Anthropogenic-biogenic interactions and regional transport drive summer ozone formation in an agricultural-urban interface of Northeast China

Abstract. Agricultural-urban interfaces (AUIs) present distinct photochemical environments shaped by the intense mixing of anthropogenic and biogenic precursors. To elucidate the mechanisms driving summer ozone (O₃) formation in these regions, we conducted an integrated study in Siping, a representative AUI in Northeast China, utilizing high-time-resolution volatile organic compound (VOC) observations (2021–2022), positive matrix factorization (PMF), and Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) simulations. Observational data indicated that while alkanes and oxygenated VOCs dictate atmospheric abundances, the O₃ formation potential is primarily governed by reactive alkenes and biogenic isoprene. PMF source apportionment identified vehicle exhaust (56.4 %) and biogenic emissions from crops and vegetation as critical VOC sources. However, WRF-Chem modeling revealed a pronounced decoupling between VOC source contributions and actual O₃ production. Regional transport and background concentrations collectively account for nearly 90 % of the ambient O₃ burden, significantly dwarfing local photochemical production. Empirical kinetic modeling approach (EKMA) analysis showed that local O₃ formation operates within a transition regime sensitive to both VOCs and NO_x. Although regional transport dominates the overall O₃ inventory, scenario simulations demonstrate that mitigating biogenic emissions is unfeasible as a natural source, and industrial emission controls yield negligible benefits due to suboptimal VOC/NO_x emission ratios. Consequently, controlling local transportation emissions emerges as the most viable and practically effective pathway to alleviate O₃ pollution in AUIs. This study provides a quantitative basis for formulating O₃ mitigation strategies in complex agricultural-urban environments, emphasizing the necessity of integrating regional joint control with targeted local vehicle emission reductions.