Some theoretical results concerning O3-NOx-VOC chemistry and NOx-VOC indicators -: art. no. 4659

[1] A series of model results is shown pertaining to ozone, reactive nitrogen (NOy), and peroxides in polluted regions. The results focus on ratios such as O-3/NOy and H2O2/HNO3 that have been proposed as indicators for O-3-NOx-VOC sensitivity. These ratios are shown to correlate with predicted NOx-VOC sensitivity for a variety of zero-dimensional (0-D) and 3-D models, but the correlation varies in situations ranging from relatively clean to highly polluted. The previously identified NOx-VOC transition values for indicators appear to be valid for moderately polluted conditions with 80-150 ppb O-3. Changes in indicator behavior are linked to odd hydrogen chemistry and in particular to changes in the ratio of O-3 to primary radical production. Changes in indicator behavior are also correlated with the values of a test ratio, O-3/(2H(2)O(2)+NOz) which can be evaluated against measurements. Ratios of the form DeltaO(3)/DeltaNO(y), representing differences relative to background values, are proposed for analyzing NOx-VOC sensitivity in individual urban plumes. Comparisons are made to extent-of-reaction parameters, which have been proposed for evaluating NOx-VOC sensitivity.