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Journal ArticleDOI

Elemental Carbon-Based Method for Monitoring Occupational Exposures to Particulate Diesel Exhaust

01 Jan 1996-Aerosol Science and Technology (Taylor & Francis Group)-Vol. 25, Iss: 3, pp 221-241
TL;DR: In this article, a thermal-optical technique for analysis of the carbonaceous fraction of particulate diesel exhaust is reported, and the speciation of organic and elemental carbon is accomplished through temperature and atmosphere control, and by an optical feature that corrects for pyrolytically generated carbon.
Abstract: Diesel exhaust has been classified a probable human carcinogen, and the National Institute for Occupational Safety and Health (NIOSH) has recommended that employers reduce workers' exposures. Because diesel exhaust is a chemically complex mixture containing thousands of compounds, some measure of exposure must be selected. Previously used methods involving gravimetry or analysis of the soluble organic fraction of diesel soot lack adequate sensitivity and selectivity for low-level determination of particulate diesel exhaust; a new analytical approach was therefore needed. In this paper, results of investigation of a thermal-optical technique for analysis of the carbonaceous fraction of particulate diesel exhaust are reported. With this technique, speciation of organic and elemental carbon is accomplished through temperature and atmosphere control, and by an optical feature that corrects for pyrolytically generated carbon, or “char,” which is formed during the analysis of some materials. The therma...
Citations
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Journal ArticleDOI
TL;DR: In this paper, the authors provided an assessment of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice.
Abstract: Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.

4,591 citations


Cites methods from "Elemental Carbon-Based Method for M..."

  • ...[107] In thermal methods based on volatility, the sample filter is first heated in inert gas to volatilize OC and then heated again with oxygen to combust the EC; cooling sometimes occurs before the second heating [e.g., Chow et al., 1993; Birch and Cary, 1996;Watson et al., 2005]....

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Journal ArticleDOI
TL;DR: The optical properties of light-absorbing, carbonaceous substance often called "soot", "black carbon", or "carbon black" have been the subject of some debate as discussed by the authors.
Abstract: The optical properties of the light-absorbing, carbonaceous substance often called “soot,” “black carbon,” or “carbon black" have been the subject of some debate. These properties are necessary to model how aerosols affect climate, and our review is targeted specifically for that application. We recommend the term light-absorbing carbon to avoid conflict with operationally based definitions. Absorptive properties depend on molecular form, particularly the size of sp 2-bonded clusters. Freshly-generated particles should be represented as aggregates, and their absorption is like that of particles small relative to the wavelength. Previous compendia have yielded a wide range of values for both refractive indices and absorption cross section. The absorptive properties of light-absorbing carbon are not as variable as is commonly believed. Our tabulation suggests a mass-normalized absorption cross section of 7.5 ± 1.2 m2/g at 550 nm for uncoated particles. We recommend a narrow range of refractive indices for s...

2,312 citations


Cites background from "Elemental Carbon-Based Method for M..."

  • ...Methods for identifying this component include exposing the sample to high temperatures (e.g., Chow et al. 1993; Birch and Cary 1996), washing the sample with solvents such as benzene (Gundel et al. 1984) or hydrogen peroxide (Ogren et al. 1983), or interpreting Raman spectroscopy (Rosen et al.…...

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  • ...This term is an operational definition based on the stability of carbon at elevated temperatures (Huntzicker et al. 1982; Chow et al. 1993; Birch and Cary 1996)....

