Trend and Control Effect of Air Pollution in 31 Key Cities of China, 2013—2019

Objective To analyze the changing trend of air pollution and the distribution characteristics of main air pollutants in 31 key cities of China during 2013—2019, to summarize and exchange the achievements and experience in air pollution prevention and control in China since 2013, and to provide data support for guiding air pollution control in China.

Methods The annual mean mass concentration data of SO₂, NO₂, PM₁₀, PM_2.5, CO_P95, and O₃-8 h_P90 in the atmosphere of 31 key cities during 2013—2019 were collected from China Statistical Yearbook from 2014 to 2020, and the data of the pollutants were evaluated based on the class Ⅱ limit standards in the Ambient air quality standards (GB 3095-2012). The comprehensive pollution index method and the Daniel trend test method were used to evaluate the overall situation and annual trend of urban air quality, and the Kruskal-Wallis H test was used to compare the mass concentrations of pollutants of different years and regions. A cluster analysis was performed for the annual mean mass concentrations of air pollutants in 31 key cities at different stages.

Results Comprehensive air pollution index tended to decrease during 2013—2019 (r_s = -1.000, P < 0.01). In 2019, PM_2.5, PM₁₀, O₃, and NO₂ were the main air pollutants, with a contribution of 24.60%, 21.25%, 21.66%, and 20.40%, respectively. From 2013 to 2019, the annual mean mass concentrations of SO₂, NO₂, PM₁₀, PM_2.5, and CO_P95 were reduced by 73.81%, 19.57%, 46.03%, 48.00%, and 44.44%, respectively, and the annual mean concentrations of SO₂, PM₁₀, PM_2.5, and CO_P95 tended to decrease (r_s ranged from -1.000 to -0.883, P < 0.05), while the annual mean concentration of O₃-8 h_P90 tended to increase slowly by 21.37% (r_s = 0.893, P < 0.05). The key cities in North China were polluted heavily, while those in South China and East China were polluted slightly. For these 31 key cities, the levels of the above air pollutants except O₃ during 2016—2019 were significantly lower than those during 2013—2015.

Conclusion Since 2013, comprehensive air pollution index has decreased year by year and air quality has been significantly improved in China, suggesting that some progress has been made in air pollution prevention and control. At present, PM₁₀, PM_2.5, O₃, and NO₂ are still the main pollutants to be prevented and controled. Collaborative management of PM_2.5 and O₃ should be strengthened in the near future, and pollutant emissions should be reduced, especially VOCs and NOx. Air pollution prevention and control should be focused especially in Beijing-Tianjin-Hebei Region and its surrounding areas.