Composition Of Diesel Exhaust Research Articles

Diesel engine emissions: are they no longer tolerable?

Emissions from diesel engines contain several hundred chemical compounds, which are emitted partly as gas and partly as particles. The composition of diesel exhaust and its concentrations in air has changed significantly over time, to the extent that now there is a distinction between "traditional" and "new technology" diesel emissions. New technology diesel engines comply with emissions from EURO 3 vehicles and higher. Starting with EURO 5, a significant further reduction of particle emissions has been achieved by increased temperature, which, however, lead to increased emissions of NOx and exceeded the NO2 emission limit. To overcome this problem, some car manufacturers installed illegal software that detected the vehicle test bench operation, resulting in low emissions during the test cycle. Detection of such devices in 2015 led to the "Diesel scandal". In 2017 the worldwide harmonized light vehicles test procedure (WLTP) was introduced for new cars, which simulates emissions under different driving conditions. It became mandatory for certification of all new vehicles by September 2018. In addition, fleet CO2 emissions have been introduced for all cars, requiring that by 2020 95% of each manufacturer's passenger car must meet the CO2 emission target of 95mg/km, and by 2021 100% of the fleet. All these regulations significantly reduced the emissions of diesel- and gasoline-driven cars, which since the introduction of the EURO 6 regulation in 2014 are almost similar for both. Since the energy efficiency of diesel motors is up to 20% higher than that of gasoline-driven cars resulting in up to 20% lower CO2 emission, there is no reason to question the future use of diesel engines. These regulations apply for new cars. However, air concentrations at sampling points close to streets with high traffic still exceed the limit values especially for NO2. In several cities this led to restrictions for passenger cars of EURO 5 and below. Since concentrations close to streets are not relevant to evaluate the long-term exposure of the population, these measures are highly debatable.

Evaluation of 1-Nitropyrene as a Surrogate Measure for Diesel Exhaust.

We investigated the viability of particle bound 1-nitropyrene (1-NP) air concentration measurements as a surrogate of diesel exhaust (DE) exposure, as compared with industry-standard elemental carbon (EC) and total carbon (TC) measurements. Personal exposures are reported for 18 employees at a large underground metal mine during four different monitoring campaigns. Full-shift personal air exposure sampling was conducted using a Mine Safety and Health Administration (MSHA) compliant diesel particulate matter (DPM) impactor cassette downstream of a GS-1 cyclone pre-selector. Each DPM filter element was analyzed for EC and organic carbon (OC) using NIOSH Method 5040. After EC and OC analysis, the remaining portion of each DPM filter was analyzed for 1-NP using liquid chromatography tandem mass spectrometry (LC/MS/MS). We observed high correlations between the quantiles of 1-NP and EC exposures across 10 different work shift task groups (r = 0.87 to 0.96), and a linear relationship with a slope between 6.0 to 6.9 pg 1-NP per µg EC. However, correlation between 1-NP and EC was weak (r =0.34) for the 91 individual sample pairs due to low EC concentrations and possible heterogeneity of DE composition. While both 1-NP and EC differentiated between high and low exposure groups categorized by job location, measurements of 1-NP, but not EC further differentiated between specific job activities. Repeated measurements on individual subjects verified the relationship between 1-NP and EC and demonstrated substantial within-subject variability in exposure. The detection limit of TC air concentration ranged between 18 and 28 µg m-3 and was limited by OC contamination of the quartz filters in the MSHA compliant DPM samplers.

Characterization of the chemical composition of PM2.5 emitted from on-road China III and China IV diesel trucks in Beijing, China

