Diesel Vehicle Emissions Research Articles

Polycyclic Aromatic Hydrocarbons (PAHs) in household dust: The association between PAHs, Cancer Risk and Sick Building Syndrome

In this study, indoor dust samples were collected from 40 houses in Shiraz; Iran, and analyzed to determine 16 Polycyclic Aromatic Hydrocarbons (PAHs) using Gas chromatography–mass spectrometry (GC-MS). The study participants completed the questionnaires consisting of a series of questions for collecting information about symptoms of sick building syndrome and parameters affecting PAHs concentrations (including traffic congestion in the area, floor level, house renovation, building age, etc.). The total PAHs concentrations in the settled dust samples ranged from 31 to 453 ngg−1 so that, phenanthrene, naphthalene and fluoranthene were the predominant congeners. Diagnostic ratios and principal component analysis (PCA) indicated the predominance of vehicular (especially diesel vehicle emissions) and cooking emissions, as the two major sources of PAHs, in indoor dust. The results of statistical analysis showed a significant association between the total PAHs concentrations and SBS symptoms (headache, skin dryness, itching, and inflammation). In addition, based on health risk assessment, the mean ILCR (Incremental Lifetime Cancer Risk) value was reported to be 3.85 × 10−5 for adults and 4.36 × 10−5 for children, indicating potential cancer risk as a result of exposure to household dust containing PAHs. The findings of this study can provide useful information to improve the quality of the indoor environment of houses.

Optimizing model parameters of artificial neural networks to predict vehicle emissions

This paper presents a novel approach to predict carbon dioxide (CO2), nitrogen oxides (NOx), and carbon monoxide (CO) emissions of diesel vehicles using artificial neural network (ANN), which offer high degrees of accuracy and practicality. Six operating parameters (velocity, engine speed, engine torque, engine coolant temperature, fuel/air ratio, and intake air mass flow) collected through on-board diagnostic interface were used as predictors of exhaust emissions. The importance of each parameter to the emission predictions were comprehensively analyzed by comparing the coefficient of determination, root mean square error, cumulative emissions, and instantaneous emission rates. The emission prediction accuracy of ANN tends to increase as more parameters were considered as model inputs at the same time. However, the level of accuracy improvement depends on the input parameters. For CO2 emissions, engine torque and fuel/air ratio were good predictors for achieving high prediction accuracy. The relative importance of intake air mass flow rate and fuel/air ratio was high for NOx and CO predictions, respectively. In addition, the emission prediction accuracy of ANN depends on the vehicle type (Euro 5, Euro 6b, Euro 6d-temp). The emission prediction accuracy of vehicles equipped with after-treatment devices (selective catalytic reduction and lean NOx trap) was lower than that of vehicles without after-treatment devices.

Effects of waste-cooking-oil biodiesel blends on diesel vehicle emissions and their reducing characteristics with exhaust after-treatment system

The waste-cooking-oil biodiesel is proven to be a clean alternative fuel, its effect on the vehicle emissions at different driving conditions needs further quantitative evaluation, especially with the exhaust after-treatment. The objective of this study is to quantify the effect of waste-cooking-oil biodiesel on the gaseous and particulate emissions from an urban bus at different driving conditions, and with a combination of diesel oxidation catalyst (DOC) and a catalyzed diesel particulate filter (CDPF) after-treatment. Results showed that the emissions depended on the driving conditions, vehicle acceleration and high speed increased the emissions. The biodiesel blends produced a reduction in the carbon monoxide (CO), total hydrocarbon (THC), particle number (PN) and particle mass (PM) emissions, but an increase in the carbon dioxide (CO2) and nitrogen oxide (NOx) emission, and this changing trend increased with not only the biodiesel blending ratio but also the vehicle speed and acceleration. The particle size distribution remained bimodal logarithm distribution after using the biodiesel, and more accumulation mode particles reduced compared with nucleation mode ones, increasing the proportion of nucleation mode particles. The after-treatment system composed of DOC and CDPF could reduce 58.0% of the CO and 53.1% of the THC when using B10 (10% biodiesel and 90% diesel by volume), and the reduction effect was enhanced with the increase of the biodiesel blending ratio, also with the increase of speed and acceleration. The after-treatment system reduced more than 99% of the PN and 94% of the PM, achieving excellent reduction effects, independent of fuel type and driving conditions.

