Spatialand Temporal Simulation For The Impacts Of Motor Vehicle Restriction Measures On PM_2.5 Concentrations Using WRF-Chem Model In Kaifeng,China

As the second largest economy in the world,China experiences severe particulate matter?PM?pollution in many of its cities.With the rapid development of urban traffic road network and the increasing number of motor vehicles in recent years,vehicle emissions and their impacts on air quality are getting more and more serious.The pollutants released from road dust and exhaust emissions caused by motor vehicles not only affect the local environment,but also affect the environmental quality of surrounding regions and even the global environment through regional transportation.To reduce the contribution of motor vehicle emissions to air pollution,many cities have adopted motor vehicle restrictions in China,such as Beijing,Kaifeng,etc.Understanding transportation emissions and their impacts on air pollution is critical for accurate forecasting,comprehensive analysis,and effective reduction of this pollution.This study aimed to evaluate the effects of vehicle restriction measures on PM_2.5.5 concentrations in Kaifeng,China.The spatial and temporal distributions of PM_2.5.5 concentrations under three different vehicle restriction scenarios were simulated using the Weather Research and Forecasting Model with Chemistry?WRF-Chem?model and multi-resolution emission inventory for China?MEIC?.Three types of motor vehicle emission control scenarios were set,including the baseline scenario?S0?in which no restriction measures were taken,two license plate tail numbers were limited every day?S1?,and odd-and-even license plate tail number were restricted?S2?.This study firstly pretreated the anthropogenic emission inventories,and the spatial distribution and time refinement of pollution concentration were carried out.Then the parameters of WRF-chem model were parameterized and the simulation were validated.In December 2017,Kaifeng was seriously polluted.There were three severe pollution processes in Kaifeng City during this period,which had a wide range of impacts,a relatively long duration and a high peak concentration of pollutants.There were significant spatial and diurnal variations of PM_2.5concentrations in Kaifeng.The high PM_2.5.5 concentrations were mainly concentrated in the southeast of Kaifeng,while the PM_2.5.5 concentration in Kaifeng and Lankao was relatively low.The peak value of PM_2.5concentration in Kaifeng area occurred between 6:00 and 7:00 in the morning,and the valley value occurred at midnight.The correlation coefficient?R?between the hourly observation and the simulation was 0.41,the normalized mean deviation?NMB?was 15.2?g·m^-3,and the mean bias?MB?was-12.6?g·m^-3,which means that the WRF-Chem model showed good performance in the PM_2.5.5 concentrations simulation in Kaifeng.Simulation results showed that monthly average concentration of PM_2.5.5 in Kaifeng was 75.99?g·m^-33 under the baseline scenario.The monthly mean PM_2.5concentration was 75.91?g·m^-33 and 73.83?g·m^-33 under the S1 and S2 scenario,respectively.This indicated the simple control of the motor vehicles emission may have little effects on the reduction of PM_2.5.5 concentrations.Since the PM_2.5.5 concentration is affected by numerous factors,such as regional transmission and complex pollution source emissions,thus regional pollution prevention and joint control are required to improve the air quality in Kaifeng.