Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Language: English
    In: Environ. Sci. Technol, 09 April 2013, Vol.47((7) ; 04, 2013)
    Description: Short-range ordered ferric arsenate (FeAsO4 · xH2O) is a secondary As precipitate frequently encountered in acid mine waste environments. Two distinct structural models have recently been proposed for this phase. The first model is based on the structure of scorodite (FeAsO4 · 2H2O) where isolated FeO6 octahedra share corners with four adjacent arsenate (AsO4) tetrahedra in a three-dimensional framework (framework model). The second model consists of single chains of corner-sharing FeO6 octahedra being bridged by AsO4 bound in a monodentate binuclear (2)C complex (chain model). In order to rigorously test the accuracy of both structural models, we synthesized ferric arsenates and analyzed their local (〈6 Å) structure by As and Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. We found that both As and Fe K-edge EXAFS spectra were most compatible with isolated FeO6 octahedra being bridged by AsO4 tetrahedra (RFe-As = 3.33 ± 0.01 Å). Our shell-fit results further indicated a lack of evidence for single corner-sharing FeO6 linkages in ferric arsenate. Wavelet-transform analyses of the Fe K-edge EXAFS spectra of ferric arsenates complemented by shell fitting confirmed Fe atoms at an average distance of ∼5.3 Å, consistent with crystallographic data of scorodite and in disagreement with the chain model. A scorodite-type local structure of short-range ordered ferric arsenates provides a plausible explanation for their rapid transformation into scorodite in acid mining environments.
    Keywords: X-Ray Absorption Spectroscopy ; Arsenates -- Chemistry ; Ferric Compounds -- Chemistry;
    ISSN: 0013936X
    E-ISSN: 15205851
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Environ. Sci. Technol, 18 November 2014, Vol.48((22) ; 11, 2014)
    Description: Floodplain soils are frequently contaminated with metal(loid)s due to present or historic mining, but data on the bioaccessibility (BA) of contaminants in these periodically flooded soils are scarce. Therefore, we studied the speciation of As and Fe in eight As-contaminated circumneutral floodplain soils ( less than or equal to 21600 mg As/kg) and their size fractions using X-ray absorption spectroscopy (XAS) and examined the BA of As in the solids by in-vitro gastrointestinal (IVG) extractions. Arsenopyrite and As(V)-adsorbed ferrihydrite were identified by XAS as the predominant As species. The latter was the major source for bioaccessible As, which accounted for 5-35% of the total As. The amount of bioaccessible As increased with decreasing particle size and was controlled by the slow dissolution kinetics of ferrihydrite in the gastric environment (pH 1.8). The relative BA of As (% of total) decreased with decreasing particle size only in a highly As-contaminated soil -- which supported by Fe XAS -- suggests the formation of As-rich hydrous ferric oxides in the gastric extracts. Multiple linear regression analyses identified Al, total As, Corg, and P as main predictors for the absolute BA of As (adjusted R2 less than or equal to 0.977). Health risk assessments for residential adults showed that (i) nearly half of the bulk soils may cause adverse health effects and (ii) particles 〈5 mu m pose the highest absolute health threat upon incidental soil ingestion. Owing to their low abundance, however, health risks were primarily associated with particles in the 5-50 and 100-200 mu m size ranges. These particles are easily mobilized from riverbanks during flooding events and dispersed within the floodplain or transported downstream.
    Keywords: Flood Plains ; Environmental Sciences ; Regression Analysis ; Spectroscopy ; Particle Size ; Rivers ; Flooded Soils ; Abundance ; Environmental Impact ; Particulates ; Ingestion ; Soil ; Health Risks ; Absorption Spectroscopy ; Flood Plains ; River Banks ; Kinetics ; Ph ; Flood Plains ; Speciation ; Risk ; Arsenic ; Public Health ; Assessments ; Soil Contamination ; Particle Size ; Solids ; Flood Plains ; Speciation ; Risk ; Arsenic ; Public Health ; Assessments ; Soil Contamination ; Particle Size ; Solids ; Freshwater Pollution ; Natural Hazards ; General (556) ; Toxicology & Environmental Safety ; Epidemiology and Public Health ; Water Resources and Supplies ; Data Acquisition;
    ISSN: 0013936X
    E-ISSN: 15205851
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Language: English
    In: Environ. Sci. Technol, 18 November 2014, Vol.48((22) ; 11, 2014)
    Description: Iron-rich organic flocs are frequently observed in surface waters of wetlands and show a high affinity for trace metal(loid)s. To date, spectroscopic speciation analyses of Fe and trace elements in these mineral-organic matter (OM) associations are missing. In this study, we investigated the speciation and distribution of Fe and As in flocs collected from low-flow streams (pH 5.3-6.3) of the naturally As-enriched peatland Gola di Lago (Switzerland) using ... Mossbauer spectroscopy and synchrotron X-ray techniques. The flocs were rich in acid carbohydrates and contained up to 22.1 wt % Fe, 34.9 wt % C, and 2620 mg/kg As. Mossbauer analyses revealed small quantities (〈5%) of Fe(II) and Fe(III)-OM complexes and the predominance of ferrihydrite (..., 51-59%) and lepidocrocite (...-FeOOH, 34-46%). The latter was not observed by synchrotron X-ray diffraction, implying a coherent scattering domain size of 〈10 nm. Iron X-ray absorption spectroscopy (XAS) confirmed the Mossbauer results, and bulk As XAS indicated the prevalence of arsenate (71-84%) in the flocs. Shell-fit analyses showed that As was entirely sorbed to Fe(III)-(oxyhydr)oxides and that both arsenate and arsenite exclusively formed monodentate-binuclear ("bridging") complexes (... = 3.31-3.34 ...). Microfocused X-ray fluorescence spectrometry documented a strong correlation between As and Fe in the flocs. These analyses also revealed intense As hotspots coinciding with abundant freshwater green algae (Closterium spp.). Microfocused As X-ray absorption near-edge structure spectra collected at algae-specific points identified up to 29% As(III), which, in combination with ~5% As(III) detected at Fe-rich points, suggests As(V) bioreduction in the algae. Our findings imply that floc (bio)organics serve primarily as nucleation sites for the precipitation of nanocrystalline Fe(III)-(oxyhydr)oxides, rendering flocs effective sorbents for trace metal(loid)s. Thus, Fe-rich freshwater flocs likely play a pivotal role for the speciation and cycling of trace elements in wetlands. (ProQuest: ... denotes formulae/symbols omitted.)
