GeoSoilEnviroCARS

GSECARS is a national user facility
for frontier research in the earth sciences using synchrotron radiation at the
Advanced Photon Source, Argonne National Laboratory.

GSECARS provides earth scientists with access to the high-brilliance hard x-rays from this third-generation synchrotron light source. All principal synchrotron-based analytical techniques in demand by earth scientists are being brought to bear on earth science problems:

• High-pressure/high-temperature crystallography and spectroscopy using the diamond anvil cell
• High-pressure/high-temperature crystallography and imaging using the large-volume press
• Powder, single crystal and interface diffraction
• Inelastic x-ray scattering
• X-ray absorption fine structure spectroscopy
• X-ray fluorescence microprobe analysis
• Microtomography

► Deadline for 2019-1 General User Proposals
Friday, October 26, 2018, 11:59 PM Chicago time

Apply for Beamtime

► GSECARS Raman Lab Open for Business !

► Science Highlights

► Researchers at 13 IDC investigate the impact of environmental release of silver nanoparticles (AgNPs) on ecosystems.

Schematic explanation of LP-XSW-FY data reduction and analysis.

Environmental significance
Among the various types of nanoparticles (NPs), silver nanoparticles (AgNPs) are widely used in everyday products and thus, they are present in the
environment. Due to their size and composition, they may be harmful to soil and aquatic ecosystems. Mineral surfaces, whether covered or not by biofilms,
are key to the fate and biogeochemistry of NPs as the solution/biofilm/mineral interface is highly reactive. For the first time, we quantified the distribution
of AgNPs at this interface and showed that depending on the type of coating, the AgNP percentage found in biofilms varied from 5% to 35%. Our results
highlight for the first time the importance of electrostatic and hydrophobic interactions within the biofilm and secondly the control of the type of coating
on their behavior in natural ecosystems.

Desmau, M., Gelabert, A., Levard, C., Ona-Nguema, G., Vidal, V., Stubbs, J.E., Eng, P.J., Benedetti, M.F. (2018) Silver nanoparticles dynamics at the solution/biofilm/mineral interface.  Environ. Sci.: Nano. 5: 2394-2405. https://doi.org/10.1039/C8EN00331A

► X-ray diffraction at 13 BMC monitored the hydrothermal precipitation of akaganeite
(β-FeOOH) and its transformation to hematite
(Fe2O3) in situ

13 BMC Experimental Setup at APS. (a) The X-ray beam is aimed at the base of the capillary (b), which is tilted at 60° from the horizontal plane. (c) Area detector. (d) The forced gas heater is positioned beneath the capillary.

K.M.Peterson (Heriot Watt University), P. J. Heaney and J.E. Post (Penn State) used TR-XRD to track the hydrothermal nucleation and growth of akaganeite and its transformation to hematite during in situ experiments between 100 and 200 °C. Abstract : Akaganeite was the only phase that formed at 100 °C. Rietveld analyses revealed that the akaganeite unit-cell volume contracted until the onset of dissolution, and subsequently expanded. This reversal at the onset of dissolution was associated with a substantial and rapid increase in occupancy of the Cl site, perhaps by OH− or Fe3+. Rietveld analyses supported the incipient formation of an OH-rich, Fe-deficient hematite phase in experiments between 150 and 200 °C. The inferred H concentrations of the first crystals were consistent with “hydrohematite.” With continued crystal growth, the Fe occupancies increased. Contraction in both a- and c-axes signaled the loss of hydroxyl groups and formation of a nearly stoichiometric hematite.

Representative time series of X-ray diffraction patterns collected at 150 °C. Akaganeite peaks are colored pink, and hematite peaks are colored blue.

Peterson, K., Heaney, P., & Post, J. Evolution in the structure of akaganeite and hematite during hydrothermal growth: An in situ synchrotron X-ray diffraction analysis. Powder Diffraction, 1-11. doi:10.1017/S0885715618000623

► Designing better extraction methods for
rare earth elements

ABSTRACT: Crystal truncation rod (CTR) measurements and density functional theory (DFT) calculations were performed to determine the atomic structure of the mineral−water interface of the {100} surface of xenotime (nominally YPO4). This mineral is important, because it incorporates a variety of rare earth elements (REEs) in its crystal structure. REEs are critical materials necessary for a variety of renewable and energy efficient technologies. Current beneficiation techniques are not highly selective for REE ore minerals, and large amounts go to waste; this is a first step toward designing more efficient beneficiation. Evidence is found for minor relaxation of the surface within the topmost monolayer with little or no relaxation in subsurface layers. Justification for ordered water at the interface is
found, where water binds to surface cations and donates hydrogen bonds to surface phosphates. The average bond lengths between cations and oxygens on water are 228 pm in the best fit to the CTR data, versus 243 and 251 pm for the DFT. No agreement on water positions bound to surface phosphates is obtained. Overall, the findings suggest that ligands used in beneficiation with a single anionic headgroup, such as fatty acids, will have limited selectivity for xenotime relative to undesirable minerals.

Stack, A.G., Stubbs, J.E., Roy, S., Srinivasan, S.G., Roy, S., Bryantsev, V.S., Eng, P.J., Custelcean, R., Gordon, A.D., Hexel, C.R. (2018) Mineral-Water Interface Structure of Xenotime (YPO₄) {100}.  J. Phys. Chem. C. 122:20232-20243. https://doi.org/10.1021/acs.jpcc.8b04015

► The Hunt for Earth’s Deep Hidden Oceans

GSECARS users Steve Jaconbsen (Northwestern), Michele Wenz (Northwestern) and Oliver Tschauner (UNLV) and other researchers from around the world are working on unraveling the mystery of freely existing H₂O in the mantle.  Quanta Magazine Interview

► Computer microtomography at 13 BMD characterized spatial heterogeneity in soil matrix from varying long term management strategies.

An example of a μCT image from an Os stained soil sample from biologically based management at 4 μm resolution. (A) A 3D scan of an entire Os stained sample. The thickness of the sample was 1 mm. (B) Image of a slice of an Os stained sample above the K-edge (74 keV). (C) Image of a slice of an Os stained sample below the K-edge (73.8 keV). (D) Difference between above and below K-edge images with non-biological pore (E), POM-NS (G), and POM-Root (F) expanded. Total image size is 8 × 8 mm for (B–D).

Study Conclusion : Analysis of grayscale gradients near pores of biological origin were found to be a useful proxy for assessing SOM spatial distribution patterns at micro-scale. Grayscale gradients of non-biological pores, in contrast, were found to be different from SOM gradients due to a pore identification artifact. Utilizing a different thresholding method may overcome this limitation.

Michelle Y. Quigley, Mark L. Rivers, Alexandra N. Kravchenko, "Patterns and Sources of Spatial Heterogeneity in Soil Matrix From Contrasting Long Term Management Practices," Front. Environ. Sci. 6 (28), 1-15 (2018). DOI: 10.3389/fenvs.2018.00028