Linking Load, Fuel, and Emission Controls to Photochemical Production of Secondary Organic Aerosol from a Diesel Engine

Abstract

Diesel engines are important sources of fine particle pollution in urban environments, but their contribution to the atmospheric formation of secondary organic aerosol (SOA) is not well constrained. We investigated direct emissions of primary organic aerosol (POA) and photochemical production of SOA from a diesel engine using an oxidation flow reactor (OFR). In less than a day of simulated atmospheric aging, SOA production exceeded POA emissions by an order of magnitude or more. Efficient combustion at higher engine loads coupled to the removal of SOA precursors and particle emissions by aftertreatment systems reduced POA emission factors by an order of magnitude and SOA production factors by factors of 2-10. The only exception was that the retrofitted aftertreatment did not reduce SOA production at idle loads where exhaust temperatures were low enough to limit removal of SOA precursors in the oxidation catalyst. Use of biodiesel resulted in nearly identical POA and SOA compared to diesel. The effective SOA yield of diesel exhaust was similar to that of unburned diesel fuel. While OFRs can help study the multiday evolution, at low particle concentrations OFRs may not allow for complete gas/particle partitioning and bias the potential of precursors to form SOA.

Characterizing source fingerprints and ageing processes in laboratory-generated secondary organic aerosols using proton-nuclear magnetic resonance (<sup>1</sup>H-NMR) analysis and HPLC HULIS determination

“…S3). These results are in qualitative agreement with the known chemistry of α-pinene SOA, in which mono-and dicarboxylic acids are the most characteristic condensable first-generation products (Jenkin et al, 2000;Jaoui and Kamens, 2001), while tricarboxylic acids such as 3-methyl-1,2,3-butanetricarboxylic acid or pinyl-diaterpenyl ester (Szmigielski et al, 2007;Yasmeen et al, 2010) are Table 1. present in lesser amounts and can contribute the observed concentrations of HULIS in this study. The HPLC fractionation of naphthalene SOA (Fig.…”

Sources and characteristics of summertime organic aerosol in the Colorado Front Range: perspective from measurements and WRF-Chem modeling

“…3d and discussed previously, there appears to be some contribution to HOA from O&G-related activities. A higher POA emission factor from O&G-related activities is not unexpected given typically high emissions from diesel engines without after-treatment technology that might be working at these sites (Ban-Weiss et al, 2008;Jathar et al, 2017); however, as mentioned before, there were no adjustments to POA emissions for the O&G sector in WRF-Chem when modifying the top-down estimates of gaseous emissions. Despite this, it is unlikely that NEI emission factors of POA from the urban areas are underestimated by up to a factor of 8 (mean HOA ∼ 0.45 µg m −3 vs. mean POA ∼ 0.05 µg m −3 ).…”

Comparison of primary and secondary particle formation from natural gas engine exhaust and of their volatility characteristics

“…If a unit factor in mg kg −1 fuel is needed, a factor of approximately 22 m 3 kg −1 fuel can be applied to multiply the particle concentration (calculation, e.g., in Jathar et al, 2017;Gordon et al, 2014b). In order to obtain emission and production factors in units of kWh −1 , a factor of 2.7 m 3 kWh −1 (mode 1) or 4 m 3 kWh −1 (mode 2) can similarly be used.…”