MS and differentiated between particulate and ionic Ag after remobilization using GFAAS. The presence of Ag-containing heteroaggregates was investigated by combining filtration with single-particle ICP-MS. Single and erratic Ag breakthrough events were mainly found in 30 cm depth and Ag NP were accumulated in the upper 20 cm of the columns. Soil-aged Ag NP showed the lowest retention of only 54%. Remobilization was induced by the reduction of ionic strength and the presence of NOM in combination with mechanical forces. The presence of calcium in the aging- as well as the remobilizing media reduced the remobilization potential. Silver NP were mainly remobilized as heteroaggregates with natural colloids, while dissolution played a minor role. Our study indicates that the breakthrough potential of Ag NP in riverbank filtration systems is generally low, but the aging in soil increases their mobility. Remobilization processes are associated to co-mobilization with natural colloids.
    Keywords: Heteroaggregation ; Nanoparticle Transformation ; Breakthrough ; Mobility ; Reversibility ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Geochimica et Cosmochimica Acta, 2006, Vol.70(3), pp.595-607
    Description: Anions of polycarboxylic low-molecular-weight organic acids (LMWOA) compete with phosphate for sorption sites of hydrous Fe and Al oxides. To test whether the sorption of LMWOA anions decreases the accessibility of micropores (〈2 nm) of goethite (α-FeOOH) for phosphate, we studied the kinetics of citrate-induced changes in microporosity and the phosphate sorption kinetics of synthetic goethite in the presence and absence of citrate in batch systems for 3 weeks (500 μM of each ion, pH 5). We also used C-coated goethite obtained after sorption of dissolved organic matter in order to simulate organic coatings in the soil. We analyzed our samples with N adsorption and electrophoretic mobility measurements. Citrate clogged the micropores of both adsorbents by up to 13% within 1 h of contact. The micropore volume decreased with increasing concentration and residence time of citrate. In the absence of citrate, phosphate diffused into micropores of the pure and C-coated goethite. The C coating (5.6 μmol C m ) did not impair the intraparticle diffusion of phosphate. In the presence of citrate, the diffusion of phosphate into the micropores of both adsorbents was strongly impaired. We attribute this to the micropore clogging and the ligand-induced dissolution of goethite by citrate. While the diffusion limitation of phosphate by citrate was stronger when citrate was added before phosphate to pure goethite, the order of addition of both ions to C-coated goethite had only a minor effect on the intraparticle diffusion of phosphate. Micropore clogging and dissolution of microporous hydrous Fe and Al oxides may be regarded as potential strategies of plants to cope with phosphate deficiency in addition to ligand-exchange.
    Keywords: Geology
    ISSN: 0016-7037
    E-ISSN: 1872-9533
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  • 4
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2016, Vol.179(2), pp.129-135
    Description: Phosphorus is one of the major limiting factors of primary productivity in terrestrial ecosystems and, thus, the P demand of plants might be among the most important drivers of soil and ecosystem development. The P cycling in forest ecosystems seems an ideal example to illustrate the concept of ecosystem nutrition. Ecosystem nutrition combines and extents the traditional concepts of nutrient cycling and ecosystem ecology. The major extension is to consider also the loading and unloading of nutrient cycles and the impact of nutrient acquiring and recycling processes on overall ecosystem properties. Ecosystem nutrition aims to integrate nutrient related aspects at different scales and in different ecosystem compartments including all processes, interactions and feedbacks associated with the nutrition of an ecosystem. We review numerous previous studies dealing with P nutrition from this ecosystem nutrition perspective. The available information contributes to the description of basic ecosystem characteristics such as emergence, hierarchy, and robustness. In result, we were able to refine Odum's hypothesis on P nutrition strategies along ecosystem succession to substrate related ecosystem nutrition and development. We hypothesize that at sites rich in mineral‐bound P, plant and microbial communities tend to introduce P from primary minerals into the biogeochemical P cycle (acquiring systems), and hence the tightness of the P cycle is of minor relevance for ecosystem functioning. In contrast, tight P recycling is a crucial emergent property of forest ecosystems established at sites poor in mineral bound P (recycling systems). We conclude that the integration of knowledge on nutrient cycling, soil science, and ecosystem ecology into holistic ecosystem nutrition will provide an entirely new view on soil–plant–microbe interactions.
