The authors report real-time data illustrating the rapid formation of nickel aluminium-layered double hydroxide precipitates at the mineral–water interface in a flow environment in as little as 31–40 min.
The interactions between the Fe(III)-reducing bacterium Shewanella oneidensis MR-1 and the phyllosilicate minerals biotite and chlorite have been studied. In washed, non-growing cell suspensions, S. oneidensis MR-1 was able to mediate the reduction of Fe(III) in biotite and chlorite in the presence and absence of an artificial electron shuttle, and to reduce as much as 36% of the starting Fe(III) in biotite, and 21% in chlorite.
In the present work, Mössbauer spectroscopy and electron microscopy indicate that irradiation (1 MGy gamma) of 2-line ferrihydrite can lead to conversion to a more crystalline phase, one similar to akaganeite. The room temperature Mössbauer spectrum of irradiated hematite shows the emergence of a paramagnetic Fe(III) phase. Spectrophotometric determination of Fe(II) reveals a radiation-induced increase in the rate and extent of ferrihydrite and hematite reduction by S. oneidensis in the presence of an electron shuttle (riboflavin).
The authors applied a gas-phase carbonylation technique previously tested on short-lived molybdenum (Mo) and tungsten (W) isotopes to the preparation of a carbonyl complex of seaborgium, the 106th element. The volatile seaborgium complex showed the same volatility and reactivity with a silicon dioxide surface as those of the hexacarbonyl complexes of the lighter homologs Mo and W. Comparison of the product’s adsorption enthalpy with theoretical predictions and data for the lighter congeners supported a Sg(CO)6 formulation. See also: http://www.sciencemag.org/content/345/6203/1491.abstract
The authors show that 1 billion-year-old microfossils from the non-marine Torridon Group are remarkably preserved by a combination of clay minerals and phosphate, with clay minerals providing the highest fidelity of preservation. Fe-rich clay mostly occurs in narrow zones in contact with cellular material and is interpreted as an early microbially-mediated phase enclosing and replacing the most labile biological material.
Shallow-sea (5 m depth) hydrothermal venting off Milos Island provides an ideal opportunity to target transitions between igneous abiogenic sulfide inputs and biogenic sulfide production during microbial sulfate reduction.
the authors present shell growth and structural responses by the economically important marine calcifier Mytilus edulis to ocean acidification scenarios (380, 550, 750, 1000 µatm pCO2). After six months of incubation at 750 µatm pCO2, reduced carbonic anhydrase protein activity and shell growth occurs in M. edulis. Beyond that, at 1000 µatm pCO2, biomineralisation continued but with compensated metabolism of proteins and increased calcite growth.
Surface-mediated reduction of Pu(V) was observed under all conditions studied. However, differences in the reaction kinetics demonstrate that the mechanism of Pu(V) reduction changes as a function of plutonium concentration. Adsorption of Pu(V) was found to be the rate-limiting step at plutonium concentrations less than approximately 10–7 M Pu(V). Plutonium reduction in these systems was attributed to trace amounts of Fe(II) in the hematite structure. Reduction of Pu(V) was found to be the rate-limiting step at concentrations higher than approximately 10–6 M Pu(V) and is attributed to the formation of PuO2+x·nH2O nanoparticles and the Nernstian favorability of Pu(IV) surface complexes.
The speciation of U at a location not impacted by the clay-rich layer is a different noncrystalline U(IV) species, consisting of U(IV) bound to organic matter in soil. Also, the clay-poor location includes an abundant sulfate supply and active microbial sulfate reduction that induce substantial pyrite (FeS2) precipitation.
'Left-handed' electrons destroy certain organic molecules faster than their mirror versions.
Ath Godelitsas's insight:
Physicists have found hints that the asymmetry of life — the fact that most biochemical molecules are ‘left-handed’ or ‘right-handed’ — could have been caused by electrons from nuclear decay in the early days of evolution. In an experiment that took 13 years to perfect, the researchers have found that these electrons tend to destroy certain organic molecules slightly more often than they destroy their mirror images.
