Fig. 3
Spearman correlation coefficients among (a) daily and (b) hourly concentrations of Cupressaceae pollen, air pollutants (NOx, O3, PM2.5) and meteorological elements (mean air temperature, relative humidity and wind speed) in the urban (upper triangular matrix) and suburban (lower triangular matrix) area. *, p < 0.05; **, p < 0.01.
