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List of Contributors xiii
Preface xv
1. Introduction 1Mihalis Lazaridis and Ian Colbeck
1.1 Introduction 1
1.2 Size and Shape 5
1.3 Size Distribution 6
1.4 Chemical Composition 10
1.5 Measurements and Sampling 11
References 12
2. Aerosol Dynamics 15Mihalis Lazaridis and Yannis Drossinos
2.1 Introduction 15
2.2 General Dynamic Equation 17
2.2.1 Discrete Particle Size Distribution 18
2.2.2 Continuous Particle Size Distribution 19
2.3 Nucleation: New Particle Formation 19
2.3.1 Classical Nucleation Theory 20
2.3.2 Multicomponent Nucleation 22
2.3.3 Heterogeneous Nucleation 23
2.3.4 Atmospheric Nucleation 24
2.4 Growth by Condensation 26
2.5 Coagulation and Agglomeration 27
2.5.1 Brownian Coagulation 28
2.5.2 Agglomeration 28
2.6 Deposition Mechanisms 32
2.6.1 Stokes Law 32
2.6.2 Gravitational Settling 32
2.6.3 Deposition by Diffusion 34
2.6.4 Deposition by Impaction 34
2.6.5 Phoretic Effects 34
2.6.6 Atmospheric Aerosol Deposition 35
2.6.7 Deposition in the Human Respiratory Tract 36
2.7 Resuspension 38
2.7.1 Monolayer Resuspension 38
2.7.2 Multilayer Resuspension 39
References 41
3. Recommendations for Aerosol Sampling 45Alfred Wiedensohler, Wolfram Birmili, Jean-Philippe Putaud, and John Ogren
3.1 Introduction 45
3.2 Guidelines for Standardized Aerosol Sampling 46
3.2.1 General Recommendations 46
3.2.2 Standardization of Aerosol Inlets 47
3.2.3 Humidity Control 49
3.3 Concrete Sampling Configurations 53
3.3.1 General Aspects of Particle Motion 53
3.3.2 Laminar Flow Sampling Configuration 54
3.3.3 Turbulent Flow Sampling Configuration 55
3.4 Artifact-Free Sampling for Organic Carbon Analysis 57
Acknowledgements 59
References 59
4. Aerosol Instrumentation 61Da-Ren Chen and David Y. H. Pui
4.1 Introduction 61
4.2 General Strategy 62
4.3 Aerosol Sampling Inlets and Transport 63
4.4 Integral Moment Measurement 64
4.4.1 Total Number Concentration Measurement: Condensation Particle Counter (CPC) 65
4.4.2 Total Mass Concentration Measurement: Quartz-Crystal Microbalance (QCM) and Tapered-Element Oscillating Microbalance (TEOM) 66
4.4.3 Light-Scattering Photometers and Nephelometers 67
4.5 Particle Surface Area Measurement 68
4.6 Size-Distribution Measurement 70
4.6.1 Techniques based on Particle-Light Interaction 70
4.6.2 Techniques based on Particle Inertia 71
4.6.3 Techniques based on Particle Electrical Mobility 74
4.6.4 Techniques based on Particle Diffusion 77
4.7 Chemical Composition Measurement 78
4.8 Conclusion 80
References 82
5. Filtration Mechanisms 89Sarah Dunnett
5.1 Introduction 89
5.2 Deposition Mechanisms 91
5.2.1 Flow Models 92
5.2.2 Diffusional Deposition 96
5.2.3 Deposition by Interception 98
5.2.4 Deposition due to Inertial Impaction 99
5.2.5 Gravitational Deposition 100
5.2.6 Electrostatic Deposition 100
5.3 Factors Affecting Efficiency 104
5.3.1 Particle Rebound 104
5.3.2 Particle Loading 106
5.4 Filter Randomness 109
5.5 Applications 109
5.6 Conclusions 110
Nomenclature 110
References 113
6. Remote Sensing of Atmospheric Aerosols 119Sagnik Dey and Sachchida Nand Tripathi
6.1 Introduction 119
6.2 Surface-Based Remote Sensing 120
6.2.1 Passive Remote Sensing 120
6.2.2 Active Remote Sensing 126
6.3 Satellite-Based Remote Sensing 126
6.3.1 Passive Remote Sensing 127
6.3.2 Active Spaceborne Lidar 135
6.3.3 Applications of Satellite-Based Aerosol Products 136
6.4 Summary and Future Requirements 141
Acknowledgements 142
References 142
7. Atmospheric Particle Nucleation 153Mikko Sipilä, Katrianne Lehtipalo, and Markku Kulmala
7.1 General Relevance 153
7.2 Detection of Atmospheric Nanoparticles 156
7.2.1 Condensation Particle Counting 156
7.2.2 Electrostatic Methods 158
7.2.3 Mass Spectrometric Methods for Cluster Detection 160
7.3 Atmospheric Observations of New Particle Formation 163
7.3.1 Nucleation 163
7.3.2 Growth 165
7.4 Laboratory Experiments 166
7.4.1 Sulfuric Acid Nucleation 166
7.4.2 Hunt for Compound X 168
7.5 Concluding Remarks and Future Challenges 169
References 170
8. Atmospheric Aerosols and Climate Impacts 181Maria Kanakidou
8.1 Introduction 181
8.2 Global Aerosol Distributions 181
