Characterization of source rocks producing respirable quartz and aluminosilicate dust in underground US coal mines.
Proceedings of the 23rd Annual International Pittsburgh Coal Conference, September 25-28, 2006, Pittsburgh, Pennsylvania. Pittsburgh, PA: University of Pittsburgh, School of Engineering, :38-39
A research effort has been undertaken at the Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) to characterize the source material producing respirable quartz and aluminosilicate dust in coal mines. Mine regulatory personnel suggested that problematic silicate mineral dust concentrations were known in some coal mines operating in southern West Virginia, Virginia and eastern Kentucky. Six mines were selected in this region for rock and dust sampling by PRL researchers based on elevated quartz concentrations in historical dust samples. Four of the coal mines sampled produced elevated respirable quartz dust concentrations on active production sections during sampling, the other two mines produced about 5% quartz, the regulatory reduced standard limit for quartz. Prior research has suggested that the source of respirable silicate dust in underground coal mines is typically immediate roof or floor lithology, not mineral matter bound within the mined coalbed. At some of the sites included in this research there were only potential quartz source rocks in either the floor or the roof units. At other sites sampled during the study, potential quartz sources existed in both the roof and floor lithologies. In the later cases, elemental data have suggested the enrichment of certain cations in the roof lithologies compared to floor rock may have the potential to distinguish potential quartz and aluminosilicate sources produced in respirable dust samples. Research results from Pennsylvanian-age coalbeds in western Pennsylvania surface mine sites has suggested the clastically derived mineral matter in the immediate roof rock, coal-bound mineral matter and the immediate floor lithology are derived from a common source material. Some of the enrichment of certain cation species in the roof units (i.e., Ca, Fe, Mg, Na) compared to immediate floor rock may be related to the percolation of fluids through the overburden and diminished probability for fluids to migrate effectively through the coal or coal precursor and into the floor units. Comparisons of the elemental composition of dust cassette mineral matter and possible source rocks have shown that the dust composition is not identical to any of the sampled potential sources rocks. It is considered likely that the mining process, including rock breakage and the entrainment of dust particles in the ventilation air stream have modified the dust composition from the starting parent materials. However, normalizing the data has shown promise in distinguishing potential source rocks using elemental ratios. Data from the single quartz rock sources sites have been used to assess the viability of the methodology. The elemental data suggests roof strata as the primary source of mineral-generated respirable dust produced during mining and captured by the dust samplers on the cassettes. This finding is contrast to the quartz dust sources identified in the field and by x-ray diffraction analysis of roof and floor rock where at least one site showed the primary silicate dust source to be in the floor. The suite of x-ray fluorescence sample data suggests a strong relationship between the overall amount of Si and the quantity of quartz in the samples. A similar relationship was not found in the parent source rocks. These findings may be significant since the potential severity of the silicosis risk to miners is strongly influenced by both the quantity of quartz and the clay minerals in the respirable dust fraction.
Quartz-dust; Mining-industry; Underground-mining; Respirable-dust; Coal-mining; Silicates; Dust-analysis
Conference/Symposia Proceedings; Abstract
Research Tools and Approaches: Control Technology and Personal Protective Equipment
Proceedings of the 23rd Annual International Pittsburgh Coal Conference, September 25-28, 2006, Pittsburgh, Pennsylvania