Table 6.

Correlation with the first-level air standard.

Correlation coefficient and correlation degree	ζ1	ζ2	ζ3	ζ4	ζ5	R1
$S_1^{\prime }$	1.000	0.807	0.333	0.637	0.591	0.674
$S_2^{\prime }$	1.000	0.638	0.333	0.558	0.955	0.697
$S_3^{\prime }$	1.000	0.988	0.522	0.708	0.333	0.710