Particulate Matter in New Technology Diesel Exhaust (NTDE) is Quantitatively and Qualitatively Very Different from that Found in Traditional Diesel Exhaust (TDE)

ABSTRACT

Diesel exhaust (DE) characteristic of pre-1988 engines is classified as a “probable” human carcinogen (Group 2A) by the International Agency for Research on Cancer (IARC), and the U.S. Environmental Protection Agency has classified DE as “likely to be carcinogenic to humans.” These classifications were based on the large body of health effect studies conducted on DE over the past 30 or so years. However, increasingly stringent U.S. emissions standards (1988–2010) for particulate matter (PM) and nitrogen oxides (NO_x) in diesel exhaust have helped stimulate major technological advances in diesel engine technology and diesel fuel/lubricant composition, resulting in the emergence of what has been termed New Technology Diesel Exhaust, or NTDE. NTDE is defined as DE from post-2006 and older retrofit diesel engines that incorporate a variety of technological advancements, including electronic controls, ultra-low-sulfur diesel fuel, oxidation catalysts, and wall-flow diesel particulate filters (DPFs). As discussed in a prior review (T. W. Hesterberg et al.; Environ. Sci. Technol. 2008, 42, 6437-6445), numerous emissions characterization studies have demonstrated marked differences in regulated and unregulated emissions between NTDE and “traditional diesel exhaust” (TDE) from pre-1988 diesel engines. Now there exist even more data demonstrating significant chemical and physical distinctions between the diesel exhaust particulate (DEP) in NTDE versus DEP from pre-2007 diesel technology, and its greater resemblance to particulate emissions from compressed natural gas (CNG) or gasoline engines. Furthermore, preliminary toxicological data suggest that the changes to the physical and chemical composition of NTDE lead to differences in biological responses between NTDE versus TDE exposure. Ongoing studies are expected to address some of the remaining data gaps in the understanding of possible NTDE health effects, but there is now sufficient evidence to conclude that health effects studies of pre-2007 DE likely have little relevance in assessing the potential health risks of NTDE exposures.

IMPLICATIONS Based on the distinct physical and chemical properties of New Technology Diesel Exhaust (NTDE), it has become clear that findings from the health effects studies conducted on traditional DE (TDE) over the last 30 years have little relevance to NTDE, which is more similar to the exhaust from compressed natural gas (CNG) or gasoline engine emissions than to traditional TDE. Once sufficient health effects data are available for NTDE, it will thus be necessary to conduct new hazard and risk assessments for NTDE that are independent of the DE toxicological database acquired on emissions from pre–2007 diesel technology.     

Total diesel exhaust particulate length measurements using a modified household smoke alarm ionization chamber

To evaluate the effectiveness of various means to combat the negative health effects of ultrafine particles emitted by internal combustion engines, a reliable, low-cost instrument for dynamic measurements of the exhaust emissions of ultrafine particulate matter (PM) is needed. In this study, an ordinary ionization-type building smoke detector was modified to serve as a measuring ionization chamber and utilized for dynamic measurements of PM emissions from diesel engines. When used with diluted exhaust, the readings show an excellent correlation with total particulate length. The instrument worked well with raw and diluted exhaust and with varying emission levels and is well suitable for on-board use.     

Regulated and unregulated emissions from modern 2010 emissions-compliant heavy-duty on-highway diesel engines

