Reactivity estimates for aromatic compounds. Part 2. Uncertainty in incremental reactivities

incremental reactivity estimates for aromatic compounds have been considered highly uncertain due to gaps in understanding the reaction mechanism for their atmospheric oxidation. In this study, uncertainties in the parameters of the SAPRC-97 chemical mechanism, including uncertainties in aromatic mechanism parameters estimated by fitting chamber data, are propagated through incremental reactivity calculations using Monte Carlo analysis with Latin hypercube sampling. For 34 volatile organic compounds, absolute incremental reactivity estimates calculated with the SAPRC-97 mechanism are generally higher, but with lower associated uncertainties, than those calculated previously with the SAPRC-90 mechanism. The uncertainty levels found for the maximum incremental reactivities (MIRs) of the aromatic compounds range from 27 to 32% (1 sigma relative to the mean) and are similar to those for VOCs with relatively well-established mechanisms. The uncertainly levels for the maximum ozone incremental reactivities (MOIRs) and equal benefit incremental reactivities (EBIRs) of the aromatics range from 38 to 75% and 30 to 520%, respectively. Uncertainties in relative MIRs, MOIRs and EBIRs for the aromatic compounds range from 13 to 24%, 21 to 62% and 21 to 360%, respectively. The chamber-derived aromatics oxidation parameters strongly influence the uncertainties in the incremental reactivities of most of the VOCs studied. (C) 2000 Elsevier Science Ltd. All rights reserved.