Contribution of Thermal Power Plants to Ambient Air Quality Levels in Colombo Metropolitan Region, Sri Lanka

Air quality models (AQMs) are essential in complex air quality management studies. Due to data limitations, AQMs are occasionally used in developing countries. This study focuses on assessing the impact of thermal power plants on ambient air quality in the Colombo Metropolitan Area (CMA), Sri Lanka, using the AQM for the first ever in Sri Lanka. Concentrations of SO2 and NO2 were measured at 18 sampling locations for 1 - and 8 -hour periods, while $\mathbf{P M}_{10}$ was measured for $\mathbf{2 4}$ hours during the southwest and northeast monsoon periods. The Factor of Two Observations (FAC2), Fractional Bias (FB), correlation coefficient (R), and Normalized Mean Square Error (NMSE) were used to evaluate the model performance. According to the results, AERMOD simulations overestimated hourly SO2 concentrations while the northeast monsoon exhibited higher pollutant concentrations. The peak value for the 24 -hour average period of NO2 exceeded the WHO air quality guideline limits of $25\mu\mathrm{g}/\mathrm{m}^{3}$, reaching $46.43\mu\mathrm{g}/\mathrm{m}^{3}$ in the southwest monsoon and $41.89\mu\mathrm{g}/\mathrm{m}^{3}$ in the northeast monsoon period, respectively. NO2 had a significant impact on other criteria air pollutants. The study emphasized the urgent attention to studies on implications for public health due to thermal power plants, mitigatory measures and appropriate policy decisions for protecting public health.