Journals
Publish with us
Publishing partnerships
About us
Blog
Journal of Mathematics
Journal overview
For authors
For reviewers
For editors
Table of Contents
Special Issues
Journal of Mathematics
/
2021
/
Article
/
Tab 5
/
Research Article
Using the Quarterly Compound Fractional Grey Model to Predict the Air Quality in 22 Cities of China
Table 5
Quality levels and corresponding concentration limits of PM
2.5
, PM
10
, SO
2
, and NO
2
.
Pollutants
Level 1 (unit:
μ
g/m
3
)
Level 2 (unit:
μ
g/m
3
)
PM
2.5
15
35
PM
10
40
70
SO
2
20
60
NO
2
40
40