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 (O) 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 O, and revealed regional transmission effects using numeric simulation and statistical methods. Temporally, higher O concentrations were observed in summer and the afternoon, with hourly peaks up to 254 µg/m. Spatially, O 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 O concentration, respectively. For regional atmospheric transmission, high O 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 O pollution. Furthermore, sensitivity analysis showed that O pollution in Siping is a co-controlled region by anthropogenic volatile organic compounds (AVOCs) and NO, which implies control in an optimal ratio of VOCs and NO emissions. Thus, our results highlight the importance of joint prevention and control of O pollution in the region, optimization of biogenic landscape ecology, and control of VOCs and NOx in both the industrial and transport sectors.