WVGES

Trace Elements in West Virginia Coals


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NOTE: The following online publication is a draft version. These pages will be updated and/or revised on an ongoing basis.

WELCOME!
These pages explore the geologic, environmental and economic aspects of trace elements in West Virginia coals.

Introduction
Summary
Planned Enhancements

Select a page, or read on.
Hazardous Air Pollutant Page
General Trace Element Page
Periodic Table
HAP Summary Statistics Table
General Elements Summary Statistics Table
Individual Coal Bed 
HAP Summary Statistics Table


INTRODUCTION

What are trace elements, and why is it important to gather information about trace elements in West Virginia coals?

Coal is made up primarily of "organic" elements (carbon, hydrogen, oxygen and nitrogen) and "inorganic" elements (primarily silicon, aluminum, iron, calcium, magnesium, titanium, sodium, potassium, and sulfur).  Organic elements comprise the combustible body of the coal, whereas the inorganic elements are present in coal in minerals that largely form the ash when the coal is burned.  Inorganic elements (e.g. silicon and aluminum) are present in most West Virginia coals in the range of several percent or more in ash forming minerals, but other "inorganic" elements, such as sulfur, present in lesser amounts, may detrimentally impact the use of West Virginia coals.

Trace elements are defined as elements present in coal in amounts of less than 1 percent by weight 1.  Generally, trace elements are present in coal in amounts much lower 1 percent, and are reported in parts-per-million (ppm) by weight in the coal.  A trace element concentration of 1 ppm =  0.0001% by weight, or expressed in another way, a 1 ppm concentration of a trace element equals one pound in one million pounds (500 tons) of coal.  Most trace elements in West Virginia coals are present at levels of 10 to 100 ppm, or less.

Highly toxic elements (e.g. arsenic, mercury, lead, and selenium) are present in West Virginia coals, though generally in very low concentrations. How hazardous elements present in very low amounts adversely impact the environment is a matter of scale. Annually, millions of tons of coal are mined and utilized (year 2000 coal production), potentially liberating large amounts of various hazardous elements.  For example, a coal fired power plant with no pollution controls in place theoretically would produce 10 tons of lead for each million tons of coal burned containing 10 ppm lead. However, modern pollution control measures provide controls against the release of large amounts of hazardous trace elements to the environment.

Because of the potential effects of trace element pollutants from coal fired power plants the U.S. Environmental Protection Agency (EPA) is currently investigating whether further regulation of trace element emissions are necessary. Title III of the Clean Air Act Amendments of 1990 concerns Hazardous Air Pollutants (HAP's), 11 of which are trace elements in West Virginia coals: Arsenic (As), Beryllium (Be), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Mercury (Hg), Manganese (Mn), Nickel (Ni), Lead (Pb), Antimony (Sb) and Selenium (Se).

The primary goal of these pages is to provide data on trace element concentrations, statistics, stratigraphic occurrences, and geographic distributions within West Virginia's coal beds. Economic and environmental impacts of various trace elements are discussed, but care must be used when interpreting the data (see Cautionary Notes page).  With pollution controls in place, significant percentages of various trace elements, importantly HAP's, are captured, thus preventing their release to the environment.


SUMMARY

Stratigraphic and areal distribution trends in the trace elements in West Virginia coals as well as statistical correlations, or lack of correlations, between various trace elements and ash yield, total sulfur, pyritic sulfur presented in these pages revealed some interesting relationships among the elements and ash yield.

A table of statistical correlations of trace elements with ash yield, in decreasing order of significance, includes Chromium (Cr), Thorium (Th), Scandium (Sc), Cesium (Cs), Rubidium (Rb), Lithium (Li), Vanadium (V), Hafnium (Hf), Cerium (Ce), Lanthanum (La), Zirconium (Zr), Tantalum (Ta), Niobium (Nb), Dysprosium (Dy), Holmium (Ho), Lead (Pb), Samarium (Sm), Europium (Eu), Gallium (Ga) and Tellurium (Te).  These elements likely occur within mineral matter in coal.  Most of these elements probably occur in silicate minerals, especially clay minerals, which make up 60-70% of the mineral matter in coals 2. A subset of these elements and many rare earth elements cross correlate among each other as component elements of the mineral monazite. These include the major components Ce, La, Th, Nd and Y, and elements detected in monazite in trace amounts, including Dy, Er, Eu, Gd, Ho, Lu, Sm, Tb and Yb.  Rubidium(Rb) and cesium (Cs) correlate well with each other and with ash yield because these elements readily substitute for potassium (K) in clay minerals by virtue of similarities in their atomic radii.  The zirconium (Zr) rich mineral zircon is a common trace mineral in West Virginia coals and is known to also contain Hf, Ta, and Nb.  Zinc (Zn) is primarily present in coal as the trace mineral sphalerite which also contains cadmium (Cd). Lead (Pb) appears to be in coal in the minerals galena and the selenium (Se) bearing clausthalite, and copper (Cu) is present in chalcopyrite.  The mineral pyrite is a significant source of sulfur (S) in West Virginia coals and contains As, Hg and Tl, probably in solid solution.  The chalcophile elements (As, Co, Ni, Pb and Sb) correlated very poorly (except Co and Ni) in West Virginia coals despite high mutual correlations in coals of the Illinois Basin 3.

Elements that did not statistically correlate with ash yield are assumed to be associated with the organic fractions of the coal.  These probably organically-bound elements in increasing order of correlation with ash yield were Cl and Br, which negatively correlated with ash yield, Be, Sb, Ge and Sr.  Boron was found to have an organic affinity in low rank Illinois Basin coals 3.  In West Virginia coals, B displayed a unique correlation with coal rank, and decreased in abundance in the coal as the rank increased.  Apparently, increased metamorphism of West Virginia coals brought about by increased temperatures, caused by depth of burial, resulted in devolatilization of boron B from the coal.  Whether the B was originally in clay minerals or the organic fraction of the coal is unknown.



PLANNED ENHANCEMENTS
Phase I of this study reports on general aspects of trace elements in West Virginia coals included in these pages.  As more data are acquired these pages will be updated.  Phase II will included data and trace element distribution maps on coals for which we have a significant amount of data.  Currently these include the Pocahontas No. 3 coal (n = 30 samples), the Pocahontas No. 4 (n = 17), Sewell (n = 53), Eagle (n = 69), Powellton (n = 39), No. 2 Gas (n = 60), Peerless (n = 18), Fire Clay (n = 19), Winifrede (n = 25), Coalburg (n = 77), Stockton (n = 51), No. 5 Block (n = 46), Lower Kittanning (n = 17), Pittsburgh (n = 43), Redstone (n = 42) and Sewickley (n = 16) coals. Phase III will include data gathered on trace minerals in West Virginia coals using the SEM mentioned throughout these pages as an "unpublished study by the WVGES".
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REFERENCES

    1.    Swaine, D.J., (1990)
    2.    Renton, J.J., (1982)
    3.    Gluskoter, H.J., et al., (1977)
 
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Page last revised: December 2, 2005


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