Figure 4

Regional variations of mean AAQI and NHAQI in Gansu (a for P-I; b for P-II) (R version 4.0.1 https://www.r-project.org/).
Regional variations of mean AAQI and NHAQI in Gansu (a for P-I; b for P-II) (R version 4.0.1 https://www.r-project.org/).