PARTICULATE-PHASE COMPOSITIONS CHARACTERISTICS FROM DIESEL BUSES RETROFITTED WITH AFTERTREATMENT OPERATING ON REAL-WORLD ROAD

摘要

Concerns about effects of particulate control technologies applied on in-use diesel vehicles on atmospheric environment prompted more measurements and analytical methods needed to assess environmental implication. An on-board particulate sampling and measurement system were used to test the particulate-phase compositions from the diesel buses retrofitted with catalyzed diesel particulate filter (CDPF) or a diesel oxidation catalyst coupled with a CDPF (DOC & CDPF) under real-world road, operating on a typical urban circuit in Shanghai of China. Based on fuel basis emission factors, CDPF and DOC & CDPF were most effective in reducing 2-, 3- and 4-ring polycyclic aromatic hydrocarbons (PAHs), above 90%, followed as to 5-ring PAHs, ～70%. The aftertreatments showed significant effective in reducing the Benzo[a]pyrene equivalent (B[a]P_(eq)) of 3-ring PAHs, while presenting lower reduction rate for the B[a]P_(eq) of 4- and 5-ring PAHs. The B[a]P_(eq) with higher toxic equivalent factor (TEF) dominated in total B[a]P_(eq) even the buses with aftertreatments. DOC & CDPF had slight advantage in reducing PAHs and their toxicity than the sole CDPF. The reduction rates of organic carbon (OC) and elemental carbon (EC) emissions factors were ～84% and ～98%, with OC/EC ratio ranging from ～1 to ～11. The particle number, mass and surface area factors were reduced by the aftertreatments, with reductions of up to 95%. According to particles diameter classification, the aftertreatments slightly influenced the percentage distributions. Whatever the buses without or with aftertreatments, it's found that the particles of D_P≤0.05 μm dominate in the total PN factor, the particles of 0.587% in the total PM factor, and the particles of 0.0592% in the total PSA factor, which are important in determining and increasing particulate toxicity.