Research on the characteristics and mechanisms of ozone pollution in Anyang City

Based on synchronous observations of O₃， its key precursors （NOₓ and speciated VOCs）， and meteorological parameters in Anyang City， by coupling a photochemical box model with relative incremental reactivity sensitivity analysis， the concentration evolution characteristics and formation mechanisms of O₃ pollution episodes in Anyang City were systematically investigated. Results indicated that： （1） O₃ exceedances displayed pronounced seasonal and diurnal patterns， which predominantly occurred from April to September with the highest frequency in June. The diurnal cycle followed a typical single-peak distribution with peak concentrations occurring during 13：00—15：00. （2） Meteorological conditions were the primary drivers of O₃ exceedances. Exceedance periods were characterized by a highly favorable photochemical regime of high temperature， low relative humidity and weak southerly winds， which significantly enhanced atmospheric oxidative capacity. Notably， the concentrations of TVOCs and NO₂ were not significantly increased compared to non-exceedance days， highlighting that the photochemical efficiency amplified by meteorological conditions， rather than precursor loading， governed the exceedance process. （3） O₃ formation during high-concentration seasons operated in a VOCs-limited regime. The concentration accumulation trajectories and peak evolution patterns differed significantly among local production- dominated， regional transport-dominated， and mixed type exceedance events. The sequential action and synergistic interaction of sustained regional transport inputs and local photochemical production constituted the core mechanism determining the diurnal O₃ profile and peak intensity. The results might provide scientific support for developing precursor emission reduction strategies and air pollution prevention and control in Anyang City.