    Keywords: Ecosystem Properties ; P Recycling ; P Nutrition Strategy ; Forest Nutrition ; P Acquiring
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 5
    Language: English
    In: Soil Science Society of America Journal, March-April, 2006, Vol.70(2), p.541(9)
    Description: Biogenetic polysugars may affect the sorption characteristics of soil mineral particles in the rhizosphere. We hypothesized that polygalacturonate [PGA, ([[C.sub.6][H.sub.7][O.sub.6]).sub.n.sup.-]] coatings on goethite reduce the diffusion of phosphate into the pores of the adsorbent. Goethite was preloaded with PGA (0-10 mg C [g.sup.-1]). The samples were characterized by [N.sub.2] and C[O.sub.2] adsorption, electrophoretic mobility measurements, and scanning electron microscopy/energy dispersive X-ray analysis (SEM-EDX). The phosphate sorption kinetics was studied with batch experiments over 2 wk at pH 5 and an initial phosphate concentration of 250 [micro]M. Pore volume and specific surface area of the goethite samples declined after PGA addition. The PGA coatings reduced the [zeta]-potential of goethite from 42.3 to -39.6 mV at the highest C loading. With increasing PGA-C content and decreasing [zeta]-potential the amount of phosphate sorbed after 2 wk decreased linearly (P 〈 0.001). Sorption of phosphate to pure and PGA-coated goethite showed an initial fast sorption followed by a slow sorption reaction. At the smallest C loading (5.5 mg C [g.sup.-1]) the portion of phosphate retained by the slow reaction was smaller than for the treatment without any PGA, while at higher C loadings the fraction of slowly immobilized phosphate increased. Our results suggest that at low C-loadings PGA impaired the intraparticle diffusion of phosphate. In contrast, the slow step-by-step desorption of PGA (〈52% within 2 wk) or the diffusion of phosphate through PGA coatings or both are rate limiting for the slow phosphate reaction at C loadings 〉 5.5 mg C [g.sup.-1].
    Keywords: Soil Phosphorus -- Research ; Soil Chemistry -- Research ; X-ray Analysis
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 6
    Language: English
    In: Soil Science Society of America Journal, Nov-Dec, 2004, Vol.68(6), p.1853(10)
    Description: Recent [N.sub.2] adsorption studies have suggested a 'pore clogging' effect on mineral soil phases caused by organic matter coatings. For methodological reasons, this pore clogging effect has been studied only after drying. Our hypothesis was that pore clogging is affected by drying of organic coatings. In our study, we used AlOOH, which has been equilibrated with dissolved organic matter (DOM) and polygalacturonic acid [[PGA; [([C.sub.6][H.sub.8][O.sub.6]).sup.n]]. To test our hypothesis, we determined the porosity of moist and freeze-dried AlOOH samples. Freeze-dried samples were analyzed by [N.sub.2] adsorption, moist samples by [sup.1]H-nuclear magnetic resonance (NMR). In addition, the samples were characterized by environmental scanning electron microscopy--energy dispersive x-ray spectroscopy (ESEM-EDX). Both, DOM and PGA significantly reduced specific surface area (SS[A.sub.BET]) of AlOOH by 34 [m.sup.2][g.sup.-1](15%) and 77 [m.sup.2] [g.sup.-1] (36%). The reduction in SS[A.sub.BET] normalized to the amount of C sorbed was 1.0 [m.sup.2] [mg.sup.-1] DOM-C and 5.9 [m.sup.2] [mg.sup.-1] PGA-C. Dissolved OM reduced the pore volume of micro- and small mesopores 〈3 nm whereas PGA also reduced the volume of larger pores. The [sup.1]H-NMR results of moist samples showed that PGA sorption reduced the amount of water in pores 〈4 nm. In addition, the pore size maximum of AlOOH increased by 150%. Polygalacturonic acid coatings created new interparticle pores of about 10- to 70-nm size that are not stable upon freeze-drying. Porosity changes upon DOM-treatment were not commensurable by [sup.1]H-NMR. Our results indicate that clogging of micro- and small mesopores is not an artifact of freeze-drying. Polygalacturonic acid seems not only to cover the mouth of AlOOH-nanometer pores but also to fill them.
