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Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Emission factors for black carbon (BC) and particle number (PN) were measured from 226 individual heavy-duty (HD) diesel-fueled trucks driving through a 1 km-long California highway tunnel in August 2006. Emission factors were based on concurrent increases in BC, PN, and CO2B concentrations (measured at 1 Hz) that corresponded to the passage of individual HD trucks. The distributions of BC and PN emission factors from individual HD trucks are skewed, meaning that a large fraction of pollution comes from a small fraction of the in-use vehicle fleet. The highest-emitting 10% of trucks were responsible for ≈ 40% of total BC and PN emissions from all HD trucks. BC emissions were log-normally distributed with a mean emission factor of 1.7 g kg −1 and maximum values of ≈ 10 g kg−1. Corresponding values for PN emission factors were 4.7 x 1015 and 4 x 1016 kg−1. There was minimal overlap among high-emitters of these two pollutants: only 1 of the 226 HD trucks measured was found to be among the highest 10% for both BC and PN. Monte Carlo resampling of the distribution of BC emission factors observed in this study revealed that uncertainties (1[sigma]) in extrapolating from a random sample of n HD trucks to a population mean emission factor ranged from ± 43% for n = 10 to ± 8% for n = 300, illustrating the importance of sufficiently large vehicle sample sizes in emissions studies. Studies with low sample sizes are also more easily biased due to misrepresentation of high-emitters. As vehicles become cleaner on average in future years, skewness of the emissions distributions will increase, and thus sample sizes needed to extrapolate reliably from a subset of vehicles to the entire in-use vehicle fleet are expected to become more of a challenge.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Emission factors for black carbon (BC) and particle number (PN) were measured from 226 individual heavy-duty (HD) diesel-fueled trucks driving through a 1 km-long California highway tunnel in August 2006. Emission factors were based on concurrent increases in BC, PN, and CO2B concentrations (measured at 1 Hz) that corresponded to the passage of individual HD trucks. The distributions of BC and PN emission factors from individual HD trucks are skewed, meaning that a large fraction of pollution comes from a small fraction of the in-use vehicle fleet. The highest-emitting 10% of trucks were responsible for ≈ 40% of total BC and PN emissions from all HD trucks. BC emissions were log-normally distributed with a mean emission factor of 1.7 g kg −1 and maximum values of ≈ 10 g kg−1. Corresponding values for PN emission factors were 4.7 x 1015 and 4 x 1016 kg−1. There was minimal overlap among high-emitters of these two pollutants: only 1 of the 226 HD trucks measured was found to be among the highest 10% for both BC and PN. Monte Carlo resampling of the distribution of BC emission factors observed in this study revealed that uncertainties (1[sigma]) in extrapolating from a random sample of n HD trucks to a population mean emission factor ranged from ± 43% for n = 10 to ± 8% for n = 300, illustrating the importance of sufficiently large vehicle sample sizes in emissions studies. Studies with low sample sizes are also more easily biased due to misrepresentation of high-emitters. As vehicles become cleaner on average in future years, skewness of the emissions distributions will increase, and thus sample sizes needed to extrapolate reliably from a subset of vehicles to the entire in-use vehicle fleet are expected to become more of a challenge.
