1. WEST VIRGINIA MINE DRAINAGE TASK FORCE SYMPOSIUM
April 22-23, 2008
Selenium Distributions in Kanawha Formation Rocks from Boone County, West Virginia
Dr. Dorothy Vesper
West Virginia University
Department of Geology & Geography
WV WRI Hydrogeology Research Center
DOE-NETL Research Fellow
Hydrogeology Research Center WV Water Research Institute

2. Selenium distribution and mode of occurrence in the Kanawha Formation, southern West Virginia, USA
Vesper DJ, M Roy and CL Rhoads (2008) International Journal of Coal Geology 73:

3. Se in rock core Overall Purpose
Better understand the chemistry of Se in coals and related strata
Help predict where Se is most likely to be found
Two topics
Distribution in rock cores - stratigraphy
Mode of occurrence in rocks
2004 – 1 core, mostly mode of occurrence

4. Location of cores
WVGES

5. Selenium by coal bed Stratigraphy Coal Se (ppm dry wt) Pittsburgh
Kittanning
Coalburg &
Winifrede
WVGES, (coals only)

6. Distribution in rock core
Bull Creek Mine (Coal River watershed)
5 rock cores
Coal, shale, mudstone, sandstone, carbolith
Kanawha Formation (Coalburg – Winifrede coal beds)
Grinding/Compositing strategy
<0.5 feet: completely composited
>0.5 – 5 feet: ~1-inch interval from top, middle, & bottom of each 1-foot length. Ground to 1/16 inch, composited, then 500 g ground to <60 mesh

7. Distribution in rock core
287 Samples
191 had Se > 0.2 mg/kg
Max 11.9 mg/kg in a mudstone
Sample prep by Research Environmental & Industrial Consultants
Lithology described
Ground/composited to <60 mesh by lithology
Total digestion using nitric acid and hydrogen peroxide (EPA Method 3050B)
Analysis for total Se using Graphite Furnace Atomic Absorption Spectroscopy (GFAA) (EPA Method 270.2)
Grinding/Compositing strategy
<0.5 feet: completely composited
>0.5 – 5 feet: ~1-inch interval from top, middle, & bottom of each 1-foot length. Ground to 1/16 inch, composited, then 500 g ground to <60 mesh

8. Bull Creek Mine 2004 Coalburg Winifrede Coalburg (upper line)
Winifrede (lower line)
Bull Creek
Winifrede
Coal River
1 km
Lick Creek

9. Distribution in rock core
How is the Se distributed?
Stratigraphy
Rock type
Formation
Location relative to coal bed
Other chemical parameters
Sulfur (S)
Total organic carbon (TOC)

10. Distribution in rock core
Do Se concentrations change with rock type?

11. Distribution in rock core
Do Se concentrations change by core?

12. Distribution in rock core
For non-coal units – distance to the coal matters
Proximate distance – shortest distance from bed to coal
0 distance = adjacent to coal
Trends agree with Mullenex (2005) for a similar section in WV
Green circles = carboliths
Green boxes – samples immediately under carboliths

13. Distribution in rock core
What is the relationship between Se & sulfur?
Green circles = carboliths
Green boxes – samples immediately under carboliths
All data (R2 = 0.21)
Coal only
Shale
Agrees with Coleman et al. (1993), Mullenex (2005), Neuzil et al. (2005) – FOR THIS REGION. Only Mullenex looked at multiple rock types

14. Distribution in rock core
What is the relationship between Se & total organic carbon (TOC)?
Green circles = carboliths
Green boxes – samples immediately under carboliths
All data
Coal
Mudstone &Shale
(only core 2)

15. Multivariate analysis
Principle component analysis (PCA)
Multivariate
Looks for commonalities between variables
Identifies “factors” which are groups of variables

16. PCA Results
PC1– Sulfur, acidic, non-carbonate, strongly related to sulfur concentration
PC2 –Carbonate, some acid, limited S
Se loads onto both the sulfur and non-sulfur PCs
Similar results obtained for PCA of coals in WV, based on WVGES database (2003)
Variables included:
PC1
PC2
Log Total S (%)
0.575
0.043
Log Potential acidity
0.475
0.452
Log Neutralization potential
-0.334
0.608
Paste pH
-0.440
-0.372
Log Total Se (mg/kg)
0.373
-0.535
Eigenvalues
2.63
1.25
% variance explained
52.6 25
169 samples; acidity and neutralization potential as calcium carbonate equivalent tons per 1000 tons

17. Map Se and S concentrations for each sample against
PCA Results
Map Se and S concentrations for each sample against
PC1 and PC2 scores for each sample
PC1
Scores
(Sulfur-rich)
R2 = 0.87
R2 = 0.36
PC2
Scores
(more neutral)
R2 = 0.36
R2 = 0.01
Scores provide the weighting of that sample on that principle component
Selenium
Sulfur

18. PCA Results Coal Neutral. potential more controlling
Mudstone, shale, sandstone
Carboliths
Coal
Sulfur more controlling

19. Conclusions of rock core study
Distribution of total Se:
Se highest in coals; rocks adjacent to coals
Not all units close to coal are high in Se; but the layers that are high in Se are typically found with two feet of the coals
Se probably present in more than 1 mode
No strong correlations with S, TOC
Extraction data indicates both organic & sulfide
PCA analysis shows no single trend for Se
Sulfide more important for coals & organic-bound for shales (?)

20. Possible Interpretation
Why these patterns in the rock record?
Steps to preservation:
Changing source through time
Immobile – during/after rock formation
(Se less mobile at low pH)

21. Possible Interpretation
Depositional environment for Kanawha Formation
Domed swamp
(Rain water fed,
Typically acidic,
Low in nutrients)
Planar swamp
(Ground water fed, neutral pH)
Modified from USGS Circular 1143 (2003),
Coal—A Complex Natural Resource

22. Possible Interpretation
Why these patterns in the rock record?
1. Less S-associated Se
Deposition in domed peat swamp, more oxidizing
Less total S in system (no source vs. loss)
Se reduction vs. S reduction

23. Possible Interpretation
2. Possible redistribution after deposition
Se conc. above & below coal have similar trends
From compaction or later fluids

24. A final thought
Depositional environments

25. Questions? Acknowledgements
U.S. Department of Interior Office of Surface Mining (OSM)
West Virginia Water Research Institute
REIC (Tim Keeney)
Decota Consulting
Pritchard Mining
Selected References
Cecil, CB, RW Stanton, SG Neuzil, FT Dulong, LF Ruppert and BS Pierce (1985). "Paleoclimate controls on the late Paleozoic sedimentation and peat formation in the central Appalachian Basin (U.S.A.)." International Journal of Coal Geology 5:
Coleman, L, LJ Bragg and RB Finkelman (1993). "Distribution and mode of occurrence of selenium in US coals." Environmental Geochemistry and Health 15(4):
Mullennex R (2005) Stratigraphic Distribution of Selenium in Upper Kanawha-Lower Allegheny Formation Strata at a Location in Southern West Virginia. The 23rd Annual Intern Pitt Coal Conf
Neuzil, SG, FT Dulong and CB Cecil (2005). Spatial trends in ash yield, sulfur, selenium, and other selected trace element concentrations in coal beds of the Appalachian Plateau Region, U.S.A. (preliminary report). Reston, VA, U.S. Geological Survey.
USGS (2005). Coal—A Complex Natural Resource, An overview of factors affecting coal quality and use in the United States with a contribution on coal quality and public health. Circular 1143.
WVGES (2003) Trace Elements in West Virginia Coals. Selenium. Online graphs and data
Questions?