[One-year Simulation of Air Pollution in Central China, Characteristics, Distribution, Inner Region...

Air pollution in Henan province is serious and is significantly impacted by pollution transmission and interactions with surrounding areas. The emission sources in 18 cities in Henan province were labeled and applied to the WRF-CMAQ traceability model for simulation in January, April, July, and October of 2017. The pollutant distribution results showed that due to the combined influence of emissions and meteorology, the concentrations of PM_2.5, NO₂, and SO₂ in Henan province were the highest in winter and the lowest in summer. The seasonal variation in O₃-8h concentration was the highest in summer, followed by spring, and the lowest in winter. There was a large difference in pollutant concentrations between different seasons. The average concentrations of PM_2.5, NO₂, and SO₂ in winter in Henan province were 4.17, 4.12, and 6.24 times those in summer, respectively, whereas the concentration of O₃-8h in summer was 2.24 times that in winter. Since PM_2.5, NO₂, and SO₂ are closely related to primary emissions and have a certain homology, the distributions of high values of these three pollutants were higher in the north and lower in the south, and the seasonal trends were more consistent. The seasonal distribution of O₃-8h varied widely, with high O₃-8h values mainly distributed in the northeastern region of Henan province in summer, when meteorological conditions contributed to O₃ production; in winter, spring, and autumn, high O₃-8h values were mainly distributed in the southern part of Henan province due to the suppression of meteorological conditions and NO consumption. The results of the study on the transport of pollutants showed that extra-provincial transport and natural sources contributed the most to the concentrations of PM_2.5, O₃-8h, NO₂, and SO₂ in winter, with 36.20%-72.32%, 77.96%-96.08%, 49.45%-78.80%, and 59.05%-88.85%, respectively. When considering only local emissions and intra-provincial transmission, the contributions of emissions to local concentrations of the four pollutants in summer were the highest in all cities of Henan province. The contributions of intra-provincial transmission to PM_2.5 and O₃-8h in spring were the largest, with 25.63%-74.69% and 30.21%-80.01%, respectively, and the contributions of intra-provincial transmission to NO₂ and SO₂ in winter were larger, with 26.02%-76.96% and 20.30%-82.34%. The transmission paths of PM_2.5, NO₂, and SO₂ were more similar in Henan province, with more transmission from north to south in winter, from west to east and southwest to northeast in spring, from southwest to northeast in summer, and from north to south in autumn; however, the transmission of PM_2.5 was more complicated. The O₃-8h transport path was more different from the others, especially in autumn when pollutants were mostly transported from north to south, but the O₃-8h transport path from southwest to northeast was obvious.