The U.S. Environmental Protection Agency (EPA) established strict regulations for highway diesel engine exhaust emissions of particulate matter (PM) and nitrogen oxides (NO_x) to aid in meeting the National Ambient Air Quality Standards. The emission standards were phased in with stringent standards for 2007 model year (MY) heavy-duty engines (HDEs), and even more stringent NO_X standards for 2010 and later model years. The Health Effects Institute, in cooperation with the Coordinating Research Council, funded by government and the private sector, designed and conducted a research program, the Advanced Collaborative Emission Study (ACES), with multiple objectives, including detailed characterization of the emissions from both 2007- and 2010-compliant engines. The results from emission testing of 2007-compliant engines have already been reported in a previous publication. This paper reports the emissions testing results for three heavy-duty 2010-compliant engines intended for on-highway use. These engines were equipped with an exhaust diesel oxidation catalyst (DOC), high-efficiency catalyzed diesel particle filter (DPF), urea-based selective catalytic reduction catalyst (SCR), and ammonia slip catalyst (AMOX), and were fueled with ultra-low-sulfur diesel fuel (~6.5 ppm sulfur). Average regulated and unregulated emissions of more than 780 chemical species were characterized in engine exhaust under transient engine operation using the Federal Test Procedure cycle and a 16-hr duty cycle representing a wide dynamic range of real-world engine operation. The 2010 engines’ regulated emissions of PM, NO_X, nonmethane hydrocarbons, and carbon monoxide were all well below the EPA 2010 emission standards. Moreover, the unregulated emissions of polycyclic aromatic hydrocarbons (PAHs), nitroPAHs, hopanes and steranes, alcohols and organic acids, alkanes, carbonyls, dioxins and furans, inorganic ions, metals and elements, elemental carbon, and particle number were substantially (90 to >99%) lower than pre-2007-technology engine emissions, and also substantially (46 to >99%) lower than the 2007-technology engine emissions characterized in the previous study.

Implications:?Heavy-duty on-highway diesel engines equipped with DOC/DPF/SCR/AMOX and fueled with ultra-low-sulfur diesel fuel produced lower emissions than the stringent 2010 emission standards established by the U.S. Environmental Protection Agency. They also resulted in significant reductions in a wide range of unregulated toxic emission compounds relative to older technology engines. The increased use of newer technology (2010+) diesel engines in the on-highway sector and the adaptation of such technology by other sectors such as nonroad, displacing older, higher emissions engines, will have a positive impact on ambient levels of PM, NOx, and volatile organic compounds, in addition to many other toxic compounds.     

柴油机排放颗粒物净化技术研究进展

柴油机被认为是城市大气微粒的主要污染源。柴油机颗粒物组成复杂并且颗粒粒径甚小,大都属于亚微米级粒子和纳米级粒子。因而柴油机颗粒物对人类健康和大气环境的影响受到世人的广泛关注。本文主要对柴油机排放颗粒物的生成机理、化学组成及危害、物理性质、检测方法和净化技术等方面进行综述与探讨。     

Fine urban and precursor emissions control for diesel urban transit buses

Particulate emission from diesel engines is one of the most important pollutants in urban areas. As a result, particulate emission control from urban bus diesel engines using particle filter technology is being evaluated at several locations in the US. A project entitled "Clean Diesel Air Quality Demonstration Program" has been initiated by the New York City Metropolitan Transit Authority (MTA) under the supervision of New York State Department of Environmental Conservation and with active participation from Johnson Matthey, Corning, Equilon, Environment Canada and RAD Energy. Under this program, several MTA transit buses with DDC Series 50 engines were equipped with Continuously Regenerating Technology (CRTTM) particulate filter systems and have been operated with ultra low sulfur diesel (<30 ppm S) in transit service in Manhattan since February 2000. These buses were evaluated over a 9-month period for durability and maintainability of the particulate filter. In addition, an extensive emissions testing program was carried out using transient cycles on a chassis dynamometer to evaluate the emissions reductions obtained with the particle filter. In this paper, the emissions testing data from the Clean Diesel Air Quality Demonstration Program are discussed in detail.     

A fuel-based assessment of off-road diesel engine emissions

The use of diesel engines in off-road applications is a significant source of nitrogen oxides (NOx) and particulate matter (PM10). Such off-road applications include railroad locomotives, marine vessels, and equipment used for agriculture, construction, logging, and mining. Emissions from these sources are only beginning to be controlled. Due to the large number of these engines and their wide range of applications, total activity and emissions from these sources are uncertain. A method for estimating the emissions from off-road diesel engines based on the quantity of diesel fuel consumed is presented. Emission factors are normalized by fuel consumption, and total activity is estimated by the total fuel consumed. Total exhaust emissions from off-road diesel equipment (excluding locomotives and marine vessels) in the United States during 1996 have been estimated to be 1.2 x 10(9) kg NOx and 1.2 x 10(8) kg PM10. Emissions estimates published by the U.S. Environmental Protection Agency are 2.3 times higher for both NOx and exhaust PM10 emissions than estimates based directly on fuel consumption. These emissions estimates disagree mainly due to differences in activity estimates, rather than to differences in the emission factors. All current emission inventories for off-road engines are uncertain because of the limited in-use emissions testing that has been performed on these engines. Regional- and state-level breakdowns in diesel fuel consumption by off-road mobile sources are also presented. Taken together with on-road measurements of diesel engine emissions, results of this study suggest that in 1996, off-road diesel equipment (including agriculture, construction, logging, and mining equipment, but not locomotives or marine vessels) was responsible for 10% of mobile source NOx emissions nationally, whereas on-road diesel vehicles contributed 33%.     

