Composition and Integrity of PAHs, Nitro-PAHs, Hopanes, and Steranes in Diesel Exhaust Particulate Matter

Abstract

Diesel exhaust particulate matter contains many semivolatile organic compounds (SVOCs) of environmental and health significance. This study investigates the composition, emission rates, and integrity of 25 SVOCs, including polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and diesel biomarkers hopanes and steranes. Diesel engine particulate matter (PM), generated using an engine test bench, three engine conditions, and ultra-low sulfur diesel (ULSD), was collected on borosilicate glass fiber filters. Under high engine load, the PM emission rate was 0.102 g/kWh, and emission rate of ΣPAHs (10 compounds), ΣNPAHs (6 compounds), Σhopanes (2 compounds), and Σsteranes (2 compounds) were 2.52, 0.351, 0.02 ~ 2 and 1μg/kWh, respectively. Storage losses were evaluated for three cases: conditioning filters in clean air at 25 °C and 33% relative humidity (RH) for 24 h; storing filter samples (without extraction) wrapped in aluminum foil at 4 °C for up to one month; and storing filter extracts in glass vials capped with Teflon crimp seals at 4 °C for up to six months. After conditioning filters for 24 h, 30% of the more volatile PAHs were lost, but lower volatility NPAHs, hopanes and steranes showed negligible changes. Storing wrapped filters and extracts at 4 °C for up to one month did not lead to significant losses, but storing extracts for five months led to significant losses of PAHs and NPAHs; hopanes and steranes demonstrated greater integrity. These results suggest that even relatively brief filter conditioning periods, needed for gravimetric measurements of PM mass, and extended storage of filter extracts can lead to underestimates of SVOC concentrations. Thus, SVOC sampling and analysis protocols should utilize stringent criteria and performance checks to identify and limit possible biases occurring during filter and extract processing.

PAHs, nitro‐PAHs, hopanes, and steranes in lake trout from Lake Michigan

“…The carrier gas was He (1.5 mL/min, pressure of 37.4 kPa, average velocity of 31 cm/s), and the mass spectrometry reagent gas was ultra–high-purity methane. Temperature programs for the SVOC analyses have been described previously [30]. The mass spectrometry detector was operated in electron impact mode for PAHs, hopanes, and steranes.…”

New Methodology for Quantifying Polycyclic Aromatic Hydrocarbons (PAHs) Using High-Resolution Aerosol Mass Spectrometry

“…P-MIP analysis depends first on identifying target molecular ions for PAH species within the mass spectra. To isolate the contributions of specific PAH-related ions in the observed signal, a list of target molecular ions was developed from three sets of sources: (1) PAH-related molecular ions that have been identified in previous AMS measurement studies (Alfarra 2004;Aiken et al 2007;D zepina et al 2007); (2) PAHs that have been prominently linked to diesel emissions (Frenich et al 2010;Pandey et al 2011;Alkurdi et al 2013;Huang et al 2013) or to particularly strong health impacts (US EPA 1992; International Agency for Research 2013); and (3) PAHs that are consistent with ions that are prominent in one or more mass spectra from the LRRI case study experiments. Table 1 lists the 53 target PAHs identified by this process, which include molecular ions from 15 UnSubPAHs, 12 MPAHs, 15 OPAHs, 7 NPAHs, and 4 APAHs.…”

“…Diesel fuel and exhaust contain higher PAH concentrations than gasoline fuel or exhaust (Mi et al 2001;Alkurdi et al 2013). Beyond the effects of the fuel, prior work has also suggested that PAH content in exhaust may be affected by engine load (Huang et al 2013), cold starts (Zielinska et al 2004;Sodeman et al 2005), and engine oil age (Zielinska et al 2004;Fujita et al 2007).…”

“…NPAHs, OPAHs, APAHs, and MPAHs have demonstrated mutagenic effects and genotoxicity, pointing towards their toxicological significance to human health, though they are typically found at lower concentrations than the analogous UnSubPAHs by 1-2 orders of magnitude (Vincenti et al 1996;Bezabeh et al 1997;Bhatia et al 1998;Layshock et al 2010;Huang et al 2013). Their lower concentrations compared to UnSubPAHs make them more difficult to measure and quantify.…”

Effects of fuels, engine load and exhaust after-treatment on diesel engine SVOC emissions and development of SVOC profiles for receptor modeling

“…Injector and detector temperatures were 275 °C and 280 °C, respectively. Temperature programs have been described previously (Huang et al, 2013). The carrier gas was helium (flow of 1.5 mL/min, pressure of 37.4 kPa, average velocity of 31 cm/s), and the reagent gas for the MS detector, operated in the negative chemical ionization (NCI) mode for NPAHs, was ultra high purity methane.…”