The composition of diesel exhaust fine particulate matter (PM2.5) is of growing interest because of its impacts on health and climatic factors and its application in source apportionment and aerosol modeling. We characterized the detailed chemical composition of the PM2.5, including the organic carbon (OC), elemental carbon (EC), water-soluble ions (WSIs), and elemental contents, emitted from China III and China IV diesel trucks (nine each) based on real-world measurements in Beijing using a portable emissions measurement system (PEMS). Carbonaceous compounds were the dominant components (totaling approximately 87%) of the PM2.5, similar to the results (greater than 80% of the PM2.5) of our previous study of on-road China III diesel trucks. In general, the amounts of individual component groups (carbonaceous compounds, WSIs, and elements) and PM2.5 emissions for China IV diesel trucks were lower than those of China III diesel trucks of the same size, except for the WSIs and elements for the light- and medium-duty diesel trucks. The EC/OC mass ratios were strongly dependent on the emission standards, and the ratios of China IV diesel trucks were higher than those of China III diesel trucks of the same size. The chemical species in the PM2.5 were significantly affected by the driving conditions. Overall, the emission factors (EFs) of the PM2.5 and OC under non-highway (NHW) driving conditions were higher than those under highway (HW) driving conditions, and the EC/OC mass ratios presented an increasing trend, with decreasing OC/PM2.5 and increasing EC/PM2.5 from NHW to HW driving conditions; similar trends were reported in our previous study. In addition, Pearson's correlation coefficients among the PM2.5 species were analyzed to determine the relationships among the various chemical components.

Effects of fuels, engine load and exhaust after-treatment on diesel engine SVOC emissions and development of SVOC profiles for receptor modeling

Diesel exhaust emissions contain numerous semivolatile organic compounds (SVOCs) for which emission information is limited, especially for idling conditions, new fuels and the new after-treatment systems. This study investigates exhaust emissions of particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), and sterane and hopane petroleum biomarkers from a heavy-duty (6.4 L) diesel engine at various loads (idle, 600 and 900 kPa BMEP), with three types of fuel (ultra-low sulfur diesel or ULSD, Swedish low aromatic diesel, and neat soybean biodiesel), and with and without a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF). Swedish diesel and biodiesel reduced emissions of PM2.5, Σ15PAHs, Σ11NPAHs, Σ5Hopanes and Σ6Steranes, and biodiesel resulted in the larger reductions. However, idling emissions increased for benzo[k]fluoranthene (Swedish diesel), 5-nitroacenaphthene (biodiesel) and PM2.5 (biodiesel), a significant result given the attention to exposures from idling vehicles and the toxicity of high-molecular-weight PAHs and NPAHs. The DOC + DPF combination reduced PM2.5 and SVOC emissions during DPF loading (>99% reduction) and DPF regeneration (83–99%). The toxicity of diesel exhaust, in terms of the estimated carcinogenic risk, was greatly reduced using Swedish diesel, biodiesel fuels and the DOC + DPF. PAH profiles showed high abundances of three and four ring compounds as well as naphthalene; NPAH profiles were dominated by nitronaphthalenes, 1-nitropyrene and 9-nitroanthracene. Both the emission rate and the composition of diesel exhaust depended strongly on fuel type, engine load and after-treatment system. The emissions data and chemical profiles presented are relevant to the development of emission inventories and exposure and risk assessments.

Chemical characterization and in vitro toxicity of diesel exhaust particulate matter generated under varying conditions.

Epidemiologic studies have linked diesel exhaust (DE) to cardiovascular and respiratory morbidity and mortality, as well as lung cancer. DE composition is known to vary with many factors, although it is unclear how this influences toxicity. We generated eight DE atmospheres by applying a 2×2×2 factorial design and altering three parameters in a controlled exposure facility: (1) engine load (27 vs 82 %), (2) particle aging (residence time ~5 s vs ~5 min prior to particle collection), and (3) oxidation (with or without ozonation during dilution). Selected exposure concentrations of both diesel exhaust particles (DEPs) and DE gases, DEP oxidative reactivity via DTT activity, and in vitro DEP toxicity in murine endothelial cells were measured for each DE atmosphere. Cell toxicity was assessed via measurement of cell proliferation (colony formation assay), cell viability (MTT assay), and wound healing (scratch assay). Differences in DE composition were observed as a function of engine load. The mean 1-nitropyrene concentration was 15 times higher and oxidative reactivity was two times higher for low engine load versus high load. There were no substantial differences in measured toxicity among the three DE exposure parameters. These results indicate that alteration of applied engine load shifts the composition and can modify the biological reactivity of DE. While engine conditions did not affect the selected in vitro toxicity measures, the change in oxidative reactivity suggests that toxicological studies with DE need to take into account engine conditions in characterizing biological effects.