8.3 Aerosol Climate Impacts 182
8.4 Simulations of Global Aerosol Distributions 186
8.5 Extinction of Radiation by Aerosols (Direct Effect) 190
8.5.1 Aerosol Optical Depth and Direct Radiative Forcing of Aerosol Components 193
8.6 Aerosols and Clouds (Indirect Effect) 194
8.6.1 How Aerosols Become CCNs and Grow into Cloud Droplets 195
8.7 Radiative Forcing Estimates 200
8.8 The Way Forward 203
References 203
9. Air Pollution and Health and the Role of Aerosols 207Pat Goodman and Otto Hänninen
9.1 Background 207
9.2 Size Fractions 208
9.3 Which Pollution Particle Sizes Are Important? 209
9.4 What Health Outcomes Are Associated with Exposure to Air Pollution? 209
9.5 Sources of Atmospheric Aerosols 210
9.6 Particle Deposition in the Lungs 210
9.7 Aerosol Interaction Mechanisms in the Human Body 211
9.8 Human Respiratory Outcomes and Aerosol Exposure 215
9.9 Cardiovascular Outcomes and Aerosol Exposure 215
9.10 Conclusions and Recommendations 216
References 216
10. Pharmaceutical Aerosols and Pulmonary Drug Delivery 221Darragh Murnane, Victoria Hutter, and Marie Harang
10.1 Introduction 221
10.2 Pharmaceutical Aerosols in Disease Treatment 223
10.2.1 Asthma 223
10.2.2 Chronic Obstructive Pulmonary Disease 224
10.2.3 Cystic Fibrosis 224
10.2.4 Respiratory Tract Infection 225
10.2.5 Beyond the Lung: Systemic Drug Delivery 225
10.3 Aerosol Physicochemical Properties of Importance in Lung Deposition 226
10.4 The Fate of Inhaled Aerosol Particles in the Lung 228
10.4.1 Paracellular Transport 229
10.4.2 Transcellular Transport 229
10.4.3 Carrier-Mediated Transport 230
10.4.4 Models for Determining the Fate of Inhaled Aerosols 231
10.5 Production of Inhalable Particles 233
10.5.1 Particle Attrition and Milling 233
10.5.2 Constructive Particle Production 235
10.6 Aerosol Generation and Delivery Systems for Pulmonary Therapy 237
10.6.1 Nebulised Disease Therapies 237
10.6.2 Pressurised Metered-Dose Inhaler Systems 241
10.6.3 Dry-Powder Inhalation 248
10.6.4 Advancing Drug-Delivery Strategies 252
10.7 Product Performance Testing 253
10.7.1 Total-Emitted-Dose Testing 253
10.7.2 Aerodynamic Particle Size Determination: Inertial Impaction Analysis 253
10.8 Conclusion and Outlook 255
References 255
11. Bioaerosols and Hospital Infections 271Ka man Lai, Zaheer Ahmad Nasir, and Jonathon Taylor
11.1 The Importance of Bioaerosols and Infections 271
11.2 Bioaerosol-Related Infections in Hospitals 272
11.3 Bioaerosol Properties and Deposition in Human Respiratory Systems 275
11.4 Chain of Infection and Infection Control in Hospitals 275
11.5 Application of Aerosol Science and Technology in Infection Control 277
11.5.1 Understanding Hospital Aerobiology and Infection Control 277
11.5.2 Bioaerosol Experiments and Models 280
11.5.3 Numerical Analysis of Particle Dispersion in Hospitals 281
11.5.4 Air-Cleaning Technologies 282
11.6 Conclusion 285
References 285
12. Nanostructured Material Synthesis in the Gas Phase 291Peter V. Pikhitsa and Mansoo Choi
12.1 Introduction 291
12.2 Aerosol-Based Synthesis 292
12.3 Flame Synthesis 292
12.4 Flame and Laser Synthesis 299
12.5 Laser-Induced Synthesis 302
12.6 Metal-Powder Combustion 309
12.7 Spark Discharge 313
12.8 Assembling Useful Nanostructures 314
12.9 Conclusions 322
References 323
13. The Safety of Emerging Inorganic and Carbon Nanomaterials 327L. Reijnders
13.1 Introduction 327
13.2 Human Health and Inhaled Persistent Engineered Inorganic and Carbon Nanomaterials 330
13.3 Human Health Hazards and Risks Linked to the Ingestion of Persistent Inorganic Nanomaterials 333
13.4 Ecotoxicity of Persistent Inorganic and Carbon Nanomaterials 335
13.5 Conclusion 336
References 336
14. Environmental Health in Built Environments 345Zaheer Ahmad Nasir
14.1 Environmental Hazards and Built Environments 345
14.2 Particulate Contaminants 348
14.2.1 Transport and Behaviour of Particles in Built Environments 349
14.3 Gas Contaminants 351
14.3.1 Biological Hazards 351
14.3.2 Physical Hazards 357
14.3.3 Ergonomic Hazards 358
14.3.4 Ventilation and Environmental Hazards 359
14.3.5 Energy-Efficient Built Environments, Climate Change and Environmental Health 361
