Podcasts about xanes

Link to bioRxiv paper: http://biorxiv.org/cgi/content/short/2020.08.17.244137v1?rss=1 Authors: Kahil, K., Varsano, N., Sorrentino, A., Pereiro, E., Rez, P., Weiner, S., Addadi, L. Abstract: Sea urchin larvae have an endoskeleton consisting of two calcitic spicules. The primary mesenchyme cells (PMCs) are the cells that are responsible for spicule formation. PMCs endocytose sea water from the larval internal body cavity into a network of vacuoles and vesicles, where calcium ions are concentrated until they precipitate in the form of amorphous calcium carbonate (ACC). The mineral is subsequently transferred to the syncytium, where the spicule forms. Using cryo-soft X-ray microscopy (cryo-SXM) we imaged intra-cellular calcium-containing particles in the PMCs and acquired Ca-L2,3 X-ray absorption near edge spectra (XANES) of these Ca-particles. Using the pre-peak/main peak (L2'/ L2) intensity ratio, which reflects the atomic order in the first Ca coordination shell, we determined the state of the calcium ions in each particle. The concentration of Ca in each of the particles was also determined by the integrated area in the main Ca absorption peak. We observed about 700 Ca-particles with order parameters, L2'/ L2, ranging from solution to hydrated and anhydrous ACC, and with concentrations ranging between 1-15 M. We conclude that in each cell the calcium ions exist in a continuum of states. This implies that most, but not all water, is expelled from the particles. This cellular process of calcium concentration may represent a widespread pathway in mineralizing organisms. Copy rights belong to original authors. Visit the link for more info

The Spring 2020 meeting of the Federal Remediation Technologies Roundtable (FRTR) will be held as a two-part webinar on Friday, May 29 and Friday, June 5, 2020. As always, FRTR meetings are open to the public. FRTR's objectives for this meeting are to: Review the state of the practice of bioremediation: Broad overview of where it is commonly applied, where it is still experimental, and what are the challenges. Discuss advances in bioremediation for organic and inorganic contaminants, including new approaches, optimization, and tools for monitoring technologies to determine successful performance. Review brief case studies to demonstrate how new technologies are being applied and optimized. Session 2: Current Research and Inorganic Contaminants New Technology Briefings Superfund Research Program (SRP); Strategic Environmental Research and Development Program (SERDP); and Environmental Security Technology Certification Program (ESTCP) Bioreactor and Vertical Wetland Remediation of Metal Contaminated Mine Influenced Water (MIW) Abstract: There are over half a million abandoned mine sites in the U.S. potentially emanating mining-influenced water, contaminating streams and soils in adjacent areas. These sites present major challenges for remediation, including seasonal inaccessibility, rough terrain, lack of energy sources, high acidity, and metal concentrations (e.g. Fe, Al, Cu, Pb, Zn, Mn, Cd, etc.). To appropriately evaluate mining-impacted water treatment techniques that can provide the best cost benefit with the desired effluent quality, decision-makers usually rely on bench-scale and pilot-scale tests before designing field-scale reactors. Traditionally, the focus has been on metal removal efficiency to determine the feasibility of the proposed treatment, but it is difficult to replicate the high efficiencies of bench-scale tests with field-scale reactors. The integration of aqueous phase analytical chemistry (e.g. pH, alkalinity, metal composition, anions, sulfides, etc.) with solids analysis (e.g. elementary composition, speciation by XPS and XANES, etc.) and microbial transformation of soluble metals provides the tools to evaluate metal removal while elucidating the involved mechanisms. The benefit of this approach is that the impact of several variables (e.g. substrate volume, mass and composition, hydraulic retention time, dissolved oxygen content in the influent, etc.) can be evaluated for metal and sulfate removal. Case studies of passive biochemical reactors using actual mine water from abandoned mine sites will be used to demonstrate the benefits of this approach. Advances in Long-term Monitoring Technologies for Supporting Bioremediation Abstract: Bioremediation for heavy metals aims to immobilize them in subsurface and to reduce aqueous concentrations for an extended time. It has been investigated for many years at the Department of Energy (DOE)'s legacy sites; particularly for uranium. A variety of bioremediation technologies and associated monitoring/modeling methodology have been evaluated. Recently, hydroxyapatite-based novel permeable reactive barriers have been developed, which has shown a very promising result at the DOE's Rifle site (Colorado), showing more than two years of immobilization without rebound. During this process, groundwater monitoring has been found to be critical for understanding groundwater system dynamics, and its effect of bioremediation outcomes. We are currently developing a new paradigm of long-term monitoring approach to support bioremediation, by taking advantage of recent advances in in situ sensors and machine learning. To view this archive online or download the slides associated with this seminar, please visit http://www.clu-in.org/conf/tio/FRTRSpring20-2_060520/

