. 2002 Nov 20;3:81. doi: 10.1186/1467-4866-3-81

Table 6.

EXAFS analyses

Cadmium EXAFS analysis
Core	Atom	R/Å	N	σ²/Å²	ΔE₀/eV

Sediments
SC4-12	Cd–S^a	2.50^e	4.0	0.0044^e	-1.0^e
34.5 cm
192 ppm
Cl-2	Cd–S^a	2.51^e	4.0	0.005 l^e	-1.4^e
55.0 cm
1222 ppm
SC4-11	Cd–S^b	2.51	1.9^e	0.0050	-4.1^e
31.5 cm	Cd–O^b	2.31^e	3.2^e	0.01 20^e
Leached

Reference precipitates^c
Cd_1.0S	Cd–S	2.51^e	4.0	0.0056^e	-1.7^e
Cd_0.25S	Cd–S	2.51^e	4.0	0.0048^e	-2.6^e

Reference compound: greenockite (CdS)^d
	Cd–S	2.52	1
	Cd–S	2.53	3
	Cd–Cd	4.12	6
	Cd–Cd	4.13	6

Scale factor (S₀²) = 1.5. ^aFirst-shell Cd–S coordination fixed at 4; R and σ²were varied. ^bFor the sulfide component, R and σ²were fixed on the average of values determined from fits to reference precipitates; N was varied. If N_Cd–S= 4 and N_cd–O= 6 are assumed, then the sulfide component is 47% and the oxide component is 53% of the total absorption spectrum. ^cCadmium sulfide was precipitated by adapting an FeS method.¹⁰XAS spectra collected on wet samples immediately after precipitation. ^dCrystallographic values for greenockite from ref. 58. ^eParameter varied in least-squares fits.


Zinc EXAFS analysis

Core	Rel. %	Atom	R/Å	N	σ²/Å²	ΔE₀/eV

Sulfide component^f
SC4-1	75	Zn–S	2.33	3.0^l	0.0065	-5.2^l
2.5 cm		Zn–Zn	3.83	8.9	0.0231^l
287 ppm		Zn–S	4.49	8.9	0.0267^l
SC4-12	78	Zn–S	2.33	3.1^l	0.0065	-6.3^l
34.5 cm		Zn–Zn	3.83	9.3	0.0221^l
515 ppm		Zn–S	4.49	9.3	0.0297^l
C3-9	90	Zn–S	2.33	3.6^l	0.0065	-5.2^l
55.0 cm		Zn–Zn	3.83	10.8	0.0259^l
486 ppm		Zn–S	4.49	10.8	0.0257^l
SC4-11	25	Zn–S	2.33	0.9^l	0.0065	-5.9^l
31.5 cm		Zn–Zn	3.82	2.6	0.0225^l
Leached		Zn–S	4.49	2.6	0.0139^l

Oxide component^g
SC4-1	25	Zn–O	2.04^l	1.7^l	0.0065	-5.2^l
2.5 cm		Zn–Me^h	3.13^l	1.0^l	0.0080
287 ppm		Zn–Meⁱ	3.13^l	0.8^l	0.0100
SC4-12	22	Zn–O	1.99^l	1.4^l	0.0065	-6.3^l
34.5 cm		Zn–Me^h	3.06^l	0.9^l	0.0080
515 ppm		Zn–Meⁱ	3.13^l	0.8^l	0.0080
		Zn–Me^j	3.21^l	1.7^l	0.0080
C3-9	10	Zn–O	2.09^l	1.4^l	0.0065	-5.2^l
55.0 cm		Zn–Me^f	3.10^l	0.4^l	0.0080
486 ppm
SC4-11	75	Zn–O	2.02^l	3.2^l	0.0065	-5.9^l
31.5 cm		Zn–Me^h	3.13^l	1.3^l	0.0080
Leached		Zn–Me^j	3.39^l	0.6^l	0.0080

Reference compound: sphalerite (ZnS)^k
		Zn–S	2.33	4
		Zn–Zn	3.83	12
		Zn–S	4.49	12

Scale factor (So²) = 1.0. ^fSulfide component: Interatomic distances (R) for Zn–S and Zn–Zn fixed on Crystallographic values in sphalerite; first-shell σ²for Zn–S was fixed on an empirical value determined from fits to sulfide reference compounds. For higher Zn–Zn and Zn–S shells, N was fixed on the value calculated from the proportion of sphalerite component determined in fits to filtered first-shell spectra and σ²was varied. ^gOxide component: Values for σ²were fixed for all shells based on empirical fits to reference compounds; R and N were varied. ^hBackscatterer is Fe or similar transition metal cation; edge-sharing octahedra. ⁱBackscatterer is Mg or Al; edge-sharing octahedra. ^jBackscatterer is Fe or Si; corner-sharing octahedra or tetrahedra. ^kCrystallographic values for sphalerite from ref. 28. ^lParameter varied in least-squares fit.


