Synchrotron Radiation in the Earth and Environmental Sciences

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Synchrotron Radiation in the Earth and
Environmental Sciences

• Mike Henderson
• University of Manchester and
• CCLRC Daresbury Laboratory
• Based on (mainly) UK community research carried
  out 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, immobilsation,
bioavailability, clean-up
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Iron oxyhydroxides EXAFS SAXS studies at DL
Goethite (hi surface area) can be 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) Fate of toxic
metal depends on amorphous host aging SAXS/WAXS
in situ data help to provide such information
Goethite
SAXS provides mean particle size data vs time
Cd K-edge EXAFS
Acid mine drainage
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Toxic metal uptake in hyperaccumulator plants Ni
in Alyssum lesbiacum
Plants cultured in laboratory EXAFS study of
leaves, roots etc. Ni complexed (de-toxified)
with amino acid histidine Impacts on
phytoremediation strategies
EXAFS
FT
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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?
Bodywall As5 As3-S (thiol) in
metallothionein (MT)? In chloragog - As5 MT
As-C in arsenobetaine?
As in Lumbricus rubellus
Giant earthworm from Colombia
Great Consols, Tavistock, Devon
25cm
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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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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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Micro-XAS of Sr in Coral
Coral skeleton of aragonite -- high-P polymorph
of CaCO3 Aragonite Sr contents reflect seawater
surface temperatures Bulk sample analyses suggest
5oC warming in 10,000yrs Micro-XAS shows major
heterogeneity- caution!
200mm
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State-of-the-art ultradilute- and ED-EXAFS
Natural waters transport rare and toxic
metals Concentration levels can be at ppm
level How is the metal complexed? With Cl,
S? Some waters precipitate amorphous
sulphides What is phase nucleated (need millisec
time- scale)? How does the phase change with
time? Only state-of-the-art EXAFS facilities
provide answers - MPW for high flux high energy
Hg L(III) EXAFS pptation from 200mM Hg and S
solns
2.5 Cu at 2.23 Å
1650 x 300 microsec scans
ESRF - ID26 12 channel Si detector
SRS SRS 9.3 1024 strip Si-microstrip detector
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Combined glancing angle XRD and XAS studies -
surface oxidation of rhodonite (Mn,Fe,Ca)SiO3
APS GSECARS 4 circle diffractometer Pristine
reacted surfaces - specular and diffuse
scattering 1 hr reflectivity oscillations
reaction layer 75 A 2.5 hr loss of oscillations
- surface leaching of Mn Absorption edge E
decreases with depth, surface oxidised High
precision goniometer important for XAS facilities
140A
H2O
1 hr
140A
30A
2.5 hr
30A
66A
66A
H2O
Pristine
2 theta
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Schematic of X-PEEM Technique
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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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X-PEEM in planetary mineralogy Meteorites
contain Fe,Ni metal alloys, oxide minerals,
silicates and organics. X-PEEM needed to map
distribution/chemical states of Ni, Fe, C, O
etc. Also applicable to samples from Moon, Mars
and cosmic dusts Santa Catharina ataxite (35
Ni) Both Ni and Fe-rich metal phases have
oxidised rims of spinels X-PEEM images (O 1s Fe,
Ni 2p) obtained at ALS on Envirosync Metal rim on
Ni phosphide with Fe 2p spectra showing natural
MXCD
2p Fe image of rim on metal phosphide
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Biomineralization in hot springs
Bacteria in hot springs precipitate As -S,
SiO2 IR microspectroscopy (SRS) - 5mm
spot Track and image reaction
1mm
3mm
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In situ, in vivo silicification of cyanobacteria
