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Extended X-ray absorption fine structure (EXAFS) spectroscopy is used to determine the ability of Phaseolus vulgaris (the bean plant) to absorb zinc sulfate and lead nitrate into its roots and leaves, with and without the presence of the chelate EDTA. Graphs compare EXAFS spectra results.

The extended X-ray absorption fine structure (EXAFS) spectroscopy proves useful in determining the binding mechanisms of Zn and Pb to Penicillium chrysogenum cell walls. Results revealed that Zn and Pb bind to the predominant phosphoryl and minor carboxyl groups with a reversed affinity. The differences in Pb and Zn isotherms can be explained by the difference in complexation affinity by reactive PO4 and COOH groups seen through EXAFS spectroscopy.

A characterization study was performed on the products formed from the extraction of selenium from process waters of seleniferous marine shales. Extraction was done by precipitating selenium with copper(II) salts and products were analyzed using x-ray diffraction, infrared and x-ray absorption spectroscopy techniques. Results from x-ray diffraction showed the incorporation of selenium in the copper thiocyanate lattice, while x-ray absorption spectroscopy showed selenium in the form of selenide, replacing sulphur in the copper thiocyanate structure.

The potential of extended X-ray absorption fine structure (EXAFS) spectroscopy as a practical approach in the direct determination of the chemical form of trace metals in soils was investigated.Lead speciation in three soils contaminated by various industrial activities was used as a case study to investigate the potential of EXAFS spectroscopy to speciate and quantify the form of trace metals in soil materials. Since lead is covalent and is present in several different forms, their individual identification cannot be accomplished by any existing analytical technique.

Copper is an essential element in the cellular electron-transport chain, but as a free ion it can catalyze production of damaging radicals. Thus, all life forms attempt to prevent copper toxicity. Plants diminish excess copper in two structural regions: rare hyperaccumulators bind cationic copper to organic ligands in subaerial tissues, whereas widespread metal- tolerant plants segregate copper dominantly in roots by mechanisms thought to be analogous. Here we show using synchrotron microanalyses that common wetlands plants Phragmites australis and Iris pseudoacorus can transform copper into metallic nanoparticles in and near roots with evidence of assistance by endomycorrhizal fungi when grown in contaminated soil in the natural environment Biomolecular responses to oxidative stress, similar to reactions used to abiotically synthesize Cu0 nanostructures of controlled size and shape, likely cause the transformation. This newly identified mode of copper biomineralization by plant roots under copper stress may be common in oxygenated environments. [ABSTRACT FROM AUTHOR]

The sorption mechanism of Zn on gibbsite and montmorillonite exchanged with Al3+ (Al-mont) or Keggin Al13 polymer (Al13-mont) was probed by powder and polarized EXAFS spectroscopy as a function of pH (5.85–7), reaction time (1–65 days), and sorbate to sorbent ratio (50–200 μM Zn/2 g montmorillonite). For all Al-mont samples, Zn is octahedrally coordinated to oxygens at ∼2.08(2) Å, and surrounded in-plane by six Al atoms at 3.02–3.06(2) Å, and another six at 6 Å. No out-of plane Si neighbors are detected. These results are interpreted as Zn incorporation in vacant octahedral sites of gibbsite-like layers at the basal and/or interlayer surface of montmorillonite particles. Zinc sorbed on the edges of gibbsite layers would give a split first oxygen shell with bond distances of 2.00(2) and 2.16(3) Å, and 2.1(8) nearest Al at 3.02 Å with no second-nearest Al, none of which were observed in Al-mont. The binding environment of Zn on Al13-mont after 1 day is similar to that on the edges of gibbsite, and is interpreted as Zn complexation at the surface of Al polymers. After 28 days, the Zn environment resembles that of Zn-sorbed Al-mont, indicating the progressive buildup of Zn-containing gibbsite-like layers parallel to montmorillonite layers. The results of this work clarify the incorporation mechanism of Zn in hydroxy-Al interlayered phyllosilicate and provide insight on the formation mechanism of this common Zn species in soil. [ABSTRACT FROM AUTHOR]

Determining how environmentally important trace metals are sequestered in soils at the molecular scale is critical to developing a solid scientific basis for maintaining soil quality and formulating effective remediation strategies. The speciation of Zn and Ni in ferromanganese nodules from loess soils of the Mississippi Basin was determined by a synergistic use of three noninvasive synchrotron-based techniques: X-ray microfluorescence (μXRF), X-ray microdiffraction (μXRD), and extended X-ray absorption fine structure spectroscopy (EXAFS). We show that Ni is distributed between goethite (α-FeOOH) and the manganese oxide lithiophorite, whereas Zn is bound to goethite, lithiophorite, phyllosilicates, and the manganese oxide birnessite. The selective association of Ni with only iron and manganese oxides is an explanation for its higher partitioning in nodules over the soil clay matrix reported from soils worldwide. This could also explain the observed enrichment of Ni in oceanic manganese nodules. The combination of these three techniques provides a new method for determining trace metal speciation in both natural and contaminated environmental materials. [ABSTRACT FROM AUTHOR]