Modeling of fugitive dust emission and control measures in stone crushing industry

Abstract

Stone crushing in India is a small scale industry, where most of the operations are performed manually. A cluster of 72 stone crushing units located at Trisoolam in Chennai is a source of high levels of dust generation in the vicinity of the crushers and in the communities surrounding them. An ambient air quality monitoring network was designed and operated over 3 months (June–August, 2006) at 17 sites across the Trisoolam area. Wind speed and direction were monitored continuously every 1 hour to determine the upwind and downwind directions for the air quality monitoring program. The TSPM concentration at the source varied 1268–4108 µg/m³ with a mean of 2759 µg/m³, whereas in ambient air varied 65–417 µg/m³ with a mean of 190 µg/m³. The percentage of particulate fractions PM_2.5, PM₁₀, PM₁₅, and PM₃₀ was 14.3, 36.6, 45 and 73.5% of the total dust respectively. The settleable particulate matter was found to be 45% and the maximum percent of particles is in the range of 3–5 µm (8 %). Both ambient dust concentration and occupational exposure level exceeded Indian National Standards at most of the locations. Mathematical models viz., FDM, ISCST3 and AERMOD were employed for prediction of dust emission from stone crushers on the surrounding areas. The impact zone for measured concentration varied 211–1350 m with a mean of 784 m. The impact zone for predicted concentrations of FDM, ISCST3 and AERMOD varied 153–2650 m, 143–1056 m, 135–1225 m with a mean of 1335 m, 501 m and 679 m respectively. The control measures adopted at these stone crushing units are not sufficient enough to bring down the concentration within the stipulated limits. There is a scope for further improvement of control measures at these stone crushing units.