William A. Glasson

Effect of Hydrocarbon and NO x on Photochemical Smog Formation under Simulated Transport Conditions

The body of information presented in this paper is directed to those individuals concerned with the effect of urban pollution on downwind areas. Concern has been expressed over the appropriate hydrocarbon and NOX control strategy to be used in minimizing the effects of ozone and NO2 on urban population centers and their downwind environs. O3 and NO2 formation were studied in smog chamber irradiations as a function of the initial NOX concentration at three hydrocarbon concentrations. By carrying out the irradiations for a period of time equivalent to one solar day in a continuously diluting system, smog formation in a chemically reacting pollutant system under transport was simulated. The results of this experimental simulation suggest that hydrocarbon reduction reduces O3 in urban as well as downwind areas while NOX reduction increases O3 in the urban area and has little effect on O 3 in downwind areas. Both hydrocarbon and NO* reduction will reduce atmospheric NO2 levels, with the effect of NO X reduction generally being more pronounced. In a previous study,1 the effect of NOX control on local and downwind oxidant formation was determined under conditions simulating transport of a reacting air mass. The study was performed at a constant surrogate hydrocarbon mixture concentration of 5.1 ppm C which is representative of a heavily polluted Los Angeles atmosphere today. Since hydrocarbon controls will reduce this worst case concentration, it is desirable to determine the effect of NOX control on O3 formation at lower hydrocarbon concentrations representative of future atmospheres. In the present study, O3 formation was studied at surrogate hydrocarbon mixture concentrations of 5.1, 2.7, and 1.4 ppm C, while NOX was varied from about 0.01 to 0.49 ppm. The effect of these variables on NO2 formation was also studied. Hydrocarbon mixture concentrations and compositions were also determined during the course of most irradiations.

Hydrocarbon Reactivity and the Kinetics of the Atmospheric Photooxidation of Nitric Oxide

The reactivity in the atmospheric photooxidation of nitric oxide has recently been determined for a large number of hydrocarbons. To aid in the application of these hydrocarbon reactivity measurements, the kinetics of the atmospheric photooxidation have been studied. The hydrocarbons investigated covered a wide range of reactivities and structures and included: 2,3-dimethyl-2-butene, 2-methyl-2-butene, 2-methyl-l-pentene, propylene, mesitylene, o-xylene, and n-hexane. The rate of nitric oxide photoxidation increases less than linearly with hydrocarbon concentration for all of the hydrocarbons studied. The degree of nonlinearity, however, varied with hydrocarbon structure and reactivity. The effect of the nitric oxide and the nitrogen dioxide concentrations on the rate of nitric oxide photooxidation also depended somewhat on hydrocarbon structure and reactivity. For all of the hydrocarbons studied, however, the nitric oxide photooxidation rate increased linearly with increased light intensity. The effect o...

Smog chamber simulation of Los Angeles pollutant transport

The body of information presented in this paper is directed to those individuals concerned with the effect of urban pollution on downwind areas. In the absence of any evidence, it has been widely assumed that increasing NO x emissions have caused oxidant levels to increase downwind of Los Angeles, i.e., Riverside and San Bernardino. This smog chamber study simulated pollutant transport from Los Angeles to the downwind areas by irradiating a typical Los Angeles hydrocarbon/NO x mixture for extended periods of time. The smog chamber experiments were extended to 22 hours to obtain an integrated light intensity equal to that which occurs in the Los Angeles area. The effects of variations of nitrogen oxide emissions on an aged air mass were examined. The results show that downwind oxidant levels are only slightly affected by large changes in NO x emissions. However, it is clear that reduced nitrogen oxide emissions will lead to an increase in oxidant in downtown Los Angeles.