Author: Timothy Ryan Dallmann Publisher: ISBN: Category : Languages : en Pages : 153
Book Description
Mobile sources contribute significantly to air pollution problems. Relevant pollutants include numerous gaseous and particle-phase species that can affect human health, ecosystems, and climate. Accurate inventories of emissions from these sources are needed to help understand possible adverse impacts, and to develop effective air quality management strategies. Unfortunately large uncertainties persist in the understanding of mobile source emissions, and how these emissions are changing over time. There are more than two hundred million motor vehicles operating in the United States alone, and measurements of emissions from these sources are sparse. Pollutant emission factor distributions are becoming increasingly skewed, and this continually increases the needed vehicle sample size in studies that seek to quantify fleet-average vehicle emission rates. This dissertation aims to evaluate long-term trends in mobile source emissions in the United States, and to make detailed measurements of emissions from present-day fleets of on-road vehicles operating in California. Novel features of this work include studies of the in-use effectiveness of modern control technologies used to reduce diesel engine emissions, and application of advanced instrumentation to measure emissions from large numbers of on-road gasoline and diesel vehicles at high time resolution and with a high level of chemical and physical detail. Long-term trends in mobile source emissions of nitrogen oxides (NOx) and fine particulate matter (PM2.5) in the United States were investigated through development of a fuel-based emission inventory. Annual emissions from on- and off-road gasoline and diesel engines were quantified for the years 1996-2006. Diesel engines were found to be the dominant mobile source of NOx and PM2.5, and on-road diesel vehicles were identified as the single largest anthropogenic source of NOx emissions in the United States as of 2005. The relative importance of diesel engines as a source of NOx grew over the ten-year time period considered here, while emissions from gasoline engines declined due to increased effectiveness and use of three-way catalytic converters. A comparison with national emission inventory estimates for 2005 found substantial differences in source contributions to overall mobile source emissions, with larger contributions from on-road diesel engines indicated in this study. The importance of diesel engines as a source of exhaust particulate matter emissions has led to the recent introduction of advanced emission control technologies in the United States, such as diesel particle filters (DPF), which have been required since 2007 for all new on-road heavy-duty (HD) diesel engines. In addition to national requirements for the use of such control devices on new engines, California has mandated accelerated clean-up of statewide emissions from older in-use diesel engines. This goal is to be achieved through filter retrofit and truck/engine replacement programs. This dissertation uses measurements of emissions from in-use HD diesel trucks at the Port of Oakland to evaluate the impacts of a DPF retrofit and truck replacement program. A plume capture method was developed to quantify black carbon (BC) and NOx emission factors for individual trucks and to characterize emission factor distributions. A comparison of emissions measured before and after the implementation of the truck retrofit/replacement rule shows a 54 " 11% reduction in the fleet-average BC emission factor, accompanied by a shift to a more highly skewed emission factor distribution. Although only particulate matter mass reductions were required in the first phase of the program, a 41 " 5% reduction in the fleet-average NOx emission factor was observed. These results provide an in-use/real-world assessment of the impact of DPF emission control systems, and a preview of emissions changes that may be expected from the extension of similar control programs to the entire HD truck fleet in California beginning in 2014. The plume capture method was further applied to measure emissions from a more diverse population of trucks observed at the Caldecott tunnel in summer 2010. Emissions from hundreds of individual trucks were measured, and emission factor distributions were characterized for nitric oxide (NO), nitrogen dioxide (NO2), carbon monoxide (CO), formaldehyde, BC, as well as optical properties of the emitted particles. Emission factor distributions for all species were skewed, with a small fraction of trucks contributing disproportionately to total emissions. For example, half of the total measured NO2 and BC were produced by only 10% of the total measurements. Total NOx and formaldehyde showed less skewed emission factor distributions compared to CO and BC. Emission factors for NO2 were found to be anti-correlated with all other pollutants considered here. Also, the fleet-average NO2 emission factor increased 34 " 18% relative to the corresponding value measured at the same location in 2006. These findings confirm that the use of catalyzed DPF