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Photolysis time (min)

FIGURE 16.7 Typical primary and secondary pollutant profiles in a propene-NOj irradiation in a smog chamber (adapted from Pitts et al„ 1975).

d. Typical Time-Concentration Profiles of Irradiated VOC-NOx-Air Mixtures

Figure 16.7 shows some typical concentration-time profiles for irradiation of a propene-NO mixture in the evacuable chamber of Fig. 16.3. The loss of the reac-tants, and the formation of the most commonly monitored secondary pollutants 03, PAN, and the oxygenates HCHO and CH3CHO are shown (Pitts et al., 1975).

With in situ spectroscopic techniques, critical data on the formation of such species as HONO, HN03, and N03, which are essential to understanding the chemistry of these systems, can also be obtained. Figure 16.8, for example, shows one portion of an FTIR spectrum obtained in a chamber run for a propene-NOx

HNOa

|—H00N02 chsono2

CHqCH = CHo

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