    Keywords: Soil Mineralogy -- Research
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 7
    Language: English
    In: Soil Science Society of America Journal, Sept-Oct, 2006, Vol.70(5), p.1547(9)
    Description: Organic coatings on Fe oxides can decrease the accessibility of intraparticle pores for oxyanions like phosphate. We hypothesized that the slow sorption of phosphate to goethite coated with polygalacturonate (PGA) is controlled by the accessibility of external goethite surfaces to phosphate rather than by diffusion of phosphate into micropores ([empty set] 〈 2 nm). We studied the phosphate sorption kinetics of pure and PGA-coated goethites that differed in their microporosity ([N.sub.2] at 77 K, 46 vs. 31 [mm.sup.3] [g.sup.-1]). Because drying may affect the structure or surface coverage of PGA, we also tested the effect of freeze-drying on the slow phosphate sorption. The samples were examined by gas adsorption ([N.sub.2], C[O.sub.2]) and electrophoretic mobility measurements. Phosphate sorption and PGA-C desorption were studied in batch experiments for 3 wk at pH 5. In PGA-coated samples, the slow phosphate sorption was independent of micropore volume. Phosphate displaced on average 57% of PGA-C within 3 wk. Similar to phosphate sorption, the PGA-C desorption comprised a rapid initial desorption, which was followed by a slow C desorption. Sorption competition between phosphate and presorbed PGA depended on the 〈10-nm porosity and the C loading of the adsorbent. The efficacy of phosphate to desorb PGA generally increased after freeze-drying. We conclude for PGA-coated goethites that (i) freeze-drying biased the slow phosphate sorption by changing the structure/surface coverage of PGA, and (ii) within the time frame studied, micropores did not limit the rate of the slow phosphate sorption. Rather, the slow, gradual desorption of PGA and/or the diffusion of phosphate through PGA coatings controlled the slow phosphate sorption to PGA-coated goethite.
    Keywords: Mineralogical Research -- Analysis ; Phosphates -- Research ; Sorption -- Research
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 8
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2004, Vol.167(2), pp.177-183
    Description: Risk assessment of heavy metal input into forest ecosystems requires information about metal fluxes from the forest floor (organic layer) into the mineral soil. Common methods for the monitoring of element fluxes are generally time‐consuming and expensive. Additionally, the reliability of the results is in part contested especially for trace elements, showing very low concentrations which are sometimes even below analytical detection limit. We used ion exchange resin tubes installed below the forest floor to determine heavy metal and As fluxes at 25 forest monitoring sites in Germany. Chloride tracer experiments and the comparison of our data with throughfall and lysimeter data, determined within the Level II monitoring network, proved the accuracy of our method. Mean trace element fluxes based on the resin method were 50 g As ha yr, 2 g Cd ha yr, 168 g Cu ha yr, 176 g Ni ha yr, and 186 g Pb ha yr.The results show that the organic layer may change into a source of heavy metals after emission has decreased. Austauscherharzröhren zur Bestimmung des Spurenelementeintrags in Mineralböden auf Waldstandorten Der Schwermetalleintrag von der Humusauflage in den Mineralboden ist eine wichtige Größe zur Risikoabschätzung der Schwermetallflüsse in Waldökosystemen. Herkömmliche Methoden zur Erfassung von Elementflüssen sind zeit‐ und kostenaufwändig. Bei Spurenelementen verringern analytische Probleme die Aussagekraft der ermittelten Daten. Mithilfe von Röhren, die mit Ionenaustauscherharz gefüllt sind und unterhalb der Humusauflage in den Boden eingebracht werden, haben wir auf 25 Waldstandorten Schwermetall‐ und As‐Flüsse gemessen. Chlorid‐Tracer‐Experimente und der Vergleich unserer Daten mit Stoffflussdaten aus dem Level‐II‐Monitoring bestätigen, dass mit unserer Methode Elementflüsse von der Humusauflage in den Mineralboden zuverlässig erfasst werden können. Mit den Austauscherharzröhren haben wir folgende durchschnittliche Elementflüsse bestimmt: 50 g As ha a, 2 g Cd ha a, 168 g Cu ha a, 176 g Ni ha a und 186 g Pb ha a. Die Ergebnisse zeigen, dass die Humusauflage nach Rückgang anthropogener Einträge zur Schwermetallquelle wird.
