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Berlin Brandenburg

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  • Dissolved Organic Matter
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  • 1
    Language: English
    In: Environmental pollution, 2011, Vol.159(5), pp.1398-1405
    Description: Arsenic mobility may increase in liquid phase due to association with colloidal Fe oxides. We studied the association of As with Fe oxide colloids in the effluent from water-saturated soil columns run under anoxic conditions. Upon exfiltration, the solutions, which contained Fe²⁺, were re-aerated and ferrihydrite colloids precipitated. The entire amount of effluent As was associated with the ferrihydrite colloids, although PO₄ ³⁻, SiO₄ ⁴⁻, CO₃ ²⁻ and dissolved organic matter were present in the effluent during ferrihydrite colloid formation. Furthermore, no subsequent release of As from the ferrihydrite colloids was observed despite the presence of these (in)organic species known to compete with As for adsorption on Fe oxides. Arsenic was bound via inner-sphere complexation on the ferrihydrite surface. FTIR spectroscopy also revealed adsorption of PO₄ ³⁻ and polymerized silica. However, these species could not impede the quantitative association of As with colloidal ferrihydrite in the soil effluents. ; p. 1398-1405.
    Keywords: Iron Oxides ; Dissolved Organic Matter ; Effluents ; Arsenic ; Adsorption ; Polymerization ; Anaerobic Conditions ; Ferrihydrite ; Iron ; Colloids ; Silica ; Fourier Transform Infrared Spectroscopy ; Soil
    ISSN: 0269-7491
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  • 2
    Language: English
    In: Environmental pollution, 2013, Vol.179, pp.315-325
    Description: Mass transfer processes of pollutants from non-aqueous phase liquids (NAPL) may control groundwater pollution at abandoned industrial sites. We studied release kinetics of polycyclic aromatic hydrocarbons (PAHs) from fresh and aged tar phases using a dialysis tubing technique. Time for equilibration ranged from several days to more than three years. For fresh tar materials the release seems to be limited by retarded pore diffusion, while for two of three aged tars diffusion limited release influenced by dissolved organic matter (DOM) was assumed. The equilibration process was driven by solubilization thermodynamics expressed by Raoult's law. Yet, solubility enhancement was observed potentially due to the presence of organic mobile sorbents. The results show that the release of PAHs from tar phases is generally rate limited and partitioning according to Raoult's law is the driving mechanism of the exchanges process. ; p. 315-325.
    Keywords: Nonaqueous Phase Liquids ; Dissolved Organic Matter ; Dialysis ; Polycyclic Aromatic Hydrocarbons ; Solubilization ; Solubility ; Mass Transfer ; Thermodynamics ; Groundwater Contamination
    ISSN: 0269-7491
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 3
    Language: English
    In: Environmental Pollution, August 2013, Vol.179, pp.315-325
    Description: Mass transfer processes of pollutants from non-aqueous phase liquids (NAPL) may control groundwater pollution at abandoned industrial sites. We studied release kinetics of polycyclic aromatic hydrocarbons (PAHs) from fresh and aged tar phases using a dialysis tubing technique. Time for equilibration ranged from several days to more than three years. For fresh tar materials the release seems to be limited by retarded pore diffusion, while for two of three aged tars diffusion limited release influenced by dissolved organic matter (DOM) was assumed. The equilibration process was driven by solubilization thermodynamics expressed by Raoult's law. Yet, solubility enhancement was observed potentially due to the presence of organic mobile sorbents. The results show that the release of PAHs from tar phases is generally rate limited and partitioning according to Raoult's law is the driving mechanism of the exchanges process. Release of PAHs from tar phases is severely restricted by retarded pore diffusion.
