Table 1.
Thirty day mean concentrations of air pollutants for pre-SD and SD in 2020 and the corresponding periods in 2015–2019, the relative changes from pre-SD to SD in 2020 and the corresponding periods in 2015–2019, and the relative changes from the periods corresponding to SD in 2015–2019 to SD in 2020.
| Pollutant/Year | Pre-SD * | SD * | Relative Change (%) Pre-SD * vs. SD * |
Relative Change (%) for SD * 2015–2019 vs. 2020 |
|---|---|---|---|---|
| PM2.5 (μg m−3) | ||||
| 2020 | 27.6 | 24.7 | −10.4 | −31.2 |
| 2015–2019 | 29.1 | 35.9 | 23.7 | |
| PM10 (μg m−3) | ||||
| 2020 | 40.4 | 44.1 | 9.1 | −29.9 |
| 2015–2019 | 56.0 | 62.9 | 12.3 | |
| NO2 (ppbv) | ||||
| 2020 | 32.0 | 26.7 | −16.4 | −26.9 |
| 2015–2019 | 34.9 | 36.5 | 4.7 | |
| O3 (ppbv) | ||||
| 2020 | 18.0 | 26.4 | 47.0 | 5.7 |
| 2015–2019 | 17.5 | 25.0 | 42.5 | |
| CO (ppbv) | ||||
| 2020 | 588.3 | 489.1 | −16.9 | −16.1 |
| 2015–2019 | 633.4 | 583.3 | −7.9 | |
| SO2 (ppbv) | ||||
| 2020 | 3.3 | 3.2 | −3.3 | −41.5 |
| 2015–2019 | 5.6 | 5.4 | −2.5 |
* For 2015–2019, the periods corresponding to pre-SD and SD in 2020 were used for the calculation.