Analysis of Black Carbon (BC) concentration distribution in relation to Lung-Deposited Surface Area (LDSA) measured in the operational drift of the underground metalliferous mine

Abstract

The assessment of air quality in underground metalliferous mines is crucial due to the high occupational exposure risks posed by diesel particulate matter (DPM) as a by-product of diesel engine emissions. This study presents the results of the analysis of black carbon (BC), as a surrogate of DPM, concentration distribution in relation to Lung-Deposited Surface Area (LDSA). The measurements were produced at the working diesel engine equipment within two sections (planes) of the mine drift, where for each plane the nine sampling points were used. Correlation factors between BC, LDSA, PMs, and airflow velocity were produced, and relationships of particle number concentration (PNC), BC, and LDSA to particle diameter were elaborated. BC at an average concentration of 2591 µg/m³ with a particle diameter of 90 nm had the worst dilution factor (0.13) within the 9 meters length between the measured points of two planes compared to LDSA (0.29) at concentration 4017 µm²/cm³ and PM₁ (0.34) at concentration 2982 µg/m³. Monte Carlo modelling analysed the concentrations distribution range of BC to PM_0.3, PM₁ and PM_2.5 considering the instruments' accuracy, and demonstrated reasonable confidence regions of BC and LDSA concentrations between each measurement point during their distribution from Plane 1 to Plane 2. Developed risk assessment produced the event tree analysis by demonstrating LDSA high exposure zones considering toxic effect timing. This study offers an integrated, spatial-temporal characterization of diesel exhaust and LDSA, thereby contributing novel insights into the dispersion of the health-relevant aerosol exposure of underground miners.