Simulation of transboundary transport fluxes of air pollutants among Beijing, Tianjin, and Hebei Province of China
京津冀污染物跨界输送通量模拟

We proposed a method for reapportionment of anthropogenic emissions weighted by key impact factors (WKIF) from a province (autonomous region, municipality) to a county in North China. Simulation of transboundary transport fluxes (TTF) of NO, NO2, SO2, CO, O3, and PM2.5 in the atmospheric boundary layer (ABL) among Beijing, Tianjin, and Hebei Province (BTH region) and net TTF in Beijing were performed from 25 December 2006 to 31 December 2007 by using the WRF-CAMx model. Biogenic emissions changed with meteorological conditions and vegetation types, and meteorological and chemical boundary conditions were updated every six hours. Results indicated that the WKIF method reasonably reflected spatial distributions of emissions in counties in North China and surface concentrations of NOx, O3, and PM2.5 at six monitoring sites in BTH region were well simulated by comparison with observations. NO, NO2, SO2, CO, O3, and PM2.5 from Beijing were transported to Tianjin mainly through northwestern routes in winter and spring, and western routes in summer and autumn whereas those from Hebei Province were transported to Beijing mainly via northwestern routes in winter and spring, southern routes in summer, and western routes in autumn. Maximum and minimum TTF of NO, NO2, SO2, CO, O3, and PM2.5 in the ABL from Beijing to Tianjin occurred in winter and summer, respectively, with TTF of CO, O3, and PM2.5 much larger than those of NO, NO2, and SO2. TTF of NO and NO2 in the ABL from Beijing to Hebei province were less than 20 tons per day in four seasons. TTF of CO, O3 and PM2.5 in the ABL from Hebei province to Beijing were much higher than those of NO and NO2, and larger than those of SO2 from Beijing to Hebei province in four seasons. Maximum net outfluxes of NO, NO2 and SO2 in the ABL in Beijing were less than 50 tons per day, and maximum net TTF of CO, O3, and PM2.5 in the ABL in Beijing ranged from 111 to 2309, from 567 to 6244, and from 715 to 1778 tons per day in four seasons, respectively. The quantified TTF among Beijing, Tianjin, and Hebei Province are very useful for policymakers to make decisions for regional emission reductions in the BTH region.