Effect of Operating and Sampling Conditions on the Exhaust Gas Composition of Small-Scale Power Generators

Small stationary diesel engines, like in generator sets, have limited emission control measures and are therefore responsible for 44% of the particulate matter (PM) emissions in the United States. The diesel exhaust composition depends on operating conditions of the combustion engine. Furthermore, the measurements are influenced by the used sampling method. This study examines the effect of engine loading and exhaust gas dilution on the composition of small-scale power generators. These generators are used in different operating conditions than road-transport vehicles, resulting in different emission characteristics. Experimental data were obtained for gaseous volatile organic compounds (VOC) and PM mass concentration, elemental composition and nitrate content. The exhaust composition depends on load condition because of its effect on fuel consumption, engine wear and combustion temperature. Higher load conditions result in lower PM concentration and sharper edged particles with larger aerodynamic diameters. A positive correlation with load condition was found for K, Ca, Sr, Mn, Cu, Zn and Pb adsorbed on PM, elements that originate from lubricating oil or engine corrosion. The nitrate concentration decreases at higher load conditions, due to enhanced nitrate dissociation to gaseous NO at higher engine temperatures. Dilution on the other hand decreases PM and nitrate concentration and increases gaseous VOC and adsorbed metal content. In conclusion, these data show that operating and sampling conditions have a major effect on the exhaust gas composition of small-scale diesel generators. Therefore, care must be taken when designing new experiments or comparing literature results.

Engine-Operating Load Influences Diesel Exhaust Composition and Cardiopulmonary and Immune Responses

Background: The composition of diesel engine exhaust (DEE) varies by engine type and condition, fuel, engine operation, and exhaust after treatment such as particle traps. DEE has been shown to increase inflammation, susceptibility to infection, and cardiovascular responses in experimentally exposed rodents and humans. Engines used in these studies have been operated at idle, at different steady-state loads, or on variable-load cycles, but exposures are often reported only as the mass concentration of particulate matter (PM), and the effects of different engine loads and the resulting differences in DEE composition are unknown.Objectives: We assessed the impacts of load-related differences in DEE composition on models of inflammation, susceptibility to infection, and cardiovascular toxicity.Methods: We assessed inflammation and susceptibility to viral infection in C57BL/6 mice and cardiovascular toxicity in APOE–/– mice after being exposed to DEE generated from a single-cylinder diesel generator operated at partial or full load.Results: At the same PM mass concentration, partial load resulted in higher proportions of particle organic carbon content and a smaller particle size than did high load. Vapor-phase hydrocarbon content was greater at partial load. Compared with high-load DEE, partial-load DEE caused greater responses in heart rate and T-wave morphology, in terms of both magnitude and rapidity of onset of effects, consistent with previous findings that systemic effects may be driven largely by the gas phase of the exposure atmospheres. However, high-load DEE caused more lung inflammation and greater susceptibility to viral infection than did partial load.Conclusions: Differences in engine load, as well as other operating variables, are important determinants of the type and magnitude of responses to inhaled DEE. PM mass concentration alone is not a sufficient basis for comparing or combining results from studies using DEE generated under different conditions.

Secondary organic aerosol production from modern diesel engine emissions

Abstract. Secondary organic aerosol (SOA) production was observed at significant levels in a series of modern diesel exhaust (DE) aging experiments conducted at the European Outdoor Photoreactor/Simulation Chamber (EUPHORE). The greatest production occurred in DE with toluene addition experiments (>40%), followed by DE with HCHO (for OH radical generation) experiments. A small amount of SOA (3%) was observed for DE in dark with N2O5 (for NO3 radical production) experiments. The analysis for a limited number (54) of polar organic compounds (POC) was conducted to assess the composition of modern DE and the formation of photochemical transformation products. Distinct POC formation in light versus dark experiments suggests the role of OH initiated reactions in these chamber atmospheres. A trend of increasing concentrations of dicarboxylic acids in light versus dark experiments was observed when evaluated on a compound group basis. The four toluene addition experiments in this study were performed at different [tol]o/[NOx]o ratios and displayed an average SOA %yield (in relation to toluene) of 5.3±1.6%, which is compared to past chamber studies that evaluated the impact of [tol]o/[NOx]o on SOA production in more simplified mixtures.

