The impact of urbanization on air quality in Africa from time and spatial perspectives

The problem of air pollution caused by urbanization in fast-growing countries has begun to receive widespread attention. Africa is facing serious air pollution problem and is experiencing rapid urbanization. However, due to the backward economy and the difficulty of obtaining data, there have been few studies on the impact of urbanization on air quality in Africa. In this paper, we use remote sensing data aerosol optical depth (AOD) to characterize air quality, and night lights to characterize urbanization. We aim to analyze the characteristics of air quality distribution in Africa and investigate the relationship between urbanization and AOD from the perspective of time by random forest and space by adopting the geographically weighted regression models (GWR). The results show that (1) in the past 10 years, though not obvious, the AOD in the African region has a slight downward trend from 2011 to 2020. And a significant spatial correlation between urbanization and AOD is confirmed; (2) treating Africa as a whole, AOD has spatial spillover effects and could be affected significantly and positively by urbanization; (3) locally, taking each country as the scale, urbanization could have different impacts on AOD for different countries. In Central Africa, the increase in urbanization will bring about an increase in AOD; and in Western Africa, the increase in urbanization will help reduce AOD; (4) improving power facilities, increasing per capita income, and strengthening commodity trade are conducive to improving air quality in Africa.