## 3 Results and Discussion
### Inter-Period Observational Approach
As important as meteorological conditions are to ozone formation and accumulation in the ambient air, a key question is whether the reduction in primary urban emissions, due to activities that were paralyzed by the strike, had an impact on the levels of ozone in Quito. We propose that a shift in emission proportions had an impact in terms of ozone production rates, mainly during those days when solar radiation was more available (Figure A1, Appendix A). As demonstrated in previous work [39], during the strict COVID-19 lockdown, there was a substantial decrease in traffic emissions in Quito, and thus NO\({}_{\times}\), comparable to the strike (Figure 2e,f). As a result, the local atmospheric chemistry shifted from a generally NO\({}_{\times}\)-saturated regime into conditions in which free radicals [OH (hydroxyl)] and HO\({}_{2}\) (hydroperoxyl)]--the core of the ozone production chemistry--were less depleted to form subspecies such as nitric acid and, instead, produced additional ozone per unit time (ozone production rates, ppb h\({}^{-1}\)). However, increased rates of ozone production were counterbalanced by meteorological conditions, as the strict lockdown also coincided with \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Inter-Period Estimated Change** & \multicolumn{2}{c}{**NO\({}_{2}\)**} & \multicolumn{2}{c}{**CO**} & \multicolumn{2}{c}{**O\({}_{3}\)**} & \multicolumn{2}{c}{**SO\({}_{2}\)**} \\ \hline S1-Carapungo & \(+41.77\) & \(0.94\) & \(-25.31\) & \(4.2\) & \(7.41\) & \(-13.82\) & \(-16.14\) & \(12.57\) \\ S2-Cotocollao & ND & ND & \(-25.58\) & \(3.39\) & \(-7.55\) & \(-31.31\) & \(2.64\) & \(9.94\) \\ S3-Belisario & \(+38.57\) & \(0.94\) & \(-15.28\) & \(3.72\) & \(-2.64\) & \(-31.98\) & \(-13.81\) & \(7.42\) \\ S4-Centro & \(+44.89\) & \(-8.51\) & \(-12.84\) & \(7.06\) & \(0.04\) & \(-29.42\) & \(-10.91\) & \(-11.24\) \\ S5-Camal & \(-33.92\) & \(2.7\) & \(-25.84\) & \(6.09\) & \(-8.32\) & \(-45.22\) & \(-10.02\) & \(18.15\) \\ S6-Guamani & \(-2.41\) & \(-1.3\) & \(-10.63\) & \(-8.33\) & \(-11.11\) & \(-14.07\) & \(-4.16\) & \(5.68\) \\ S7-Chillos & \(-32.63\) & \(-11.54\) & \(-23.47\) & \(-4.81\) & \(-14.07\) & \(-14.57\) & \(1.99\) & \(-19.46\) \\ Overall Mean & \(-32.37\) & \(-2.80\) & \(-19.85\) & \(16.2\) & \(-5.18\) & \(-25.77\) & \(-7.20\) & \(3.29\) \\ \cline{2-10}  & \(+15.39\) & \(+5.82\) & \(\pm 6.67\) & \(\pm 5.83\) & \(\pm 7.32\) & \(\pm 12.01\) & \(\pm 7.48\) & \(\pm 13.56\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: An inter-period analysis of the 12-day period before the strike (20 September 2019–1 October 2019) comparison with pollutant concentration changes pre-strike (2 October 2019–13 October 2019) and post-strike (14 October 2019–25 October 2019). Negative values show consequential percent reduction of pollution, while positive values show an increase during or after the national strike. The color scale is based on a gradient color in red, yellow, and green. The greener is the cell, the higher is the pollution drop. a period of increased cloudiness and rain. Such conditions had the effect of cleaning the atmosphere. Therefore, even though the strike did not last very long, it shares similar traits to the COVID-19 lockdown from the perspective that primary emissions decreased and meteorology was similar. Finally, for concentrations of SO\({}_{2}\), during the strike (\(-7.2\)\(\pm\) 7.48%) and post-strike (\(+3.29\)\(\pm\) 13.56%), the change is much smaller, with sustained peaks in the southern valley of the city, where a thermoelectric plant is located (Figure 2d,h,l). This indicates there were close to no changes in power generation during the strike. However, further away from the power plant, an impact of reduced city traffic circulation can be observed in almost all the sites during the strike.