[Emission Characteristics of Polycyclic Aromatic Hydrocarbons and Their Derivatives from Exhaust PM_2.5 of China Ⅴ and China Ⅵ Diesel Trucks Based on On-road Measurements].

Exhaust emissions from diesel vehicles are one among the major sources of PM_2.5 and polycyclic aromatic hydrocarbons （PAHs） emitted by diesel vehicles are of concern due to their notable impact on health. To better understand the toxicity of diesel vehicle emissions, we used an on-road sampling system to collect PM_2.5 samples from four light-duty diesel trucks （LDDTs） and two heavy-duty diesel trucks （HDDTs） under the China Ⅴ and China Ⅵ emission standard. Further, 16 polycyclic aromatic hydrocarbons （pPAHs）, 18 nitro-polycyclic aromatic hydrocarbons （NPAHs）, and five oxygenated polycyclic aromatic hydrocarbons （OPAHs） were analyzed by GC-MS, and mileage-based emission factors were calculated. The results showed that a decrease in emission factors （EFs） of PM_2.5-bound pPAHs, NPAHs, and OPAHs was observed with improved emission standards. The EFs of pPAHs, NPAHs, and OPAHs from LDDTs of the China Ⅵ emission standard were （217.92±109.92）, （5.21±2.51）, and （10.74±5.99） μg·km^-1, respectively, which were reduced by 63%, 55%, and 66% compared to those with China Ⅴ. Due to incomplete combustion, higher emission factors （EFs） were observed for HDDTs than for LDDTs with the same emission standard （China Ⅴ）. The EFs of PM_2.5-bound pPAHs, NPAHs, and OPAHs emitted from the diesel vehicles were higher with increasing mileages, which was related to increased engine wear. Phenanthrene and fluorenone were the most abundant pPAHs and OPAHs components, while 5-nitro acenaphthene and 2-nitro fluoranthrene + 3-nitro fluoranthrene were the major NPAHs components. The benzo （a） pyrene equivalent toxicity （BaPeq） of pPAHs, NPAHs, and OPAHs of China Ⅵ vehicles was significantly reduced compared to that of China Ⅴ vehicles, which might be related to improvements in exhaust technology. The emission results showed that the diesel vehicles of the three largest-amount models in Luohe City emitted 1 965 kg pPAHs, 33 kg NPAHs, and 105 kg OPAHs, respectively. The emissions of PAHs and their derivatives were mainly from the China V heavy-duty diesel vehicles, suggesting the need to strengthen the control of this model. The results of this study will be valuable for formulating more stringent regulations and emission control technologies for PAHs and their derivatives and for the protection of human health.