    Keywords: Aging ; Coal Tar ; Manufactured Gas Plant Sites ; Tar Processing Facilities ; Reactive Transport ; Dissolved Organic Matter ; Polycyclic Aromatic Hydrocarbons ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 4
    Language: English
    In: Environmental Pollution, 2011, Vol.159(5), pp.1398-1405
    Description: Arsenic mobility may increase in liquid phase due to association with colloidal Fe oxides. We studied the association of As with Fe oxide colloids in the effluent from water-saturated soil columns run under anoxic conditions. Upon exfiltration, the solutions, which contained Fe , were re-aerated and ferrihydrite colloids precipitated. The entire amount of effluent As was associated with the ferrihydrite colloids, although PO , SiO , CO and dissolved organic matter were present in the effluent during ferrihydrite colloid formation. Furthermore, no subsequent release of As from the ferrihydrite colloids was observed despite the presence of these (in)organic species known to compete with As for adsorption on Fe oxides. Arsenic was bound via inner-sphere complexation on the ferrihydrite surface. FTIR spectroscopy also revealed adsorption of PO and polymerized silica. However, these species could not impede the quantitative association of As with colloidal ferrihydrite in the soil effluents. ► Ferrihydrite (Fh) colloids precipitated from a solution derived from soil. ► Arsenic that was discharged from soil entirely associated with these colloids. ► Arsenic was strongly bound to the Fh surface via inner-sphere complexation. ► A complexation of As by organic species discharged from soil was not detected. ► (In)organic solutes in the solution from soil could not impede the As–Fh association. Natural concentrations of competing (in)organic species in soil-derived solutions do not impede the strong and quantitative association between As and colloidal ferrihydrite.
    Keywords: Iron Hydroxide ; Phosphate ; Silicate ; Carbonate ; Dissolved Organic Matter ; Engineering ; Environmental Sciences ; Anatomy & Physiology
    ISSN: 0269-7491
    E-ISSN: 1873-6424
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  • 5
    Language: English
    In: Geochimica et cosmochimica acta, 2012, Vol.77, pp.444-456
    Description: Recent studies on the microbial reduction of synthetic iron oxide colloids showed their superior electron accepting property in comparison to bulk iron oxides. However, natural colloidal iron oxides differ in composition from their synthetic counterparts. Besides a potential effect of colloid size, microbial iron reduction may be accelerated by electron-shuttling dissolved organic matter (DOM) as well as slowed down by inhibitors such as arsenic. We examined the microbial reduction of OM- and arsenic-containing ferrihydrite colloids. Four effluent fractions were collected from a soil column experiment run under water-saturated conditions. Ferrihydrite colloids precipitated from the soil effluent and exhibited stable hydrodynamic diameters ranging from 281 (±146)nm in the effluent fraction that was collected first and 100 (±43)nm in a subsequently obtained effluent fraction. Aliquots of these oxic effluent fractions were added to anoxic low salt medium containing diluted suspensions of Geobacter sulfurreducens. Independent of the initial colloid size, the soil effluent ferrihydrite colloids were quickly and completely reduced. The rates of Fe²⁺ formation ranged between 1.9 and 3.3fmolh⁻¹cell⁻¹, and are in the range of or slightly exceeding previously reported rates of synthetic ferrihydrite colloids (1.3fmolh⁻¹cell⁻¹), but greatly exceeding previously known rates of macroaggregate-ferrihydrite reduction (0.07fmolh⁻¹cell⁻¹). The inhibition of microbial Fe(III) reduction by arsenic is unlikely or overridden by the concurrent enhancement induced by soil effluent DOM. These organic species may have increased the already high intrinsic reducibility of colloidal ferrihydrite owing to quinone-mediated electron shuttling. Additionally, OM, which is structurally associated with the soil effluent ferrihydrite colloids, may also contribute to the higher reactivity due to increasing solubility and specific surface area of ferrihydrite. In conclusion, ferrihydrite colloids from soil effluents can be considered as highly reactive electron acceptors in anoxic environments. ; p. 444-456.
