MEASUREMENT OF VOC REACTIVITIES USING A PHOTOCHEMICAL FLOW REACTOR

A commercial ambient air monitoring instrument, the Airtrak 2000, has been modified for use as a photochemical flow reactor and used to meas ure the absolute and incremental reactivity of 18 single test VOCs and the incremental reactivity of six multicomponent VOC mixtures. A flow technique is a useful supplement to traditional static chamber experi ments. The static chamber technique involves periodic sampling of an i rradiated mixture in a photochemical chamber. Under these conditions, the irradiated mixture is always in transition. Using a flow system, a steady-state condition is established within the flow reactor that is representative, in this case, of the early stages of the smog forming process in the atmosphere. The measurement technique also allows chan ges in the background chamber reactivity to be monitored and taken int o account. The incremental reactivity of 13 of the 18 test compounds m easured is compared with previously reported results from a static cha mber experiment, and the two data sets are generally in good agreement . The additivity of reactivity was tested by measuring the incremental reactivity of six multicomponent mixtures, the components being compo unds measured individually in this study. The measured reactivity of a mixture was compared to that calculated from the sum of the measured reactivity of the mixture's individual components. The results show th at reactivity is additive for the concentration range studied.