Inter-City Air Pollutant Transport In The Beijing-Tianjin-Hebei Urban Agglomeration

The Beijing-Tianjin-Hebei urban agglomeration has a high population density,is undergoing economic development at a rapid rate,and experiences calm weather in autumn and winter.The problem of atmospheric compound pollution caused by pollutants such as particulate matter（PM）,SO₂,and NO_x has increasingly concerned about.The Beijing-Tianjin-Hebei urban agglomeration is one of the key targets of air pollution control measures in China.The three major causes of atmospheric heavy pollution are pollutants emissions,meteorological conditions and regional transmission,and regional transmission is affected by the first two reasons.To explore trans-regional transmission rule of atmospheric pollution in Beijing-Tianjin-Hebei urban agglomeration,it can provide scientific support for the long-term planning of coordinated control of air pollution.In this study,the Weather Research and Forecasting（WRF）model coupled with the California Puff（CALPUFF）air quality model was used to establish the contribution matrix of four major air pollutants(NO_x,SO₂,PM_2.5 and PM₁₀)in the Beijing-Tianjin-Hebei urban agglomeration in China in winter,which is the season characterized by the highest levels of pollution.We quantitative analyzed the influence of emission inventories（Environmental Statistics Emission Inventory and Multi-resolution Emission Inventory for China（MEIC））,policy implementation（Action Plan for the Prevention and Control of Air Pollution in 2013）and meteorological conditions on pollutants transmission rules.Aiming at meeting the national air quality standards,we used the linear optimization model to establish the emission reduction schemes of pollutants in Beijing-Tianjin-Hebei region.And we compared different pollutant emission reduction schemes（The traditional emission reduction schemes and optimized emission reduction schemes）from different perspectives such as economic and emission intensity.The results showed that:first,the concentration of pollutants under two emission inventories showed a central distribution,with Tangshan as the centre in north and Shijiazhuang-Handan as centre in the south.However,the simulated concentration of pollutants under the environmental emission inventory was larger than that in MEIC emission inventory,which was closer to the actual measured concentrations.Besides,there were still some significant differences in the transmission roles of some cities based on different emission inventory inputs.For example,for the four pollutants,the transmission direction between Baoding,Xingtai and its surrounding cities were completely opposite under the two emission inventories.Baoding was the relative source city among the thirteen cities based on the MEIC emissions inventories.However,based on Environmental Statistics Emission Inventory,Baoding was a receptor city.Besides,we found that the emissions of SO₂,PM_2.5 and PM₁₀ in Beijing-Tianjin-Hebei urban agglomeration had declined since the implementation,in 2013,of the“Action Plan for the Prevention and Control of Air Pollution”.But for NO_x,the emissions in most cities had declined,with the emissions of pollutants in some cities（e.g.Langfang）increased.We also found that the implementation of environmental policies changed the transmission range and transmission intensity of source cities.For example,after the implementation of the environmental policy,the transmission range of Shijiazhuang had become significantly smaller,and its transmission intensity also decreased.Finally,aiming at meeting the national air quality secondary standard,it had smaller impact on the pollutant emissions,emission intensity and GDP in optimized emission reduction schemes.The optimized emission reduction scheme is the best emission reduction schemes in Beijing-Tianjin-Hebei region.It has a lower impact on the economy of the Beijing-Tianjin-Hebei urban agglomeration and was easier to implement.