Table 2.
Analysis of the percentage of changes in 06:00–09:00 a.m. hourly medians of CO and NOx for all monitoring stations in the MCMA for the whole March to May period and for each month in the years 2018, 2019, and 2020.
| Period | CO ppb |
NOx ppb |
% of change with respect to March of each year |
||
|---|---|---|---|---|---|
| Median | Median | CO | NOx | ||
| 2018 | 3 months | 1044.5 | 85.3 | ||
| March | 1067.5 | 89.8 | 0 | 0 | |
| April | 1084.0 | 86.1 | 1.54 | −4.04 | |
| May | 986.3 | 79.8 | −7.61 | −11.15 | |
| 2019 | 3 months | 958.3 | 76.7 | ||
| March | 1012.3 | 87.6 | 0 | 0 | |
| April | 927.4 | 72.7 | −8.39 | −16.99 | |
| May | 938.4 | 70.0 | −7.31 | −20.08 | |
| 2020 | 3 months | 754.8 | 56.6 | ||
| March | 882.0 | 80.6 | 0 | 0 | |
| April | 717.5 | 52.6 | −18.65 | −34.75 | |
| May | 760.6 | 49.6 | −13.76 | −38.42 | |