Gas-phase and semivolatile organic emissions from a modern nonroad diesel engine equipped with advanced aftertreatment

ABSTRACT

U.S. Tier 4 Final and Euro Stage IV and V regulations for nonroad compression-ignition engines have led to the development of exhaust aftertreatment technologies optimized for nonroad engines and duty cycles. In this study, several aftertreatment configurations consisting of state-of-the-art diesel oxidation catalysts (DOCs), diesel particulate filters (DPFs), copper (Cu) zeolite– and vanadium-based selective catalytic reduction (SCR) catalysts, and ammonia oxidation (AMOX) catalysts are evaluated using both nonroad transient (NRTC) and steady (8-mode NRSC) cycles in order to understand both component- and system-level effects of diesel aftertreatment on gas-phase, semivolatile, and particle-phase and particle-bound unregulated organic emissions. Organic emissions reported in this work include total hydrocarbon (THC), n-alkanes, branched alkanes, saturated cycloalkanes, aromatics, aldehydes, ketones, hopanes, steranes, and soluble organic fraction (SOF). Brake-specific emissions are reported for four configurations, including engine-out, DOC+CuZ-SCR+AMOX, V-SCR+AMOX, and DOC+DPF+CuZ-SCR+AMOX, and conversion of engine-out emissions is reported for the three aftertreatment configurations. Mechanisms responsible for the reduction of organic species are discussed in detail. This summary of emissions from a current nonroad diesel engine equipped with advanced aftertreatment can be used to more accurately model the impact of anthropogenic emissions on the atmosphere with tools such as the U.S. Environmental Protection Agency’s Motor Vehicle Emissions Simulator (MOVES2014a) model.

Implications: Anthropogenic emissions are a source of significant human health and environmental risk. This study, focused on the treatment of exhaust emissions from a modern nonroad diesel engine with a variety of aftertreatment configurations, examines the impact that human industrial activity can have on air pollution. In particular, we focus on the remediation of gas-phase and semivolatile organic emissions by emission reduction technologies. This detailed summary of emissions from a current nonroad diesel engine equipped with advanced aftertreatment can be used to more accurately model the impact of anthropogenic emissions on the atmosphere with tools such as the U.S. Environmental Protection Agency’s MOVES2014a model.     

Generation and characterization of diesel exhaust in a facility for controlled human exposures

An idling medium-duty diesel truck operated on ultralow sulfur diesel fuel was used as an emission source to generate diesel exhaust for controlled human exposure. Repeat tests were conducted on the Federal Test Procedure using a chassis dynamometer to demonstrate the reproducibility of this vehicle as a source of diesel emissions. Exhaust was supplied to a specially constructed exposure chamber at a target concentration of 100 microg x m(-3) diesel particulate matter (DPM). Spatial variability within the chamber was negligible, whereas emission concentrations were stable, reproducible, and similar to concentrations observed on the dynamometer. Measurements of nitric oxide, nitrogen dioxide, carbon monoxide, particulate matter (PM), elemental and organic carbon, carbonyls, trace elements, and polycyclic aromatic hydrocarbons were made during exposures of both healthy and asthmatic volunteers to DPM and control conditions. The effect of the so-called "personal cloud" on total PM mass concentrations was also observed and accounted for. Conventional lung function tests in 11 volunteer subjects (7 stable asthmatic) did not demonstrate a significant change after 2-hr exposures to diesel exhaust. In summary, we demonstrated that this facility can be effectively and safely used to evaluate acute responses to diesel exhaust exposure in human volunteers.     

