Nonlinear Response Characteristics and Control Scheme for Ozone and Its Precursors Based on Orthogonal Experimental Methods

There is a highly nonlinear relationship between ozone concentrations and its precursor emissions in different regions and at different times, which makes developing effective prevention and control measures difficult. An orthogonal experimental method was introduced to assess the influence of ozone precursors and their interactions on ozone formation, clarify the sensitivity of ozone generation, and propose an optimal control scheme. Based on the WRF-Chem air quality model and an emission inventory of air pollutants in Wuhai City in 2018, this study used an ozone pollution event in the Haibowan urban area (August 17 to 20 2018) to investigate the nonlinear response of ozone formation to its precursors. The orthogonal experiment shows that NOx, VOCs interactions with CO, CO, and interactions between pollutants and meteorological factors are the main factors affects ozone concentrations in the Haibowan urban area. Ozone generation was most sensitive to NOx concentrations during the hours 12:00-18:00 when standard values were exceeded. The ozone concentrations decreased significantly by 12.6 μg·m-3 (7.8%) as NOx, VOCs, and CO were reduced by 60%, 30%, and 30%, respectively. Through the analysis of chemical reaction mechanisms, it is concluded that VOCs and CO affect the photochemical reaction by reacting with·OH, HO2·and other free radicals, which causes the significant interaction between VOCs and CO in the generation of ozone. This method provides a new approach for researching the nonlinear response of ozone formation to its precursors and for proposing ozone pollution control schemes.