The behaviour of airborne particulates inside houses : its relevance to nuclear safety

In the context of the safety of nuclear installations, there is general concern over the release and dispersal of radioactive pollutants in particulate form into the atmosphere. Such a release may lead to radiation exposure to individuals under radioactive fall-out conditions in the form of direct gamma exposure, through inhalation or by the particulate material being deposited on internal and external surfaces of buildings. This project addresses the protection offered by buildings to the occupants, against such exposure pathways. A computer model (BHOUSE) has been developed to simulate the exchange and transport of pollution in aerosol form for a building. A particular aspect investigated, mainly through modelling, has been the protection afforded by buildings through the deposition indoors of aerosols which might infiltrate into the buildings in question. On the one hand this process is likely to reduce indoor air concentrations, thus reducing inhalation dose, on the other hand it may lead to the problem of long-term contamination inside buildings. A related consideration is the safety provided by the building, to the occupants inside, against the direct radiation emitted by the externally deposited activity. Various benchmarking exercises have been carried out to investigate the indoor air and contaminant dispersal. These exercises have included: pollution ingress rate to a building under a variety of conditions; effect of wet external deposition on mechanical transport rate; variation of indoor pollution level with and without vacuum cleaner operating and the calculation of inhalation dose rates. Measures to obtain higher protection factors against particulate inhalation have also been suggested. Predictions obtained with the model have been compared with an existing model. This comparison aimed to identify common features and significant differences between models. Such studies clearly relate to other non-nuclear aspects of indoor air quality research. A better understanding of the importance of individual parameters affecting indoor air quality has been achieved. The thesis also reports results obtained through participation in a joint experimental programme between Imperial College, the Danish Riso National Laboratory and the Building Research Establishment (BRE) which yielded measured indoor deposition velocities in an experimental terraced house using monodisperse aerosol labelled with a stable tracer. The deposition behaviour of particles with different sizes have also been studied. Neutron activation analysis was used to estimate aerosol concentration levels on air filters inside rooms, with the use of the Imperial College nuclear reactor. The resulting average deposition velocities were used in the model in order to illustrate the protection afforded by buildings against inhalation dose, for the aerosol sizes which were investigated. A critical review has also been conducted on aerosol test chamber studies

Zero-Gravity Atmospheric Cloud Physics Experiment Laboratory-engineering concepts/design tradeoffs. Volume 2: Detailed approaches

For abstract, see N75-10953

Organic aerosol and global climate modelling: a review

The present paper reviews existing knowledge with regard to Organic Aerosol (OA) of importance for global climate modelling and defines critical gaps needed to reduce the involved uncertainties. All pieces required for the representation of OA in a global climate model are sketched out with special attention to Secondary Organic Aerosol (SOA): The emission estimates of primary carbonaceous particles and SOA precursor gases are summarized. The up-to-date understanding of the chemical formation and transformation of condensable organic material is outlined. Knowledge on the hygroscopicity of OA and measurements of optical properties of the organic aerosol constituents are summarized. The mechanisms of interactions of OA with clouds and dry and wet removal processes parameterisations in global models are outlined. This information is synthesized to provide a continuous analysis of the flow from the emitted material to the atmosphere up to the point of the climate impact of the produced organic aerosol. The sources of uncertainties at each step of this process are highlighted as areas that require further studies

Aerosol science and technology: History and reviews

Aerosol Science and Technology: History and Reviews captures an exciting slice of history in the evolution of aerosol science. It presents in-depth biographies of four leading international aerosol researchers and highlights pivotal research institutions in New York, Minnesota, and Austria. One collection of chapters reflects on the legacy of the Pasadena smog experiment, while another presents a fascinating overview of military applications and nuclear aerosols. Finally, prominent researchers offer detailed reviews of aerosol measurement, processes, experiments, and technology that changed the face of aerosol science. This volume is the third in a series and is supported by the American Association for Aerosol Research (AAAR) History Working Group, whose goal is to produce archival books from its symposiums on the history of aerosol science to ensure a lasting record. It is based on papers presented at the Third Aerosol History Symposium on September 8 and 9, 2006, in St. Paul, Minnesota, USA

Fundamentals of air pollution engineering

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. Seinfel

On observations of newly formed nanoparticles : their detection, characterization and abundance in various environments

New particle formation (NPF) is a dominant source for atmospheric aerosol particles in terms of their number concentration, and a major contributor to the number of cloud con-densation nuclei globally. Atmospheric aerosol particles have impact on Earth’s climate via direct and indirect effects. In addition to climate, aerosol particles have impact on human health. In polluted environments, airborne pollutants, especially particulate matter, shorten the lifetime expectancy by several years. Understanding the processes of NPF is in a key role, for example, while identifying the most effective acts to improve the air quality in megacities or assessing the role of anthropogenic emissions in climate change. A NPF event consists of formation of molecular clusters and their subsequent growth into larger particle sizes by condensable vapors and/or coagulation In order to quantify NPF events, measurements of particle number size distribution close to the size where gas-to-particle conversion takes place are necessary. The gas-to-particle conversion takes place in the 1-2 nm size range, where there exist electrically charged and neutral molecular clusters. On one hand, in most of the environments such clusters are present also in the absence of NPF events. The growth of the small clusters to the 2-3 nm size range is, on the other hand, indicative of a NPF event. In this thesis, we gather knowledge on the concentration of sub-3 nm aerosol particles by conducting both long-term and campaign-like measure-ments with particle size magnifier (PSM; Airmodus Ltd.). Our results were compared with the other available PSM data, from sites around the world, and presented in compilation study. In all the sites the sub-3 nm particle concentration had a daytime maximum. Gener-ally, the highest concentrations were observed at the sites with the highest anthropogenic influence. In this thesis, we also conducted a campaign to observe particle formation in a cleanroom environment, where PSM was used for the first time to monitor concentration of nanoparticles in such an environment. The results showed that sub-2 nm clusters were observed to be always present in this clean room in relatively small concentrations. Short periods of high concentrations were observed during active manufacturing processes in the clean room. Instrumental development was one important aspect of this thesis. We experimented with the possibility of using two commercial condensation particle counters (CPCs), with nomi-nal lower limit close to 10 nm, for the detection of sub-3 nm particles. Optimized operating temperatures and flow rates were tested in laboratory conditions and by using simulation tools. We showed that commercially-available CPCs can be optimized down to sub-3 nm detection. In addition, a differential mobility particle sizer (DMPS) was specially built to measure particle number size distributions in the sub-10 nm size range using PSM and half-mini differential mobility analyzer (DMA). Due to the improved overall transmission of our system, the counting uncertainty compared to a harmonized DMPS was reduced to a half in the sub-10 nm size range. An ion mobility-mass spectrometry was utilized to investigate the structures and hydration of iodine pentoxide iodic acid clusters, similar to ones observed during coastal nucleation events. The number of water molecules in hydrated clusters was sufficient to convert io-dine pentoxide into iodic acid but the water sorption beyond this amount was limited

Physico-chemical speciation and ocean fluxes of Polycyclic Aromatic Hydrocarbons

Thesis (Ph. D.)--Joint Program in Oceanography, Massachusetts Institute of Technology/Woods Hole Oceanographic Institution, 1997.Includes bibliographical references.by Örjan Gustafsson.Ph.D