Simulation of atmospheric mercury dispersion and deposition in Tehran city

Abstract

In this study, dispersion and deposition of atmospheric mercury (Hg) in Tehran city was simulated using WRF-SMOKE-CMAQ models. The Weather Research and Forecasting (WRF) model was used to simulate the meteorological parameters. For validation of WRF results, the simulated wind speeds and temperatures were compared with the parameters measured at a meteorological station in Tehran city for 11 days (8 days in fall and 3 days in winter) in 2010–2011. The correlation coefficient (r) for temperature and wind speed was 0.94 and 0.49, respectively, indicating there was good agreement between measured and modeled results. An atmospheric mercury emission inventory was developed using the United Nations Environment Programme (UNEP), the United States Environmental Protection Agency AP-42 (US-EPA AP-42), and related papers. Sparse Matrix Operator Kernel Emissions (SMOKE) was used to allocate the atmospheric mercury emissions to the modeling domain, and the Community Multiscale Air Quality (CMAQ) model was used to simulate the concentration and deposition of atmospheric mercury. To validate the results of the CMAQ model, the simulated atmospheric particulate mercury (PHg) concentrations for 11 days were compared with the measured results at two different stations (Bagh Ferdows and Bahman Square) where it was measured by the Tehran Air Quality Control Company (AQCC). Comparison between the results from the modeled and measurements of PHg in fall was better than winter. Concentrations and dry depositions of the various forms of atmospheric mercury were higher in areas closer to mercury stationary emission sources.