Primary Gas- and Particle-Phase Emissions and Secondary Organic Aerosol Production from Gasoline and Diesel Off-Road Engines

Abstract

Dilution and smog chamber experiments were performed to characterize the primary emissions and secondary organic aerosol (SOA) formation from gasoline and diesel small off-road engines (SOREs). These engines are high emitters of primary gas- and particle-phase pollutants relative to their fuel consumption. Two- and 4-stroke gasoline SOREs emit much more (up to 3 orders of magnitude more) nonmethane organic gases (NMOGs), primary PM and organic carbon than newer on-road gasoline vehicles (per kg of fuel burned). The primary emissions from a diesel transportation refrigeration unit were similar to those of older, uncontrolled diesel engines used in on-road vehicles (e.g., premodel year 2007 heavy-duty diesel trucks). Two-strokes emitted the largest fractional (and absolute) amount of SOA precursors compared to diesel and 4-stroke gasoline SOREs; however, 35-80% of the NMOG emissions from the engines could not be speciated using traditional gas chromatography or high-performance liquid chromatography. After 3 h of photo-oxidation in a smog chamber, dilute emissions from both 2- and 4-stroke gasoline SOREs produced large amounts of semivolatile SOA. The effective SOA yield (defined as the ratio of SOA mass to estimated mass of reacted precursors) was 2-4% for 2- and 4-stroke SOREs, which is comparable to yields from dilute exhaust from older passenger cars and unburned gasoline. This suggests that much of the SOA production was due to unburned fuel and/or lubrication oil. The total PM contribution of different mobile source categories to the ambient PM burden was calculated by combining primary emission, SOA production and fuel consumption data. Relative to their fuel consumption, SOREs are disproportionately high total PM sources; however, the vastly greater fuel consumption of on-road vehicles renders them (on-road vehicles) the dominant mobile source of ambient PM in the Los Angeles area.

Diesel-related hydrocarbons can dominate gas phase reactive carbon in megacities

“…The number of possible structural isomers increases exponentially with carbon number (Goldstein and Galbally, 2007) and beyond around C 9 it becomes impossible to accurately identify the structure of every hydrocarbon present in air. Using the retention behaviour of each compound on chromatographic columns it is however possible to assign individual species to particular chemical classes and functionalities.…”

“…Several recent field studies have investigated the relative importance of gasoline, diesel and biogenic emissions in generating SOA (Gentner et al, 2012;Bahreini et al, 2012;Gordon et al, 2013;Platt et al, 2013;Gordon et al, 2014a, b;Jathar et al, 2014;Ensberg et al, 2014). These have been carried out predominately in the US, particularly in California, where current diesel usage is rather low by global standards.…”

Particulate organic nitrates observed in an oil and natural gas production region during wintertime

“…Recent studies of organic matter in ambient aerosol have focused on anthropogenic emissions of gasoline, diesel (Gordon et al, 2013;Jathar et al, 2013;Gentner et al, 2012;Bahreini et al, 2012), motor oil (Worton et al, 2014) and biogenic VOCs Paulot et al, 2009;Froyd et al, 2010) as precursors. For long-chain aliphatics, laboratory experiments and simulations have demonstrated substantial contribution of organic nitrates in the resulting particulate matter (Jordan et al, 2008;Lim and Ziemann, 2009;Matsunaga and Ziemann, 2010), but there exist few field observations capable of assessing whether these mechanisms are representative of the ambient processes.…”

Development of organic gas exhaust speciation profiles for nonroad spark-ignition and compression-ignition engines and equipment

“…This is in contrast to the on-road sector, which has more well-characterized speciated emission data (EPA, 2008(EPA, , 2013Khalek et al, 2009). Our review found that many nonroad engine studies that have speciation data are for older technology engines, based on testing with fuels that are no longer representative of most of the market (Gabele, 1997;EPA, 2004;Volckens et al, 2008), or based on fuels that have never been widely used (Gordon et al, 2013;MargaraGomez et al, 2012;Chai et al, 2013;Zhang and Balasubramanian, 2014). One federal test program reviewed did not have full speciation needed to develop exhaust gas speciation profiles (National Renewable Energy Laboratory [NREL] and Oak Ridge National Laboratory [ORNL], 2009).…”