Chromium EXAFS analysis

Core	Atom	R/Å	N	σ²/Å²	ΔE₀/eV

Oxide component^m
SC2-7	Cr–O	1.97^s	6.0	0.0035^s	-8.5^s
19.5 cm	Cr–Meⁿ	3.01^s	1.9^s	0.0100
<2 μm	Cr–Me^o	3.00^s	1.7^s	0.0100
392 ppm	Cr–Fe	3.42^s	1.8^s	0.0080
SC4-1	Cr–O	1.98^s	6.0	0.0041^s	-8.9^s
1.5 cm	Cr–Me^p	2.97^s	1.6^s	0.0080
243 ppm	Cr–Fe	3.44^s	1.9^s	0.0080
SC4-12	Cr–O	1.97^s	6.0	0.0041^s	-6.0^s
34.5 cm	Cr–Me^p	3.02^s	1.1^s	0.0100
766 ppm	Cr–Fe	3.44^s	2.2^s	0.0080
SC4-11	Cr–O	1.98^s	6.0	0.0037^s	-8.8^s
31.5 cm	Cr–O^p	3.00^s	1.8^s	0.0100
Leached	Cr–Fe	3.42^s	1.2^s	0.0080

Reference compounds
Cr₂S₃^q	Cr-S	2.42	6
	Cr–Cr	2.79	2
	Cr-S	4.20	6
K₂Cr₂O₇^r	Cr–O	1.52, 1.54,	4
		1.73, 1.85
	Cr–Cr	3.13	1
	Cr–K	3.26	1

Scale factor (So²) = 0.90. ^mOxide component: First-shell Cr–O coordination fixed at 6; σ²was varied. For higher shells, values for σ²were fixed based on empirical fits to reference compounds; R and N were varied. ⁿBackscatterer is Mg or Al; edge-sharing octahedra. ^oBackscatterer is Fe or similar transition metal cation; edge-sharing octahedra. ^pFit with single shell of Fe atoms; probably a disordered shell of Al, Mg, and Fe atoms. ^qCrystallographic values from ref. 59. ^rCrystallographic values from ref. 60. ^sParameter varied in least-squares fits.


Iron EXAFS analysis

Core	Rel. %	Atom	R/Å	N^w	σ²/Å²	Δ E₀/eV

Pyrite component^t
SC4-1	35.6	Fe–S	2.25	0.80	0.0011	-7.2^w
2.5 cm		Fe–S	3.44	0.80	0.0066
		Fe–Fe	3.82	1.60	0.0066

SC4-12	38.5	Fe–S	2.25	0.92	0.0011	-6.7^w
34.5 cm		Fe–S	3.44	0.92	0.0066
		Fe–Fe	3.82	1.84	0.0066
SC4-11	21.4	Fe–S	2.25	0.66	0.0011	-8.3^w
31.5 cm		Fe–S	3.44	0.66	0.0066
Leached		Fe–Fe	3.82	1.32	0.0066

Oxide component
SC4-1	64.4	Fe–O	2.00^w	2.64	0.0048	-3.4^w
2.5 cm		Fe–Fe	3.10^w	0.53	0.0050
		Fe–Si	3.26	1.43	0.0057
		Fe–Fe	3.39^w	0.29	0.0057
SC4-12	61.5	Fe–O	2.00^w	2.79	0.0048	-3.2^w
34.5 cm		Fe–Fe	3.09^w	0.62	0.0050
		Fe–Si	3.26	1.15	0.0057
		Fe–Fe	3.43^w	0.41	0.0057
SC4-11	78.6	Fe–O	2.00^w	3.12	0.0048	-0.5^w
31.5 cm		Fe–Fe	3.09^w	0.92	0.0050
Leached		Fe–Si	3.26	0.82	0.0057
		Fe–Fe	3.39^w	0.41	0.0057

Reference compound: pyrite (FeS2)^v
		Fe–S	2.25	6
		Fe–S	3.44	6
		Fe–Fe	3.82	12

^tPyrite component: Interatomic distances (R) were fixed on crystallo-graphic values from pyrite and σ²was fixed on values determined from fits to reference sulfide compounds. N for each shell was floated as a linked variable in proportions based on the known coordination in pyrite. Relative percent (Rel. %) for pyrite or oxide components is calculated from the integrated fit areas of all atomic shells comprising each component (normalized to 100%). ^uOxide component: Values for σ²were fixed for all shells based on empirical fits to reference compounds of similar composition and structure; R and N were varied, except for the Fe–Si shell, which will co-vary with Fe shells if floated independently. This shell was fixed on a typical crystallo-graphic distance for Fe–Si in phyllosilicates. ^vCrystallographic values from ref. 61. ^wParameter varied in least-squares fit.