VOC composition of current motor vehicle fuels and vapors, and collinearity analyses for receptor modeling

Abstract

The formulation of motor vehicle fuels can alter the magnitude and composition of evaporative and exhaust emissions occurring throughout the fuel cycle. Information regarding the volatile organic compound (VOC) composition of motor fuels other than gasoline is scarce, especially for bioethanol and bio-diesel blends. This study examines the liquid and vapor (headspace) composition of four contemporary and commercially available fuels: gasoline (<10% ethanol), E85 (85% ethanol and 15% gasoline), ultra-low sulfur diesel (ULSD), and B20 (20% soy-biodiesel and 80% ULSD). The composition of gasoline and E85 in both neat fuel and headspace vapor was dominated by aromatics and n-heptane. Despite its low gasoline content, E85 vapor contained higher concentrations of several VOCs than those in gasoline vapor, likely due to adjustments in its formulation. Temperature changes produced greater changes in the partial pressures of 17 VOCs in E85 than in gasoline, and large shifts in the VOC composition. B20 and ULSD were dominated by C9 to C16 n-alkanes and low levels of the aromatics, and the two fuels had similar headspace vapor composition and concentrations. While the headspace composition predicted using vapor–liquid equilibrium theory was closely correlated to measurements, E85 vapor concentrations were underpredicted. Based on variance decomposition analyses, gasoline and diesel fuels and their vapors VOC were distinct, but B20 and ULSD fuels and vapors were highly collinear. These results can be used to estimate fuel related emissions and exposures, particularly in receptor models that apportion emission sources, and the collinearity analysis suggests that gasoline- and diesel-related emissions can be distinguished.

Evaluation of a Modified Receptor Model for Solving Multiple Time Resolution Equations: A Simulation Study

“…A lower R 2 of 0.516 and higher percentage contributions (15% for VOC and 11% for PM 2.5 ) were observed for diesel exhaust, compared to those of natural gas in the original D Comb data set (Table 3, D FCor ). The problem of profile collinearity might be solved by including additional species to reduce similarity between profiles (Chin and Batterman, 2012). These above analyses indicated a trade-off between high and low contributors when they correlated with each other.…”

“…On the other hand, for the low contributors of coal combustion and natural gas, their R 2 increased to 0.784 and 0.953, respectively, although their percentage contribution estimates also increased. Source profile collinearity was investigated by replacing natural gas in D Comb with diesel exhaust which has a profile highly correlated with that of vehicle exhaust (Chin and Batterman, 2012). A lower R 2 of 0.516 and higher percentage contributions (15% for VOC and 11% for PM 2.5 ) were observed for diesel exhaust, compared to those of natural gas in the original D Comb data set (Table 3, D FCor ).…”

Source Apportionment of Volatile Organic Compounds at an International Airport

“…However, gasoline compositions in recent literature that have reported similar target species, including n-butane, npentane, 2-methyl butane, toluene, and m,p-xylene (Harley and Kean, 2004;Na et al, 2004;Chin and Batterman, 2012). In a 2006 study of diesel fuel in Taiwan, the top five VOCs were C 13 -C 16 and C 18 straght-chain alkanes, accounting for 46% of target compounds (Peng et al, 2006).…”

“…In a 2006 study of diesel fuel in Taiwan, the top five VOCs were C 13 -C 16 and C 18 straght-chain alkanes, accounting for 46% of target compounds (Peng et al, 2006). Chin and Batterman (2012) indicated that C 9 -C 16 straightchain alkanes of diesel fuel were dominant and account for 90% of TVOCs. Branched paraffines (29.94%) represent the largest proportion of C 5 -C 9 VOC composition of jet fuels, follow by monocyclic paraffines (20.34%), n-paraffines (19.69%), alkyl benzenes (14.05%), and others (15.98%) (van der Westhuizen et al, 2011).…”

Photooxidation of cyclohexene in the presence of SO&lt;sub&gt;2&lt;/sub&gt;: SOA yield and chemical composition

“…Alkenes are widely emitted from biogenic and anthropogenic sources (Kesselmeier et al, 2002;Chin and Batterman, 2012), and their gas-phase oxidation reactions with OH, NO 3 , or O 3 are among the most important processes in the atmosphere (Atkinson, 1997;Stewart et al, 2013;Paulson et al, 1999). Reactions of ozone with alkenes are an important source of free radicals in the lower atmosphere and thus highly influence the oxidative capacity of the atmosphere (Paulson and Orlando, 1996).…”