Synchrotron Radiation in the Earth and Environmental Sciences

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Synchrotron Radiation in the Earth and
Environmental Sciences

• Mike Henderson
• CCLRC Daresbury Laboratory and
• University of Manchester
• Based on UK community research carried out
• mainly on SRS ESRF, APS, ALS

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Planet Earth
Nature
Environmental Science
Man
Earth Science
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Natural Environment Science Challenges.
Real systems chemically and physically complex
Periodic table - mainly light elements
(Zlt20) Concentrations gt to ltppm Solid-liquid-gas
Crystalline/ amorphous Chemically heterogeneous
(ltmicron to gtm) Water crucial - hydrous and
anhydrous phases Inorganic-organic-bio-
interactions Reactions at interfaces
SR is the ideal probe
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Molecular Environmental Sciences
Fundamental processes controlling the geochemical
and biological influences of cycling of elements
and organics between the crust (lithosphere),
hydrosphere, biosphere, and atmosphere at the
molecular level. Transport, immobilisation,
bioavailability, clean-up
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Iron oxyhydroxides EXAFS studies at DL
Goethite (hi surface area) - used in
environmental clean-up Toxic metal cycling -
immobilisation controls bioavailability FeOOH
colloids (goethite) adsorb metals - how
complexed? EXAFS Cd-O octahedral complex Cd-Fe
longer range data Inner sphere complex -
bi-dentate sharing 2 O with (Fe-O6)
Cd K-edge EXAFS
Goethite
Acid mine drainage
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Marina Fomina Geoffrey Gadd XAS study of
Toxic Metal Uptake in Fungae

• Largest biomass in soils
• Symbiotic plants/mycorrhiza
  cyanobacteria/lichens
• Exude protons and chelating agents - metal
  mobilization

Cu coordination in Beauveria caledonica

• In Beauveria caledonica EXAFS spectrum and
  Fourier transform very similar to copper
  oxalate (moolooite)
• Cu pptation on fungal hyphae heterogeneous 35
  total Cu accumulated by mycelium as oxalate -
  microfocus

Culture
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As speciation in earthworms from EXAFS
Old mines land contaminated with As (up to
5wt) Soils commonly As5 but also As3 which is
toxic Earthworms indicate soil health Survive
ingestion of As - how is As3 detoxified? Body
wall As5 As3-S (thiol) in metallothionein(MT)?
In chloragog - As5 MT As-C in
arsenobetaine?
Great Consols, Tavistock, Devon
As5
As3
As in Lumbricus rubellus
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Biological treatment of nuclear waste
Geobacter sulfurreducens reduces soluble U(VI) to
insoluble U(IV) Biogenic U(IV) transfers
electrons to soluble Tc(VII) Results in
co-precipitation of Tc(IV)/U(IV) - (immobile).
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Element Speciation in Hydrothemal Solutions at
High T and P from X-ray Absorption Spectroscopy
How are elements transported? Complex stability
vs metal / anion concentration? Complex stability
vs T and P Element solvation?
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Aqueous electrolyte solutions H2O phase diagram
Density (g/cc) ? Dielectric constant e
Critical point P 221 bar T 374oC ? 0.317 e
8.7
Saturated vapour pressure curve (svp)
Room T P 1 bar T 25oC ? 0.997 e 80.3
0.1 m NaCl 25oC 100 ionised 300oC 50
ion-pair (NaClo) at Critical Point 99.9 ion
pair
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Hydration and complexing of Pd(II) in
hydrothermal solutions to 300oC
K-edge Pd EXAFS for 0.01 m PdCl2 in 0.01 m HCl
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Pd K-edge EXAFS data for nitrate and chloride
aqueous solutions
N First shell (OH2 or Cl) coordination
number 2?2 Debye-Waller factor (Å2)
Molecular Dynamics gives 2.05 Å MD gives Pd-O
2.08, Pd-Cl 2.33 Å
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In situ high-T XAS to identify speciation of Cu
in natural fluid inclusions in quartz from
granite Andrew Berry - ANU and Imperial College
Cu K-? fluorescence scan
Optical image

• Cu(H2O)62 at 25 C CuCl2- at 200
  C
• either CuCl2- or CuCl(H2O) at 400 C
• Cu coordination and valency changes are fully
  reversible.
• No CuS complexes detected

