Temporal and spatial trends in air quality in Beijing

Abstract

Air quality is one of the most critical environmental issues in Beijing, China. In this study, temporal and spatial variations in air quality in Beijing are characterised by two aggregate indexes, the air pollution index (API) and air quality index (AQI). API is calculated from PM10, SO2, and NO2 to indicate air quality before 2013. From then on, API was replaced with AQI, which is calculated from PM2.5, PM10, SO2, NO2, O3, and CO. API decreased significantly during 2001–2017, and AQI decreased significantly during 2013–2017 (p < 0.001). In addition, these two indexes were negatively correlated to tree cover ratio and positively correlated to energy consumption intensity. In terms of seasonal characteristics, API was highest in spring and lowest in summer, reflecting trends in natural emission sources. AQI was highest in winter and lowest in summer, primarily due to anthropogenic emissions resulting from heating demand and industrial production. Regarding spatial variability, air quality reflects the differences in the different functional zones in Beijing, likely due to the different land-use composition and structure as well as the energy consumption intensity. Moreover, population and automobile density also played a role in the differences in air quality status. Our results indicate that, while air quality in Beijing has improved, seasonal effects, land use, automobile density and emission intensity are major factors that continue to influence air quality. Therefore, further improvements in Beijing’s air quality should take seasonality, urbanized land optimization and major pollutant sources into account when developing future emission-reduction policies.