Characteristics and Sources of Volatile Organic Compounds in the Nanjing Industrial Area

In this study, 56 volatile organic compounds species (VOCs) and other pollutants (NO, NO2, SO2, O3, CO and PM2.5) were measured in the northern suburbs of Nanjing from September 2014 to August 2015. The total volatile organic compound (TVOC) concentrations were higher in the autumn (40.6 ± 23.8 ppbv) and winter (41.1 ± 21.7 ppbv) and alkanes were the most abundant species among the VOCs (18.4 ± 10.0 ppbv). According to the positive matrix factorization (PMF) model, the VOCs were found to be from seven sources in the northern suburbs of Nanjing, including liquefied petroleum gas (LPG) sources, gasoline vehicle emissions, iron and steel industry sources, industrial refining coke sources, solvent sources and petrochemical industry sources. One of the sources was influenced by seasonal variations: it was a diesel vehicle emission source in the spring, while it was a coal combustion source in the winter. According to the conditional probability function (CPF) method, it was found that the main contribution areas of each source were located in the easterly direction (mainly residential areas, industrial areas, major traffic routes, etc.). There were also seasonal differences in concentration, ozone formation potential (OFP), OH radical loss rate (LOH) and secondary organic aerosols potential (SOAP) for each source due to the high volatility of the summer and autumn temperatures, while combustion increases in the winter. Finally, the time series of O3 and OFP was compared to that PM2.5 and SOAP and then they were combined with the wind rose figure. It was found that O3 corresponded poorly to the OFP, while PM2.5 corresponded well to the SOAP. The reason for this was that the O3 generation was influenced by several factors (NOx concentration, solar radiation and non-local transport), among which the influence of non-local transport could not be ignored.

Diesel vehicle emission accounts for the dominate NOx source to atmospheric particulate nitrate in a coastal city: Insights from nitrate dual isotopes of PM2.5

Nitrate has long been focused due to its dominant proportion in PM2.5. In this study, PM2.5 samples were non-consecutively collected in a coastal city located in Western Pacific from March 6, 2019 to January 16, 2020. On the basis of the determination of water soluble inorganic ions and nitrogen and oxygen isotopic signatures of nitrate, its formation pathways were estimated by isotope fractionation calculation and NOx source contributions were quantified with stable isotope analysis in R (SIAR) model. Results showed that δ15N-NO3− ranged from −3.7‰ to 32.1‰, and δ18O-NO3− varied from 38.1‰ to 101.4‰. Nitrate formation was dominated by oxidation of NO2 with hydroxyl radical (OH) in spring, summer, and fall, while it was mainly controlled by N2O5 heterogeneous hydrolysis in winter. Quantitative analysis of NOx sources contributing to nitrate by using SIAR model showed that estimated annual average contributions from diesel vehicle emission, gasoline vehicle emission, biogenic soil emission, biomass burning, and coal combustion were 25.6%, 21.4%, 21.1%, 17.4%, and 14.5%, respectively. The control of diesel vehicle emission is vital to nitrate reduction and air quality improvement in spring, summer, and fall, while coal combustion is the primary NOx source to nitrate in winter. Posterior distribution of source contribution results from SIAR model presented more stable results in spring.

Impact of exposure to ambient fine particulate matter-bound polycyclic aromatic hydrocarbons on blood thrombogenicity in adults

