Shifting patterns of Ozone Season due to policy and human activity in Beijing between 2013 and 2023

Abstract. Since 2013, Beijing has implemented a series of stringent measures to control air pollution, resulting in significant improvements in air quality. This study analyzed the variations in ozone pollution in Beijing over the past decade, focusing on the influence of human activities and environmental management policies from 2013 to 2023. Over this period, the duration of the Ozone Season in Beijing has prolonged, with the onset of ozone pollution occurring earlier and its cessation extending later during the year. Additionally, there has been a rise in the low percentile concentrations of the maximum 8-hour moving average of ozone (MDA8), and the overall exposure time to ozone has shifted to later over the years. While diurnal peak concentrations during the Ozone Season have decreased, trough concentrations have increased, resulting in a more subdued diurnal variation. Furthermore, both the maximum generation and consumption rates of ozone have decreased in absolute terms, with the maximum generation rate showing a tendency to occur earlier in the day. To better protect human health and enhance the effectiveness of environmental policies, it is essential to closely monitor the evolving patterns of urban ozone pollution.