Geological Society of America

203 Environmental Geoscience

Wednesday, 19 October 2005
8:00 AM - 12:00 PM

GAS VENT MINERALOGY AND GEOCHEMISTRY: THE BURNING-CULM BANKS OF SOUTH AFRICA

Paper number: 203-6
Program: Technical Sessions
Time: 9:15 AM – 9:30 AM

Authors

Glenn Blair Stracher Presenting Author
East Georgia College, Swainsboro, GA
J. Denis N. Pone
University of Witwatersrand, Johannesburg, N/A
Robert B. Finkelman
U.S. Geological Survey, Reston, VA
Harold J. Annegarn
University of Johannesburg, Johannesburg, N/A
John McCormack
University of Nevada, Reno, NV
Donald R. Blake
University of California, Irvine, Irvine, CA
Paul Schroeder
Univ of Georgia, Athens, GA

Abstract

Spontaneous combustion of coal as a consequence of opencast mining in South Africa, the world's fifth largest producer of hard coal, occurs frequently and is cause for concern, considering the volume of noxious fumes, dust, and particulate matter mobilized. In addition to consuming a valuable natural resource, gas exhaled from vents in culm banks and solid combustion by-products encrusting these vents may serve as vectors for the transmission of toxins to nearby floral and faunal habitats as well as to coal miners and people living in nearby communities. The toxins may be transmitted by atmospheric and water pollution, inhaled wind-blown dust particles, and food grown in soils polluted by derivatives of these solids.

Twelve assemblages of solids encrusting the outer perimeter of active gas vents and fissures, in addition to thirteen gas samples, were collected from burning-culm banks in the Witbank and Sasolburg coalfields northeast of Johannesburg, South Africa. In addition to bituminous coal, the culm banks consist of variable proportions of sandstone, mudstone, and regolith that may affect the composition of combustion by-products by interacting with the coal-fire gas prior to its exhalation at the surface.

Preliminary analyses reveal that the solids consist of a potentially toxic mixture of S, S_xO_y, S_xO_yN_z, S_xO_yN_zAl_w, and S_xN_yCl_z compounds with crystalline habits that include cubes and rhombic dipyramids. Trace elements associated with some of the solids include As, Pb, Cu, Ge, and Hg. The gases are comprised of a complex mixture of hydrocarbons, halides, greenhouse gases, and toxic concentrations of CO, benzene, and toluene. The affects of numerous compounds in the gas on human health are unknown and merit investigation. Establishing criteria for toxicity is necessary for determining the need for environmental regulation.