Traceability and policy suggestions for ozone pollution in heavy industrial city in Northeast China

In the heavy industrial city of Northeast China, there has been a significant decrease in particulate matter pollution while experiencing a sharp increase in ozone (O₃) pollution. However, the main influencing factors and source contributions to O3 remain unclear. Taking the case of Siping as an example, this study analyzed the spatiotemporal characteristics, assessed local source contributions to O₃, and revealed regional transmission effects using numeric simulation and statistical methods. Temporally, higher O₃ concentrations were observed in summer and the afternoon, with hourly peaks up to 254 µg/m³. Spatially, O₃ pollution was mainly contributed by background concentrations (34.52%), external transport (34.50%), and local emissions (30.98%) during the case study period (June 11-18, 2021). Among the local emission sources, biological emissions, the industrial sector, and the traffic sector accounted for 35.30%, 32.09%, and 23.58% of the O₃ concentration, respectively. For regional atmospheric transmission, high O₃ pollution was accompanied by wind from the southwest directions, and the trajectory of air mass transport suggests that eastern Mongolia, the Korean Peninsula, and its neighboring regions contribute to O₃ pollution. Furthermore, sensitivity analysis showed that O₃ pollution in Siping is a co-controlled region by anthropogenic volatile organic compounds (AVOCs) and NO_X, which implies control in an optimal ratio of VOCs and NO_X emissions. Thus, our results highlight the importance of joint prevention and control of O₃ pollution in the region, optimization of biogenic landscape ecology, and control of VOCs and NOx in both the industrial and transport sectors.