Study on the relationship between heat island effect, PM 2.5 and urbanization in the Beijing-Tianjin-Tangshan region

With the rapid progress of urbanization in Beijing-Tianjin-Tangshan region, heat island effect and air pollution have become common environmental problems in the study area. How to coordinate the relationship between urbanization and ecological environment is extremely urgent. Therefore, based on geographical weighted regression model, Tapio decoupling theory and environmental Kuznets curve, this paper systematically analyzes the relationship between heat island effect, PM 2.5 and urbanization in Beijing-Tianjin-Tangshan region. The results show that: 1) The intensity of heat island is mainly increasing in urban built-up areas, and has a certain relationship with economic development, which is shown as "Beijing > Tianjin > Tangshan > Langfang". In addition, the increase of heat island intensity slows down in the later stage of the study. 2) The concentration of PM 2.5 increased from 2001 to 2013, the air quality improved significantly after 2013. And PM 2.5 has obvious seasonal and daily variation characteristics. Furthermore, PM 2.5 concentration has significant spatial agglomeration and diffusion. The average interaction distance between cities in Beijing-Tianjin-Tangshan region is 190km. 3) In the whole study period, the urbanization process in the study area has been moving forward despite fluctuations. There are obvious differences in urbanization among the cities in the urban agglomeration. The urbanization of Beijing and Tianjin is developing rapidly, and the spatial expansion is in the form of concentric circles or along the extension axis. 4) Geographical weighted regression model finds that urbanization has a high impact on heat island effect and PM 2.5 , and both are positively correlated. The decoupling theory indicates that the relationship between urbanization and heat island effect in the study area is dominated by expansion negative decoupling and weak decoupling, while the relationship between urbanization and PM 2.5 is mainly weak decoupling and strong decoupling. The environmental Kuznets curve draws the conclusion that the relationship between heat island effect, PM 2.5 and urbanization in the study area presents an "N-shaped" respectively. In general, the relationship between heat island effect, PM 2.5 and urbanization of Beijing-Tianjin-Tangshan region had become more and more harmonious from 2001 to 2017.