    Keywords: Heavy Metals ; Arsenic ; Forest Soils ; Element Fluxes ; Exchange Resin Tubes
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 9
    Language: English
    In: Journal of Plant Nutrition and Soil Science, June 1999, Vol.162(3), pp.309-314
    Description: We extracted molybdenum (Mo) from eight acid forest soils (19 A, E, and B horizons) in NE‐Bavaria and from one site in the Ore Mountains, using (1) anion exchange‐resin, (2) 0.2 M ammonium oxalate, and (3) ascorbic acid/ammonium oxalate. The Mo concentrations in the anion exchange‐resin fraction varied between 5 and 28 μg kg. Oxalate‐extractable Mo ranged from 44 to 407 μg kg and after reduction of iron (Fe) with ascorbic acid, 135 to 1071 μg Mo kg were extracted. The lowest concentrations of Mo were measured in acid and sesquioxide impoverished E horizons. The total concentrations of Mo in spruce needles correlated with ion exchange resin extractable Mo, indicating that this fraction represents Mo readily available to plants. The Mo and Fe dissolution kinetics during oxalate extraction were studied on 8 of the soil samples to obtain further information on Mo mobilization. Oxalate extractable iron (Fe) was mobilized within a few hours. A first order equation was applicable to the Fe dissolution kinetics with the rate constants ranging between 0.9 and 9.0 h. The mobilization of Mo occurred in two distinct stages. An initially rapid dissolution was followed by a further increase in extractable Mo but with slower kinetics. A combined first order‐diffusion equation was found to be appropriate for modelling the results. The first order rate constants for Mo mobilization ranged from 0.6 to 11.4 h. However, correlations between the rates of reaction of Mo and Fe could not be established, indicating that Mo is either not distributed equally along Fe minerals or that there is another pool, possibly the organic substance of the soil, from which Mo is extractable by oxalate. Molybdän‐Fraktionen und ‐Freisetzungs‐ kinetik in sauren Waldböden Wir extrahierten Molybdän (Mo) mittels (1) Anionenaustauscherharz, (2) 0,2 M Ammoniumoxalat und (3) Ascorbinsäure/Ammoniumoxalat aus sauren Waldböden (19 A‐, E‐ und B‐Horizonte) von insgesamt 9 Standorten im Fichtelgebirge, Frankenwald und Erzgebirge. Die Mo‐Gehalte im Harzextrakt lagen zwischen 5 und 28 μg kg oxalatextrahierbares Mo betrug 44 bis 407 μg kg und nach Reduktion kristalliner Eisenoxide mit Ascorbinsäure wurden Gehalte von 135 bis 1071 μg Mo kg extrahiert. Niedrige Mo‐Gehalte traten in sauren und sesquioxidarmen Eluvialhorizonten auf. Zusammenhänge zwischen Austauscherharz‐extrahierbarem Mo und den Mo‐Nadelgehalten von Fichten deuten darauf hin, daß diese Fraktion ein Maß für die Mo‐Pflanzenverfügbarkeit darstellt. Um weitere Aufschlüsse über die Mo‐Mobilität zu erhalten, wurde an 8 Bodenproben die Freisetzungskinetic von Mo und Eisen (Fe) bei der Extraktion mit 0,2 M Ammoniumoxalat untersucht. Das gesamte oxalatlösliche Fe (Fe) wurde innerhalb weniger Stunden mobilisiert. Die Kinetik folgt dem Modell 1. Ordnung mit Geschwindigkeitskonstanten (k) zwischen 0,9 und 9,0 h. Molybdän wird zunächst ebenfalls rasch mobilisiert (k: 0,6—11,4 h). Jedoch ist die Mo‐Lösungskinetik von einem vermutlich diffusionsgesteuerten Mobilisierungsprozeß überlagert. So ließ sich die Mo‐Freisetzung durch ein kombiniertes Modell beschreiben, das Auflösung und Diffusion Rechnung trägt. Obwohl die Geschwindigkeitskonstanten der Fe‐ und Mo‐Mobilisierung eine vergleichbare Spanne abdecken, korrelieren sie nicht. Dies deutet darauf hin, daß Mo entweder nicht gleichmäßig auf die Fe‐Oxide verteilt ist, oder daß mit der Oxalat‐Extraktion noch ein weiterer leicht mobilisierbarer Mo‐Pool, möglicherweise die organische Substanz, erfaßt wird.