SiO2 binding to cell walls/ sheaths Response of
internal proteins and lipids Micro-FTIR at ALS -
1.4.3 - 5 micron spot
ester CO stretch
carboxylate COO stretch
Post SiO2
6.3
pH 2.9
Pre-SiO2
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Soft X-ray Microspectroscopy in Environmental
Science
Zone plates produce 20-50nm focus beams Optimal
energy range 100-3000eV Energy tuned to enhance
chemical contrast Water window between C and O
edges Also tune to, eg., N, P K- Ca, Mn, Fe
L-edges Image to 20nm resolution under real
conditions Wet, frozen complementary to IR,
cryo-TEM
Zone plate
Fe-image
4mum
C-XANES reconstruction of cell structure in
coalified wood
Water-window image of frozen hydrated alga
Microtubule map in frozen cell Ag-enhanced,
Au-labelled.
500nm
Humic acids from soil (wet)
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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 (2p
3d)
Excellent probe for electronic structure
valency, crystal field local coordination Low
energy electron yield detection very surface
sensitive (lt10nm) Fluorescence yield better
bulk sensitivity( 0.1 mum)
Mn
Mn
V
V
Sulvanite
Cu
Cu3V5S4 or Cu 23V2S4 ??
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Cu L-edge spectroscopy monitors electronic
structure
Ground state for Cu2 d9, CuO 60 3d9, 40
3d10L Final state for CuO 931 eV 2p3d10, 939eV
2p3d9s (peak A) Final state 2 peaks 935eV
2p3d10L 945eV 2p3d10Ls (peak B) Ground state
Cu1 mainly d10, some d9s mixed with ligand
d10Ls Main 1 peaks 932-933eV small peaks at
931eV Cu2 contam. Broad structure above main
peak due to excitations to ligand band
2
2
1
L3
L2
B
A
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Cu L-edge S K-edge spectroscopy of sulphides
Bornite - L3 3 peaks - A (932.6eV), B (936),
C (938) Stoichio - large A/B non-stoichio -
small A/B Final states A cd10Ls2 B cd10s
C cd9s2 Extra electrons (Xs metal) fill holes,
reduce A C intensities Peak A in L3 due to
holes in ligand S band (L) Chalcopyrite also
large peak at A in Cu L3 Reflected in sharp peak
in S K-edge at 2470eV
Bornite Cu L-edges
Xs ve 0.12 0.25 0.49 0.58 0.76 1.86 1.35 2.88 4.
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Sulphide K-edges
Cu
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Volcanic activity depends on magma properties
Mobile magma erupts fairly quietly basalt low
SiO2 - low volatile content Viscous magma
explosive rhyolite high SiO2 high volatile
content Viscosity depends on composition
decreases as T, SiO2 and dissolved volatiles
increase (mainly H2O CO2 and F can be important)
Hawaii Mt St Helens
Viscosity (poise) vs T
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Basic structure of silicate melts and glasses
Network formers - SiO4, AlO4, TiO4?,
FeO4?? Network modifiers AlO6, FeO6,
larger cations Ca, Na, K
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Si K-edge XAS of silicate minerals and glasses
(melts)
XANES spectra reflect how Si-O units are
linked Usually SiO4 tetrahedra rarely
SiO6 Silicate glasses similar to tridymite 6
rings? But specialised glass compositions also
contain SiO6 XANES peaks allow proportions to be
estimated
Fleet et al. (UWO)
Si-P-O glasses
Geological glasses
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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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High-P/T in situ studies of Earths mantle
materials.

• Volatiles crucial in deep Earth - H2O, CO2, O2
• Eq. Of State - need molar volumes at P/T
• ED-XRD in multi-anvil press on 16.4 at SRS
• Need to characterise KCl phase transition
• In situ breakdown of KClO3 ? KCl 1.5O2
• dP/dT ? 0, ?V 0, Vsolids(P,T) fixes volume O2
• O2 1/3 smaller than shock wave data
• D layer could reflect exchange of metals
  and O between core and mantle

Oxygen molar vol vs. P
White X-ray beam
Sample assembly
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SR Prospects for Earth/Environmental Sciences
Research
2004 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, ???