Vertical Distribution and Influence Mechanism of Ozone Over Chaohu Lake, China

Ground-level ozone (O₃) pollution is a major environmental challenge facing the Yangtze River Delta(YRD) region during the summer and autumn seasons. However, the vertical structure of ozone around large water bodies and its association with the planetary boundary layer (PBL) remain unclear. As a key interface between the Earth's surface and the free atmosphere, the PBL plays a crucial role in ozone formation, dispersion, and vertical transport, necessitating further investigation. This study utilized ozone, wind profilings, ozone precursor NO₂, and concurrent meteorological observation data from July to December 2023 along the eastern shore of Lake Chaohu to systematically analyze the distribution characteristics of ozone and its precursor NO₂ and their interactions with the PBL.The results indicate that: (1) The eastern shore of Chaohu Lake generally meets the standards for a Class I area. Notably, the period from August to October experiences a high incidence of ozone pollution, with daily peak concentrations occurring at 15:00. (2) Correlation analysis revealed that surface meteorological factors such as temperature, sunshine, and air pressure significantly influence ozone levels. During the transition between northeast and southeast winds, ozone-rich air masses from the YRD are advected into the airspace over Lake Chaohu, exacerbating the accumulation of pollutants and enhancing ozone production. (3) High ozone concentrations on polluted days are closely related to the vertical structure of the PBL under stable atmospheric circulation conditions. During such periods, the PBL exhibits higher temperatures, lower wind speeds, and reduced relative humidity. Additionally, the presence of a stabilization layer between 1500 and 3000 m contributes to elevated ozone concentrations below 1300 m. Furthermore, vertical transport through the pollution belt within the height range of 1000 to 1500 m significantly contributes to ozone exceedances. (4) Vertical velocity (ω) under stable weather conditions exacerbates surface pollution by vertically transporting ozone within the boundary layer downward to the surface, and there are temporal differences in the effects of vertical wind shear (VWS) on ozone: weak VWS before 09:00 promotes the accumulation of the precursor NO2, whereas small VWS after 12:00 increases the risk of surface ozone pollution. In summary, surface ozone concentration is regulated by local photochemical reactions, PBL dynamical structure and regional weather systems at multiple scales. This study reveals for the first time the coupling mechanism between the vertical distribution of ozone and the PBL in the middle and lower reaches of the Yangtze River lakes region, which provides a key scientific basis for the optimization of cross-regional ozone pollution prevention and control strategies.