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Rural vehicles (RVs) could contribute significantly to on-road vehicle emissions, especially PM2.5 and NOx; This study tested 10 three-wheeled (3-W) RVs and 8 four-wheeled (4-W) RVs on real roads in Hebei Province using a portable emissions measurement system to investigate gaseous concentrations (CO, NOx, and HC) and the carbonaceous composition (EC and OC) of the PM2.5 emitted. The results showed that the tightening emission standards resulted in the CO, HC, and PM2.5 emissions for China II RVs decreasing, but may increasing NOx emission for China II 3-W RVs. The emission level of PM2.5 for China II RVs is between Euro II LDDTs and Euro III LDDTs. The emission factors (EFs) of OC and EC for 3-W RVs were 0.035 ± 0.019 and 0.058 ± 0.055 g km-1, respectively, and for 4-W RVs, they were 0.046 ± 0.018 and 0.031 ± 0.024 g km-1, respectively. The carbonaceous component represents the main fraction of PM2.5 emitted from RVs (84.6% and 87.2% for 3-W and 4-W RVs, respectively), similar to other diesel vehicles. The average distance-based EFs of OC increased with increasing vehicle size (3-W RVs < 4-W RVs). The CO2-based EFs of OC and EC decreased with increasing vehicle mass, consistent with the emission laws of light-, medium-, and heavy-duty diesel trucks. Driving cycles that included more cruise mode and less creep mode resulted in a higher average EC/OC ratio (1.57) for 3-W RVs than for 4-W RVs (0.63), and resulted in the average EC/OC ratios for both types of RV were lower than for highway LDDTs.

To study the formation process of secondary organic aerosols (SOA) in a vehicle exhaust plume near the exhaust gas discharge outlet, a new multipoint sampling system was established. The system has five sampling heads and includes a particulate matter multi-channel film sampling system, a CO2/CO analyzer system, a volatile organic compound (VOC) sampling system, a particulate matter real-time analyzer system, and sensor interfaces. The vehicle exhaust near the exhaust nozzle can be sampled at multiple locations simultaneously using the new multipoint sampling system. Additionally, the system can be used to measure and analyze variations in the fine particulate matter, including the carbonaceous and ionic components, and organic compounds in the plume near the exhaust nozzle. This paper introduces the construction and application of the multipoint sampling system. The motor vehicle exhaust multipoint sampling system is reliable and can accurately capture the characteristics of the exhaust plume near the discharge outlet area. Changes in the CO2 concentration were used to determine whether exhaust was accurately collected at the sampling points. The relationship between the dilution rate and distance was calculated on the basis of on-road test results using the following equation: DR = 21.4X1.16. This equation can be used for modeling purposes, especially in comparisons of model results and observations and in the evaluation of dispersion models.

With the increasingly strict supervision of road mobile sources and the ongoing progress in research, the relative contribution of non-road mobile sources to the total emissions has grown in prominence. Therefore, accurately estimating the emissions from non-road mobile sources is essential to developing effective policies for improving air quality. Hence, this study established an inventory of nine air pollutants, viz., CO, NOx, HC, PM2.5, PM10, BC, OC, VOCs, and SO2, emitted by four types of non-road mobile sources, viz., construction machinery, agricultural machinery, vessels, and diesel locomotives, in China for the period 1990–2017. These emissions increased continually from 1990 till 2014, after which they decreased before increasing again during 2017. With the exception of SO2, which primarily originated from vessels, agricultural machinery accounted for the largest proportion of emissions for all of the pollutants, contributing 67.7% (1472.5 Gg) and 46.1% (2170.4 Gg) of the total CO and NOx from non-road mobile sources, respectively. Additionally, the spatial distribution of the investigated pollutants revealed high concentrations on the North China Plain and in the Southeast China coastal area. Our findings demonstrate the necessity of improving the registration system for non-road mobile sources as well as the urgency of obtaining accurate emission factors for them by further researching their emission characteristics.

To study the emission characteristics of carbonyl compounds for in-use diesel vehicles on real roads, nine in-use heavy-duty diesel trucks (HDDTs) representing different emission standards from China 0 to China 3 were tested on roads in Xiamen using an on-board carbonyl compound sampling system with a 2,4-DNPH cartridge. High-performance liquid chromatography (HPLC) was used to quantify the carbonyl compound emission factors. In total, 10 carbonyl compounds were detected for all the tested vehicles in this work. Formaldehyde, acetaldehyde and propanal were the three largest contributors of carbonyl emissions, accounting for 47.9%, 21.0% and 9.9% of the total carbonyls, respectively. The emission standards had a significant effect on the emission factors and profiles of the carbonyl compounds from the test vehicles. The total emissions of carbonyls from the test vehicles with China 0, China 1, China 2 and China 3 emission standards were 318.4, 232.8, 108.1 and 88.8 mg/km, respectively. The relative contribution of formaldehyde to the total carbonyl emissions increased with increasing stringency of the emission standards. Driving patterns also affected the vehicular carbonyl emissions. The total carbonyl emissions under highway driving cycles were lower than those under non-highway driving cycles. In addition, the ozone-formation potential of the carbonyls from the tested diesel vehicles was analyzed. This work represents a preliminary step in measuring carbonyl emission characteristics using portable emission measurement systems (PEMS). More attention should be paid to carbonyl emissions from HDDTs.