Objective: To investigate the effects of exposure to ambient fine particulate matter-bound polycyclic aromatic hydrocarbons on blood coagulation in adults. Methods: A total of 73 adult volunteers were recruited in a cohort study and had four clinical visits from November 2014 to January 2016. Blood samples were obtained and used to measure biomarkers of blood thrombogenicity, including soluble CD40 Ligand (sCD40L), soluble P-selection (sCD62P) and Fibrinogen (FIB). White blood cell (WBC), 8-Hydroxy-2'-Deoxyguanosine (8-OHdG), matrix metalloproteinase-2 (MMP-2) and HDL cholesterol efflux capacity (HDL-CEC) were also determined. Daily concentrations of ambient fine particulate matter-bound polycyclic aromatic hydrocarbons (PAHs) were measured throughout the study period, and positive matrix factorization (PMF) approach was used to identity PAHs sources. Linear mixed-effect models including single-pollutant model, two-pollutant model and stratification analysis were constructed to estimate the effects of exposure to ambient fine particulate matter-bound PAHs on blood thrombogenicity in adults after adjusting for potential confounders. Results: The mean age of participants was (23.3±5.4) years. During the study period, the median level of PM2.5-bound PAHs was (55.29±74.99) ng/m3. Six sources of PM2.5-bound PAHs were identified by PMF, with traffic sources contributing more than 50%. The linear mixed-effect model showed that PAHs exposure had a significant effect on elevated blood thrombogenicity. Significant elevations in sCD40L, sCD62P and FIB associated with per IQR increase (60.33 ng/m3) in exposure to PAHs were 14.36% (95%CI:6.94%-22.28%), 9.33% (95%CI: 1.71%-17.51%) and 2.07% (95%CI:0.44%-2.07%) at prior 5 days, respectively. Blood thrombogenicity levels were significantly and positively correlated with source-specific PAHs, especially gasoline vehicle emissions, diesel vehicle emission and coal burning at prior 1 or 5 days. Stronger associations between PAHs and increased blood thrombogenicity were found in participants with high plaque vulnerability, reduced HDL function, and high levels of inflammation and oxidative stress. Conclusion: Acute exposure to ambient fine particulate matter-bound PAHs, especially PAHs from traffic sources may promote blood thrombogenicity in adults, and PAHs have stronger effects on participants with reduced vascular function and high levels of inflammation and oxidative stress.

Evaluation of Measurement Procedures for Solid Particle Number (SPN) Measurements during the Periodic Technical Inspection (PTI) of Vehicles.

Periodic technical inspection (PTI) of vehicles guarantees safety and environmental compliance during their lifetime. Particulate matter emissions of diesel vehicles are controlled with opacity measurements. After the introduction of diesel particulate filters (DPFs), particulate matter emissions have drastically decreased and the sensitivity of the opacity method is questioned. Several countries have already or are planning to introduce a solid particle number (SPN) method at their PTI that will either substitute or complement opacity measurements. However, there are differences in the measurement procedures and the limit values. In this study, we compared the different approaches and investigated topics which are still not well defined, such as the uncertainty of the SPN-PTI instruments, repeatability of the procedures, impact of the DPF fill state, and the correlation between type-approval SPN emissions and SPN concentrations during PTI tests. Finally, we compared the SPN-PTI instruments with the opacity meters. Our results showed that SPN-PTI measurements can detect tampered and defective DPFs. We also made suggestions on the measurement procedures and the concentration limit.

Effect of Tampering on On-Road and Off-Road Diesel Vehicle Emissions

Illegal manipulation (i.e., tampering) of vehicles is a severe problem because vehicle emissions increase orders of magnitude and significantly impact the environment and human health. This study measured the emissions before and after representative approaches of tampering of two Euro 6 Diesel light-duty passenger cars, two Euro VI Diesel heavy-duty trucks, and a Stage IV Diesel non-road mobile machinery (NRMM) agricultural tractor. With tampering of the selective catalytic reduction (SCR) for NOx, the NOx emissions increased by more than one order of magnitude exceeding 1000 mg/km (or mg/kWh) for all vehicles, reaching older Euro or even pre-Euro levels. The tampering of the NOx sensor resulted in relatively low NOx increases, but significant ammonia (NH3) slip. The particle number emissions increased three to four orders of magnitude, reaching 6–10 × 1012 #/km for the passenger car (one order of magnitude higher than the current regulation limit). The tampered passenger car’s NOx and particle number emissions were one order of magnitude higher even compared to the emissions during a regeneration event. This study confirmed that (i) tampering with the help of an expert technician is still possible, even for vehicles complying with the current Euro standards, although this is not allowed by the regulation; (ii) tampering results in extreme increases in emissions.

Maternal exposure to traffic-related ambient particles and risk of gestational diabetes mellitus with isolated fasting hyperglycaemia: A retrospective cohort study in Beijing, China.

