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...

https://www.tandfonline.com/doi/pdf/10.1080/02786829608965393

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

During the last few years, research on toxicologically relevant properties of engineered nanoparticles has increased tremendously. A number of international research projects and additional activities are ongoing in the EU and the US, nourishing the expectation that more relevant technical and toxicological data will be published. Their widespread use allows for potential exposure to engineered nanoparticles during the whole lifecycle of a variety of products. When looking at possible exposure routes for manufactured Nanoparticles, inhalation, dermal and oral exposure are the most obvious, depending on the type of product in which Nanoparticles are used. This review shows that (1) Nanoparticles can deposit in the respiratory tract after inhalation. For a number of nanoparticles, oxidative stress-related inflammatory reactions have been observed. Tumour-related effects have only been observed in rats, and might be related to overload conditions. There are also a few reports that indicate uptake of nanoparticles in the brain via the olfactory epithelium. Nanoparticle translocation into the systemic circulation may occur after inhalation but conflicting evidence is present on the extent of translocation. These findings urge the need for additional studies to further elucidate these findings and to characterize the physiological impact. (2) There is currently little evidence from skin penetration studies that dermal applications of metal oxide nanoparticles used in sunscreens lead to systemic exposure. However, the question has been raised whether the usual testing with healthy, intact skin will be sufficient. (3) Uptake of nanoparticles in the gastrointestinal tract after oral uptake is a known phenomenon, of which use is intentionally made in the design of food and pharmacological components. Finally, this review indicates that only few specific nanoparticles have been investigated in a limited number of test systems and extrapolation of this data to other materials is not possible. Air pollution studies have generated indirect evidence for the role of combustion derived nanoparticles (CDNP) in driving adverse health effects in susceptible groups. Experimental studies with some bulk nanoparticles (carbon black, titanium dioxide, iron oxides) that have been used for decades suggest various adverse effects. However, engineered nanomaterials with new chemical and physical properties are being produced constantly and the toxicity of these is unknown. Therefore, despite the existing database on nanoparticles, no blanket statements about human toxicity can be given at this time. In addition, limited ecotoxicological data for nanomaterials precludes a systematic assessment of the impact of Nanoparticles on ecosystems.

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The potential risks of nanomaterials: a review carried out for ECETOC

Particulate matter in the atmosphere: which particle properties are important for its effects on health?

Analysis and abatement of air pollution involve a variety of technical disciplines. Formation of the most prevalent pollutants occurs during the combustion process, a tightly coupled system involving fluid flow, mass and energy transport, and chemical kinetics. Its complexity is exemplified by the fact that, in many respects, the simplest hydrocarbon combustion, the methane-oxygen flame, has been quantitatively modeled only within the last several years. Nonetheless, the development of combustion modifications aimed at minimizing the formation of the unwanted by-products of burning fuels requires an understanding of the combustion process. Fuel may be available in solid, liquid, or gaseous form; it may be mixed with the air ahead of time or only within the combustion chamber; the chamber itself may vary from the piston and cylinder arrangement in an automobile engine to a 10-story-high boiler in the largest power plant; the unwanted byproducts may remain as gases, or they may, upon cooling, form small particles. 

The only effective way to control air pollution is to prevent the release of pollutants at the source. Where pollutants are generated in combustion, modifications to the combustion process itself, for example in the manner in which the fuel and air are mixed, can be quite effective in reducing their formation. Most situations, whether a combustion or an industrial process, however, require some degree of treatment of the exhaust gases before they are released to the atmosphere. Such treatment can involve intimately contacting the effluent gases with liquids or solids capable of selectively removing gaseous pollutants or, in the case of particulate pollutants, directing the effluent flow through a device in which the particles are captured on surfaces. 

The study of the generation and control of air pollutants can be termed air pollution engineering and is the subject of this book. Our goal here is to present a rigorous and fundamental analysis of the production of air pollutants and their control. The book is intended for use at the senior or first-year graduate level in chemical, civil, environmental, and mechanical engineering curricula. We assume that the student has had basic first courses in thermodynamics, fluid mechanics, and heat transfer. The material treated in the book can serve as the subject of either a full-year or a one-term course, depending on the choice of topics covered. 

In the first chapter we introduce the concept of air pollution engineering and summarize those species classified as air pollutants. Chapter 1 also contains four appendices that present certain basic material that will be called upon later in the book. This material includes chemical kinetics, the basic equations of heat and mass transfer, and some elementary ideas from probability and turbulence. 

Chapter 2 is a basic treatment of combustion, including its chemistry and the role of mixing processes and flame structure. Building on the foundation laid in Chapter 2, we present in Chapter 3 a comprehensive analysis of the formation of gaseous pollutants in combustion. Continuing in this vein, Chapter 4 contains a thorough treatment of the internal combustion engine, including its principles of operation and the mechanisms of formation of pollutants therein. Control methods based on combustion modification are discussed in both Chapters 3 and 4. 

