Source Analysis of Ozone Pollution in Liaoyuan City's Atmosphere Based on Machine Learning Models and HYSPLIT Clustering Method.

Firstly, this study investigates the spatiotemporal distribution characteristics of the ozone (O) pollution in Liaoyuan City using monitoring data from 2015 to 2024. Then, three machine learning models (ML)-random forest (RF), support vector machine (SVM), and artificial neural network (ANN)-are employed to quantify the influence of meteorological and non-meteorological factors on O concentrations. Finally, the HYSPLIT clustering method and CMAQ model are utilized to analyze inter-regional transport characteristics, identifying the causes of O pollution. The results indicate that O pollution in Liaoyuan exhibits a distinct seasonal pattern, with the highest concentrations found in spring and summer, peaking in the afternoon. Among the three ML models, the random forest model demonstrates the best predictive performance (R = 0.9043). Feature importance identifies NO as the primary driving factor, followed by meteorological conditions in the second quarter and land surface characteristics. Furthermore, regional transport significantly contributes to O pollution, with approximately 80% of air mass trajectories in heavily polluted episodes originating from adjacent industrial areas and the sea. The combined effects of transboundary precursors and O transport with local emissions and meteorological conditions further increase the O pollution level. This study highlights the need to strengthen coordinated NO and VOCs emission reductions and enhance regional joint prevention and control strategies in China.