Chemical characteristics of particulate matter emitted from a heavy duty diesel engine and correlation among inorganic and PAH components

This study investigated the chemical characteristics of the particulate matter emitted from a diesel engine (Diesel Particulate Matter, DPM) and the correlations between polycyclic aromatic hydrocarbons (PAHs) species as well as between PAHs and inorganic elements in DPM through dynamometer testing. There were six sets of speed-load conditions. Engine speeds varied from 1000 to 1600 rpm, while engine loadings were 60% and 100% of engine load. Total carbon accounted for 82 ± 9% of the total DPM mass, followed by 15 inorganic elements (6.3 ± 1.4%), and 12 particle-phase PAHs (p-PAHs) (0.034 ± 0.013%). The three-ring and four-ring p-PAHs constituted 54 ± 25% and 27 ± 19% of the total p-PAHs mass, respectively, much higher than that of two-ring p-PAHs (11 ± 10%) and five-ring (9 ± 5%). The fluoranthene/(fluoranthene + pyrene) and benzo[a]anthracene/(benzo[a]anthracene + chrysene) ratios were below or in the lower range of ambient ratios indicative of diesel vehicle emissions observed in previous studies with on-board testing system. Strong positive correlation (r > 0.99, p < 0.05) among isomeric p-PAHs (between phenanthrene and anthracene, as well as among benzo[a]pyrene, benzo[b]fluoranthene and benzo[k]fluoranthene) were observed. Furthermore, the weight percentages of some inorganic elements and p-PAHs in total DPM were correlated.