Pyrite-induced hydroxyl radical formation and its effect on nucleic acids

Background  

Pyrite, the most abundant metal sulphide on Earth, is known to spontaneously form hydrogen peroxide when exposed to water. In this study the hypothesis that pyrite-induced hydrogen peroxide is transformed to hydroxyl radicals is tested.     

Stochastic Modelling of Mineral Exploration Targets

Mathematical Geosciences - Mineral deposits are metal enrichment anomalies, occurring as local manifestations of the interplay between various geological processes that operate at a wide range of...     

Developing interactive geospatial holograms for spatial decision-making

Spatial decision-making in time-critical situations requires effective and usable two-dimensional and three-dimensional (3D) cartographic products. Holographic displays allow decision makers to work with auto-stereoscopic maps without the hassle of interacting with complex user interfaces or additional vision hardware. Holographic production processes have advanced greatly in a short period and now support timely and full integration of digital 3D models in geospatial holograms. George Mason University’s and Zebra Imaging’s research on interactive holographic motion displays showcases the leadership in moving cartography and geovisualization research in the US forward. In close cooperation with academic researchers, decision makers, and domain experts, the usability and usefulness of these cartographic products is tested and design guidelines for effective geospatial holograms are being developed.     

The White Angel: A unique wollastonite‐bearing,mass‐fractionated refractory inclusion from the Leoville CV3 carbonaceous chondrite

Abstract— We report the study of an unusual compact type A refractory inclusion, named the White Angel, from the Leoville CV3 meteorite. The petrologic, mineral chemical, isotopic, and trace‐element signatures of this once‐molten Ca‐Al‐rich inclusion (CAI), which contains large, equant wollastonite crystals, indicate a short multistage history that occurred very early, before substantial decay of ²⁶Al. Magnesium in the inclusion is isotopically heavy, with F_Mg reaching 18‰/amu, in the range of fractionated and with unidentified nuclear effects (FUN) inclusions. However, the absence of any nuclear anomalies in Ca and Ti and an inferred ²⁶Al/²⁷Al ratio of (5.5 ± 0.9) × 10^?5 indicate that the White Angel belongs to the F inclusions. Silicon and oxygen are also mass fractionated in favor of the heavy isotopes, but to a lesser extent. The O isotopes show a range in ¹⁶O excesses. On an O three‐isotope plot, data points lie on a line parallel and to the right of the carbonaceous chondrite anhydrous mineral mixing line, with wollastonite being the most ¹⁶O‐rich phase. The chondrite‐normalized rare earth and trace‐element pattern of the whole inclusion is the complement of an ultrarefractory pattern indicating that precursor phases of the CAI must have condensed in an Al‐, heavy rare earth element (HREE)‐depleted reservoir. Melting of those precursor phases in an ¹⁶O‐rich environment and evaporation led to mass‐dependent isotopic fractionation of Mg, Si, and O. Partial isotopic exchange with a reservoir containing unfractionated Mg took place at a later stage but before any measurable decay of ²⁶Al. Some minerals (melilite and perovskite) in the White Angel equilibrated oxygen isotopes with a relatively ¹⁶O‐poor reservoir that was also mass‐fractionated toward the heavy isotopes, different from that with which the normal or FUN inclusions interacted.     

Direct Trace Element Determination in Oil and Gas Produced Waters with Inductively Coupled Plasma‐Optical Emission Spectrometry: Advantages of High‐Salinity Tolerance

Waters co‐produced during petroleum extraction are the largest waste streams from oil and gas development. Reuse or disposal of these waters is difficult due to their high salinities and the sheer volumes generated. Produced waters (PWs) may also contain valuable mineral commodities. While an understanding of produced water trace element composition is required for evaluating the associated resource and waste potential of these materials, measuring trace elements in brines is challenging due to the dilution requirements of typical methods. Alternatively, inductively coupled plasma‐optical emission spectrometry (ICP‐OES) has shown promise as being capable of direct measurements of trace elements within PWs with minimal dilution. Here, we evaluate direct ICP‐OES trace element quantification in PWs for seventeen trace elements (As, Al, Ba, Be, Cd, Cr, Co, Cu, Hg, Mo, Ni, Pb, Rb, Sb, U, V and Zn) within fifteen PWs from five U.S. continuous reservoirs. The total analytical uncertainties associated with the trace element levels determined using ICP‐OES were estimated to be better than ± 30% (2s) except for Rb, which could not be determined due to ionisation interferences. The ICP‐OES results are compared with trace element levels determined using inductively coupled plasma‐mass spectrometry from the same samples. Our results demonstrate the potential for direct analysis of high‐salinity waters using ICP‐OES with minimal dilution and provide trace element concentrations in waters from several important U.S. petroleum‐generating reservoirs where available data are sparse.     

Anthropogenic disturbance history influences the temporal coherence of paleoproductivity in two lakes

We investigated how the history of local disturbances in a watershed can influence the regional coherence of ecosystem properties in lakes that have similar morphometry and climatic conditions. We measured sedimentary δ¹³C, δ¹⁵N, C:N and %BSiO₂ in Sooke Lake Reservoir (SOL) and Shawnigan Lake (SHL), which are located within 4 km of each other on Vancouver Island, Canada. SOL is an impounded lake whose watershed has been fully protected over the last century, although the lake level has been raised 3 times via impoundment during this period. SHL has a similar limnological regime, but the surrounding watershed has been developed extensively for residential uses. We investigated how a pulse disturbance regime in SOL (i.e. repeated dam raising) and a press disturbance regime in SHL (i.e. persistent development) influenced the variability of paleoindicators in each system over time. We found that these contrasting disturbance regimes reduced the regional temporal coherence of aquatic productivity between the two lakes (indicated by %BSiO₂), but did not influence the regional coherence of nutrient status or the main carbon sources of the lakes (indicated by %C, %N and δ¹³C). In contrast, an indicator of the sources and cycling of nitrogen (δ¹⁵N) showed increased coherence. Local disturbances also affected the variability of the paleoindicators within each system over time. In SOL, impoundments led to both declines (%N, δ¹⁵N) and increases (δ¹³C) in the variability of paleoindicators. In SHL, persistent watershed development led to lower variability of two paleoindicators (%N, %BSiO₂). Overall, our data suggest that local disturbances can influence the %BSiO₂ and C:N ratio of lake sediments, but are less likely to alter the regional coherence of %C, %N and δ¹³C between lakes. Biplob Das and Anita Narwani contributed equally to this work.     

Relation between flow,surface‐layer armoring and sediment transport in gravel‐bed rivers

This study investigates trends in bed surface and substrate grain sizes in relation to reach‐scale hydraulics using data from more than 100 gravel‐bed stream reaches in Colorado and Utah. Collocated measurements of surface and substrate sediment, bankfull channel geometry and channel slope are used to examine relations between reach‐average shear stress and bed sediment grain size. Slopes at the study sites range from 0·0003 to 0·07; bankfull depths range from 0·2 to 5 m and bankfull widths range from 2 to 200 m. The data show that there is much less variation in the median grain size of the substrate, D_50s, than there is in the median grain size of the surface, D₅₀; the ratio of D₅₀ to D_50s thus decreases from about four in headwater reaches with high shear stress to less than two in downstream reaches with low shear stress. Similar trends are observed in an independent data set obtained from measurements in gravel‐bed streams in Idaho. A conceptual quantitative model is developed on the basis of these observations to track differences in bed load transport through an idealized stream system. The results of the transport model suggest that downstream trends in total bed load flux may vary appreciably, depending on the assumed relation between surface and substrate grain sizes. Copyright © 2007 John Wiley & Sons, Ltd.