Table 2 Distribution of the element-to-PM _2.5 mass proportions and interquartile range (IQR) of the monthly averages of these ratios

Al

0.55

1.64

3.26

6.68

12.71

816

4.94

Na

0.47

2.36

6.29

14.21

27.71

797

11.42

Br

0.09

0.19

0.31

0.62

2.33

814

0.39

Ca

1.02

2.38

4.00

5.89

9.50

816

3.36

Cl

0.16

0.80

2.20

5.16

15.87

720

4.64

Cr

0.03

0.06

0.10

0.14

0.26

800

0.04

Cu

0.26

0.54

0.75

1.08

1.94

815

0.36

Fe

2.92

6.37

9.07

12.41

18.70

816

5.23

K

3.58

5.97

8.30

12.02

23.43

816

7.23

Mn

0.13

0.29

0.46

0.65

1.04

816

0.21

Ni

0.01

0.02

0.03

0.05

0.09

751

0.02

Pb

0.31

0.64

0.99

2.63

8.24

815

2.74

Se

0.01

0.04

0.08

0.15

0.33

755

0.10

Si

1.91

4.44

8.56

16.42

28.68

816

13.47

S

9.59

22.79

36.72

52.13

81.10

816

22.33

Zn

0.79

1.39

2.05

2.88

4.96

816

0.93