Study of Miller timing on exhaust emissions of a hydrotreated vegetable oil (HVO)-fueled diesel engine

The effect of intake valve closure (IVC) timing by utilizing Miller cycle and start of injection (SOI) on particulate matter (PM), particle number, and nitrogen oxide (NO_x) emissions was studied with a hydrotreated vegetable oil (HVO)-fueled nonroad diesel engine. HVO-fueled engine emissions, including aldehyde and polyaromatic hydrocarbon (PAH) emissions, were also compared with those emitted with fossil EN590 diesel fuel. At the engine standard settings, particle number and NO_x emissions decreased at all the studied load points (50%, 75%, and 100%) when the fuel was changed from EN590 to HVO. Adjusting IVC timing enabled a substantial decrease in NO_x emission and combined with SOI timing adjustment somewhat smaller decrease in both NO_x and particle emissions at IVC??50 and??70 °CA points. The HVO fuel decreased PAH emissions mainly due to the absence of aromatics. Aldehyde emissions were lower with the HVO fuel with medium (50%) load. At higher loads (75% and 100%), aldehyde emissions were slightly higher with the HVO fuel. However, the aldehyde emission levels were quite low, so no clear conclusions on the effect of fuel can be made. Overall, the study indicates that paraffinic HVO fuels are suitable for emission reduction with valve and injection timing adjustment and thus provide possibilities for engine manufacturers to meet the strictening emission limits.

Implications: NO_x and particle emissions are dominant emissions of diesel engines and vehicles. New, biobased paraffinic fuels and modern engine technologies have been reported to lower both of these emissions. In this study, even further reductions were achieved with engine valve adjustment combined with novel hydrotreated vegetable oil (HVO) diesel fuel. This study shows that new paraffinic fuels offer further possibilities to reduce engine exhaust emissions to meet the future emission limits.

Supplementary Materials: Supplementary materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association for a complete list of analysed PAH compounds.     

Regulated and unregulated emissions from highway heavy-duty diesel engines complying with U.S. Environmental Protection Agency 2007 emissions standards

As part of the Advanced Collaborative Emissions Study (ACES), regulated and unregulated exhaust emissions from four different 2007 model year U.S. Environmental Protection Agency (EPA)-compliant heavy-duty highway diesel engines were measured on an engine dynamometer. The engines were equipped with exhaust high-efficiency catalyzed diesel particle filters (C-DPFs) that are actively regenerated or cleaned using the engine control module. Regulated emissions of carbon monoxide, nonmethane hydrocarbons, and particulate matter (PM) were on average 97, 89, and 86% lower than the 2007 EPA standard, respectively, and oxides of nitrogen (NOx) were on average 9% lower. Unregulated exhaust emissions of nitrogen dioxide (NO2) emissions were on, average 1.3 and 2.8 times higher than the NO, emissions reported in previous work using 1998- and 2004-technology engines, respectively. However, compared with other work performed on 1994- to 2004-technology engines, average emission reductions in the range of 71-99% were observed for a very comprehensive list of unregulated engine exhaust pollutants and air toxic contaminants that included metals and other elements, elemental carbon (EC), inorganic ions, and gas- and particle-phase volatile and semi-volatile organic carbon (OC) compounds. The low PM mass emitted from the 2007 technology ACES engines was composed mainly of sulfate (53%) and OC (30%), with a small fraction of EC (13%) and metals and other elements (4%). The fraction of EC is expected to remain small, regardless of engine operation, because of the presence of the high-efficiency C-DPF in the exhaust. This is different from typical PM composition of pre-2007 engines with EC in the range of 10-90%, depending on engine operation. Most of the particles emitted from the 2007 engines were mainly volatile nuclei mode in the sub-30-nm size range. An increase in volatile nanoparticles was observed during C-DPF active regeneration, during which the observed particle number was similar to that observed in emissions of pre-2007 engines. However, on average, when combining engine operation with and without active regeneration events, particle number emissions with the 2007 engines were 90% lower than the particle number emitted from a 2004-technology engine tested in an earlier program.     

