A Large Proportion of the Neonatal Iron Pool Is Acquired from the Gestational Diet in a Murine Model.

Background: Iron is crucial for growth and development, but excess iron is harmful. Neonatal mice have elevated concentrations of circulating iron, but the source of this iron is unclear. This lack of understanding makes it difficult to optimize early life iron balance.

Tracking Initial Fe(II)-Driven Ferrihydrite Transformations: A Mössbauer Spectroscopy and Isotope Investigation.

Transformation of nanocrystalline ferrihydrite to more stable microcrystalline Fe(III) oxides is rapidly accelerated under reducing conditions with aqueous Fe(II) present. While the major steps of Fe(II)-catalyzed ferrihydrite transformation are known, processes in the initial phase that lead to nucleation and the growth of product minerals remain unclear. To track ferrihydrite-Fe(II) interactions during this initial phase, we used Fe isotopes, Mössbauer spectroscopy, and extractions to monitor the structural, magnetic, and isotope composition changes of ferrihydrite within ∼30 min of Fe(II) exposure.

Evaluation of airborne particulates and associated metals originating from steel slag applied to rural unpaved roads.

Various metals have toxic effects by the inhalation route, and electric arc furnace (EAF) steel slag is known to contain metals with a potential for toxicity to humans. In some states, EAF slag is applied to unpaved (gravel) roads as a low-cost supplement to limestone and other crushed stone, where it may be a public health concern for the local population. This study compared the mass of selected metals in the PM size fraction of fugitive dust from roads where slag was applied to metals in fugitive dust where slag was not applied.

Redox Potentials of Magnetite Suspensions under Reducing Conditions.

Predicting the redox behavior of magnetite in reducing soils and sediments is challenging because there is neither agreement among measured potentials nor consensus on which Fe(III) | Fe(II) equilibria are most relevant. Here, we measured open-circuit potentials of stoichiometric magnetite equilibrated over a range of solution conditions. Notably, electron transfer mediators were not necessary to reach equilibrium.

Abiotic reduction of nitrite by Fe(II): a comparison of rates and NO production.

Abiotic reduction of nitrite (NO) by Fe(II) species (, chemodenitrification) has been demonstrated in a variety of natural environments and laboratory studies, and is a potentially significant source of atmospheric nitrous oxide (NO) emissions. It is, however, unclear how chemodenitrification rates and NO yields vary among heterogeneous Fe(II) species under similar conditions and whether abiotic reduction competes with biological NO reduction. Here, we measured rates of NO reduction and extents of NO production by several Fe(II) species under consistent, environmentally relevant conditions (, pH 7.

Natural organic matter inhibits Ni stabilization during Fe(II)-catalyzed ferrihydrite transformation.

Trace metals, such as nickel (Ni), are often found associated with ferrihydrite (Fh) in soil and sediment and have been shown to redistribute during Fe(II)-catalyzed transformation of Fh. Fe(II)-catalyzed transformation of Fh, however, is often inhibited when natural organic matter (NOM) is associated with Fh. To explore whether NOM affects the behavior of Ni during Fe(II)-catalyzed transformation of Fh, we tracked Ni distribution, Fe atom exchange, and mineral transformation of Fh and Fh coprecipitated with Suwannee River natural organic matter (SRNOM-Fh).

Abiotic Degradation of Chlorinated Solvents by Clay Minerals and Fe(II): Evidence for Reactive Mineral Intermediates.

For decades, there has been evidence that Fe-containing minerals might contribute to abiotic degradation of chlorinated ethene (CE) plumes. Here, we evaluated whether Fe(II) in clay minerals reduces tetrachloroethene (PCE) and trichloroethene (TCE). We found that structural Fe(II) in both low (SWy-2) and high (NAu-1) Fe clay minerals did not reduce PCE or TCE under anoxic conditions.

Reactivity of As and U co-occurring in Mine Wastes in northeastern Arizona.

