Air Pollution and the Public Perception Level and Self-Protection Demand in Three Cities of China: Fractional Grey Modelling Analysis

Figure 3

The relationship between Baidu index of the perception levels and AQI. (a) Beijing. (b) Tianjin. (c) Shijiazhuang. (d) AQI of three cities.

(a)

(b)

(c)

(d)