Research On PM_2.5 Pollution Characteristics And Source Apportionment Of Different Emission In Tianjin Based On Numerical Simulation

With the rapid development of society and economy,as well as the acceleration of urbanization,air quality in China is facing some challenges.The phenomena of regional haze,which is represented by high concentration of fine particulate matter(PM_2.5)occurs frequently in China.In recent years,with the effective control measures of pollution source emissions,both of the number of haze days and the concentration of PM_2.5 in Tianjin have shown a downward trend.Although air quality has improved significantly,the regional smog pollution still occurs from time to time.In order to further improve atmospheric quality in Tianjin and carry out targeted industry control,the analysis of PM_2.5 pollution sources by industry is particularly important.To this end,this study simulated the PM_2.5 pollution characteristics of Tianjin in January,April,July,and October 2016 based on the Models-3/CMAQ three-dimensional air quality model,and compared and verified it with the PM_2.5 monitoring concentration of the actual site.Based on the CMAQ-based source analysis"zero-out method",a source-by-industry source analysis study of PM_2.5 pollution in Tianjin was conducted under a unified model framework.The main research contents are as follows:（1）Models-3/CMAQ air quality model system was set up,which included meso-scale weather forecasting model WRF（Weather Research and Forecasting Model）,emission source inventory processing model SMOKE（Sparse Matrix Operator Kernel Emission System）,and the multi-scale air quality model CMAQ（Community Modeling and Analysis System）,and localized processing of model parameters.（2）Based on the MEIC anthropogenic source emission inventory and Tianjin wind-eroded open source particulate matter emission inventory（natural source）,Models-3/CMAQ models were used to simulate PM_2.5 concentration fields.The simulation results were compared with the actual monitoring concentrations of 24 national/municipal monitoring stations in Tianjin to verify the accuracy of the simulation results.Except for the 4 monitoring stations（Binshui East Road,Dazhigu No.8 Road,Hangtian Road and Huaihe Road）,the absolute values of the normalized mean deviation（NMB）of the remaining 20 monitoring stations were all less than15%.The average error（NME）was less than 25%and the average R² of the correlation index was 0.72.The verification results showed that the simulation results of Models-3/CMAQ model were more accurate.（3）From the perspective of spatial distribution,in 2016,areas with severe PM_2.5 pollution in Tianjin were mainly distributed in Beichen District,northern urban area,southern Wuqing District,western Ninghe District and southwest of Baodi District.The pollution in Jinnan District and Binhai New Area was relatively light.From the perspective of time distribution,the PM_2.5 pollution concentration in Tianjin in January and October was significantly higher than that in April and July,and the maximum PM_2.5 concentration in January could be greater than100μg/m³.（4）Based on the“zero-out method”source analysis method adopted by the Models-3/CMAQ model,the contribution of the industrial source of Tianjin in 2016 to the concentration of PM_2.5 was 33%,the contribution rate of civilian sources was about 28%,and the power source contribution was about 7%,the transportation source contribution was about 24%,the agricultural source contribution was 4%,and natural sources were about 4%.In 2016,man-made sources in Tianjin contributed 96%to PM_2.5 concentration,while natural sources only contributed 4%.