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Sulfur L- and K-edge XANES of organic
compounds (Kasrai et al., Univ Western Ontario)
Identification of kerogens in Kimmeridge oil
shales from France Combination of K- and L-edge
data for S speciation Thiophenes main S species
in unheated samples
Model fits for asphaltene
thiophene ?? 66 22 C-S-C 12
C-S-S-C 50 Ph-S-Ph 50 C-S-C 50
C-SH 50 C-S-S-C
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S K-edge XAS 17th C warship VASA (Jalilehvand
et al.)
VASA sank in Stockholm harbour on maiden voyage
in 1628 Recovered in 1990 after 333 yrs in cold
brackish waters Oak surfaces now show presence of
sulfates and elemental S XAS of wood cores - S
species (0.2-4) penetrated to 10cms Sulfuric
acid causes wood hydrolysis - threat to
preservation
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Micro-XAS for Environmental Sciences
Sample heterogeneity is the norm on scales of a
few ?m
Mapping heavy metals in soils shows presence of
hotspots. Probe allows characterisation e.g.,
toxic Cr6 present
Metals immobilised by fungi in contaminated soils
characterised e.g., Zn complexed as an oxalate
Fe
Cr
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X-ray PhotoEmission Electron Microscopy (X-PEEM)
Spectroscopy
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Hydrothermal Mid-Ocean Ridge Vent Activity
Metal sulphide precipitation Black smokers
X-PEEM (at ALS) images zoning 2p spectra show
Cu and Fe2 Microbial effects?
10 microns
Red Iron Green Copper
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Redox imaging in upper mantle phases by X-PEEM
Upper mantle Mg-rich silicates (olivine,
pyroxene) Deep mantle (1050km) magnesiowustite
(Mg,Fe)O SiO2 In situ SR high-P/T experiments
define structures and transitions X-PEEM images
oxidation states for magnesiowustite with
exsolved magnetite
Fe3
Fe2
10mm
10mm
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Mineralogy, Petrology and High-pressure research
SR allows study of fundamental properties and
structures of Earth materials as well as In
situ high-P/-T studies of mineral structures
materials
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L-edge spectroscopy of 3d transition elements.

• Dipole transition from core 2p to empty 3d
  states
• (2p63dn 2p63dn1)
• Large coulombic interaction high probability
  of
• occurrence (contrast 1s 3d)
• Element specific L2,3 spectra rich in
• electronic structure information
• valency, site symmetry, crystal field
• L-edge core-hole lifetime broadening
• 3-4x smaller than for K-edge transitions
• (sharp multiplet structure)
• But
• Low energy, so surface sensitive technique (lt
  100Å)

Fe L-edge region 700-730eV
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Magnetism and XMCD

• Different X-ray absorption spectra obtained when
• helicity of circularly polarised light changed R
  to L
• OR
• direction of magnetisation changed ve to -ve
• ? XMCD

L3 L2
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Fe XMCD for ferrite spinels

• XMCD is not just element specific
• e- transitions to unoccupied 3d states depend on
  surrounding atoms ? site specific
• Spectra calculated using Atomic Multiplet Theory

Spinel structure
Calculated spectra
Fe2 in Td
Fe2 in Oh
Fe3 in Td
Fe3 in Oh
Magnetite
Red Td Blue Oh OhTd 21
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Natural magnetite XMCD spectrum for Fe

• Many natural ferrite spinels with formulae very
  close to pure magnetite (Fe3O4), show spectra of
  type
• Solid line experimental magnetite XMCD
  spectrum
• Dotted line calculated XMCD spectrum.
• A. Fe3O4 B. Oxidised Fe3-dO4 d cation
  vacancy

Stoichiometric
Oxidised
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Vicky Coker Nano-spinel synthesis by
Fe(III)-reducing bacteria
Geobacter sulfurreducens Cobalt-substituted
magnetites
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Multi-Anvil Press - Walker Cell 250kbar,
2000oC, 10mg
Cell
Ceramic sample holder
WC anvils
Press
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In situ high-P/T equilibria and dynamics in large
volume multi-anvil pressure vessels
Breakdown of volatile-bearing minerals in the
mantle (hydrates and carbonates) triggers melting
(volcanism) and earthquake activity.
At SRS, with ED-XRD, talc has been observed to
alter to water-rich 10- angstrom phase in a few
minutes
Below 300km, this new phase will break down,
releasing water which rises into the upper mantle
to cause melting.
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SR Prospects for Earth/Environmental Sciences
Research
2005 on SRS mini-probe XAS (30mum), mini-probe
for XRD in DAC (100mum) helical undulator - soft
X-ray XAS and MXCD Future with Diamond
Microprobes (lt1 micron spot) - XAS,
XRD Ultra-dilute EXAFS (1-10 micromolar
lt1ppm) X-ray/ IR/ UV spectromicroscopy at tuned
wavelengths - chemical state imaging Real
sytems (water/ nutrient solutions) Real time
reaction kinetics (10 microsec) Geo-Bio
interactions 2007 on Diamond Micro-XAS
X-PEEM high-P/-T Followed by SAXS/WAXS XRD
specialised XAS Later still MXCD, soft X-ray
microscopy, ???

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Diamond beamlines 2007- 2009
Environmental Sci
Earth Sci