Comprehensive characterization of the particulate IVOCs and SVOCs from heavy-duty diesel vehicles using two-dimensional gas chromatography time-of-flight mass spectrometry

Abstract. Tailpipe emissions from three heavy-duty diesel vehicles (HDDVs), complying with varying emission standards and installed with diverse aftertreatment technologies, are collected at a certified chassis dynamometer laboratory. The HDDV-emitted intermediate-volatility and semi-volatile organic compound (I/SVOC) emission and the gas-particle partitioning of the I/SVOCs are investigated. Over four thousand compounds are identified and grouped into twenty-one categories. The dominant compound groups of particulate I/SVOCs are alkanes and phenolic compounds. For HDDVs without aftertreatment devices, i.e., diesel oxidation catalyst (DOC) and diesel particulate filter (DPF), the emitted I/SVOCs partition dramatically into the gas phase (accounting for ~ 93 % of the total I/SVOC mass), with a few exceptional categories: hopane, 4-ring polycyclic aromatic hydrocarbons (PAH4rings), and PAH5rings. For HDDVs with DPF and DOC, the particulate fractions are reduced to a negligible level, i.e., less than 2 %. Nevertheless, 50 % of the total 2-ring PAH mass is detected in the particle phase, which is much higher than the high-molecular-weight PAHs, arising from the positive sampling artifact of quartz filter absorbing organic vapours. The positive sampling artifact of quartz filter absorbing organic vapors is clearly observed and uncertainties are discussed and quantified. Particulate I/SVOCs at low-speed, middle-speed, and high-speed phases are collected and analysed separately. EF distribution of the speciated OA on a two-dimensional volatility basis set (2D-VBS) space reveals that the fractions of OA with O : C (oxygen to carbon) ratio > 0.3 (0.4, 0.5) are 18.2 % (11.5 %, 9.5 %), 23 % (15.4 %, 13.6 %), and 29.1 % (20.6 %, 19.1 %) at low-speed, middle-speed, and high-speed stages. The results help to resolve the complex organic mixtures and trace the evolution of OA.