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Variations in average enrichment factors of Fe (EFFe), concentrations of NOx, SO2, and O3, and numbers of on-road vehicles among the three stages in Hangzhou.
| Stage | EFFe | NOx (ppb) | SO2 (ppb) | O3 (ppb) | Vehicle numbers (Normalized) |
|---|---|---|---|---|---|
| Pre-lockdown | 13.3 | 37.5 ± 17.5 | 1.6 ± 0.7 | 10.1 ± 6.9 | 1.00 |
| COVID-19 lockdown | 1.6 | 6.8 ± 2.7 | 1.3 ± 0.4 | 29.3 ± 10.5 | 0.19 |
| Post-lockdown | 6.6 | 23.4 ± 9.2 | 1.7 ± 0.5 | 23.4 ± 9.2 | 0.72 |
