Simulations Of Atmospheric BaP Pollution Of Emission Reduction Of Residential Coal Combustion In Beijing-Tianjin-Hebei Region

Residential coal combustion is an important source of atmospheric pollutants in the Beijing-Tianjin-Hebei region.The emission control policy formulated for residential coal-fired emission sources can effectively reduce the total emission of atmospheric pollutants in the Beijing-Tianjin-Hebei region and play an important role in improving air quality in the region.This study is based on the latest global high-resolution atmospheric BaP emission inventory（PKU-BaP-2014）.The inventory had updated emission data for residential sources based on survey data which is in the Beijing-Tianjin-Hebei region’s residential coal-fired governance related policies and action plan in Beijing.In the implementation of residential coal-fired control measures in cities and towns in the Tianjin-Tianjin region,there were three simulation scenarios with a baseline simulation scenario and low reductions and high reductions.Using the Integrated Air Quality Modeling System Models-3/CMAQ for the four typical seasons including 2014 as the baseline scenario representing months（January,April,July and October）and low reductions and high reductions under two emission reduction scenarios The impact of residential coal-fired emission reduction on the environmental impact of BaP pollution in the atmosphere was simulated,and the improvement effect of the Beijing-Tianjin-Hebei residential coal-fired emission reduction on the BaP pollution in the atmosphere was evaluated to provide a scientific basis for residential coal-fired treatment and air quality improvement in the region.The main conclusions obtained are as follows:（1）The atmospheric Ba P source emission in the Beijing-Tianjin-Hebei region has obvious seasonal variation characteristics.The source emission rate in January is relatively large.The source emission rates in April,July,and October are small and the change is not obvious,which is equivalent to the heating season coal-fired emissions.With regard to the increase,the total amount of atmospheric BaP source emissions in each month was 13.60 tons,8.15 tons,8.55 tons and 8.19 tons,respectively.In terms of spatial distribution,the atmospheric emission rates of BaP in the densely populated areas of southern Beijing,Tianjin,Hebei,Baoding,Shijiazhuang,Hengshui,and Xingtai are relatively high,while those in the north of Beijing,Tianjin,Hebei,including Chengde,Zhangjiakou and Qinhuangdao are sparse.The atmospheric emission rate of BaP in the area is small.（2）Comparing the simulation results of the particle phase BaP concentration and dry and wet settlement with the actual measured data in some areas,the results show that the BaP concentration and the dry and wet settlement of the particle phase have little difference between the simulated value and the measured value,and the magnitude is basically the same.The result of the verification is within an acceptable range and the overall simulation results are better.（3）The baseline scenario simulation results show that the seasonal variation of BaP concentration in the atmosphere is significant,with a higher concentration in January,followed by April and October,and the lowest in July.The annual concentration of BaP in the atmosphere of Beijing,Tianjin and Hebei is 2.45 ng/m³,which exceeds the national air quality standard（1 ng/m³）.The spatial distribution of atmospheric BaP concentration and source emissions is basically the same,and has obvious diffusion and transmission effects.There is a positive correlation between BaP concentration and PM_2.5 concentration.The atmospheric sedimentation of atmospheric BaP is similar to the spatial distribution of concentration and source emissions.Wet deposition is related to precipitation and is mainly concentrated in the northern part of Beijing-Tianjin-Hebei.In general,the atmospheric deposition flux of BaP in Beijing-Tianjin-Hebei is higher than that of dry deposition flux.The total sedimentation flux of BaP is relatively large in October and April,and the seasonal variation characteristics are smaller in July and January.The total sedimentation fluxes in Tianjin,Shijiazhuang,and Bohai are larger in spatial distribution.（4）The simulation results of two reduction scenarios with low reductions and high reductions are compared with the simulation results of the baseline scenario.The atmospheric BaP concentration decreased most significantly in January because of the total atmospheric BaP emissions of atmospheric coal in January.There is a large proportion of emissions,with a slight decrease in BaP concentrations in April,July and October.In January,the overall BaP concentration in Beijing,Tianjin,and Hebei decreased by 22.38%under the scenario of low reduction and 35.55%under the scenario of high reduction.From the urban scale,the concentration of BaP in Beijing,Tianjin,Baoding and Langfang decreased most significantly.Compared with the baseline scenario,the reductions were 34.88%,23.20%,30.30%,and 36.12%under the low-reduction scenario,and 41.40%,35.59%,42.70%,46.83%under the high reduction scenario respectively.The characteristics of BaP dry and wet deposition decline are similar to those of BaP concentration decrease.（5）The BaP concentration and PM_2.5 concentration have similar seasonal variations and spatial distributions,and there is a certain positive correlation between the two concentrations in the atmosphere.The reduction ratios of BaP concentration under the two reduction scenarios and the reductions in the two emission reduction scenarios also showed a certain positive correlation with the reduction ratio of PM_2.5concentrations.In April,July,and October,the correlation between the decrease in BaP concentration and PM_2.5 concentration was better than in January.Compared with the high reduction scenario and the low reduction scenario,the atmospheric BaP concentration and PM_2.5 concentration decrease more significantly.（6）On the whole,the establishment of the"banned coal zone"in Beijing,Tianjin and Hebei has a better effect on the reduction of atmospheric BaP pollution in Beijing,Tianjin,Baoding and Langfang,and the reduction of Beijing-Tianjin-Hebei residential coal-fired joint prevention and control measures can more effectively reduce the regional atmosphericPM_2.5and BaP concentration.