Dust emission from crushing of hard rock aggregates

Abstract

Dust constitutes one of the major environmental concerns near many aggregate quarries, with crushing often being the most significant source. In this study, dust emissions and dispersion measurements were conducted under real operating conditions at six aggregate quarries in southern Finland. Five of them represent granitic rocks and one a limestone quarry.Dust concentrations during crushing were measured at varying distances with time intervals of five seconds. The variation in dust concentration was high within all the measured distances, ranging from 10 to 200 m.Crushing produces mainly coarse (TSP and PM10) dust particles, which settle near the dust source. The mass concentration of coarse particles in this investigation varied from few tens of μg/m3 to over 6.5 × 103 μg/m3 downwind from the crusher.The mass concentration of fine particles (PM2.5 and PM1) ranged between ten μg/m3 and few hundreds of μg/m3 downwind from the crusher. The fine particles originated mainly from machinery used in the quarries and remote sources, such as nearby traffic.In quarries operating with secondary crushing, the background concentrations were achieved approximately from a 350 m distance for coarse particles. Local dust sources, such as hauling, impacted the results inside the quarry. Crushing produced more dust compared to comparable studies for drilling. The dust concentrations at the limestone quarry were approximately 50% of concentrations measured at quarries with granitic rocks.