References 362
15. Particle Emissions from Vehicles 369Jonathan Symonds
15.1 Introduction 369
15.2 Engine Concepts and Technologies 370
15.2.1 Air-Fuel Mixture 370
15.2.2 Spark-Ignition Engines 371
15.2.3 Compression-Ignition Engines 372
15.2.4 Two-Stroke Engines 372
15.2.5 Gas-Turbine Engines 373
15.3 Particle Formation 373
15.3.1 In-Cylinder Formation 373
15.3.2 Evolution in the Exhaust and Aftertreatment Systems 375
15.3.3 Noncombustion Particle Sources 375
15.3.4 Evolution in the Environment 376
15.4 Impact of Vehicle Particle Emissions 376
15.4.1 Health and Environmental Effects 376
15.4.2 Legislation 376
15.5 Sampling and Measurement Techniques 378
15.5.1 Sample Handling 378
15.5.2 Mass Measurement 379
15.5.3 Solid-Particle-Number Measurement 380
15.5.4 Sizing Techniques 382
15.5.5 Morphology Determination 382
15.6 Amelioration Techniques 385
15.6.1 Fuel Composition 385
15.6.2 Control by Engine Design and Calibration 385
15.6.3 Particulate Filters 386
Acknowledgements 388
References 388
16. Movement of Bioaerosols in the Atmosphere and the Consequences for Climate and Microbial Evolution 393Cindy E. Morris, Christel Leyronas, and Philippe C. Nicot
16.1 Introduction 393
16.2 Emission: Launch into the Atmosphere 395
16.2.1 Active Release 397
16.2.2 Passive Release 397
16.2.3 Quantifying Emissions 398
16.3 Transport in the Earth's Boundary Layer 399
16.3.1 Motors of Transport 399
16.3.2 Quantifying Near-Surface Flux 400
16.4 Long-Distance Transport: From the Boundary Layer into the Free Troposphere 404
16.4.1 Scale of Horizontal Long-Distance Transport 404
16.4.2 Altitude of Long-Distance Transport 405
16.5 Interaction of Microbial Aerosols with Atmospheric Processes 406
16.6 Implications of Aerial Transport for Microbial Evolutionary History 407
References 410
17. Disinfection of Airborne Organisms by Ultraviolet-C Radiation and Sunlight 417Jana S. Kesavan and Jose-Luis Sagripanti
17.1 Introduction 417
17.2 UV Radiation 418
17.3 Sunlight 419
17.4 Selected Organisms 421
17.4.1 Bacterial Endospores 421
17.4.2 Vegetative Bacteria 422
17.4.3 Viruses 423
17.5 Effects of UV Light on Aerosolized Organisms 423
17.5.1 Cell Damage Caused By UV Radiation 423
17.5.2 Photorepair 424
17.5.3 Typical Survival Curve for UV Exposure 425
17.5.4 The UV Rate Constant 427
17.5.5 RH and Temperature Effects 428
17.5.6 Bacterial Clusters 429
17.6 Disinfection of Rooms Using UV-C Radiation 429
17.7 Sunlight Exposure Studies 430
17.8 Testing Considerations 431
17.8.1 Test Methodology in Our Laboratory 432
17.9 Discussion 435
References 435
18. Radioactive Aerosols: Tracers of Atmospheric Processes 441Katsumi Hirose
18.1 Introduction 441
18.2 Origin of Radioactive Aerosols 442
18.2.1 Natural Radionuclides 442
18.2.2 Anthropogenic Radionuclides 444
18.3 Tracers of Atmospheric Processes 446
18.3.1 Transport of Radioactive Aerosols 446
18.3.2 Dry Deposition 448
18.3.3 Wet Deposition 449
18.3.4 Resuspension 450
18.3.5 Other Processes 452
18.3.6 Application of Multitracers 452
18.3.7 Atmospheric Residence Time of Radioactive Aerosols 454
18.4 Tracer of Environmental Change 457
18.5 Conclusion 460
References 461
Index 469
Mihalis Lazaridis1 and Ian Colbeck2
1Department of Environmental Engineering, Technical University of Crete, Greece
2School of Biological Sciences, University of Essex, UK
An aerosol is defined as a suspension of liquid or solid in a gas. Aerosols are often discussed as being either ‘desirable’ or ‘undesirable’. The former include those specifically generated for medicinal purposes and those intentionally generated for their useful properties (e.g. nanotechnology, ceramic powders); the latter are often associated with potential harmful effects on human health (e.g. pollution). For centuries, people thought that there were only bad aerosols. Early writers indicated a general connection between lung diseases and aerosol inhalation. In 1700, Bernardo Ramazzini, an Italian physician, described the effect of dust on the respiratory organs, including descriptions of numerous cases of fatal dust diseases (Franco and Franco, 2001).