The Spring 2020 meeting of the Federal Remediation Technologies Roundtable (FRTR) will be held as a two-part webinar on Friday, May 29 and Friday, June 5, 2020. As always, FRTR meetings are open to the public. FRTR's objectives for this meeting are to: Review the state of the practice of bioremediation: Broad overview of where it is commonly applied, where it is still experimental, and what are the challenges. Discuss advances in bioremediation for organic and inorganic contaminants, including new approaches, optimization, and tools for monitoring technologies to determine successful performance. Review brief case studies to demonstrate how new technologies are being applied and optimized. Session 2: Current Research and Inorganic Contaminants New Technology Briefings Superfund Research Program (SRP); Strategic Environmental Research and Development Program (SERDP); and Environmental Security Technology Certification Program (ESTCP) Bioreactor and Vertical Wetland Remediation of Metal Contaminated Mine Influenced Water (MIW) Abstract: There are over half a million abandoned mine sites in the U.S. potentially emanating mining-influenced water, contaminating streams and soils in adjacent areas. These sites present major challenges for remediation, including seasonal inaccessibility, rough terrain, lack of energy sources, high acidity, and metal concentrations (e.g. Fe, Al, Cu, Pb, Zn, Mn, Cd, etc.). To appropriately evaluate mining-impacted water treatment techniques that can provide the best cost benefit with the desired effluent quality, decision-makers usually rely on bench-scale and pilot-scale tests before designing field-scale reactors. Traditionally, the focus has been on metal removal efficiency to determine the feasibility of the proposed treatment, but it is difficult to replicate the high efficiencies of bench-scale tests with field-scale reactors. The integration of aqueous phase analytical chemistry (e.g. pH, alkalinity, metal composition, anions, sulfides, etc.) with solids analysis (e.g. elementary composition, speciation by XPS and XANES, etc.) and microbial transformation of soluble metals provides the tools to evaluate metal removal while elucidating the involved mechanisms. The benefit of this approach is that the impact of several variables (e.g. substrate volume, mass and composition, hydraulic retention time, dissolved oxygen content in the influent, etc.) can be evaluated for metal and sulfate removal. Case studies of passive biochemical reactors using actual mine water from abandoned mine sites will be used to demonstrate the benefits of this approach. Advances in Long-term Monitoring Technologies for Supporting Bioremediation Abstract: Bioremediation for heavy metals aims to immobilize them in subsurface and to reduce aqueous concentrations for an extended time. It has been investigated for many years at the Department of Energy (DOE)'s legacy sites; particularly for uranium. A variety of bioremediation technologies and associated monitoring/modeling methodology have been evaluated. Recently, hydroxyapatite-based novel permeable reactive barriers have been developed, which has shown a very promising result at the DOE's Rifle site (Colorado), showing more than two years of immobilization without rebound. During this process, groundwater monitoring has been found to be critical for understanding groundwater system dynamics, and its effect of bioremediation outcomes. We are currently developing a new paradigm of long-term monitoring approach to support bioremediation, by taking advantage of recent advances in in situ sensors and machine learning. To view this archive online or download the slides associated with this seminar, please visit http://www.clu-in.org/conf/tio/FRTRSpring20-2_060520/

