Impact of Thermal Power Industries in the Beijing–Tianjin–Hebei Region on the Haze Formation in Beijing Studied by the Two-Way Coupled WRF–CMAQ Model: Assessments of Different Emission Control Policies

Over the past three decades, Beijing has suffered from severe air pollution and heavy haze because of its decade-long burst of economic growth and rapidly expanding clout. In this study, eight different emission control policies aiming to improve the air quality of Beijing by reducing emissions of the thermal power plants over the Beijing-Tianjin-Hebei (BTH) region were assessed by the two-way coupled WRF-CMAQ model for the four simulation months in the base year 2013. The performance evaluations of the WRF-CMAQ model with the observations at Beijing show that the model demonstrates a good skill in reproducing all pollutants (CO, NO₂, PM_2.5 and PM₁₀) in Beijing for all four simulation months. The results show that the implementation of these emission control policies for the thermal power plants over the BTH region could reduce the concentrations of different pollutants in Beijing by varying degrees, depending on the months and pollutants. The results indicate that the annual mean reduction percentages in Beijing are between -5.3% and -6.3% for PM_2.5, PM₁₀, NO₂ and SO₂ for the cases 2 (“special emissions limits”) and 3 (“ultra-low emission standards”), while they are between -2.2% and -3.0% for the case 4 (“adjustment of structures”). All these three current emission control policies caused similar reduction percentages between -18.9% and -20.7% for CO in Beijing. It was also found that the newly-designed emission control policies (case 5 (“Extremely ultra-low”), case 6 (“Near zero”), and case 7 (“Green power generation”)) can further reduce the pollution levels in Beijing with mean reduction percentages between -8.6% and -14.8% for PM_2.5, PM₁₀, NO₂ and SO₂ and between -23.0% and -27.7% for CO on the basis of model simulations in January. The sensitivity test for the case 8 “No thermal power plants” reveals that the thermal power plants in the BTH region made 37.6%, 23.1%, 23.0%, 23.8% and 24.0% contribution to the concentrations of CO, SO₂, NO₂, PM_2.5 and PM₁₀ in Beijing annually, respectively. The similar conclusions like those in Beijing can be obtained for these major cities in the BTH region with somehow slightly different percentages.