[Characterization of Atmospheric Composite Pollution Prediction and Dynamic Cross-transmission in the Beijing-Tianjin-Hebei Urban Agglomeration].

The dynamic cross-transmission characteristics of air pollution between cities were explored based on the data of AQI， PM_2.5， and other important pollutant concentrations and meteorological indicators in the Beijing-Tianjin-Hebei urban agglomeration from 2017 to 2023， using a Copula function-based feature selection model to identify the key features of composite atmospheric pollution， constructing a Bayesian Extreme Gradient Boosting （BOA-XGBoost） model for dynamic prediction of composite atmospheric pollution in urban agglomeration， and combining complex network analysis and SHAP interpretable modeling. The results show that： ① The feature selection model based on Copula function successfully identified the atmospheric pollutants that were highly correlated with the AQI as PM_2.5， PM₁₀， O₃， and NO₂ and meteorological factors as the average temperature and average humidity.② Compared with other models， the BOA-XGBoost model performed optimally under the comprehensive evaluation system， in which the R²， MAE， RMSE， and MAPE of the Beijing test set reached 0.970 4， 3.965 5， 8.351 8， and 0.062 4， respectively. ③ The pollution transmission network of the Beijing-Tianjin-Hebei urban agglomeration has gradually evolved into a "core-periphery" model， with Tianjin and Cangzhou as the core nodes of pollution transmission weakening and Zhangjiakou， Chengde， and Qinhuangdao being in the periphery for a long time. ④ There was heterogeneity in the strength of pollution transport between urban subgroups， but pollution transport was weakened within them. Pollutant contributions showed that PM_2.5 and PM₁₀ dominated the AQI changes in the subgroups， followed by O₃， while other pollutants had small and complex effects. ⑤ The city cluster mainly consisted of "double-high" and "double-low" cities， with Beijing switching from "double-high" to "sink" in 2020. The "double-high" cities such as Tianjin and Shijiazhuang will remain the center of pollution transmission.