Gas emissions, tars, and secondary minerals at the Ruth Mullins and Tiptop coal mine fires

Abstract

Both the Tiptop and Ruth Mullins coal fires, Kentucky, were reinvestigated in 2009 and 2010. The Tiptop fire was not as active in 2009 and may have been on the path to burning out at the time of the 2009 visit. The Ruth Mullins coal mine fire, Perry County, Kentucky, has been the subject of several field investigations, including November 2009–February 2010 investigations in which we measured gas emissions, collected minerals and tars, and characterized the nature of the fire. Vents exhibiting the greatest gas flux (>100,000 mg/s/m2) are those with the largest amount of condensate minerals and tars. Vents with moderate gas flux (10,000–100,000 mg/s/m2) are less likely to contain condensate minerals, but are collocated with tars, and vents with the lowest flux (<10,000 mg/s/m2) generally lack both minerals and tars. Aliphatic hydrocarbons present in the gases include C1-C9 compounds, and aromatics include BTEX compounds. Diffuse-CO2 emissions are concentrated along the fracture zones overlying abandoned mine works. The area of peak diffuse flux corresponds to the trend of the collapsed portal that forms vent 5. The greatest vent emissions were also recorded at vent 5. The snow-melt zone mapped in January 2010 overlies the areas of peak diffuse-CO2 emissions measured in November; together they delineate the zone of active combustion. Comparison of greenhouse gas emissions from the two sources shows that vent emissions exceed diffuse emissions. The highly fractured, quartz-cemented roof rock funnels the majority of emissions toward the vents. Significant decreases are seen in estimates of yearly greenhouse emissions based on data gathered from November 2009 to February 2010, with estimates from November significantly exceeding any previously published estimates. For example, September 2009 estimates from vent 3 alone indicated that 19 ± 7.5 T CO2/yr were emitted while the November 2009 estimates were 1800 ± 690 T/yr. Barometric pressure was lower in November than September. This implies that there are many factors influencing the seasonal variations in fire emissions and that more frequent monitoring will be necessary to derive accurate estimates of coal fires' contribution to the carbon budget.