The contribution of the precursors nitric oxide (NO), nitrogen dioxide (NO2), and meteorological factors were evaluated in relation to the formation of nocturnal O3 in Campo Grande – MS, Brazil. The maximum nocturnal level identified in the study for NO2, NO, and O3 were 49.5, 58.0, and 30.0 μg.m-3, followed by the minimum values of 10.0, 6.0, and 9.0 μg m-3 and averages of 27.4, 21.2, and 18.3 μg m-3, respectfully. The effect of NO2 and NO titration emitted by anthropic sources in the urban area, which has the highest levels of NO2 and NO in comparison with other locations, may be the main driving force of the lowest nocturnal O3 value. During the night, O3 titration at ground level occurred, resulting in the average value of the jNO2/k3 ratio, recorded as 25.6 with maximum and minimum values of 35.4 and 19.8 μg m-3. It suggests that urban locations with wind speeds values of positive ∆jNO2/k3 can lead to the accumulation of O3 at night. The average ratio between the concentration of nocturnal ozone and diurnal surface ozone for Campo Grande was 55%.
Key words: Daily variability sustainability; Nitric oxide; Nitrogen dioxide; Photochemistry
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