Particulate matter (aerosols) constitutes the second major category of air pollutants when classified on the basis of physical state. Chapter 5 is devoted to an introduction to aerosols and principles of aerosol behavior, including the mechanics of particles in flowing fluids, the migration of particles in external force fields, Brownian motion of small particles, size distributions, coagulation, and formation of new particles from the vapor by homogeneous nucleation. Chapter 6 then treats the formation of particles in combustion processes. 

Chapters 7 and 8 present the basic theories of the removal of particulate and gaseous pollutants, respectively, from effluent streams. We cover all the major air pollution control operations, such as gravitational and centrifugal deposition, electrostatic precipitation, filtration, wet scrubbing, gas absorption and adsorption, and chemical reaction methods. Our goal in these two chapters, above all, is to carefully derive the basic equations governing the design of the control methods. Limited attention is given to actual equipment specification, although with the material in Chapters 7 and 8 serving as a basis, one will be able to proceed to design handbooks for such specifications. 

Chapters 2 through 8 treat air pollution engineering from a process-by-process point of view. Chapter 9 views the air pollution control problem for an entire region or airshed. To comply with national ambient air quality standards that prescribe, on the basis of health effects, the maximum atmospheric concentration level to be attained in a region, it is necessary for the relevant governmental authority to specify the degree to which the emissions from each of the sources in the region must be controlled. Thus it is generally necessary to choose among many alternatives that may lead to the same total quantity of emission over the region. Chapter 9 establishes a framework by which an optimal air pollution control plan for an airshed may be determined. In short, we seek the least-cost combination of abatement measures that meets the necessary constraint that the total emissions not exceed those required to meet an ambient air quality standard. 

Once pollutants are released into the atmosphere, they are acted on by a variety of chemical and physical phenomena. The atmospheric chemistry and physics of air pollution is indeed a rich arena, encompassing the disciplines of chemistry, meteorology, fluid mechanics, and aerosol science. As noted above, the subject matter of the present book ends at the stack (or the tailpipe); those readers desiring a treatment of the atmospheric behavior of air pollutants are referred to J. H. Seinfeld, Atmospheric Chemistry and Physics of Air Pollution (Wiley-Interscience, New York, 1986). 

We wish to gratefully acknowledge David Huang, Carol Jones, Sonya Kreidenweis, Ranajit Sahu, and Ken Wolfenbarger for their assistance with calculations in the book.
Finally, to Christina Conti, our secretary and copy editor, who, more than anyone else, kept safe the beauty and precision of language as an effective means of communication, we owe an enormous debt of gratitude. She nurtured this book as her own; through those times when the task seemed unending, she was always there to make the road a little smoother. 

R. C. Flagan
J. H. Seinfeld

Fundamentals of Air Pollution Engineering

Review of motor vehicle particulate emissions sampling and measurement: From smoke and filter mass to particle number

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.

https://www.tandfonline.com/doi/pdf/10.1080/02786828208958580

Diesel Particulates—What They Are and Why

Eliminating the conventional liquid cooling system of a diesel engine to conserve energy normally rejected to that heat sink offers promise as a means for improving fuel economy. Such low-heat-rejection (LHR) diesels have generally been advanced for heavy-duty vehicles. In this study, application of the concept is analyzed for a light-duty indirect-injection diesel of the type used in passenger cars. The naturally aspirated LHR diesel is found to offer no fuel economy advantage, principally because of the deteriorated volumetric efficiency arising from hot cylinder walls. It is found that most of the energy conserved by deleting the cooling system is diverted to the exhaust gas. Methods examined for recovering the lost volumetric efficiency and/or harnessing the increased energy content of the exhaust include supercharging, adding a bottoming cycle, and combining the diesel with turbomachinery. The latter option is judged superior for the passenger-car application.

Diesel for Passenger-Car Application Exploratory Study of the Low-Heat-Rejection Diesel for Passenger-Car Application

Casing Modification for Increasing the Surge Margin of a Centrifugal Compressor in an Automotive Turbine Engine

A gas turbine engine which may otherwise be of conventional configuration, single or plural shaft, regenerative or nonregenerative, is provided with a controlled bypass from the compressor to the turbine bypassing the combustion apparatus. Flow through this bypass is controlled so as to maintain the fuel-air ratio in the combustion chamber substantially constant notwithstanding variations in fuel flow and airflow with the load carried by the engine. Control of flow through the bypass may respond to setting of the fuel control device, to compressor discharge pressure, or to burner outlet temperature.

Charles A. Amann

Papers

Diesel Particulates—What They Are and Why

Diesel for Passenger-Car Application Exploratory Study of the Low-Heat-Rejection Diesel for Passenger-Car Application

Casing Modification for Increasing the Surge Margin of a Centrifugal Compressor in an Automotive Turbine Engine

Gas turbine engine with combustion chamber bypass for fuel-air ratio control and turbine cooling

Dirigible air bearing transport device