Identification of Surrogate Measures of Diesel Exhaust Exposure in a Controlled Chamber Study

Exposure to diesel exhaust (DE) has been associated with acute cardiopulmonary and vascular responses, chronic noncancer health effects, and respiratory cancers in humans. To better understand DE exposures and eventually their related health effects, we established a controlled chamber experiment wherein human volunteer subjects were exposed to approximately 100 microg/m3 DE. In general, human exposure assessment for DE is based on ambient air measurements of surrogates such as elemental carbon (EC) or total organic carbon (OC) collected on filters. As specific health effect mechanisms and dose-response are obscured bythe complex composition of DE, the linkage from exposure to internal dose can presumably be improved by use of specific biomarkers and metabolites in blood, breath, or urine. Because EC and OC are not suitable as biomarkers, in this study, we focus on identifying compounds that are demonstrated indicators of DE and can also be found in biological fluids. We measured an assortment of volatile, semivolatile, and particle-bound aromatic compounds in the chamber air and report their airborne concentrations in DE and purified air, as well as the estimated values of the corresponding exposure ratios (mean DE air concentration:mean purified air concentration). These estimated exposure ratios were used to identify naphthalene (Nap) and phenanthrene (Phe) as potentially useful surrogates for DE exposure that could also serve as biomarkers. Estimated mean levels of Nap and Phe associated with the nominal 100 microg/m3 DE were 2600 and 765 ng/m3 with estimated exposure ratios of 252 and 92.4, respectively. Nap levels were significantly correlated with OC and total particle-bound polycyclic aromatic hydrocarbons (PAHs); Phe levels were significantly correlated with total volatile + semivolatile PAHs. These results suggest that Nap and Phe may be particularly useful surrogates for DE concentrations. While Nap and Phe are not validated here as internal biomarkers of DE exposure, we are currently assessing human biological specimens collected during this study and will discuss those results in ensuing papers.

FeSrTiO3-based resistive oxygen sensors for application in diesel engines

SrTi0.4Fe0.6O2.8 (STFO60) powders were prepared by self-propagating high-temperature synthesis (SHS) and subsequent ball-milling (BM) treatment, and then deposited on an interdigited alumina substrate by screen-printing to fabricate a planar resistive oxygen sensor for direct injection (DI) diesel engines. The electrical characteristics and response to oxygen of the STFO60 sensor have been carefully examined first in a bench system with synthetic gases thus simulating diesel exhaust composition. The results obtained highlighted the promising performances of the sensor in terms of the temperature resistance independence as well as sensor response at the high oxygen concentrations typical of diesel engines. Cross-sensitivity tests also indicated that the sensor response is not influenced by main components in the exhausts, such as HC, CO2, NOx, CO. The STFO60 sensor was then tested as an oxygen probe on a diesel engine car under real driving conditions. Road tests confirmed that the performances of the resistive sensor are comparable with those of a commercial lambda probe.

Ports in a Storm

In many parts of the world, shipping-related emissions have already exceeded or are expected to soon exceed those from land-based sources. Shipping emissions can be reduced substantially by using some of the same technologies being applied to land-based sources, including cleaner engines and fuels, exhaust control methods, and operational modifications. Various ports are testing the feasibility of these mechanisms with varying degrees of success. What is perhaps most greatly needed is expedited creation of better regulations at all levels, from the International Maritime Organization to port city authorities.

Outdoor air pollution and lung cancer: recent epidemiologic evidence.

Outdoor air pollution and lung cancer: recent epidemiologic evidence.