Field Measurements of Particulate Matter Emissions,Carbon Monoxide,and Exhaust Opacity from Heavy-Duty Diesel Vehicles

ABSTRACT

Diesel particulate matter (PM) is a significant contributor to ambient air PM₁₀ and PM_2.5 particulate levels. In addition, recent literature argues that submicron diesel PM is a pulmonary health hazard. There is difficulty in attributing PM emissions to specific operating modes of a diesel engine, although it is acknowledged that PM production rises dramatically with load and that high PM emissions occur during rapid load increases on turbocharged engines. Snap-acceleration tests generally identify PM associated with rapid transient operating conditions, but not with high load. To quantify the origin of PM during transient engine operation, continuous opacity measurements have been made using a Wager 650CP full flow exhaust opacity meter. Opacity measurements were taken while the vehicles were operated over transient driving cycles on a chassis dynamometer using the West Virginia University (WVU) Transportable Heavy Duty Vehicle Emissions Testing Laboratories. Data were gathered from Detroit Diesel, Cummins, Caterpillar, and Navistar heavy-duty (HD) diesel engines. Driving cycles used were the Central Business District (CBD) cycle, the WVU 5-Peak Truck cycle, the WVU 5-Mile route, and the New York City Bus (NYCB) cycle. Continuous opacity measurements, integrated over the entire driving cycle, were compared to total integrated PM mass. In addition, the truck was subjected to repeat snap-acceleration tests, and PM was collected for a composite of these snap-acceleration tests. Additional data were obtained from a fleet of 1996 New Flyer buses in Flint, MI, equipped with electronically controlled Detroit Diesel Series 50 engines. Again, continuous opacity, regulated gaseous emissions, and PM were measured. The relationship between continuous carbon monoxide (CO) emissions and continuous opacity was noted. In identifying the level of PM emissions in transient diesel engine operation, it is suggested that CO emissions may prove to be a useful indicator and may be used to apportion total PM on a continuous basis over a transient cycle. The projected continuous PM data will prove valuable in future mobile source inventory prediction.     

Hydrocarbon emissions speciation in diesel and biodiesel exhausts

Diesel engine emissions are composed of a long list of organic compounds, ranging from C₂ to C₁₂₊, and coming from the hydrocarbons partially oxidized in combustion or produced by pyrolisis. Many of these are considered as ozone precursors in the atmosphere, since they can interact with nitrogen oxides to produce ozone under atmospheric conditions in the presence of sunlight. In addition to problematic ozone production, Brookes, P., and Duncan, M. [1971. Carcinogenic hydrocarbons and human cells in culture. Nature.] and Heywood, J. [1988. Internal Combustion Engine Fundamentals.Mc Graw-Hill, ISBN 0-07-1000499-8.] determined that the polycyclic aromatic hydrocarbons present in exhaust gases are dangerous to human health, being highly carcinogenic.The aim of this study was to identify by means of gas chromatography the amount of each hydrocarbon species present in the exhaust gases of diesel engines operating with different biodiesel blends. The levels of reactive and non-reactive hydrocarbons present in diesel engine exhaust gases powered by different biodiesel fuel blends were also analyzed.Detailed speciation revealed a drastic change in the nature and quantity of semi-volatile compounds when biodiesel fuels are employed, the most affected being the aromatic compounds. Both aromatic and oxygenated aromatic compounds were found in biodiesel exhaust. Finally, the conservation of species for off-side analysis and the possible influence of engine operating conditions on the chemical characterization of the semi-volatile compound phase are discussed.The use of oxygenated fuel blends shows a reduction in the Engine-Out emissions of total hydrocarbons. But the potential of the hydrocarbon emissions is more dependent on the compositions of these hydrocarbons in the Engine-Out, to the quantity; a large percent of hydrocarbons existing in the exhaust, when biodiesel blends are used, are partially burned hydrocarbons, and are interesting as they have the maximum reactivity, but with the use of pure biodiesel and diesel, the most hydrocarbons are from unburned fuel and they have a less reactivity. The best composition in the fuel, for the control of the hydrocarbon emissions reactivity, needs to be a fuel with high-saturated fatty acid content.     

