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

incremental reactivity estimates for aromatic compounds have been considere d 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 me chanism parameters estimated by fitting chamber data, are propagated throug h incremental reactivity calculations using Monte Carlo analysis with Latin hypercube sampling. For 34 volatile organic compounds, absolute incrementa l reactivity estimates calculated with the SAPRC-97 mechanism are generally higher, but with lower associated uncertainties, than those calculated pre viously with the SAPRC-90 mechanism. The uncertainty levels found for the m aximum 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 th e maximum ozone incremental reactivities (MOIRs) and equal benefit incremen tal reactivities (EBIRs) of the aromatics range from 38 to 75% and 30 to 52 0%, respectively. Uncertainties in relative MIRs, MOIRs and EBIRs for the a romatic compounds range from 13 to 24%, 21 to 62% and 21 to 360%, respectiv ely. The chamber-derived aromatics oxidation parameters strongly influence the uncertainties in the incremental reactivities of most of the VOCs studi ed. (C) 2000 Elsevier Science Ltd. All rights reserved.