Particle- and gas-phase PAHs toxicity equivalency quantity emitted by a non-road diesel engine with non-thermal plasma technology

Polycyclic aromatic hydrocarbon (PAH) toxicity equivalency quantity (TEQ, denoted by benzo(a)pyrene equivalent (BaP_eq) concentration) is more meaningful when evaluating the influence of non-road diesel engines PAH toxicity on environment. Particle- and gas-phase PAH BaPeq concentrations were calculated based on gas chromatography-mass spectrometer (GC-MS) results and toxic equivalency factors. A non-thermal plasma (NTP) reactor was applied to a non-road diesel engine to decrease PAH TEQ content. Only the gas-phase Nap BaP_eq concentration increased slightly with the action of NTP at three different generator power outputs. BaP dominated the BaP_eq concentration for 15 samples with, and without NTP except in the gas-phase at 4 kW. Almost all medium molecular weight (MMW) and high molecular weight (HMW) PAH TEQs increased for particle- and gas-phases at 3 kW power output compared to 2 kW without the use of NTP. Particle-phase Nap, Acp, and AcPy (low molecular weight, LMW) TEQ were under detection at 3 and 4 kW, while gas-phase BkF, IND, DBA, and BghiP (HMW) concentrations were below the limits of detection. The most abundant PAH TEQ compounds were MMW and HMW PAHs for gas- and particle-phase while they were BaA, CHR, BbF, BaP, and IND for PM aggregation. The total BaP_eq emission factors were 15.1, 141.4, and 46.5 μg m⁻³ at three engine loads, respectively. Significant BaP_eq concentration percentage reduction was obtained (more than 80 and 60 %) with the use of NTP for particle- and gas-phases. A high TEQ content was observed for PM aggregation (38.8, 98.4, and 50.0 μg kg⁻¹) which may have caused secondary PAH toxicity emissions. With the action of NTP, the breakup of MMW and HMW into LMW PAHs led to reduction of some PAH concentrations.