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Journal ArticleDOI
TL;DR: In this article, the authors show that brown carbon may severely bias measurements of atmospheric "black carbon" and "elemental carbon" over vast parts of the troposphere, especially those strongly polluted by biomass burning, where the mass concentration of C brown is high relative to that of soot carbon.
Abstract: Although the definition and measurement techniques for atmospheric "black carbon" ("BC") or "elemental carbon'' ("EC") have long been subjects of scientific controversy, the recent discovery of light-absorbing carbon that is not black ("brown carbon, C brown ") makes it imperative to reassess and redefine the components that make up light-absorbing carbonaceous matter (LAC) in the atmosphere. Evidence for the atmospheric presence of C brown comes from (1) spectral aerosol light absorption measurements near specific combustion sources, (2) observations of spectral properties of water extracts of continental aerosol, (3) laboratory studies indicating the formation of light-absorbing organic matter in the atmosphere, and (4) indirectly from the chemical analogy of aerosol species to colored natural humic substances. We show that brown carbon may severely bias measurements of "BC" and "EC" over vast parts of the troposphere, especially those strongly polluted by biomass burning, where the mass concentration of C brown is high relative to that of soot carbon. Chemical measurements to determine "EC" are biased by the refractory nature of C brown as well as by complex matrix interferences. Optical measurements of "BC" suffer from a number of problems: (1) many of the presently used instruments introduce a substantial bias into the determination of aerosol light absorption, (2) there is no unique conversion factor between light absorption and "EC" or "BC" concentration in ambient aerosols, and (3) the difference in spectral properties between the different types of LAC, as well as the chemical complexity of C brown , lead to several conceptual as well as practical complications. We also suggest that due to the sharply increasing absorption of C brown towards the UV, single-wavelength light absorption measurements may not be adequate for the assessment of absorption of solar radiation in the troposphere. We discuss the possible consequences of these effects for our understanding of tropospheric processes, including their influence on UV-irradiance, atmospheric photochemistry and radiative transfer in clouds.

1,706 citations


Cites background or methods from "Elemental Carbon-Based Method for M..."

  • ...Thermochemical analysis was originally applied to urban aerosols, including particularly diesel soot (Ellis and Novakov, 1982; Cadle et al., 1983; Cachier et al., 1989a; Birch and Cary, 1996)....

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  • ...Birch and Cary (1996) note that with an “optimized” setting they find only 0.86% ECa in cigarette smoke, while with a “less than optimal” setting 20–30% of the carbon in cigarette smoke was designated elemental....

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  • ...In this method, the transmittance or reflectance of the filter sample is monitored during the thermographic analysis (Chow et al., 1993; Birch and Cary, 1996)....

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Journal ArticleDOI
TL;DR: The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.
Abstract: Organic compound emission rates for volatile organic compounds (VOC), gas-phase semivolatile organic compounds, and particle-phase organic compounds are measured from residential fireplace combustion of wood. Firewood from a conifer tree (pine) and from two deciduous trees (oak and eucalyptus) is burned to determine organic compound emissions profiles for each wood type including the distribution of the alkanes, alkenes, aromatics, polycyclic aromatic hydrocarbons (PAH), phenol and substituted phenols, guaiacol and substituted guaiacols, syringol and substituted syringols, carbonyls, alkanoic acids, resin acids, and levoglucosan. Levoglucosan is the major constituent in the fine particulate emissions from all three wood types, contributing 18−30% of the fine particulate organic compound emissions. Guaiacol (2-methoxyphenol), and guaiacols with additional substituents at position 4 on the molecule, and resin acids are emitted in significant quantities from pine wood combustion. Syringol (2,6-dimethoxyphenol) and syringols with additional substituents at position 4 on the molecule are emitted in large amounts from oak and eucalyptus firewood combustion, but these compounds are not detected in the emissions from pine wood combustion. Syringol and most of the substituted syringols are found to be semivolatile compounds that are present in both the gas and particle phases, but two substituted syringols that have not been previously quantified in wood smoke emissions, propionylsyringol and butyrylsyringol, are found exclusively in the particle phase and can be used to help trace hardwood smoke particles in the atmosphere. Benzene, ethene, and acetylene are often used as tracers for motor vehicle exhaust in the urban atmosphere. The contribution of wood smoke to the ambient concentrations of benzene, ethene, and acetylene could lead to an overestimate of the contribution of motor vehicle tailpipe exhaust to atmospheric VOC concentrations.