Responses of cultured human airways epithelial cells treated with diesel exhaust extracts will vary with the engine load

Epidemiologic evidence suggests that increased morbidity and mortality are associated with the concentrations of ambient air particulate matter (PM). Many sources contribute to the particulate fraction of ambient air pollution, including diesel exhaust particulates (DEP). Diesel exhaust also contributes gas-phase pollutants to the atmosphere, and gaseous copollutants may influence the toxicity of PM. The composition of diesel exhaust varies greatly depending on the engine load conditions as well as other factors. To determine whether different diesel exhaust composition can affect lung cell resposes, the effects of of diesel exhaust extracts derived from different engine loads were examined on normal human bronchial epithelial cells (NHBE) in vitro. Diesel exhaust was collected into chilled impingers containing phosphate-buffered saline (PBS). Cultured NHBE cells were treated with 0 to 500 microg/well extract from approximately 0% engine load (termed low load or LL) or extract from approximately 75% engine load (termed high load or HL) for 24 h. The HL extract was cytotoxic at 500 microg compared to controls as measured by (51)Cr release. Production of the neutrophil chemotaxin interleukin 8 (IL-8) was decreased 4.7-fold in cells treated with 500 microg LL extract, whereas cells treated with 500 microg HL extract showed a 2.4-fold increase in IL-8 release. Production of the inflammatory and immune system mediator prostaglandin E(2) (PGE(2)) was increased up to 2.5-fold in cells treated with HL extract, but unchanged with other treatments. Melittin stimulation of cells showed that the LL extract had an inhibitory effect on PGE(2) release at 500 microg. Differences in carbonyl content of the extracts were found by high performance liquid chromatography/mass spectroscopy HPLC/MS, with the HL extract having more intermediate size carbonyls (i.e. with six to nine carbons). The data suggest that the response of NHBE cells to treatment with diesel exhaust will vary depending on the constituent components of the exhaust.

Effect of comprex supercharging on diesel emissions

Diesel engine emissions are highly complex mixtures. They consist of a wide range of organic and inorganic compounds distributed among the gaseous and particulate phases. Particulates and NO x emissions are the important components of the Diesel exhaust. The composition of Diesel exhaust varies considerably, depending on engine type, operating conditions, fuel, and lubricating oil. In this research, the effects of supercharging, which is one of the engine operational parameters, on Diesel emissions have been investigated. For this purpose, a comprex, CX (pressure wave supercharger) was designed and manufactured and then matched to an indirect injection Diesel engine. During the engine tests, the emission parameters (CO, SO x , NO x and smoke density) have been observed and measured for different pulley ratios at full load conditions. The results showed that CX supercharging may be an alternative way of NO x reduction with some modifications.

Characterization of Fine Particle Material in Ambient Air and Personal Samples from an Underground Mine

Personal samplers representing 4 job classifications and stationary samplers at 2 locations in an underground mine were deployed to measure fine particle carbon (organic/elemental), ions (sulfate plus nitrate), elements (metals and others), and speciated organic compounds including polycyclic aromatic hydrocarbons (PAH), oxygenated PAH, and hopanes/steranes. Chemically segregated size distribution was investigated after collection with a multistage impactor placed at 1 sampling site. All samples exceeded the currently proposed mine air standard of 160 w g/m 3 total carbon, and most exceeded the interim standard of 400 w g/m 3 . Carbon accounted for about 70% of the fine particle mass (described as a reconstructed mass of all measured chemical species); sulfate and ore/waste rock-derived metals constituted most of the remainder. Most of the personal samples were more concentrated than the ambient samples; 1 sample exceeded 2.5 mg/m 3 total mass. The PAH consisted mostly of gas-phase/semivolatile compounds and minor amounts of the particle-phase species, which is consistent with the composition of diesel exhaust, the major source of fine particle material in the mine. Size-segregated chemistry showed that the majority of the material below 1 w m of aerodynamic diameter was carbon, with the largest amount at approximately 0.2 w m. Metals, derived primarily from resuspended ore/waste rock, comprised the majority of the material above 1 w m. Results are placed in context of current mine-monitoring techniques that aim to regulate diesel particulate material.

