Measurement of PM and its chemical composition in real-world emissions from non-road and on-road diesel vehicles

摘要

With the rapid growth in the number of both non-road and on-road diesel vehicles, the adverse effects of particulate matter (PM) and its constituents on air quality and human health have attracted increasing attentions. However, studies on the characteristics of PM and its composition emitted from diesel vehicles are still scarce, especially under real-world driving conditions. In this study, six excavators and five trucks that provided a wide range of emission standards and operation modes were tested, and PM emissions and their constituents – including organic carbon (OC), elemental carbon (EC), water-soluble ions (WSIs), elements, and organic species like polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and hopanes – as well as steranes were analyzed and characterized. The average emission factors for PM (EFsubPM/sub) from excavator and truck emissions were 829?±?806 and 498?±?234?mg?kgsup?1/sup fuel, respectively. EFsubPM/sub and PM constituents were significantly affected by fuel quality, operational mode, and emission standards. A significant correlation (iR/isup2/sup?=?0.?79, ip/i?&?0.?01) was found between EFsubPM/sub for excavators and the sulfur contents in fuel. The highest average EFsubPM/sub for working excavators was 904?±?979?mg?kgsup?1/sup fuel as a higher engine load required in this mode. From pre-stage?1 to stage?2, the average EFsubPM/sub for excavators decreased by 58?%. For trucks, the average non-highway EFsubPM/sub at 548?±?311?mg?kgsup?1/sup fuel was higher than the highway EFsubPM/sub at 497?±?231?mg?kgsup?1/sup fuel. Moreover, the reduction rates were 63.5 and 65.6?% when switched from China?II and?III to China?IV standards, respectively. Generally, the PM composition emitted from excavators was dominated by OC (39.?2?±?21.?0?%) and EC (33.?3?±?25.?9?%); PM from trucks was dominated by EC (26.?9?±?20.?8?%), OC (9.?89?±?12?%), and WSIs (4.?67?±?5.?74?%). The average OC?∕?EC ratios for idling and working excavators were 3 to 4 times higher than those for moving excavators. Although the EFsubPM/sub for excavators and trucks was reduced with the constraint of regulations, the element fractions for excavators increased from 0.49?% in pre-stage?1 to 3.03?% in stage?2, and the fraction of WSIs for the China?IV truck was 5 times higher than the average value of all other-level trucks. Furthermore, as compared with other diesel vehicles, wide ranges were found for excavators of the ratios of benzo[a]anthracene?∕?(benzo[a]anthracene?+?chrysene) (0.26–0.86), indeno[1,2,3-cd]pyrene?∕?(indeno[1,2,3-cd]pyrene?+?benzo[ghi]perylene) (0.20–1.0), and fluoranthene?∕?(fluoranthene?+?pyrene) (0.24–0.87), which might be a result of the complex characteristics of the excavator operation modes. A comparison of our results with those in the literature revealed that on-board measurement data more accurately reflect actual conditions. Although the fractions of the 16 priority PAHs in PM from the excavator and truck emissions were similar, the equivalent concentrations of total benzo[a]pyrene of excavators were 31 times than that for trucks, implying that more attention should be paid to non-road vehicle emissions.