The reactivity of co-occurring arsenic (As) and uranium (U) in mine wastes was investigated using batch reactors, microscopy, spectroscopy, and aqueous chemistry. Analyses of field samples collected in proximity to mine wastes in northeastern Arizona confirm the presence of As and U in soils and surrounding waters, as reported in a previous study from our research group. In this study, we measured As (< 0.

Mineral Defects Enhance Bioavailability of Goethite toward Microbial Fe(III) Reduction.

Surface defects have been shown to facilitate electron transfer between Fe(II) and goethite (α-FeOOH) in abiotic systems. It is unclear, however, whether defects also facilitate microbial goethite reduction in anoxic environments where electron transfer between cells and Fe(III) minerals is the limiting factor. Here, we used stable Fe isotopes to differentiate microbial reduction of goethite synthesized by hydrolysis from reduction of goethite that was further hydrothermally treated to remove surface defects.

Effect of bicarbonate and phosphate on arsenic release from mining-impacted sediments in the Cheyenne River watershed, South Dakota, USA.

The mobilization of arsenic (As) from riverbank sediments affected by the gold mining legacy in north-central South Dakota was examined using aqueous speciation chemistry, spectroscopy, and diffraction analyses. Gold mining resulted in the discharge of approximately 109 metric tons of mine waste into Whitewood Creek (WW) near the Homestake Mine and Cheyenne River at Deal Ranch (DR), 241 km downstream. The highest concentrations of acid-extractable As measured from solid samples was 2020 mg kg-1 at WW and 385 mg kg-1 at DR.

Reduction of PCE and TCE by magnetite revisited.

Here we revisit whether the common mixed-valent Fe mineral, magnetite, is a viable reductant for the abiotic natural attenuation of perchloroethylene (PCE) and trichloroethylene (TCE) in anoxic groundwater plumes. We measured PCE and TCE reduction by stoichiometric magnetite as a function of pH and Fe(ii) concentration. In the absence of added Fe(ii), stoichiometric magnetite does not reduce PCE and TCE over a three month period under anoxic conditions.

Fe(II)-Catalyzed Transformation of Organic Matter-Ferrihydrite Coprecipitates: A Closer Look Using Fe Isotopes.

Ferrihydrite is a common Fe mineral in soils and sediments that rapidly transforms to secondary minerals in the presence of Fe(II). Both the rate and products of Fe(II)-catalyzed ferrihydrite transformation have been shown to be significantly influenced by natural organic matter (NOM). Here, we used enriched Fe isotope experiments and Fe Mössbauer spectroscopy to track the formation of secondary minerals, as well as electron transfer and Fe mixing between aqueous Fe(II) and ferrihydrite coprecipitated with several types of NOM.

The Role of Defects in Fe(II)-Goethite Electron Transfer.

Despite substantial experimental evidence for Fe(II)-Fe(III) oxide electron transfer, computational chemistry calculations suggest that oxidation of sorbed Fe(II) by goethite is kinetically inhibited on structurally perfect surfaces. We used a combination of Fe Mössbauer spectroscopy, synchrotron X-ray absorption and magnetic circular dichroism (XAS/XMCD) spectroscopies to investigate whether Fe(II)-goethite electron transfer is influenced by defects. Specifically, Fe L-edge and O K-edge XAS indicates that the outermost few Angstroms of goethite synthesized by low temperature Fe(III) hydrolysis is iron deficient relative to oxygen, suggesting the presence of defects from Fe vacancies.

Post Gold King Mine Spill Investigation of Metal Stability in Water and Sediments of the Animas River Watershed.

We applied spectroscopy, microscopy, diffraction, and aqueous chemistry methods to investigate the persistence of metals in water and sediments from the Animas River 13 days after the Gold King Mine spill (August 5, 2015). The Upper Animas River watershed, located in San Juan Colorado, is heavily mineralized and impacted by acid mine drainage, with low pH water and elevated metal concentrations in sediments (108.4 ± 1.