Side Reactions in the Selective Catalytic Reduction of NOx with Various NO2 Fractions

The main and side reactions of the three selective catalytic reduction (SCR) reactions with ammonia over TiO2−WO3−V2O5 catalysts have been investigated using synthetic gas mixtures matching the composition of diesel exhaust. The three SCR reactions are standard SCR with pure NO, fast SCR with an equimolar mixture of NO and NO2, and NO2 SCR with pure NO2. At high temperatures the selective catalytic oxidation (SCO) of ammonia and the formation of nitrous oxide compete with the SCR reactions. Water strongly inhibits the SCO of ammonia and the formation of nitrous oxide, thus increasing the selectivity of the SCR reactions. However, water also inhibits SCR activity, most pronounced at low temperatures. NO2 fractions exceeding 50% enhance the formation of nitrous oxide at low temperatures. If the feed of NOx consists of pure NO2, the formation of nitrous oxide may occur by two different reactions having different temperature regimes. The reaction responsible for N2O formation at low temperatures probably invo...

What is new in diesel.

We review information from the past 5 years on changes in diesel exhaust (DE) emissions and developments in the study of DE toxicity. New DE technologies have changed the composition of DE considerably, reducing emissions of many of the components of health concern. The increasing similarity of modern diesel and compressed natural-gas engine emissions needs to be reflected in any regulatory analysis. Even for historical DE emissions, considerable study of DE exposure in animals or humans has not produced data useful for risk assessment. DE inhalation exposure in most species (hamsters, guinea pigs, mice) does not produce lung tumors. Inhalation studies of DE in rats found lung tumors only with lung overload, and tumors also occurred when inert dusts were inhaled at overload concentrations. The animal data are reassuring and show that DE is not a concern at ambient exposure levels. Re-analyses of occupational epidemiology have been shown to have serious shortcomings that do not allow the derivation of a quantitative cancer risk. Studies of railroad workers found no dose response; rather cancer risk appeared to decrease for individuals with greater DE exposure. Studies of truck drivers also suffer from serious flaws because of misconceptions about the year that diesel was introduced, lack of an adequate latency period, and the realization that drivers exhibited increased lung cancer risk even prior to the diesel era. Recent industrial hygiene studies of drivers show that DE was not likely to be a primary source of particles or polycyclic aromatic hydrocarbons. Further, there is no dose response across occupations. In fact, the occupation (underground miners) with the highest exposure to DE does not exhibit increased cancer risks. This new information seriously weakens earlier risk characterizations of DE by various regulatory groups. New research and better exposure measurements are needed before a reliable risk assessment of DE can be produced.

The Effect of an Oxidation Precatalyst on the NOx Reduction by Ammonia SCR

The performances of oxidation and SCR catalysts were investigated individually and as a combined system for the removal of NOx by ammonia. Experiments were carried out with synthetic gas mixtures matching the composition of diesel exhaust. Introducing an oxidation catalyst upstream of the SCR catalyst enhances the removal of NOx at low temperatures. The beneficial effects of combining the two catalysts are the oxidation of unburned hydrocarbons that inhibit the SCR reaction and the conversion of NO to NO2 on the oxidation catalyst. NO2 fractions up to 50% of total NOx enhance the NOx conversion at temperatures below 300 °C. However, excess NO2 should be avoided because the reaction of NO2 with ammonia is slow, resulting in a decreased NOx conversion. Above 350 °C, the NOx conversion essentially does not depend on the ratio NO2/NOx or on the presence of hydrocarbons in the feed. A simple mathematical prediction of the NOx conversion for the combined system is also possible. The parameters used in this calculation are the ratio NO2/NOx behind the oxidation catalyst and the experimentally determined conversions of pure NO or NO2 over the SCR catalyst.

Diesel Exhaust CompositionandOdorStudies

The composition of diesel exhaust was determined by infrared spectra, colorimetry, gas chromatography and fluorescence studies. A group of panelist were enclosed in a room constructed to maintain a constant very low odor level with temperature and humidity control. To establish odor thresholds, experiments were performed using various concentrations of the exhaust gases. Values were determined for CO/sub 2/, CO, NO, NO/sub 2/, SO/sub 2/, C/sub 2/H/sub 4/, C/sub 2/H/sub 2/, acrolein, and formaldehyde. These findings are the first results of a series of psychophysical experiments. The verification of the importance of NO/sub 2/ and CH in the detectability of diesel exhaust requires extensive further odor studies on pure compounds and mixtures.