1,188 citations

Journal ArticleDOI
TL;DR: In this article, a two-stage dilution source sampling system was used to quantify gas and particle-phase tailpipe emissions from late-model medium duty diesel trucks using a two stage dilution sampling system.
Abstract: Gas- and particle-phase tailpipe emissions from late-model medium duty diesel trucks are quantified using a two-stage dilution source sampling system. The diesel trucks are driven through the hot-start Federal Test Procedure (FTP) urban driving cycle on a transient chassis dynamometer. Emission rates of 52 gas-phase volatile hydrocarbons, 67 semivolatile and 28 particle-phase organic compounds, and 26 carbonyls are quantified along with fine particle mass and chemical composition. When all C_1−C_(13) carbonyls are combined, they account for 60% of the gas-phase organic compound mass emissions. Fine particulate matter emission rates and chemical composition are quantified simultaneously by two methods: a denuder/filter/PUF sampler and a traditional filter sampler. Both sampling techniques yield the same elemental carbon emission rate of 56 mg km^(-1) driven, but the particulate organic carbon emission rate determined by the denuder-based sampling technique is found to be 35% lower than the organic carbon mass collected by the traditional filter-based sampling technique due to a positive vapor-phase sorption artifact that affects the traditional filter sampling technique. The distribution of organic compounds in the diesel fuel used in this study is compared to the distribution of these compounds in the vehicle exhaust. Significant enrichment in the ratio of unsubstituted polycyclic aromatic hydrocarbons (PAH) to their methyl- and dimethyl-substituted homologues is observed in the tailpipe emissions relative to the fuel. Isoprenoids and tricyclic terpanes are quantified in the semivolatile organics emitted from diesel vehicles. When used in conjunction with data on the hopanes, steranes, and elemental carbon emitted, the isoprenoids and the tricyclic terpanes may help trace the presence of diesel exhaust in atmospheric samples.

988 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a general hypothesis is developed that dust overloading, which is typified by a progressive reduction of particle clearance from the deep lung, reflects a breakdown in alveolar macrophage (AM)-mediated dust removal due to the loss of AM mobility.

466 citations

Journal ArticleDOI
TL;DR: Comparaison avec les appareils deja existants sur le marche d'un nouvel echantillonneur de particules inhalables developpement et essai d' un nouveau echantillionneur d'Etats-Unis.
Abstract: Developpement et essai d'un nouvel echantillonneur de particules inhalables. Comparaison avec les appareils deja existants sur le marche

276 citations

Journal ArticleDOI
TL;DR: Diesel exhaust, inhaled chronically at a high concentration, is a pulmonary carcinogen in the rat and Logistic regression modeling demonstrated a significant relationship between tumor prevalence and both exposure concentration and soot lung burden.

254 citations

Journal ArticleDOI
TL;DR: The hypothesis that occupational exposure to diesel exhaust results in a small but significantly elevated risk for lung cancer is supported, based on results taken in conjunction with other reported results.
Abstract: The risk of lung cancer as a result of exposure to diesel exhaust from railroad locomotives was assessed in a cohort of 55,407 white male railroad workers 40 to 64 yr of age in 1959 who had started railroad service 10 to 20 years earlier. The cohort was traced until the end of 1980, and death certificates were obtained for 88% of 19,396 deaths; 1,694 lung cancer cases were identified. Yearly railroad job from 1959 to death or retirement was available from the Railroad Retirement Board, and served as an index of diesel exhaust exposure. Directly standardized rates and a proportional hazards model were used to calculate the relative risk of lung cancer based on work in a job with diesel exhaust exposure beginning in 1959. A relative risk of 1.45 (95% CI = 1.11, 1.89) for lung cancer was obtained in the group of workers 40 to 44 yr of age in 1959, the group with the longest possible duration of diesel exposure. The cohort was selected to minimize the effect of past railroad asbestos exposure, and analysis with workers with possible asbestos exposure excluded resulted in a similarly elevated risk. Workers with 20 yr or more elapsed since 1959, the effective start of diesel exposure for the cohort, had the highest relative risk. These results taken in conjunction with other reported results support the hypothesis that occupational exposure to diesel exhaust results in a small but significantly elevated risk for lung cancer.

192 citations

Journal ArticleDOI
TL;DR: The diesel passenger car offers a substantial advantage in fuel economy over its gasoline-powered counterpart, but the long-range future of the diesel in this application is threatened by future federal standards on exhaust particular emissions as discussed by the authors.
Abstract: The diesel passenger car offers a substantial advantage in fuel economy over its gasoline-powered counterpart, but the long-range future of the diesel in this application is threatened by future federal standards on exhaust particular emissions. These particulates are primarily combustion-generated carbonaceous soot in combination with a solvent-extractable hydrocarbon fraction. Particulate production involves an incompletely understood series of phenomena that includes nucleation, surface growth, agglomeration, dehydrogenation, oxidation, and adsorption and condensation of gaseous hydrocarbons. The contemporary state of understanding of these events is reviewed as they apply to the passenger-car diesel engine.

129 citations