Temporal variations in ambient air quality indicators in Shanghai municipality, China

Official data on daily PM_2.5, PM₁₀, SO₂, NO₂, CO, and maximum 8-h average O₃ (O₃_8h) concentrations from January 2015 to December 2018 were evaluated and air pollution status and dynamics in Shanghai municipality were examined. Factors affecting air quality, including meteorological factors and socio-economic indicators, were analyzed. The main findings were that: (1) Overall air quality status in Shanghai municipality has improved and number of days meeting 'Chinese ambient air quality standards' (CAAQS) Grade II has increased. (2) The most frequent major pollutant in Shanghai municipality is O₃ (which exceeded the standard on 110 days in 2015, 84 days in 2016, 126 days in 2017, 113 days in 2018), followed by PM_2.5 (120days in 2015, 104 days in 2016, 67 days in 2017, 61 days in 2018) and NO₂ (50 days in 2015, 67 days in 2016, 79 days in 2017, 63 days in 2018). (3) PM_2.5 pollution in winter and O₃ pollution in summer are the main air quality challenges in Shanghai municipality. (4) Statistical analysis suggested that PM_2.5, PM₁₀, SO₂ and NO₂ concentrations were significantly negatively associated with precipitation (Prec) and atmosphere temperature (T) (p < 0.05), while the O₃ concentration was significantly positively associated with Prec and T (p < 0.05). Lower accumulation of PM, SO₂, NO₂, and CO and more serious O₃ pollution were revealed during months with higher temperature and more precipitation in Shanghai. The correlation between the socio-economic factors and the air pollutants suggest that further rigorous measures are needed to control PM_2.5 and that further studies are needed to identify O₃ formation mechanisms and control strategies. The results provide scientific insights into meteorological factors and socio-economic indicators influencing air pollution in Shanghai.