    Keywords: Molybdenum ; Availability ; Resin Extraction ; Spruce Stand ; Diffusion Controlled Mobilization
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 10
    Language: English
    In: Journal of Plant Nutrition and Soil Science, December 2000, Vol.163(6), pp.571-575
    Description: It is widely accepted that the fixation of oxyanions is due to diffusion of the ions into the pores and interdomains of iron oxides. Most studies have used batch techniques, which do not allow to clearly differentiate chemisorption from mass transport phenomena. Thus, it is not yet clear, whether strengthening of chemical Mo bonding occurs along with residence time, in addition to diffusion processes. In this study we used pressure jump relaxation (p‐jump), a very fast kinetic technique, to (1) elucidate the Mo/goethite interaction and to (2) analyze the effects of aging the Mo/goethite complex on Mo chemisorption. A synthetic goethite was incubated with Mo solution (1 mM Mo) for 12, 24, and 72 hours at pH 4. At the end of the incubations p‐jump experiments were performed on the suspensions at temperatures ranging from 283 to 303 K. Relaxation kinetics were modelled using a combination of two first order terms. In addition, the amount of Mo sorbed to the goethite after different incubation times was determined by graphite furnace atomic absorption spectroscopy. The MoO/goethite systems revealed a fast relaxation time (= reciprocal of rate constant, about 4 ms), that decreased with increasing temperature and a slow one (about 60 ms) that did not depend on temperature. Activation energy of the fast process was 76 kJ mol. We did not observe any effects of incubation time on the fast process. However, the amount of Mo sorbed to the iron oxide increased with increasing incubation time. We conclude that the fast relaxation represents Mo chemisorption to the goethite. Slow relaxation seems to be due to Mo transport within the suspension. The pressure jump results indicate, that the dominant surface species of Mo sorbed to goethite do not change along with residence time. Mechanismen der Molybdänsorption an Eisenoxide Die Fixierung von Oxyanionen durch Eisenoxide wird im allgemeinen auf die Diffusion von Ionen in die Interdomänenräume von Eisenoxiden zurückgeführt. Weil es mit Hilfe herkömmlicher Batch‐Experimente nicht möglich ist, zwischen Chemisorptions‐ und Massentransport‐Prozessen zu unterscheiden, ist bislang unklar, ob zusätzlich Veränderungen der chemischen Bindung bei längeren Sorptionszeiten für die Festlegung von Oxyanionen verantwortlich sind. Ziel dieser Untersuchung ist es, mittels Druck‐Sprung (p‐jump), einer sehr schnellen kinetischen Methode, die Mechanismen der Mo‐Fixierung an Eisenoxide aufzuklären. Ein synthetischer Goethit wurde bei pH 4 mit molybdathaltiger Lösung (1 mM Mo) 12, 24 und 72 h inkubiert. Nach dieser Vorinkubation wurden p‐jump‐Versuche mit den verschieden lange gealterten Suspensionen bei Temperaturen zwischen 283 und 303 K durchgeführt. Die Relaxationskinetik wurde dabei durch die Kombination zweier Terme erster Ordnung beschrieben. Zusätzlich wurde die Menge an sorbiertem Mo nach den unterschiedlichen Inkubationszeiten bestimmt. Für das Mo/Goethit‐System ergaben sich eine schnelle (ca. 4 ms) und eine langsame (ca. 60 ms) Relaxationszeit (= Kehr‐wert der Geschwindigkeitskonstante). Während die schnelle Relaxation sehr stark temperaturabhängig war, zeigte die langsame Relaxation keinen Temperatureinfluss. Die Aktivierungsenergie für den schnellen Prozess betrug 76 kJ mol. Obwohl die sorbierte Mo‐Menge mit der Inkubationszeit deutlich zunahm, war die Relaxationszeit unabhängig von der Dauer der Vorinkubation. Die Ergebnisse deuten darauf hin, dass die schnelle Relaxation durch die Chemisorption von Mo an den Goethit hervorgerufen wird. Die langsame Relaxation ist vermutlich auf Durchmischungsphänomene innerhalb der Suspensionen zurückzuführen. Die Untersuchung deutet darauf hin, dass Mo‐Fixierung allein auf Transportprozesse, nicht aber auf die Veränderung der chemischen Bindung zurückzuführen ist.
    Keywords: Molybdenum‐Fixation ; Sorption Mechanism ; Kinetic Approach ; P‐Jump ; Diffusion
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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