Exhaust and evaporative volatile organic compounds emissions from vehicles fueled with ethanol-blended-gasoline.

By 2020, China has implemented the use of 10% ethanol-blended-gasoline (E10), which is expected to notably impact vehicular volatile organic compounds (VOCs) emissions. The adoption of E10 reduced certain emissions but raised concerns with about more reactive oxygenated volatile organic compounds (OVOCs). This study aimed to evaluate the impact of E10 on the total VOCs emissions from both exhaust and evaporative emissions by conducting tests on the CHINA V (or CHINA VI) light-duty gasoline vehicles (LDGVs) using 0% ethanol blended gasoline (E0) and E10. E10 reduces VOCs emissions in the exhaust, and reduces the ozone and secondary organic aerosol generation potential of VOCs in the exhaust, as evidenced by the lower emission factors (EFs), ozone formation potentials (OFPs) and secondary organic aerosol formation potential (SOAFPs) in the CHINA V LDGVs. Evaporative emissions showed differences in emitted VOCs, with lower EFs, OFPs and SOAFPs for the CHINA V LDGVs fueled with E10. The CHINA VI LDGVs also exhibited reduced EFs, OFPs and SOAFPs. These findings highlight the environmental benefits of E10 in the CHINA VI-compliant LDGVs; however, the effectiveness of the earlier CHINA V standard vehicles requires further evaluation.

The contributions of non-methane hydrocarbon emissions by different fuel type on-road vehicles based on tests in a heavily trafficked urban tunnel.

Automobile exhaust is a major source of volatile organic compounds (VOCs) in metropolitan areas, yet it is difficult to accurately determine the contributions of different types of on-road vehicles. Tunnel tests are an effective way to measure real-world vehicle emissions, and the data collected are also suitable for receptor modeling to analyze the contributions of non-methane hydrocarbons (NMHCs) from different types of vehicles, as the closed environment ensures good mixing and minimal aging. In this study, tunnel tests were conducted inside a heavily trafficked city tunnel in Guangzhou in south China, and the positive matrix factorization (PMF) model was applied to the inlet-outlet incremental NMHC data. The results revealed that gasoline vehicles (GVs), Liquefied Petroleum Gas vehicles (LPGVs), and diesel vehicles (DVs) were responsible for 39 %, 45 % and 16 % of NMHCs, and 52 %, 23 %, and 24 % of the ozone formation potentials, respectively. LPGVs were the largest contributor of (56 %) alkanes, and GVs were the largest contributor of aromatics (61 %) and C2-C4 alkenes (55 %). With the video-recorded traffic counts the emissions of different fuel types are further compared on a per-vehicle-per-kilometer basis, and the results reveal that LPGVs and GVs were comparable in the OFPs of NMHCs emitted per kilometer, while on average a DV emitted 2.0 times more NMHCs than a GV with 2.4 times more OFPs. This study highlights substantial contribution of reactive alkenes and aromatics by DVs and the benefits of strengthening diesel exhaust control in terms of preventing ozone pollution.

Comparison of CO2, NOx, and VOCs emissions between CNG and E10 fueled light-duty vehicles.

In China, natural gas (NG) is the main vehicle fuel after gasoline and diesel, and the number of NG vehicles ranks first in the world. At present, there are many studies on the conventional gaseous pollutants and particulate matter of NG vehicles, but very few studies on their VOCs. In this study, the chassis dynamometer is used to test CNG/E10 bi-fuel light-duty vehicles, analyze the advantages of CNG in CO2, fuel thermal efficiency, and cost, and discuss its disadvantages in NOx emission. Most importantly, the emission characteristics and ozone formation potential of VOCs in the exhaust of CNG vehicles were analyzed in the study. Compared with E10, CNG fuel can reduce CO2 emission by about 20 %, improve thermal efficiency by about 13 %, and save fuel costs by about 50 %. However, it will increase NOx and NO2 emissions by about 10 % and 13 % respectively. As for VOCs, the emission factor of VOCs from CNG fuel is about 54 % of E10 fuel. The VOCs group with the highest proportion in the exhaust of CNG-fueled vehicles is alkanes, >80 %. while the alkanes and alkenes with the highest proportion in E10 fuel are 30 % and 23 % respectively. C2 VOCs emitted by CNG account for >70 %, while C2 VOCs emitted by E10 are <60 %, followed by C4 VOCs, about 10 % - 30 %. The OFPs of VOCs in CNG exhaust is about 13.7 % of E10. Alkenes contribute the most to ozone, and the OFPs of alkenes in CNG and E10 vehicle exhaust accounts for about 55.3 % and 78.8 % of TVOCs respectively. The results of this study are helpful to improve people's understanding of the environmental value of using NG vehicles.

[Pollution Characteristics and Emission Factors of VOCs from Vehicle Emissions in the Tianjin Tunnel].

The pollution characteristics and emission factors (EFs) of the volatile organic compounds (VOCs) of vehicles were investigated using the tunnel test method on weekdays and weekends in the Wujinglu Tunnel in Tianjin, China. Gas samples in the tunnel were collected with 3.2 L stainless steel canisters and 99 VOCs species were analyzed by gas chromatography-mass spectrometry (GC-MS). The concentration levels, variation characteristics, and EFs of the VOCs were analyzed. The ozone formation potentials (OFPs) and secondary organic aerosol formation potentials (SOAFPs) of the VOCs in the tunnel were calculated. Moreover, a comparison of the study results with current literature was conducted. The total concentrations of VOCs at the inlet and midpoint are (190.85±51.15) µg·m-3 and (257.44±62.02) µg·m-3, respectively. The total EFs are (45.12±10.97) mg·(km·veh)-1 and the EFs for alkanes, alkenes, alkynes, aromatics, halocarbons, and oxygenated volatile organic compounds (OVOCs) are (22.79±7.15), (5.04±1.20), (0.78±0.34), (9.86±2.81), (0.26±0.17), and (6.25±2.27) mg·(km·veh)-1, respectively. They are notably smaller than the values obtained in a previous test in 2009. Isopentane, toluene, ethylene, methyl tert-butyl ether (MTBE), and ethane were the top five species among the VOC EFs. The ratios of methyl tert-butyl ether/benzene (MTBE/B) and methyl tert-butyl ether/toluene (MTBE/T) are 1.07 and 0.77, respectively. This implies that the contribution of evaporative emissions from vehicles to VOCs emissions cannot be ignored. The OFPs and SOAFPs in the tunnel are (145.50±37.85) and (43.87±12.75) mg·(km·veh)-1, respectively. Compared with the test in 2009, the OFPs and SOAFPs are 94.23% and 90.88% smaller, respectively. The sharp decrease of the OFPs and SOAFPs is closely related to stricter emission standards and the upgrade of oil products.