The significant effects of loading mass on emissions of intermediate and semi-volatile volatility organic compounds from diesel trucks

Abstract

Diesel vehicles are an important emission source of intermediate-volatility and semi-volatile organic compounds (I/SVOCs). Previous studies rarely reported the impacts of loading mass on diesel I/SVOC emissions. Here, we applied a non-targeted screening characterization method to characterize detailed I/SVOC emissions of two diesel trucks by using a two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-ToF-MS), and explored the impact from various loading mass conditions. The results indicated that higher loading mass could reduce total I/SVOC emissions of tested trucks, which was consistent with the trend in organic carbon (OC) but opposite to that of elemental carbon (EC). The chemical composition was also affected by loading mass. Saturated hydrocarbon compounds tend to account for a higher fraction of the total I/SVOCs under empty loading mass conditions, which were probably emitted due to incomplete combustion, compared with the chemical composition of diesel fuels. The fractions of unsaturated hydrocarbons and oxygenated volatile organic compounds (OVOCs) increased with higher loading mass, suggesting that thermal decomposition and oxidation processes become more important. Furthermore, we mapped the I/SVOCs into the two-dimensional volatility basis set (2D-VBS) according to loading mass conditions, which served as the input profiles for further atmospheric modeling of secondary organic aerosol (SOA).