    Keywords: X-Rays ; Absorption Spectroscopy ; Hot Spots ; Aquatic Plants ; Wetlands ; Diffraction ; Arsenates ; Iron ; Trace Elements ; Trace Elements in Precipitation ; Spectral Analysis ; Correlations ; Environmental Sciences ; Precipitation ; Spectroscopy ; Spectrometry ; Nucleation ; Wetlands ; Diffraction ; Trace Elements in River Water ; Trace Elements in Surface Waters ; Algae ; Peatlands ; Fluorescence ; Surface Water ; Arsenates ; Spectroscopy ; Streams ; Trace Elements ; Spectrometry ; Sorbents ; Absorption Spectroscopy ; Wetlands ; Carbohydrates ; Iron ; Ph ; Speciation ; X-Rays ; Arsenic ; Absorption ; Trace Elements ; Wetlands ; Spectroscopy ; Streams ; Iron ; Speciation ; X-Rays ; Arsenic ; Absorption ; Trace Elements ; Wetlands ; Spectroscopy ; Streams ; Iron ; Closterium ; Switzerland ; Swamps, Marshes (556.56) ; Water Pollution ; Water Resources and Supplies ; Data Acquisition ; Methods and Instruments;
    ISSN: 0013936X
    E-ISSN: 15205851
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Environ. Sci. Technol, 14 February 2014, Vol.48((1) ; 01, 2014)
    Description: Arsenic is a toxic trace element, which commonly occurs as contaminant in riverine floodplains and associated wetlands affected by mining and ore processing. In this study, we investigated the solid-phase speciation of As in river floodplain soils characterized by circumneutral pH (5.7-7.1) and As concentrations of up to 40.3 g/kg caused by former mining of arsenopyrite-rich ores. Soil samples collected in the floodplain of Ogosta River (Bulgaria) were size-fractionated and subsequently analyzed using a combination of X-ray fluorescence (XRF) spectrometry, powder X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and selective chemical extraction of poorly crystalline mineral phases. Arsenic and Fe were found to be spatially correlated and both elements were strongly enriched in the fine soil particle size fractions (〈2 mu m and 2-50 mu m). Between 14 and 82% of the total As was citrate-ascorbate extractable. Molar As/Fe ratios were as high as 0.34 in the bulk soil extracts and increased up to 0.48 in extracts of the fine particle size fractions. Arsenic K-edge XAS spectra showed the predominance of As(V) and were well fitted with a reference spectrum of As(V) adsorbed to ferrihydrite. Whereas no As(III) was detected, considerable amounts of As(-I) were present and identified as arsenopyrite originating from the mining waste. Iron K-edge XAS revealed that in addition to As(V) adsorbed to ferrihydrite, X-ray amorphous As(V)-rich hydrous ferric oxides ("As-HFO") with a reduced number of corner-sharing FeO sub(6) octahedra relative to ferrihydrite were the dominating secondary As species in the soils. The extremely high concentrations of As in the fine particle size fractions (up to 214 g/kg) and its association with poorly crystalline Fe(III) oxyhydroxides and As-HFO phases suggest a high As mobilization potential under both oxic and anoxic conditions, as well as a high bioaccessibility of As upon ingestion, dermal contact, or inhalation by humans or animals.
    Keywords: Particle Size ; Absorption Spectroscopy ; Arsenic ; Flood Plains ; Ores ; River Discharge ; Wetlands ; Diffraction ; Mining ; Ph of Soil ; Flood Plains ; Trace Elements in Soil ; Environmental Sciences ; Weathering ; Wetlands ; Diffraction ; Spectroscopy ; Soil Particles ; Trace Elements in River Water ; Spectrometry ; Particle Size ; Arsenic ; Fluorescence ; Ingestion ; Trace Elements ; Soil ; Absorption Spectroscopy ; Flood Plains ; Mining Wastes ; Weathering ; Wetlands ; Mining ; Chemical Extraction ; Iron ; Rivers ; Flood Plains ; X-Rays ; Arsenic ; Soil Contamination ; Water Analysis ; Particle Size ; Wetlands ; Mine Wastes ; Rivers ; Flood Plains ; X-Rays ; Arsenic ; Soil Contamination ; Water Analysis ; Particle Size ; Wetlands ; Mine Wastes ; Bulgaria ; Freshwater ; Toxicology & Environmental Safety ; Runoff (556.16) ; Freshwater Pollution ; Water Resources and Supplies ; Data Acquisition ; Mechanical and Natural Changes;
    ISSN: 0013936X
    E-ISSN: 15205851
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages