Photochemical Conversion of NO to NO2 by Hydrocarbons in an Outdoor Chamber

Significant differences occur between results of chamber work conducted outdoors versus work conducted indoors under constant light intensity. Under outdoor conditions at constant NO_X]_O, lower HC]o resulted in lower NO₂]_max and NO₂ dosage during the daylight hours. The percent reduction in NO₂]_max was a function of the HC]₀ reduction and the NO_X]_O level. Under all experimental conditions the 10 hour N0₂ average to maximum N0₂ concentration ratio appeared to be constant at 0.73 during the daylight hours. A regression equation relating NO_x]_max to NO_X]_O, HC]_O, and measures of solar radiation accounted for 92% of the variance in the data. Although there is unavoidable confoundment between HC]₀ and solar radiation, the HC term in this regression equation can introduce ±20 % change in N0₂]_max - This variation can be partially offset or enhanced by variations in solar radiation.