Ambient particles have been associated with gestational diabetes mellitus (GDM), however, no study has evaluated the effects of traffic-related ambient particles on the risks of GDM subgroups classified by oral glucose tolerance test (OGTT) values. A retrospective analysis was conducted among 24,001 pregnant women who underwent regular prenatal care and received OGTT at Haidian Maternal and Child Health Hospital in Beijing, China, 2014-2017. A total of 3,168 (13.2%) pregnant women were diagnosed with GDM, including 1,206 with isolated fasting hyperglycaemia (GDM-IFH). At a fixed-location monitoring station, routinely monitored ambient particles included fine particulate matter (PM2.5), black carbon (BC) and particles in size ranges of 5-560nm (PNC5-560). Contributions of PNC5-560 sources were apportioned by positive matrix factorization model. Logistic regression model was applied to estimate odds ratio (OR) of ambient particles on GDM risk. Among the 24,001 pregnancy women recruited in this study, 3,168 (13.2%) were diagnosed with GDM, including 1,206 with isolated fasting hyperglycaemia (GDM-IFH) and 1,295 with isolated post-load hyperglycaemia (GDM-IPH). We observed increased GDM-IFH risk with per interquartile range increase in first-trimester exposures to PM2.5 (OR=1.94; 95% Confidence Intervals: 1.23-3.07), BC (OR=2.14; 1.73-2.66) and PNC5-560 (OR=2.46; 1.90-3.19). PNC5-560 originated from diesel and gasoline vehicle emissions were found in associations with increases in GDM-IFH risk, but not in GDM-IPH risk. Our findings suggest that exposure to traffic-related ambient particles may increase GDM risk by exerting adverse effects on fasting glucose levels during pregnancy, and support continuing efforts to reduce traffic emissions for protecting vulnerable population who are at greater risk of glucose metabolism disorder.

Research on Application Characteristics of Zirconia-Based High-Temperature NOx Sensors

The zirconia solid electrolyte SOFC (solid oxide fuel cell) has the characteristics of oxygen ion conduction function, high-temperature resistance, thermoelectric coupling effect, etc. A NOx sensor based on zirconia solid electrolyte has common characteristics and problems with the SOFC in principle and application. The research objective of this paper is to solve the application problems of smart NOx sensors in diesel vehicles or gasoline vehicles. Improvements in the application performance of the NOx sensor can help the NOx emissions of gasoline vehicles or diesel vehicles better meet the requirements of emission regulations. The smart NOx sensor is a regulatory sensor required by vehicles for China’s Phase VI Vehicle Exhaust Emission Regulations or Euro Phase VI Vehicle Exhaust Emission Regulations. The smart NOx sensor is a key sensor device for improving fuel efficiency and reducing pollution. Moreover, its measurement performance includes dynamic immunity to interference, response speed, and measurement accuracy, which are key factors affecting vehicle emissions. This paper focuses on the impact of the physical structure, electrode characteristics, and control strategies of the sensor on its performance during the application. An excellent sensor structure, electrode structure, and control strategy are given based on application analysis and experimental testing. The results show that the application performance of this smart NOx sensor meets the requirements of exhaust aftertreatment systems.

Comprehensive characterization of polycyclic aromatic hydrocarbon emissions from heavy-duty diesel vehicles utilizing GC × GC-ToF-MS

Comprehensive characterization of diesel vehicle emitted polycyclic aromatic hydrocarbon (PAH) emissions is yet to achieve due to the limitation of analytical methods. Therefore, we herein developed a two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-ToF-MS) method and quantified the total PAHs from diesel vehicles based on their characteristic fragments and mass spectral patterns. Overall, the emission factors (EFs) of total PAHs (gas + particle) are observed to range from 4.1 ± 2.5 mg km−1 to 51.4 ± 22.2 mg km−1 under cold-start and hot-start conditions for one China IV and two China VI heavy-duty diesel vehicles (HDDVs), of which the un-speciated PAHs account for more than 97%. Gaseous PAHs (g-PAHs) are dominated by three-ring PAHs, whereas particulate PAHs (p-PAHs) are dominated by two-ring PAHs. The total PAHs partition significantly into the gas phase for whole fleets and cycles, except that five-ring PAHs partition almost completely into the particle phase. The aftertreatment technologies (e.g., diesel particulate filter, DPF) significantly reduce the total PAH emissions by 49.8 ± 33.2%. The minimum toxic equivalency factors (TEFs) are deployed to estimate the toxicity of the total PAHs. Much higher toxicity is obtained than those in previous studies, indicating that the PAH toxicity of diesel vehicle emissions might be largely underestimated.