Idle emissions from heavy-duty diesel and natural gas vehicles at high altitude

Idle emissions of total hydrocarbon (THC), CO, NOx, and particulate matter (PM) were measured from 24 heavy-duty diesel-fueled (12 trucks and 12 buses) and 4 heavy-duty compressed natural gas (CNG)-fueled vehicles. The volatile organic fraction (VOF) of PM and aldehyde emissions were also measured for many of the diesel vehicles. Experiments were conducted at 1609 m above sea level using a full exhaust flow dilution tunnel method identical to that used for heavy-duty engine Federal Test Procedure (FTP) testing. Diesel trucks averaged 0.170 g/min THC, 1.183 g/min CO, 1.416 g/min NOx, and 0.030 g/min PM. Diesel buses averaged 0.137 g/min THC, 1.326 g/min CO, 2.015 g/min NOx, and 0.048 g/min PM. Results are compared to idle emission factors from the MOBILE5 and PART5 inventory models. The models significantly (45-75%) overestimate emissions of THC and CO in comparison with results measured from the fleet of vehicles examined in this study. Measured NOx emissions were significantly higher (30-100%) than model predictions. For the pre-1999 (pre-consent decree) truck engines examined in this study, idle NOx emissions increased with model year with a linear fit (r2 = 0.6). PART5 nationwide fleet average emissions are within 1 order of magnitude of emissions for the group of vehicles tested in this study. Aldehyde emissions for bus idling averaged 6 mg/min. The VOF averaged 19% of total PM for buses and 49% for trucks. CNG vehicle idle emissions averaged 1.435 g/min for THC, 1.119 g/min for CO, 0.267 g/min for NOx, and 0.003 g/min for PM. The g/min PM emissions are only a small fraction of g/min PM emissions during vehicle driving. However, idle emissions of NOx, CO, and THC are significant in comparison with driving emissions.     

Emissions of polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs from heavy-duty diesel vehicles with DPF and SCR

In total, 24 polycyclic aromatic hydrocarbons (PAHs) in both gas and particle phases and 35 nitro-PAHs in particle phase were analyzed in the exhaust from heavy-duty diesel vehicles equipped with after-treatment for particulate matter (PM) and NO_X control. The test vehicles were carried out using a chassis dynamometer under highway cruise, transient Urban Dynamometer Driving Schedule (UDDS), and idle operation. The after-treatment efficiently abated more than 90% of the total PAHs. Indeed, the particle-bound PAHs were reduced by >99%, and the gaseous PAHs were removed at various extents depending on the type of after-treatment and the test cycles. The PAHs in gas phase dominated the total PAH (gas + particle phases) emissions for all the test vehicles and for all cycles; that is, 99% of the two-ring and 98% of the three-ring and 97% of the four-ring and 95% of the carcinogenic PAHs were in the gas-phase after a diesel particle filter (DPF) and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must include this volatile fraction and cannot be based on the particle fraction only. The selective catalytic reduction (SCR) did not appear to promote nitration of the PAHs in general, although there might be some selective nitration of phenanthrene. Importantly the after-treatmtent reduced the equivalent B[a]P (B[a]Peq) emissions by >95%, suggesting a substantial health benefit.

Implications: This study demonstrated that after-treatments, including diesel particulate filters (DPF), diesel oxidation catalysts (DOC), and selective catalytic reduction (SCR), significantly reduce the emissions of PAHs from heavy-duty diesel engines. The gas-phase PAHs dominate the total PAH (gas + particle phases) emissions from heavy-duty diesel vehicles retrofitted with various DPFs and not bound to the very small amount of particulate matter left after a DPF. Consequently, an evaluation of the toxicity of DPF exhaust must also include this volatile fraction and cannot be based on the particle fraction only.

Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association.     

