An analysis of the effects of weather and air pollution on tropospheric ozone using a generalized additive model in Western China: Lanzhou, Gansu

In recent years, near-surface ozone (O3) concentrations have been increasing, which aggravates O3 pollution. Due to the environmental threat it poses to human health, O3 pollution has become a hot topic among researchers. In this paper, we used a generalized additive model (GAM) to evaluate the complex nonlinear relationships between O3 concentration and the factors influencing O3 concentration from 2013 to 2017 in Lanzhou in Western China. We considered factors such as long-term trend, seasonality at a quarterly interval, and the weekend effect. The results showed that O3 concentration in Lanzhou was affected by many factors, and these influencing factors were correlated with each other. In the single-factor model, the adjusted coefficient of determination (R2) was 0.594, and the total deviance explained of O3 concentration was 62.3%. We detected significantly nonlinear relationships between O3 concentration and the influencing factors like air temperature, sunshine hours, wind speed, relative humidity, and the concentrations of NO2 and PM2.5. In particular, air temperature was the main driving factor for O3 concentration, which explained 24.2% of the variance (F = 350.84). In addition, we built a double-factor model to investigate the interactive influences of these influencing factors on O3 concentration variation. In the fitted double-factor model, R2 was 0.636 and the total deviance explained was 68.1%, both of which were higher (i.e., better performance) than that in the single-factor model. Among these studied influencing factors, the interaction between air temperature and air pollutants showed the greatest influence on O3 concentration variation. The results of this study can be used to assist local environmental authorities to take proactive measures for O3 pollution control in Lanzhou, Gansu. •The ozone concentration in Lanzhou is significantly correlated with meteorological elements and other pollutants.•Temperature is the main driving factor for the change of ozone concentration in Lanzhou.•The interaction between temperature and other influencing factors has a significant impact on ozone concentration.•The generalized additive model (GAM) with interaction term can explain the change of ozone concentration more reasonably.