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

Abstract

Abstract. 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 (EF PM ) from excavator and truck emissions were 829 ± 806 and 498 ± 234 mg kg −1 fuel, respectively. EF PM and PM constituents were significantly affected by fuel quality, operational mode, and emission standards. A significant correlation (R 2 = 0.79, p < 0.01) was found between EF PM for excavators and the sulfur contents in fuel. The highest average EF PM for working excavators was 904 ± 979 mg kg −1 fuel as a higher engine load required in this mode. From pre-stage 1 to stage 2, the average EF PM for excavators decreased by 58 %. For trucks, the average nonhighway EF PM at 548 ± 311 mg kg −1 fuel was higher than the highway EF PM at 497 ± 231 mg kg −1 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 EF PM 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 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.

Chemical Compositions of PM2.5 Emitted from Diesel Trucks and Construction Equipment

“…For example, Zhang et al (2015) measured the real-world PM 2.5 emissions of HDDTs (pre-stage and stage I) using a portable emissions measurement system (PEMS), reporting that carbon fractions contributed 89% of PM 2.5 mass. Cui et al (2017) reported that OC and EC proportions ranged from 18.1 to 84.6% in PM measured from five trucks and six excavators. The relationship between EC and OC concentrations can be used to evaluate the sources of carbonaceous aerosols (Tao et al 2014;Turpin and Huntzicker 1995) In vehicle exhaust research, it can also indicate the effectiveness of the diesel oxidation catalysts (DOC), which remove the OC fraction via oxidation (Cheng et al 2015).…”

“…The measured masses were 44.9 ± 7.9, 59.3 ± 12.8, 45.8 ± 11.2% of PM 2.5 for tested LDDTs, HDDTs and construction equipment, respectively. The discrepancy of mass fractions may be attributed to the engine model, fuel quality, unmeasured species and analytical errors such as distribution of OC and EC by the TOR method (Cui et al 2017;Chow et al 2015). As shown in Fig.…”

“…Previous studies have shown that mobile sources contributed 12.6-44% to PM pollution, which is predominantly from diesel exhaust (Huang et al 2015;Cai et al 2016;Cui et al 2017;Reff et al 2009). In China, diesel vehicles are responsible for 99% of vehicle emissions although they only account for 15.2% of on-road vehicles .…”

“…The fingerprints of diesel exhaust are needed as input data for receptor models and source-oriented models Simon et al 2010). Diesel exhaust emissions have been investigated by different approaches, including tunnel tests, roadside tests, classic dynamometer measurements and on-road tests using portable emission measurement system (PEMS) Chen et al 2017;Cheng et al 2010;Cui et al 2016Cui et al , 2017Wang et al 2003;Wu et al 2016). For example, USEPA SPECIATE database contains speciation profiles for a comprehensive list of emission sources.…”

“…Cui et al (2016) characterized PM 2.5 emitted in two urban tunnels in Yantai and drafted the source profiles of gasoline and diesel-fueled vehicles. Cui et al (2017) tested non-road and on-road diesel vehicles of a wide range of emission standards and operation modes (pre-stage 1 to stage 2; China II to China IV) using an improved PEMS.…”