systems is leading to increased primary NO2 emissions. Absorption and scattering cross-section emission factors were used to calculate the aerosol single scattering albedo (SSA, at 532 nm) for individual truck exhaust plumes, which averaged 0.14 " 0.03. This value of aerosol SSA is very low compared to typical values (0.90-0.99) observed in ambient air studies. It is indicative of a strongly light-absorbing aerosol, due to the high BC emissions that are a characteristic feature of diesel exhaust PM emissions. Measurements at the Caldecott tunnel also included efforts to quantify light-duty (LD) gasoline vehicle emission factors, and further investigation of the relative contributions of on-road gasoline and diesel engines to air pollutant emissions. Measurements of CO, NOx, PM2.5, BC, and organic aerosol (OA) were made in a tunnel traffic bore where LD vehicles account for>99% of total traffic. Measured pollutant concentrations were apportioned between LD gasoline vehicles and diesel trucks, and fleet-average emission factors were quantified for LD gasoline vehicles using a carbon balance method. Diesel trucks contributed 18 " 3, 22 " 5, 44 " 8% of measured NOx, OA, and BC concentrations, respectively, despite accounting for
Author: Sara Danielle Forestieri Publisher: ISBN: 9781321362497 Category : Languages : en Pages :
Book Description
Eight light-duty gasoline low emission vehicles (LEV I) were tested on a Chassis dynamometer using the California Unified Cycle (UC) at the Haagen-Smit vehicle test facility at the California Air Resources Board in El Monte, CA during September 2011. The UC includes a cold start phase followed by a hot stabilized running phase. In addition, a light-duty gasoline LEV vehicle and ultra-low emission vehicle (ULEV), and a light-duty diesel passenger vehicle and gasoline direct injection (GDI) vehicle were tested on a constant velocity driving cycle. A variety of instruments with response times ≥ 0.1 Hz were used to characterize how the emissions of the major PM components varied for the LEVs during a typical driving cycle. This study focuses primarily on emissions of black carbon (BC). These measurements allowed for the determination of BC emission factors throughout the driving cycle, providing insights into the temporal variability of BC emission factors during different phases of a typical driving cycle.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Average particle number concentrations and size distributions from (almost equal to)61,000 light-duty (LD) vehicles and (almost equal to)2500 medium-duty (MD) and heavy-duty (HD) trucks were measured during the summer of 2006 in a San Francisco Bay area traffic tunnel. One of the traffic bores contained only LD vehicles, and the other contained mixed traffic, allowing pollutants to be apportioned between LD vehicles and diesel trucks. Particle number emission factors (particle diameter D{sub p}> 3 nm) were found to be (3.9 ± 1.4) x 1014 and (3.3 ± 1.3) x 1015 kg−1 fuel burned for LD vehicles and diesel trucks, respectively. Size distribution measurements showed that diesel trucks emitted at least an order of magnitude more particles for all measured sizes (10
Author: OECD Publisher: OECD Publishing ISBN: 9264888853 Category : Languages : en Pages : 149
Book Description
Non-exhaust emissions of particulate matter constitute a little-known but rising share of emissions from road traffic and have significant negative impacts on public health. This report synthesizes the current state of knowledge about the nature, causes, and consequences of non-exhaust particulate emissions. It also projects how particulate matter emissions from non-exhaust sources may evolve in future years and reflects on policy instrument mixes that can address this largely ignored environmental issue.
Author: Frank Balck Publisher: ISBN: Category : Trucks Languages : en Pages : 22
Book Description
Apportionment of air pollution to sources requires knowledge of source emission strengths and/or chemical and physical characteristics. The literature is deficient in data useful for this purpose for heavy-duty motor vehicles, which can be important sources of air pollution in select microenvironments. Emission factors are developed in this study for heavy-duty gasoline trucks using chassis dynamometer simulations of urban driving conditions. The sensitivity of the emissions to such considerations as the characteristics of the speed-time driving schedule, vehicle payload, and chassis configuration are examined. Emissions characterization includes total and individual hydrocarbons, aldehydes, carbon monoxide, oxides of nitrogen, total particulate matter, particulate organics, lead, bromine, chlorine, and the fraction of total particulate less than 2 microns. Preliminary comparisons of emissions obtained using transient engine and transient chassis test procedures are also reported.
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Author: 
Author: Robert A. Harley
Author: Timothy Ryan Dallmann
Author: Thomas W. Kirchstetter
Author: George Alexander Ban-Weiss
Author: Sara Danielle Forestieri
Author: 
Author: Robert A. Harley
Author: OECD
Author: Frank Balck