Characterization of fine particle material in ambient air and personal samples from an underground mine

Abstract

Personal samplers representing 4 job classifications and stationary samplers at 2 locations in an underground mine were deployed to measure fine particle carbon (organic/elemental), ions (sulfate plus nitrate), elements (metals and others), and speciated organic compounds including polycyclic aromatic hydrocarbons (PAH), oxygenated PAH, and hopanes/steranes. Chemically segregated size distribution was investigated after collection with a multistage impactor placed at 1 sampling site. All samples exceeded the currently proposed mine air standard of 160 μg/m3 total carbon, and most exceeded the interim standard of 400 μg/m3. Carbon accounted for about 70% of the fine particle mass (described as a reconstructed mass of all measured chemical species); sulfate and ore/waste rock-derived metals constituted most of the remainder. Most of the personal samples were more concentrated than the ambient samples; 1 sample exceeded 2.5 mg/m3 total mass. The PAH consisted mostly of gas-phase/semivolatile compounds and minor amounts of the particle-phase species, which is consistent with the composition of diesel exhaust, the major source of fine particle material in the mine. Size-segregated chemistry showed that the majority of the material below 1 μm of aerodynamic diameter was carbon, with the largest amount at approximately 0.2 μm. Metals, derived primarily from resuspended ore/waste rock, comprised the majority of the material above 1 μm. Results are placed in context of current mine-monitoring techniques that aim to regulate diesel particulate material.