BACKGROUNDDuring rapid urbanization of cities in the Beijing-Tianjin-Hebei Region, the extensive economic development mode of 'high energy consumption, high pollution and high emission' has caused a series of atmospheric pollution problems. It is crucial to coordinate the relationship between economic development and atmospheric environmental quality.

OBJECTIVESTo investigate the relationship between the urbanization and the atmospheric environmental quality of the three cities of Beijing, Tianjin and Shijiazhuang.

METHODSBased on the data of various indicators of atmospheric environmental quality and urbanization in Beijing, Tianjin, and Shijiazhuang from 2004 to 2017, the entropy method was used to study the evolution of atmospheric environmental quality in the process of urbanization in multiple dimensions. The annual average concentration of urban atmospheric pollutants SO₂, NO₂, PM₁₀, and the number of days better than level 2 were 4 atmospheric environmental quality indicators, and 10 development indicators including regional GDP, per capita GDP, proportion of tertiary industries, and built-up area were selected to construct comprehensive index models and regression fitting.

RESULTSThe impact of urbanization on atmospheric environmental quality was the result of the combined effect of various factors. The relationship between comprehensive urbanization index and comprehensive atmospheric environmental pollution index in Beijing, Tianjin and Hebei was 'inverted U-shaped', 'positive U-shaped' and 'inverted N-shaped', respectively. The 10 urbanization indicators were classified into structural effects, scale effects and activity effects, and further analyze the impact of various effects on the atmospheric environmental pollution index. For Beijing, the dependent variables of the three types of effects all had negative impacts on atmospheric environmental quality. For Tianjin, the built-up area in the structure effect and scale effect, and the per capita GDP, GDP, resident consumption level and the total retail sales of consumer goods in the activity effect had negative correlations with atmospheric environmental quality. The impact of each dependent variable of the three effects on atmospheric environmental quality was unclear for Shijiazhuang.

CONCLUSIONSThe EKC hypothesis can reflect the relationship between the urbanization and atmospheric environmental quality to a certain extent. For the cities like Beijing that have basically completed the transformation of economic development, the EKC hypothesis is established obviously. But for the cities like Tianjin and Shijiazhuang that have not completed the economic restructuring, the relationship between urbanization and atmospheric environmental quality is uncertainty. Further study should be necessary.