Effects of water-emulsified fuel on a diesel engine generator’s thermal efficiency and exhaust

Water-emulsified diesel has proven itself as a technically sufficient improvement fuel to improve diesel engine fuel combustion emissions and engine performance. However, it has seldom been used in light-duty diesel engines. Therefore, this paper focuses on an investigation into the thermal efficiency and pollution emission analysis of a light-duty diesel engine generator fueled with different water content emulsified diesel fuels (WD, including WD-0, WD-5, WD-10, and WD-15). In this study, nitric oxide, carbon monoxide, hydrocarbons, and carbon dioxide were analyzed by a vehicle emission gas analyzer, and the particle size and number concentration were measured by an electrical low-pressure impactor. In addition, engine loading and fuel consumption were also measured to calculate the thermal efficiency. Measurement results suggested that water-emulsified diesel was useful to improve the thermal efficiency and the exhaust emission of a diesel engine. Obviously, the thermal efficiency was increased about 1.2 to 19.9%. In addition, water-emulsified diesel leads to a significant reduction of nitric oxide emission (less by about 18.3 to 45.4%). However, the particle number concentration emission might be increased if the loading of the generator becomes lower than or equal to 1800 W. In addition, exhaust particle size distributions were shifted toward larger particles at high loading. The consequence of this research proposed that the water-emulsified diesel was useful to improve the engine performance and some of exhaust emissions, especially the NO emission reduction.

Implications:The accumulated test results provide a good basis to resolve the corresponding pollutants emitted from a light-duty diesel engine generator. By measuring and analyzing transforms of exhaust pollutant from this engine generator, the effects of water-emulsified diesel fuel and loading on emission characteristics might be more clear. Understanding reduction of pollutant emissions during the use of water-emulsified diesel helps improve the effectiveness of the testing program. The analyzed consequences provide useful information to the government for setting policies to curb pollutant emissions from a light-duty diesel engine generator more effectively.     

Evaluations of the chemical mass balance method for determining contributions of gasoline and diesel exhaust to ambient carbonaceous aerosols

The US. Department of Energy Gasoline/Diesel PM Split Study was conducted to assess the sources of uncertainties in using an organic compound-based chemical mass balance receptor model to quantify the relative contributions of emissions from gasoline (or spark ignition [SI]) and diesel (or compression ignition [CI]) engines to ambient concentrations of fine particulate matter (PM2.5) in California's South Coast Air Basin (SOCAB). In this study, several groups worked cooperatively on source and ambient sample collection and quality assurance aspects of the study but worked independently to perform chemical analysis and source apportionment. Ambient sampling included daily 24-hr PM2.5 samples at two air quality-monitoring stations, several regional urban locations, and along freeway routes and surface streets with varying proportions of automobile and truck traffic. Diesel exhaust was the dominant source of total carbon (TC) and elemental carbon (EC) at the Azusa and downtown Los Angeles, CA, monitoring sites, but samples from the central part of the air basin showed nearly equal apportionments of CI and SI. CI apportionments to TC were mainly dependent on EC, which was sensitive to the analytical method used. Weekday contributions of CI exhaust were higher for Interagency Monitoring of Protected Visual Environments (IMPROVE; 41+/-3.7%) than Speciation Trends Network (32+/-2.4%). EC had little effect on SI apportionment. SI apportionments were most sensitive to higher molecular weight polycyclic aromatic hydrocarbons (indeno[123-cd]pyrene, benzo(ghi)perylene, and coronene) and several steranes and hopanes, which were associated mainly with high emitters. Apportionments were also sensitive to choice of source profiles. CI contributions varied from 30% to 60% of TC when using individual source profiles rather than the composites used in the final apportionments. The apportionment of SI vehicles varied from 1% to 12% of TC depending on the specific profile that was used. Up to 70% of organic carbon (OC) in the ambient samples collected at the two fixed monitoring sites could not be apportioned to directly emitted PM emissions.     

Comparison of vehicle exhaust emissions from modified diesel fuels

Three diesel fuels, one oil sand-derived (OSD) diesel serving as base fuel, one cetane-enhanced base fuel, and one oxygenate [diethylene glycol dimethyl ether (DEDM)]-blended base fuel, were tested for their emission characterizations in vehicle exhaust on a light-duty diesel truck that reflects the engine technology of the 1994 North American standard. Both the cetane-enhanced and the oxygenate-blended fuels were able to reduce regulated [CO, particulate matter (PM), total hydrocarbon (THC)] and nonregulated [polyaromatic hydrocarbons (PAHs), carbonyls, and other volatile organic chemicals] emissions, except for nitrogen oxides (NO(x)), compared with the base fuel. Although burning a fuel that contains oxygen could conceivably yield more oxygenated compounds in emissions, the oxygenate-blended diesel fuel resulted in reduced emissions of formaldehyde along with hydrocarbons such as benzene, 1,3-butadiene, and PAHs. Reductions in nitro-PAH emissions have been observed in both the cetane-enhanced and oxygenated fuels. This further demonstrates the benefits of using a cetane enhancer and the oxygenated fuel component.     

