The Experts below are selected from a list of 228 Experts worldwide ranked by ideXlab platform
Angela G Stewart - One of the best experts on this subject based on the ideXlab platform.
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effect of desferrioxamine b and suwannee river Fulvic Acid on fe iii release and cr iii desorption from goethite
Geochimica et Cosmochimica Acta, 2016Co-Authors: Angela G Stewart, Karen A Hudsonedwards, W E DubbinAbstract:Abstract Siderophores are biogenic chelating ligands that facilitate the solubilisation of Fe(III) and form stable complexes with a range of contaminant metals and therefore may significantly affect their biogeochemical cycling. Desferrioxamine B (DFOB) is a trihydroxamate siderophore that acts synergistically with Fulvic Acid and low molecular weight organic ligands to release Fe from Fe(III) oxides. We report the results of batch dissolution experiments in which we determine the rates of Cr(III) desorption and Fe(III) release from Cr(III)-treated synthetic goethite as influenced by DFOB, by Fulvic Acid, and by the two compounds in combination. We observed that adsorbed Cr(III) at 3% surface coverage significantly reduced Fe(III) release from goethite for all combinations of DFOB and Fulvic Acid. When DFOB (270 μM) was the only ligand present, dissolved Fe(III) and Cr(III) increased approximately 1000-fold and 16-fold, respectively, as compared to the ligand-free system, a difference we attribute to the slow rate of water exchange of Cr(III). Suwannee River Fulvic Acid (SRFA) acts synergistically with DFOB by (i) reducing the goethite surface charge leading to increased HDFOB + surface excess and by (ii) forming aqueous Fe(III)–SRFA species whose Fe(III) is subsequently removed by DFOB to yield aqueous Fe(III)–DFOB complexes. These observations shed new light on the synergistic relationship between DFOB and Fulvic Acid and reveal the mechanisms of Fe(III) acquisition available to plants and micro-organisms in Cr(III) contaminated environments.
David Y. Chang - One of the best experts on this subject based on the ideXlab platform.
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Retention behavior of suwannee river Fulvic Acid components in RP-HPLC
Science of The Total Environment, 2003Co-Authors: Farada Y. Saleh, David Y. ChangAbstract:Chromatographic data of RP - HPLC hasbeen used to provide additional information on the properties of the reference Suwannee River Fulvic Acid components. The polarities of the Fulvic Acid components were found to range from 5.86 to 10.15, and the total solubility parameters to range from 14.12 to 20.92. The estimated hydrocarbonaceous surface areas of the polar moieties range from 30 to 120A2. The hydrophobic neutral constituents represent ∼ 30% of the total Fulvic Acid peaks and can be resolved into five components with k' ranging from 0.5 to 2.0. Their uv and fluorescence chromatograms show what appears to be a regular retention pattern of a homologous series. The uv-visible scans of three of these peaks provide further evidence to this interpretation.
W E Dubbin - One of the best experts on this subject based on the ideXlab platform.
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effect of desferrioxamine b and suwannee river Fulvic Acid on fe iii release and cr iii desorption from goethite
Geochimica et Cosmochimica Acta, 2016Co-Authors: Angela G Stewart, Karen A Hudsonedwards, W E DubbinAbstract:Abstract Siderophores are biogenic chelating ligands that facilitate the solubilisation of Fe(III) and form stable complexes with a range of contaminant metals and therefore may significantly affect their biogeochemical cycling. Desferrioxamine B (DFOB) is a trihydroxamate siderophore that acts synergistically with Fulvic Acid and low molecular weight organic ligands to release Fe from Fe(III) oxides. We report the results of batch dissolution experiments in which we determine the rates of Cr(III) desorption and Fe(III) release from Cr(III)-treated synthetic goethite as influenced by DFOB, by Fulvic Acid, and by the two compounds in combination. We observed that adsorbed Cr(III) at 3% surface coverage significantly reduced Fe(III) release from goethite for all combinations of DFOB and Fulvic Acid. When DFOB (270 μM) was the only ligand present, dissolved Fe(III) and Cr(III) increased approximately 1000-fold and 16-fold, respectively, as compared to the ligand-free system, a difference we attribute to the slow rate of water exchange of Cr(III). Suwannee River Fulvic Acid (SRFA) acts synergistically with DFOB by (i) reducing the goethite surface charge leading to increased HDFOB + surface excess and by (ii) forming aqueous Fe(III)–SRFA species whose Fe(III) is subsequently removed by DFOB to yield aqueous Fe(III)–DFOB complexes. These observations shed new light on the synergistic relationship between DFOB and Fulvic Acid and reveal the mechanisms of Fe(III) acquisition available to plants and micro-organisms in Cr(III) contaminated environments.
Farada Y. Saleh - One of the best experts on this subject based on the ideXlab platform.
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Retention behavior of suwannee river Fulvic Acid components in RP-HPLC
Science of The Total Environment, 2003Co-Authors: Farada Y. Saleh, David Y. ChangAbstract:Chromatographic data of RP - HPLC hasbeen used to provide additional information on the properties of the reference Suwannee River Fulvic Acid components. The polarities of the Fulvic Acid components were found to range from 5.86 to 10.15, and the total solubility parameters to range from 14.12 to 20.92. The estimated hydrocarbonaceous surface areas of the polar moieties range from 30 to 120A2. The hydrophobic neutral constituents represent ∼ 30% of the total Fulvic Acid peaks and can be resolved into five components with k' ranging from 0.5 to 2.0. Their uv and fluorescence chromatograms show what appears to be a regular retention pattern of a homologous series. The uv-visible scans of three of these peaks provide further evidence to this interpretation.
Michael Schünke - One of the best experts on this subject based on the ideXlab platform.
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INFLUENCE OF Fulvic Acid ON THE COLLAGEN SECRETION OF BOVINE CHONDROCYTES IN VITRO
Cell and tissue research, 1999Co-Authors: Niki Ioannidis, Bodo Kurz, U. Hansen, Michael SchünkeAbstract:High concentrations of Fulvic Acid and selenium deficiency in drinking water are the main causative factors of Kashin-Beck disease, an endemic degenerative chronic osteoarticular disorder found in China. The influence of Fulvic Acid on collagen secretion was investigated in articular chondrocyte cultures from bovine interphalangeal joints. Collagen secretion in 7-day-old chondrocyte monolayers was determined by measuring [3H]-proline incorporation into collagen macromolecules after a 24-h application in cultured supernatants. Additionally, collagen secretion was measured with a collagen assay based on a dye-binding method of soluble collagens. Both methods showed a dose-dependent increase of collagen secretion after treatment with Fulvic Acid. The collagen was identified by immunoblotting and immunocytochemistry as type II collagen. Fulvic Acid also induced H2O2 production in cartilage cells. After co-incubation with catalase and Fulvic Acid, the cells secreted the same amount of H2O2 or collagen as the non-treated controls, indicating an influence of H2O2 on collagen secretion. Chondrocytes were then treated directly with H2O2. This led to increased collagen secretion showing a positive correlation with the concentration of H2O2 up to 1 pM H2O2. Larger amounts of H2O2 decreased collagen secretion. Effects of reactive oxygen species, such as lipid peroxidation or lactate dehydrogenase (LDH) release from damaged cells, were not inducable by Fulvic Acid (