Detailed Characterization of Solid and Volatile Particle Emissions of Two Euro 6 Diesel Vehicles

The solid particle number emissions of Diesel vehicles are very low due to the particulate filters as exhaust aftertreatment devices. However, periodically, the trapped particles are oxidized (i.e., active regeneration) in order to keep the backpressure at low levels. The solid particle number emissions during regenerations are only partly covered by the regulations. Many studies have examined the emissions during regenerations, but their contribution to the overall emissions has not been addressed adequately. Furthermore, the number concentration of volatile particles, which is not included in the regulations, can be many of orders of magnitude higher. In this study, the particulate emissions of two light-duty Euro 6 vehicles were measured simultaneously at the tailpipe and the dilution tunnel. The results showed that the weighted (i.e., considering the emissions during regeneration) solid particle number emissions remained well below the applicable limit of 6 × 1011 #/km (solid particles > 23 nm). This was true even when considering solid sub-23 nm particles. However, the weighted volatile particle number emissions were many orders of magnitude higher, reaching up to 3 × 1013 #/km. The results also confirmed the equivalency of the solid particle number results between tailpipe and dilution tunnel locations. This was not the case for the volatile particles which were strongly affected by desorption phenomena. The high number of volatiles during regenerations even interfered with the 10 nm solid particle number measurements at the dilution tunnel, even though a catalytic stripper equipped instrument was also used in the dilution tunnel.

Study of durability of diesel vehicle emissions performance based on real driving emission measurement

Diesel vehicle emissions generally deteriorate with vehicle mileage due to the wear and deterioration of vehicle parts. Most of the experimental studies on vehicle emission durability were carried out based on the standard operation cycles of engine or vehicle, few research investigated vehicle emission deterioration characteristics under real driving conditions. In this research, the real driving emission (RDE) test method was used to investigate and evaluate the emission deterioration characteristics of two China-V diesel vehicles equipped with DOC and SCR systems. The experimental results show the emissions of CO and NOx from the N2 and N3 diesel vehicles increase with the vehicle mileage, showing the tendency of emission deterioration. The calculated deterioration factors of N2 and N3 diesel vehicle CO and NOx emissions are greater than the recommended values in China standard HJ 438–2008, which means experimental study on the vehicle emissions durability is necessary. The vehicle emissions deterioration depends on real driving conditions and the vehicle usage over vehicle lifetime.

Physicochemical and cell toxicity properties of particulate matter (PM) from a diesel vehicle fueled with diesel, spent coffee ground biodiesel, and ethanol

The literature shows that information about the physical, chemical, and cell toxicity properties of particulate matter (PM) from diesel vehicles is not rich as the existence of a remarkable number of studies about the combustion, performance, and emissions of diesel vehicles using renewable liquid fuels, particularly biodiesels and alcohols. Also, the PM analyses from combustion of spent coffee ground biodiesel have not been comprehensively explored. Therefore, this research is presented. Pure diesel, 90% diesel + 10% biodiesel, and 90% diesel + 9% ethanol + 1% biodiesel, volume bases, were tested under a fast idle condition. STEM, SEM, EDS, Organic Carbon Analyzer, TGA/DSC, and Raman Spectrometer were employed for investigating the PM physical and chemical properties, and assays of cell viability, cellular reactive oxygen species, interleukin-6, and tumor necrosis factor-alpha were examined for investigating the PM cell toxicity properties. It is found that the application of both biodiesel and ethanol has the potential to change the PM properties, while the impact of ethanol is more than biodiesel on the changes. Regarding the important aspects, biodiesel can be effective for better human health (due to a decrease in cell death (−60.8%)) as well as good diesel particulate filter efficiency (due to lower activation energy (−7.6%) and frequency factor (−83.2%)). However, despite a higher impact of ethanol on the reductions in activation energy (−24.8%) and frequency factor (−99.0%), this fuel causes an increase in cell death (84.1%). Therefore, biodiesel can be an appropriate fuel to have a positive impact on human health, the environment, and emissions catalysts performance, simultaneously.