柴油车排气颗粒物的后处理技术

本文分析探讨了柴油机排气颗粒物的组成、危害及后处理技术。介绍了颗粒捕集器及其消极和积极再生方法、采用氧化催化剂或四效催化剂的催化净化器和低温等离子体 -催化净化技术。     

Selected ion chromatograms and tandem mass spectrometry for detection of trace polycyclic aromatic hydrocarbons in diesel exhaust

Polycyclic aromatic hydrocarbon (PAH) measurements are essential for scientists and engineers who investigate these anthropogenic compounds. Diesel engines contribute to the problem, so analysts are measuring PAHs from these sources. However, diesel exhaust presents special problems for precise analytical measurements. The exhaust matrix is very complex; consequently, PAH detection sensitivity deteriorates, especially for trace PAHs in the exhaust. Yet, these are conditions and amounts that exist in real samples. Nonetheless, selected ion chromatogram (SIC) and tandem mass spectrometry (MS/MS) techniques improve trace PAH detection; ion trap technology makes both mass techniques possible. The purpose of this investigation was to evaluate SIC and MS/MS for applications to measure PAHs in diesel exhaust samples. The signal-to-noise ratio for accurate quantitation improves, relative to traditional mass techniques, because these techniques ignore or eliminate interfering components. On a VF-5MS chromatographic column, these techniques improve sensitivity and reproducibility. They produce a superior limit of detection in the useful range for PAH samples extracted from actual engine exhaust, 10-30 pg for the smaller PAHs and 1-6 ng for the larger PAHs. The results with SIC and MS/MS are reproducible, so analysts can report PAH amounts with defined statistical confidence intervals. SIC and MS/MS improve detection for trace PAHs in convoluted diesel exhaust samples.     

Diesel engines: environmental impact and control.

The diesel engine is the most efficient prime mover commonly available today. Diesel engines move a large portion of the world's goods, power much of the world's equipment, and generate electricity more economically than any other device in their size range. But the diesel is one of the largest contributors to environmental pollution problems worldwide, and will remain so, with large increases expected in vehicle population and vehicle miles traveled (VMT) causing ever-increasing global emissions. Diesel emissions contribute to the development of cancer; cardiovascular and respiratory health effects; pollution of air, water, and soil; soiling; reductions in visibility; and global climate change. Where instituted, control programs have been effective in reducing diesel fleet emissions. Fuel changes, such as reduced sulfur and aromatics content, have resulted in immediate improvements across the entire diesel on- and off-road fleet, and promise more improvements with future control. In the United States, for example, 49-state (non-California) off-road diesel fuel sulfur content is 10 times higher than that of national on-road diesel fuel. Significantly reducing this sulfur content would reduce secondary particulate matter (PM) formation and allow the use of control technologies that have proven effective in the on-road arena. The use of essentially zero-sulfur fuels, such as natural gas, in heavy-duty applications is also expected to continue. Technology changes, such as engine modifications, exhaust gas recirculation, and catalytic aftertreatment, take longer to fully implement, due to slow fleet turnover. However, they eventually result in significant emission reductions and will be continued on an ever-widening basis in the United States and worldwide. New technologies, such as hybrids and fuel cells, show significant promise in reducing emissions from sources currently dominated by diesel use. Lastly, the turnover of trucks and especially off-road equipment is slow; pollution control agencies need to address existing emissions with in-use programs, such as exhaust trap retrofits and smoke inspections. Such a program is underway in California. These and other steps that can be continued and improved will allow the use of the diesel engine, with its superior fuel consumption, to continue to benefit society while greatly reducing its negative environmental and health impacts. The next ten years can and must become the "Decade of Clean Diesel."