Dispersion modelling of particulate matter concentrations of sand product plants in a mineral complex

BACKGROUND AND OBJECTIVES: Sand and gravel product plants are among the significant sources of dust pollutants. This study was conducted to estimate dust concentrations released from these plants in a mineral complex in the southwest of Tehran.METHODS: Initially, the amount of silt and moisture content of the samples taken from these plants were determined according to the American Society for Testing and Materials C۱۳۶ and D۲۲۱۶ methods, respectively. Accordingly, the rates of particulate matter emissions from these plants were determined by the AP-۴۲ dust emission estimation methods published by the United States Environmental Protection Agency. Next, a Gaussian model was used to estimate the particulate matter concentrations in the surrounding residential areas. Finally, the simulated concentrations were compared with the United States Environmental Protect Agency and World Health Organization standards.FINDINGS: Results showed that hauling operations, with producing ۷۰%, ۸۶%, and ۹۰% of total PM۲.۵, PM۱۰ and total suspended particulates, respectively, were the major sources of dust emission in the sand and gravel product plants. The lowest dust emission was related to stockpiling handling, producing ۰.۲۴%, ۰.۳۳%, and ۰.۱۶% of the total PM۲.۵, PM۱۰ and total suspended particulates. The results of the presented model indicated that ۲۴-hour average concentrations of PM۲.۵, PM۱۰, and total suspended particulates produced by mining activities were about ۳۶, ۱۸۳, and ۶۹۰ µg/m۳ in the working zone and less than ۳۰, ۱۰۰, and ۴۰۰ µg/m۳ beyond the mineral complex boundary, respectively. Thus, annual average dust concentrations were negligible. The concentrations of PM۲.۵ and PM۱۰ produced by these plants in the mineral complex ambient air were higher than the standard average values recommended by the United States Environmental Protect Agency and World Health Organization. However, the concentrations of PM۲.۵ and PM۱۰ from these plants in the residential areas around the complex, were below the standard limits proposed by the Environmental Protection Agency.CONCLUSION: Sand and gravel mining activities increased the concentrations of particulate matter in the air of the surrounding areas and, to some extent, farther cities. PM۲.۵ and PM۱۰ resulting from the sand and gravel mining activities could damage the workers in the mineral complex. They exceeded the ۲۴-hour average permissible limits proposed by the United States Environmental Protection Agency about ۱ and ۳۳ µg/m۳, respectively. This study showed the necessity of changing the industrial policies adopted to decrease dust emission rates. The results of this study can help the air pollution experts develop proper strategies for improving the air quality in the vicinity of surface mines.

Keywords:

AERMOD model , Air Quality , Emission factor , Particulate Matter , Sand and gravel product plant