QUANTIFICATION OF INDIVIDUAL VOC REACTIVITY USING A CHEMICALLY DETAILED, 3-DIMENSIONAL PHOTOCHEMICAL MODEL

Urban ozone reduction strategies targeting volatile organic compounds (VOCs) have focused primarily on controlling the total mass of VOC emitted, neglecting the variation in potential ozone formation by individual species. This variation in ozone potential, termed reactivity, is examined here using a three-dimensional Eulerian photochemical airshed model with a detailed chemical mechanism, Three metrics were examined to quantify the impact of individual VOCs on ozone levels; peak ozone, population-weighted exposure, and spatial-weighted exposure. Reactivities were dependent on the metric used, although the overall trends were very similar. Reactivities differed by over an order of magnitude between species. The Eulerian modeling results are compared with those of a similar study performed using a zero-dimensional model, which is the basis for reactivity quantification for alternative fuel regulations by the California Air Resources Board. The results were well correlated between models for metrics calculated at similar precursor ratios; however, notable differences in reactivity were predicted for some important species, probably due to the multi-day simulation periods and the inclusion of cloud cover by the airshed model.