[Exhaust Emission Characteristics of Typical Alkanes from Heavy-Duty Diesel Vehicles Based on a Portable Emission Measurement System].

: The on-road emissions of typical alkanes from 11 heavy-duty diesel vehicles with different emission standards (from China Ⅰ to China Ⅳ) were tested using a portable emission measurement system(PEMS) and quantified by gas chromatography-mass spectrometry (GC-MS). Our aim was to analyze the emission characteristics of typical alkanes in heavy-duty diesel vehicle exhaust. The results show that the emission standard significantly affected the emission factors (EFs) of n-alkanes and hopanes. Vehicles with higher emission standards had lower EFs. Compared with China Ⅰ vehicles, the total EFs of n-alkanes, 17α(H),21β(H)-C30 hopane (C30-hopane), and 22S- and 22R-17α(H),21β(H)-homohopane (22S-C31 and 22R-C31 homohopane) from China Ⅳ vehicles were significantly reduced by 72.23%, 64.95%, 70.78%, and 74.68%, respectively. The peak carbon numbers of gaseous n-alkanes were 17 to 18, while they were 18 to 21 in particulate n-alkanes. The 22S-C31 homohopane/(22S-C31 homohopane + 22R-C31 homohopane) ratios ranged from 0.46 to 0.56, with an average of 0.50, which conform to the characteristics of hopanes in petroleum. The total EFs of n-alkanes had a good linear relationship with the total EFs of C30-hopane, and the R2 was 0.9268. Furthermore, the driving conditions had a great influence on the emissions of n-alkanes and hopanes. Specifically, the EFs of n-alkanes and hopanes on non-highway roads were 1.69 to 2.42 times greater than those on highways.