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

Abstract

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.