Description: Das Projekt "The mechanisms of ligand adsorption and iron oxide dissolution in the presence of biogenic surfactants" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Institut für Biogeochemie und Schadstoffdynamik durchgeführt. Many microorganisms and plants produce and release bio-surfactants, for example, in the soil directly surrounding active plant roots (called the rhizosphere). Surfactants are organic compounds with hydrophilic head groups and hydrophobic tails. They generally have a high affinity for mineral surfaces due to electrostatic and hydrophobic interactions. Adsorption of surfactants onto mineral surfaces has pronounced effects on the physico-chemical properties of the mineral-water interface (e.g., surface charge, hydrophobicity). Therefore, we hypothesized that presence of surfactants may have strong effects on a variety of reactions between microorganisms or plant roots exudates and mineral surfaces occurring in soils and other natural environments. One such reaction is the acquisition of the essential nutrient iron by microorganisms or plants through the release of siderophores. Siderophores are organic compounds that strongly bind iron and that promote dissolution of iron bearing minerals by a so called ligand-controlled dissolution mechanism. The specific objective of this work was to study the influence of surfactants on the ligand-controlled dissolution of goethite (a-FeOOH), one of the most common iron oxide minerals in soils and sediments. Two different siderophores and a synthetic ligand (EDTA) were chosen as the complexing ligands. Sodium dodecyl sulfate (synthetic) and rhamnolipids (biogenic) were used as surfactants. Our results revealed that low amounts of adsorbed surfactants significantly increase the ligand-controlled dissolution rates of goethite. The dissolution rates were not proportional to the amount of adsorbed ligands, as stipulated by the rate law of ligand-controlled dissolution. We hypothesized that the enhancement of dissolution rates in the presence of surfactants is related to changing surface speciation of the adsorbed ligand and changes of the surface protonation by proton co-adsorption with the surfactants. Our results suggest that bio-surfactants may play an important role in the iron acquisition by bacteria and roots of certain plant species which release siderophores under iron-limiting conditions.
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Ethylendiamintetraessigsäure ? Natriumsulfat ? Biotensid ? Eisenoxid ? Natrium ? Sulfat ? Eisen ? Biogeochemie ? Zürich ? Biopharmazeutikum ? Eisenbakterien ? Nährstoff ? Tensid ? Bodenmikroorganismen ? Gebühr ? Adsorption ? Mineralwasser ? Pflanzenart ? Rhizosphäre ? Wirkung ? Pflanzenwurzel ? Bakterien ? Organische Verbindung ? Mineralboden ? Beschaffung ? Bodenbewirtschaftung ? Chemikalien ? Gesetz ? Studie ? Mikroorganismen ? Sediment ? Boden ? Wirkung ? Auflösen ? Arbeit ? Lagerung ? Mineral ? MECHANISMEN ? SPEZIFISCH ? GRUPPE ? UMLAND ? UNTER ? VERBINDUNG ? Art [Spezies] ? VERHAELTNIS ? BETRAG ? Bepflanzung ? EIN ? Gebühr [Abgabe] ? BEISPIEL ? Muskelarbeit ? VERWANDT ? Vermehrung ? WICHTIG ? STARK ? NATUERLICHE UMWELT ? EINGESCHRAENKT ? OBERFLAECHE ? ERGEBNIS ? SCHNITTSTELLE ? SONSTIG ?
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 2006-04-01 - 2006-12-31
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