Quantification of Uncertainty in Reactivity Adjustment Factors from Reformulated Gasolines and Methanol Fuels

Abstract

Speciated data for motor vehicle exhaust emissions of volatile organic compounds (VOCs) have been combined with estimates of uncertainty in the calculated photochemical reactivities of the VOCs to evaluate the resulting uncertainty in the overall reactivity of the exhaust. Mean reactivity adjustment factor (RAF) values for exhaust emissions from reformulated gasolines relative to conventional gasoline ranged from 0.85 to 0.93, with uncertainties of about 10% at the 1σ level. The mean RAF value for M85 (85% methanol, 15% gasoline) in variable/flexible-fueled vehicles relative to emissions from gasoline in conventional vehicles was 0.42, with an uncertainty of 17%. For the gasoline-based fuels, the variability of the exhaust composition data was a major contributor to the uncertainty in the RAFs. For M85, rate constant uncertainties in the reactivities of the VOCs in the exhaust contributed almost two-thirds of the total uncertainty in the RAF values.

Effect of Chemical Product Yield Uncertainties on Reactivities of VOCs and Emissions from Reformulated Gasolines and Methanol Fuels

“…A more detailed description of the methodology used for the incremental reactivity and uncertainty calculations has been presented elsewhere (4,5). Uncertainty estimates for the incremental reactivities are calculated by propagating probability distributions for SAPRC90 chemical parameters through the box model simulations, using Monte Carlo analysis with Latin hypercube sampling.…”

“…In the previous studies (4,5), uncertain rate parameters in the SAPRC90 mechanism were assumed to vary independently. In the previous studies (4,5), uncertain rate parameters in the SAPRC90 mechanism were assumed to vary independently.…”

“…For comparison with the results of the previous study (5), uncertainty estimates incorporating product yield uncertainties and correlations across chemical parameters have been calculated for the RAFs of exhaust emissions associated with vehicle operation on M85 and on a test gasoline. For comparison with the results of the previous study (5), uncertainty estimates incorporating product yield uncertainties and correlations across chemical parameters have been calculated for the RAFs of exhaust emissions associated with vehicle operation on M85 and on a test gasoline.…”

Investigation on VOC Emissions from Automobile Sources by Means of Online Mass Spectrometry

“…Therefore, it is important to assess the effects of VOC emissions using an ozone formation potential (OFP) parameter [62,[64][65][66], such as the maximum incremental reactivity (MIR) [67,68]. Because of this, automobile exhaust evaluations using an OFP have often been performed not only on tailpipe exhaust [69][70][71][72][73][74][75][76][77] but also on evaporative emissions [78][79][80]. In those studies, the VOC compositions were analyzed using traditional analytical chemistry techniques such as GC with flame ionization detection (GC/FID) or GC/MS.…”

Evaporative emissions in three-day diurnal breathing loss tests on passenger cars for the Japanese market

“…Therefore, it is important to assess the effects of VOC emissions using an ozone formation potential (OFP) parameter (Dimitriades, 1996;Kirchstetter et al, 1999;Martien et al, 2003;Chen and Luo, 2012), such as maximum incremental reactivity (MIR) (Carter, 2010;Carter and Heo, 2013). Hence, evaluations of automobile exhausts using an OFP have often been performed not only on tailpipe exhaust (Yang and Milford, 1996;Olson et al, 2000;Schmitz et al, 2000;Farrugia and Olson, 2005;Nakashima et al, 2010;Adam et al, 2011;Tsai et al, 2012;Wang et al, 2013;Costagliola et al, 2014), but also on evaporative emissions (Burns et al, 1992;Harley et al, 2000;Gentner et al, 2013). In those studies, the VOC compositions were analyzed using traditional analytical chemistry techniques, such as gas chromatography with flame ionization detection or gas chromatographymass spectrometry (GCeMS).…”