Fe(II)-catalyzed recrystallization of goethite revisited.

Results from enriched (57)Fe isotope tracer experiments have shown that atom exchange can occur between structural Fe in Fe(III) oxides and aqueous Fe(II) with no formation of secondary minerals or change in particle size or shape. Here we derive a mass balance model to quantify the extent of Fe atom exchange between goethite and aqueous Fe(II) that accounts for different Fe pool sizes. We use this model to reinterpret our previous work and to quantify the influence of particle size and pH on extent of goethite exchange with aqueous Fe(II).

Stable U(IV) complexes form at high-affinity mineral surface sites.

Uranium (U) poses a significant contamination hazard to soils, sediments, and groundwater due to its extensive use for energy production. Despite advances in modeling the risks of this toxic and radioactive element, lack of information about the mechanisms controlling U transport hinders further improvements, particularly in reducing environments where U(IV) predominates. Here we establish that mineral surfaces can stabilize the majority of U as adsorbed U(IV) species following reduction of U(VI).

Reaction of U(VI) with titanium-substituted magnetite: influence of Ti on U(IV) speciation.

Reduction of hexavalent uranium (U(VI)) to less soluble tetravalent uranium (U(IV)) through enzymatic or abiotic redox reactions has the potential to alter U mobility in subsurface environments. As a ubiquitous natural mineral, magnetite (Fe3O4) is of interest because of its ability to act as a rechargeable reductant for U(VI). Natural magnetites are often impure with titanium, and structural Fe(3+) replacement by Ti(IV) yields a proportional increase in the relative Fe(2+) content in the metal sublattice to maintain bulk charge neutrality.

Fate of CuO and ZnO nano- and microparticles in the plant environment.

The environmental fate of metal oxide particles as a function of size was assessed by comparing the behavior of CuO or ZnO nanoparticles (NPs) to that of the corresponding microparticles (MPs) in a sand matrix, with and without wheat (Triticum aestivum L.) growth. After 14 days of incubation in the planted sand, the CuO and ZnO NPs were increased from their nominal sizes of <50 nm and <100 nm, to ~317 nm and ~483 nm, respectively.

Influence of Fe(2+)-catalysed iron oxide recrystallization on metal cycling.

Recent work has indicated that iron (oxyhydr-)oxides are capable of structurally incorporating and releasing metals and nutrients as a result of Fe2+-induced iron oxide recrystallization. In the present paper, we briefly review the current literature examining the mechanisms by which iron oxides recrystallize and summarize how recrystallization affects metal incorporation and release. We also provide new experimental evidence for the Fe2+-induced release of structural manganese from manganese-doped goethite.

Fe electron transfer and atom exchange in goethite: influence of Al-substitution and anion sorption.

The reaction of Fe(II) with Fe(III) oxides and hydroxides is complex and includes sorption of Fe(II) to the oxide, electron transfer between sorbed Fe(II) and structural Fe(III), reductive dissolution coupled to Fe atom exchange, and, in some cases mineral phase transformation. Much of the work investigating electron transfer and atom exchange between aqueous Fe(II) and Fe(III) oxides has been done under relatively simple aqueous conditions in organic buffers to control pH and background electrolytes to control ionic strength. Here, we investigate whether electron transfer is influenced by cation substitution of Al(III) in goethite and the presence of anions such as phosphate, carbonate, silicate, and natural organic matter.

Influence of magnetite stoichiometry on U(VI) reduction.

Hexavalent uranium (U(VI)) can be reduced enzymatically by various microbes and abiotically by Fe(2+)-bearing minerals, including magnetite, of interest because of its formation from Fe(3+) (oxy)hydroxides via dissimilatory iron reduction. Magnetite is also a corrosion product of iron metal in suboxic and anoxic conditions and is likely to form during corrosion of steel waste containers holding uranium-containing spent nuclear fuel. Previous work indicated discrepancies in the extent of U(VI) reduction by magnetite.