| In recent years,the long-lasting and wide-ranging severe air pollution episodes in Beijing-Tianjin-Hebei region and its surrounding areas have aroused widespread concern in society.According to the Air Pollution Prevention&Control Action Plan,it is clearly required to comprehensively control scattered coal to further improve air quality and win the"Defense of The Blue Sky".Carbonaceous aerosols are important components of atmospheric particles,and more carbonaceous aerosols are from the combustion of fossil fuels.The effects of organic carbon(OC)and elements carbon(EC)are absorption and scattering,and the direct and indirect effects have important impacts on the atmospheric environment,climate change and human body health.Therefore,it is highly important to investigate the pollution distribution characteristics and the evaluation for future atmospheric pollution control of the representative sites in the Beijing-Tianjin-Hebei region before and after the establishment of the zone banned on coal combustion.In this study,the DRI Model 2001A analyzer was used to determine the concentration of OC and EC of PM2.5 samples in Beijing,Tianjin,Shijiazhuang,Baoding and Xinglong in the Beijing-Tianjin-Hebei region from June 2016 to January 2018.I analyzed the mass concentration distribution characteristics of PM2.5 and PM10,the spatial and temporal distribution characteristics of OC and EC,seasonal changes of carbonaceous components,the correlation and ratios of OC and EC,and the distribution characteristics of primary organic carbon(POC)and secondary organic carbon(SOC).The results showed that the average mass concentration of PM2.5 of all sites decreased by 86.8%,72.1%,37.4%,33.2%,and 28.5%respectively in autumn 2017compared with autumn 2016.Compared with autumn 2016,the average concentration of PM2.5 in winter 2017 of all sites decreased by 73.7%,73.3%,59.6%,49.3%,and 48.0%,respectively.In 2016(214 days),the number of days exceeding the second-level concentration limit of the average mass concentration of PM2.5 of all sites,accounting for41.1%,35.0%,48.1%,48.1%,and 10.3%,respectively.In 2017(363 days),the number of days exceeding the limit accounted for about 23.8%,22.2%,36.4%,38.4%and 6.6%respectively.The nighttime OC concentration range in all sites were larger than daytime.The EC concentration ranges in Beijing,Baoding and Xinglong at night were larger than daytime's,while the EC concentration ranges in Tianjin and Shijiazhuang at night were smaller than daytime's.In winter 2016,Beijing,Tianjin,Shijiazhuang and Baoding all showed the highest average mass concentration of OC and EC during both day and night,and the day-night concentration differences were larger in winter of 2016.The carbonaceous aerosols at all sites are mainly OC.In the winter of 2017,the average mass concentration of OC and EC showed the following spatial distribution,Baoding>Shijiazhuang>Tianjin>Beijing>Xinglong.Compared with the autumn and winter of2016,the average mass concentration of OC2 at five sites decreased by more than 30.0%and 38.0%in corresponding seasons of 2017,respectively.The R2(P<0.01)in Beijing,Tianjin,Shijiazhuang,Baoding and Xinglong in winter of 2017 were 0.9341,0.9034,0.8464,0.8524 and 0.9576,respectively,there are similar sources between OC and EC in every site.The OC/EC ratios of each site in autumn and winter of 2017 were 2.7±0.9 and3.0±0.6,1.6±0.4 and 3.1±0.5,1.4±0.4 and 3.1±0.6,2.1±0.4 and 3.7±0.7,2.1±0.8,and1.7±0.7,respectively.The values of(OC/EC)pri by the MRS method in Beijing,Tianjin,Shijiazhuang,Baoding and Xinglong were 2.48,2.19,3.03,2.77,and 1.91,respectively.All sites are mainly from primary emissions.Based on the results above,urban sites are mainly affected by motor vehicle emissions and fossil fuel combustion,Xinglong is mainly affected by biomass and fossil fuel combustion emissions and biogenic emissions,the"Coal Banned Zone"exert obvious effects on the reduction to emissions. |
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