Source Apportionment And The Policy Of Changing Fuel From Coal To Natural Gas Impact Of PM_2.5 In Lanzhou City Based On Source Model

In recent years,with the frequent occurrence of pollution events such as smog,public environmental awareness had been gradually strengthened by government propaganda.More and more attention has been paid to fine particulate matter(PM_2.5),so local government takes a series of measures to control PM_2.5 pollution.With the deepening of regulation,the accurate understanding of the contribution of different sources to PM_2.5 is of great significance in the fine management control.Based on the survey results of various enterprises in Lanzhou City,fossil fuel combustion emissions inventory was established by coefficient method and material balance algorithm,and then its contribution to secondary fine particles was evaluated.The emissions inventory was used into WRF-Chem model for simulation.After the simulation results of the meteorological and chemical parameterization schemes were evaluated in the model,the source apportionment of PM_2.5 and its components was further studied.Following the equivalent coal consumption of the gas boiler was calculated based on the calorific value,the emissions inventory before the implementation of the?coal to gas?policy was established to assess the impact of this policy on the environmental air quality of Lanzhou City through model simulation.The main conclusions are as follows:1.In Lanzhou City,power plants,steel industry and cement manufacturing industry had made great contributions to secondary inorganic aerosols in fossil fuel burning.Secondary inorganic aerosol contributed by combustion of standard coal in the steel industry is the largest.Secondary organic aerosol formation potential?SOAFP?that the thermal supply?coal?or power plants contributes is more than others in the urban.In other regions,high-energy industries such as cement manufacturing,brick and tile manufacturing,and steel smelting make more contribution to SOAFP than others.the mass ratio of SOAFP per VOCs from fossil fuel combustion(3.16kg·t^-1)is the larger than those from biomass combustion(1.38kg·t^-1)2.The WRF-Chem model was used to simulate the pollution situation in Lanzhou in January 2016.Sensitivity experiments of WRF-Chem are evaluated by using the different boundary layer parameterizations,land surface process scheme and gas phase chemical scheme for prediction of PM_2.5 within the surface layer.Statistical analysis shows that the YSU boundary layer parameterizations and the Noah land surface process scheme,combined with the SAPRC99/MOSAIC scheme,can bestly simulate the temporal and spatial variation of PM_2.5 in Lanzhou during this simulation period using the high-resolution emission inventory for lanzhou in 2016.Compared with the simulation results of the MEIC emission inventory,the high-resolution emission inventory can more accurately represent the pollutant emission intensities in Lanzhou City.Combined with the results of the meteorological simulation,the source of PM_2.5error between the numerical simulation and Monitoring consequences is comprehensively analyzed.Removing the local emission inventory for further simulation,the result shows that the local source is mainly contribution to PM_2.5during this simulation period,but the influence of foreg sources cannot be ignored under special weather conditions.Then we use the brute force method to analyze the contribution of each source to PM_2.5.in the urban.The contribution of foreign source was 8.22%,the contribution of local industrial and heating source?26.58%?is the largest,followed by residential source?24.54%?,another sources?18.71%?,transportation source?16.55%?,agricultural ammonia source?5.34%?and natural source?0.05%?.In the rural,the contribution of external source was 8.22%,contribution of local other sources?26.54%?is the largest,followed by industrial and heating source?23.52%?,residential source?22.87%?,mobile source?9.66%?,agricultural ammonia source?4.69%?and natural source?0.06%?.In the process,the contribution of various sources to the components of PM_2.5 was further obtained.3.The simulation result shows that the policy has a huge significant reduction in SO₂ and PM_2.5 concentration in ambient air based on the emission inventories before and after the implementation of implementation of the?coal to gas?policy.Compared with the pollutant concentration change from 2012 to 2016 at Lanyuan Hotel site,the implementation of the energy restructuring policy is one of the important factors of the decline in SO₂ and PM_2.5 in Lanzhou from 2012 to 2016.