Ti K-edge XANES spectra have been collected on a series of Ti-bearing silicate glasses with metasilicate and tetrasilicate compositions. The intensity of the preedge feature in these spectra has been found to change with glass composition and varies from 29 to 58% (normalized intensity) suggesting a variation in structural environent around the absorbing atom. The pre-edge peak intensity increases for the alkali titanium tetrasilicate glasses from 35% to 58% in the order Li < Na < K < Rb, Cs whereas for the metasilicate compositions there is a maximum for the K-bearing glass. The pre-edge peak intensity remains constant for the alkaline earth titanium metasilicate glasses, Ca and Sr (34%) but increases slightly for Ba (41%). As the intensity of this feature is inversely correlated with coordination number, a comparison of the pre-edge intensity data for the investigated glasses with those of materials of known coordination number leads us to establish a regression equation and to infer that the average coordination number of Ti in these glasses ranges from 4.8 to 5.8. Large alkali cations appear to stabilize a relatively low average coordination number for Ti in silicate melts. The Ti structural environment results appear also to vary as a function of SiO2 content within the K2O-TiO2-SiO2 system. A number of physical properties of the melts from which these glasses were quenched and of other Ti-bearing silicate melts, have been determined in recent years. Clear evidence of a variable coordination number of Ti, consistent with the interpretation of the present XANES data is available from density measurements. These and other property determinations are compared with the present spectroscopic observations in an attempt to relate structure and properties in these melts which contain a major component with variable coordination number.

The effect of pressure on titanium coordination in glasses, with composition K2TiSi4O11, quenched isobarically from liquids equilibrated at high pressure (5, 10, 15, 20, 25, 30 kbar respectively) and T=1600° C has been investigated by X-ray absorption spectroscopy (XAS). The XANES spectra collected at the Ti K-edge clearly show a variation with pressure that is related to changes in the geometrical environment around the Ti atoms. By comparison with spectra of standard materials, the XANES spectra of the glasses suggest a relatively low average coordination number (near 5) in samples quenched at low pressure and a higher coordination number (near 6) in samples quenched from the highest pressure. The combination of XANES data with density and compressibility measurements supports the idea that a mixture of 6- and lower coordinated (4- and/ or 5-coordinated) Ti geometries are present in the 1 bar glass, and an increasing proportion of 6-coordinated Ti occurs in the glasses synthesized at progressively higher pressures.

The effect of composition on the relaxed adiabatic bulk modulus (K0) of a range of alkali- and alkaline earth-titanosilicate [X 2 n/n+ TiSiO5 (X=Li, Na, K, Rb, Cs, Ca, Sr, Ba)] melts has been investigated. The relaxed bulk moduli of these melts have been measured using ultrasonic interferometric methods at frequencies of 3, 5 and 7 MHz in the temperature range of 950 to 1600°C (0.02 Pa s < s < 5 Pa s). The bulk moduli of these melts decrease with increasing cation size from Li to Cs and Ca to Ba, and with increasing temperature. The bulk moduli of the Li-, Na-, Ca- and Ba-bearing metasilicate melts decrease with the addition of both TiO2 and SiO2 whereas those of the K-, Rb- and Cs-bearing melts increase. Linear fits to the bulk modulus versus volume fraction of TiO2 do not converge to a common compressibility of the TiO2 component, indicating that the structural role of TiO2 in these melts is dependent on the identity of the cation. This proposition is supported by a number of other property data for these and related melt compositions including heat capacity and density, as well as structural inferences from X-ray absorption spectroscopy (XANES). The compositional dependence of the compressibility of the TiO2 component in these melts explains the difficulty incurred in previous attempts to incorporate TiO2 in calculation schemes for melt compressibility. The empirical relationship KV-4/3 for isostructural materials has been used to evaluate the compressibility-related structural changes occurring in these melts. The alkali metasilicate and disilicate melts are isostructural, independent of the cation. The addition of Ti to the metasilicate composition (i.e. X2TiSiO5), however, results in a series of melts which are not isostructural. The alkaline-earth metasilicate and disilicate compositions are not isostructural, but the addition of Ti to the metasilicate compositions (i.e. XTiSiO5) would appear, on the basis of modulus-volume systematics, to result in the melts becoming isostructural with respect to compressibility.