This book is the collection of papers from the latest International Uranium Mining and Hydrogeology Conference (UMH VII) held in September 2014, in Freiberg, Germany. It is divided to five sessions: Uranium Mining, Uranium and Phosphates, Clean-up technologies for water and soil. Uranium and daughter nuclides and basic research and modeling. Each session covers a wide range of related topic and provides readers with up to date research and solutions on those matters.
Synchrotron radiation-based micro-X-ray diffraction showed the calcification had a similar structure to hydroxylapatite (HAp). Transmission electron microscopy showed some structurally HAp-like spherical particles with a diameter of ~200 nm and acicular crystals ~100 nm×~20 nm in size. Selected-area electron diffraction indicated that these mineral particles belonged to the hexagonal crystal system. Fourier-transform infrared (FTIR) spectroscopy showed three typical peaks at 1469 cm−1, 1455 cm−1 and 1413 cm−1, indicating that the carbonate group in the calcification plaque substituted for a hydroxyl group to form B-type CHAp (Ca10(PO4,CO3)x(OH)y).
The reduction of U(VI) by synthetic and naturally occurring pyrite was investigated at pH 3.0–9.5. In contrast to thermodynamic calculations that were used to predict UO2(s) precipitation, a mixed U(IV) and U(VI) product (e.g., U3O8/U4O9/U3O7) was only observed at pH 6.21–8.63 and 4.52–4.83 for synthetic and natural pyrite, respectively. Under acidic conditions, the reduction of UO22+ by surface-associated Fe2+ may not be favored because the mineral surface is nearly neutral or not negative enough.
The authors show that late Eocene climate records revealing marked monsoon-like patterns in rainfall and wind south and north of the Tibetan–Himalayan orogen. This is indicated by low oxygen isotope values with strong seasonality in gastropod shells and mammal teeth from Myanmar, and by aeolian dust deposition in northwest China.
A conspicuous biomorphic ovoid structure has been discovered in the Nakhla martian meteorite, made of nanocrystalline iron-rich saponitic clay and amorphous material. To infer the origin of the ovoid, a large set of analytical tools was employed, including scanning electron microscopy and backscattered electron imaging, wavelength-dispersive X-ray analysis, X-ray mapping, Raman spectroscopy, time-of-flight secondary ion mass spectrometry analysis, high-resolution transmission electron microscope imaging, and atomic force microscope topographic mapping. It is evident that the martian subsurface contains niche environments where life could develop.
The first natural-occurring quasicrystal, icosahedrite, was recently discovered in the Khatyrka meteorite, a new CV3 carbonaceous chondrite. The authors here present in situ synchrotron X-ray diffraction experiments on synthetic icosahedral AlCuFe using multianvil device to explore possible temperature-induced phase transformations at pressures of 5 GPa and temperature up to 1773 K.
The authors suggest that biogenic activity has produced around 3.1 × 109 moles of reduced sulphur and 1010 moles of CO2, promoting the formation of ca. 1.19 Mt of carbonates, 114,000 t of galena, 638 t of silver sulphides and 6.5 t of gold.
Using in situ specular and resonant anomalous X-ray reflectivity measurements, the authors investigated the interaction of the calcite (104) surface with a dilute Pb- and EDTA-bearing solution that is slightly undersaturated with respect to calcite. The X-ray results reveal Pb coherently substituting for Ca in the near-surface layers of strained calcite with Pb/(Pb + Ca) atom fractions as high as 0.28 in the outermost layer. The larger ionic radius of Pb2+ relative to Ca2+ is accommodated in calcite by vertical displacements of Pb relative to the Ca site. In situ atomic force microscopy images obtained during the reaction suggest that Pb incorporation below the surface occurs after initial dissolution followed by regrowth of a strained epitaxial Pb-rich calcite solid-solution at the calcite (104)–water interface.
The authors combined bulk characterization, sequential extractions, and spatially resolved μ-focus spectroscopic analyses and investigated the occurrence and distribution of Se and other associated elements (Fe, As, Cr, Ni, and Zn) and determined the Se speciation at the μ-scale in typical, low bulk Se containing shales.