Exploration of the atmospheric chemistry of nitrous acid in a coastal city of southeastern China: results from measurements across four seasons

Abstract. Because nitrous acid (HONO) photolysis is a key source of hydroxyl (OH) radicals, identifying the atmospheric sources of HONO is essential to enhance the understanding of atmospheric chemistry processes and improve the accuracy of simulation models. We performed seasonal field observations of HONO in a coastal city of southeastern China, along with measurements of trace gases, aerosol compositions, photolysis rate constants (J), and meteorological parameters. The results showed that the average observed concentration of HONO was 0.54 ± 0.47 ppb. Vehicle exhaust emissions contributed an average of 1.45 % to HONO, higher than the values found in most other studies, suggesting an influence from diesel vehicle emissions. The mean conversion frequency of NO2 to HONO in the nighttime was the highest in summer due to water droplets evaporating under high-temperature conditions. Based on a budget analysis, the rate of emission from unknown sources (Runknown) was highest around midday, with values of 4.51 ppb h−1 in summer, 3.51 ppb h−1 in spring, 3.28 ppb h−1 in autumn, and 2.08 ppb h−1 in winter. Unknown sources made up the largest proportion of all sources in summer (81.25 %), autumn (73.99 %), spring (70.87 %), and winter (59.28 %). The photolysis of particulate nitrate was probably a source in spring and summer while the conversion from NO2 to HONO on BC enhanced by light was perhaps a source in autumn and winter. The variation of HONO at night can be exactly simulated based on the HONO / NOx ratio, while the J(NO3-_R) × pNO3- should be considered for daytime simulations in summer and autumn, or 1/4× (J(NO3-_R) × pNO3-) in spring and winter. Compared with O3 photolysis, HONO photolysis has long been an important source of OH except for summer afternoons. Observation of HONO across four seasons with various auxiliary parameters improves the comprehension of HONO chemistry in southeastern coastal China.

Traffic-generated air pollution – Exposure mediated expression of factors associated with demyelination in a female apolipoprotein E−/− mouse model

Epidemiology studies suggest that exposure to ambient air pollution is associated with demyelinating diseases in the central nervous system (CNS), including multiple sclerosis (MS). The pathophysiology of MS results from an autoimmune response involving increased inflammation and demyelination in the CNS, which is higher in young (adult) females. Exposure to traffic-generated air pollution is associated with neuroinflammation and other detrimental outcomes in the CNS; however, its role in the progression of pathologies associated with demyelinating diseases has not yet been fully characterized in a female model. Thus, we investigated the effects of inhalation exposure to mixed vehicle emissions (MVE) in the brains of both ovary-intact (ov+) and ovariectomized (ov−) female Apolipoprotein (ApoE−/−) mice. Ov + and ov− ApoE−/− mice were exposed via whole-body inhalation to either filtered air (FA, controls) or mixed gasoline and diesel vehicle emissions (MVE: 200 PM μg/m3) for 6 h/d, 7 d/wk., for 30 d. We then analyzed MVE-exposure mediated alterations in myelination, the presence of CD4+ and CD8+ T cells, reactive oxygen species (ROS), myelin oligodendrocyte protein (MOG), and expression of estrogen (ERα and ERβ) and progesterone (PROA/B) receptors in the CNS. MVE-exposure mediated significant alterations in myelination across multiple regions in the cerebrum, as well as increased CD4+ and CD8+ staining. There was also an increase in ROS production in the CNS of MVE-exposed ov− and ov + ApoE−/− mice. Ov− mice displayed a reduction in cerebral ERα mRNA expression, compared to ov + mice; however, MVE exposure resulted in an even further decrease in ERα expression, while ERβ and PRO A/B were unchanged across groups. These findings collectively suggest that inhaled MVE-exposure may mediate estrogen receptor expression alterations associated with increased CD4+/CD8+ infiltration, regional demyelination, and ROS production in the CNS of female ApoE−/− mice.

A multi-pronged approach to strengthen diesel vehicle emission monitoring

China is constructing an vehicle emission monitoring system, aimed at combining remote OBD, periodic inspections, remote sensing and roadside checks. In this study, the exhaust emissions from diesel vehicles were investigated and analysed.