    Keywords: Colloids ; Iron Oxides ; Dissolved Organic Matter ; Effluents ; Arsenic ; Hydrodynamics ; Solubility ; Ferrihydrite ; Geobacter Sulfurreducens ; Iron ; Surface Area ; Soil
    ISSN: 0016-7037
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 6
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2003, Vol.166(2), pp.204-209
    Description: Dissolved organic matter (DOM) in soils is partially adsorbed when passing through a soil profile. In most adsorption studies, water soluble organic matter extracted by water or dilute salt solutions is used instead of real DOM gained by lysimeters or ceramic suction cups. We investigated the adsorption of DOM gained from three compartments (forest floor leachate and soil solution from 20 cm (Bg horizon) and 60 cm depth (2Bg horizon)) on the corresponding clay and fine silt fractions ( Bg 〉 2Bg. Dissolved organic matter in the 2Bg horizon can be regarded as slightly reactive, because adsorption was low. Desorption of DOM from the subsoil samples was reflected more realistically with a non‐linear regression approach than with initial mass isotherms. The results show that the extent of DOM adsorption especially in subsoils is controlled by the composition and by the origin of the DOM used as adsorptive rather than by the mineralogical composition of the soil or by contents of soil organic matter. We recommend to use DOM gained when investigating the fate of DOM in subsoils. Adsorption “wirklich” gelöster organischer Substanz an die Ton‐ und Feinschluff‐Fraktionen eines Pseudogleys unter Wald Die gelöste organische Substanz (DOM) in Böden unterliegt bei der Passage eines Bodenprofils Adsorptionsprozessen. In den meisten Adsorptionsstudien wurde wasserlösliche organische Substanz, die mit Wasser oder einer verdünnten Salzlösung extrahiert wurde, anstelle von realer, mit Lysimetern oder keramischen Saugkerzen gewonnener DOM benutzt. Wir untersuchten die Adsorption von in drei Kompartimenten gewonnener DOM (Auflagenperkolat und Bodenlösung aus 20 cm (Sw‐Horizont) und 60 cm Tiefe (IISd‐Horizont)) an die korrespondierenden Ton‐ und Feinschluff‐Fraktionen ( Sw 〉 IISd ab. Gelöste organische Substanz im IISd‐Horizont kann als schwach reaktiv angesehen werden, da die Adsorption gering war. Die Desorption von DOM aus Unterbodenproben wurde von einem nicht‐linearen Regressionsansatz realistischer wieder gegeben als mit der Initial‐mass‐Isotherme. Adsorption und Desorption von Sulfat und Fluorid weisen auf unterschiedliche Adsorptionsprozesse in den jeweiligen Horizonten hin. Die Ergebnisse zeigen, dass die Zusammensetzung und die Herkunft der als Adsorptiv benutzten DOM das Ausmaß der DOM‐Adsorption insbesondere in Unterböden steuert, weniger die mineralogische Zusammensetzung des Bodens oder die Gehalte an organischer Bodensubstanz. Bei Untersuchungen zum Verbleib von DOM in Unterböden empfehlen wir die Verwendung von gewonnener DOM.
    Keywords: Stagnic Gleysol ; Dissolved Organic Matter ; Adsorption ; Clay Fraction ; Fine Silt Fraction
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 7
    Language: English
    In: Journal of Plant Nutrition and Soil Science, August 2007, Vol.170(4), pp.514-521
    Description: Dissolved organic matter (DOM) is involved in many important biogeochemical processes in soil. As its collection is laborious, very often water‐soluble organic matter (WSOM) obtained by extracting organic or mineral soil horizons with a dilute salt solution has been used as a substitute of DOM. We extracted WSOM (measured as water‐soluble organic C, WSOC) from seven mineral horizons of three forest soils from North‐Rhine Westphalia, Germany, with demineralized HO, 0.01 M CaCl, and 0.5 M KSO. We investigated the quantitative and qualitative effects of the extractants on WSOM and compared it with DOM collected with ceramic suction cups from the same horizons. The amounts of WSOC extracted differed significantly between both the extractants and the horizons. With two exceptions, KSO extracted the largest amounts of WSOC (up to 126 mg C kg) followed by HO followed by CaCl. The HO extracts revealed by far the highest molar UV absorptivities at 254 nm (up to 5834 L mol cm) compared to the salt solutions which is attributed to solubilization of highly aromatic compounds. The amounts of WSOC extracted did not depend on the amounts of Fe and Al oxides as well as on soil organic C and pH. Water‐soluble organic matter extracted by KSO bore the largest similarity to DOM due to relatively analogue molar absorptivities. Therefore, we recommend to use this extractant when trying to obtain a substitute for DOM, but as WSOM extraction is a rate‐limited process, the suitability of extraction procedures to obtain a surrogate of DOM remains ambiguous.
    Keywords: Dissolved Organic Matter ; Water‐Soluble Organic Matter ; Extraction ; Forest Soil ; Stagnosol
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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