Advances in emission control of diesel vehicles in China

Diesel vehicles have caused serious environmental problems in China. Hence, the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in the latest China VI standard. To fulfill this stringent legislation, two major technical routes, including the exhaust gas recirculation (EGR) and high-efficiency selective catalytic reduction (SCR) routes, have been developed for diesel engines. Moreover, complicated aftertreatment technologies have also been developed, including use of a diesel oxidation catalyst (DOC) for controlling carbon monoxide (CO) and hydrocarbon (HC) emissions, diesel particulate filter (DPF) for particle mass (PM) emission control, SCR for the control of NOx emission, and an ammonia slip catalyst (ASC) for the control of unreacted NH3. Due to the stringent requirements of the China VI standard, the aftertreatment system needs to be more deeply integrated with the engine system. In the future, aftertreatment technologies will need further upgrades to fulfill the requirements of the near-zero emission target for diesel vehicles.

Size-fractionated nonpolar organic compounds of traffic aerosol emissions in a highway tunnel

Size-fractionated aerosol samples (PM0.25, PM0.25-1, PM1-2.5, and PM2.5-10) were collected in a highway tunnel in Shanghai, China. The concentrations of nonpolar organic compounds (NPOCs), i.e., n-alkanes, polycyclic aromatic hydrocarbons (PAHs) and hopanes in the aerosol samples at the tunnel inlet and outlet, emission factors (EFs) of individual NPOCs in PM10, and EFs of size-fractionated individual NPOCs were analyzed comprehensively. NPOC concentrations in this tunnel were lower than the earlier tunnel results, which might be attributed to the tunnel configuration effect on the pollution dilution along the tunnel, in addition to the improvement of engine technology and fuel quality during past decades. n-Alkane homologs for C14–C35 exhibited a smooth hump-like distribution pattern with the most abundance at C22 and 1–2 carbon number shifts of Cmax in comparison to those in other tunnels due to different fleet and fuel compositions. The most abundant PAHs from diesel (e.g., Nap, Phe, Flu and Pyr) and gasoline (e.g., BghiF, BbkF, BeP, DBA and BghiP) vehicle emissions presented concentration increases of 1.8–5.8 times from the tunnel inlet to outlet. The individual n-alkane and PAH distributions exhibited obvious size dependence, while it was expected that the relative abundances and homolog distributions of hopanes were very similar for different size stages. Several diagnostic ratios, e.g., fossil/plant n-alkanes and LMW/HMW PAHs, were evidently size dependent, indicating different sources of size-fractionated n-alkanes and PAHs.

Impacts of De‐NOx system layouts of a diesel passenger car on exhaust emission factors and monetary penalty

AbstractAutomobile emissions are significantly dependent on the after‐treatment system performance, which is partly determined by exhaust temperature. Regarding diesel passenger cars, after‐treatment systems generally include diesel oxidation catalyst (DOC), diesel particulate filter (DPF), and selective catalytic reduction (SCR). The layouts affect their temperature variations because of the heat loss and thermal capacity of tailpipes and after‐treatment systems. As for the original layout of DOC+DPF+SCR, nitrogen oxides (NOx) emissions are the main concerns of diesel vehicle emissions, especially under cold‐start conditions. Ammonia Creation and Conversion Technology (ACCT) system shows excellent performance of reducing cold‐start NOx emissions; additionally, the damage costs of individual exhaust emissions are different greatly, which may change the priority of emission reductions when considering monetary penalty. In this article, the impacts of the after‐treatment system layouts on the exhaust emission reductions were investigated based on a diesel passenger car; additionally, SCR and ACCT systems as the De‐NOx devices were adopted individually in corresponding scenarios; the after‐treatment system layouts were assessed from the viewpoints of both emission factors and monetary penalty. The results indicated that the ACCT system presented much better NOx reduction effectiveness than SCR system over different layouts. NOx reduction efficiency was very sensitive to vehicle operation conditions over the upstream layouts of NOx reduction devices. The layout‐1 of DOC+ACCT+DPF showed the lowest global emission factors from the diesel passenger car. DPF was much easier to achieve regeneration under the original layout conditions due to its shortest distance to the engine. The layout‐2 of ACCT+DOC+DPF had the minimum monetary penalty factor of exhaust emissions from this diesel passenger car.