Aerosols are at the core of environmental problems, such as global warming, photochemical smog, stratospheric ozone depletion and poor air quality. Recognition of the effects of aerosols on climate can be traced back to 44 BC, when an eruption from Mount Etna was linked to cool summers and poor harvests. People have been aware of the occupational health hazard of exposure to aerosols for many centuries. It is only relatively recently that there has been increased awareness of the possible health effects of vehicular pollution, and in particular submicron particles.
The existence of particles in the atmosphere is referred to in the very early literature (see Husar, 2000; Calvo et al., 2012). In the 1800s, geologists studied atmospheric dust in connection with soil formation, and later that century meteorologists recognised the ability of atmospheric particles to influence rain formation, as well as their impact on both visible and thermal radiation (Husar, 2000).
The environmental impact of the long-range transport of atmospheric particles has also been widely discussed (Stohl and Akimoto, 2004). Around 1600, Sir Francis Bacon reported that the Gasgogners of southern France had filed a complaint to the King of England claiming that smoke from seaweed burning had affected the wine flowers and ruined the harvest. During the eighteenth century, forest fires in Russia and Finland resulted in a regional haze over Central Europe. Even then, Wargentin (1767) and Gadolin (1767) (quoted in Husar, 2000) indicated that it would be possible to map the path of the smoke based on the locations of the fires and its appearance at different locations. Danckelman (1884) mentions that hazes and smoke from burnings in the African savannah have been observed in various regions of Europe since Roman times.
The possibility of atmospheric particles forming from gaseous chemical reactions was pointed out by Rafinesque (1819). In his paper entitled ‘Thoughts on Atmospheric Dust’, he makes a number of pertinent observations: ‘Whenever the sun shines in a dark room, its beams display a crowd of lucid dusty molecules of various shapes, which were before invisible as the air in which they swim, but did exist nevertheless. These form the atmospheric dust; existing every where in the lower strata of our atmosphere’; ‘The size of the particles is very unequal, and their shape dissimilar’.
In spite of the widespread occurrence of aerosols in nature and their day-to-day creation in many spheres of human activity, it is only in comparatively recent times that a scientific study has been made of their properties and behaviour. During the late nineteenth and early twentieth centuries, many scientists working in various fields became interested in problems that would now be considered aerosol-related. The results were fairly often either byproducts of basic research, related to other fields or just plain observations that roused curiosity. Several of the great classical physicists and mathematicians were attracted by the peculiar properties of particulate clouds and undertook research on various aspects of aerosol science, which have since become associated with their names, for example Stokes, Aitken and Rayleigh.
Whatever the usage, the fundamental rules governing the behaviour of aerosols remain the same. Rightly or wrongly, the terms ‘aerosols’ and ‘particles’ are often freely interchanged in the literature. Aerosols range in size range from 0.001 µm (0.001 µm =10−9 m = 1 nm = 10 Å) to 100 µm (10−4 m), so the particle sizes span several orders of magnitude, ranging from almost macroscopic down to near molecular sizes. All aerosol properties depend on particle size, some very strongly. The smallest aerosols approach the size of large gas molecules and have many of the same properties; the largest are visible grains that have properties described by Newtonian physics.
Figure 1.1 shows the relative size of an aerosol particle (diameter 0.1 µm) compared with a molecule (diameter 0.3 nm, average spacing 3 nm, mean free path 70 nm (defined as the average distance travelled by a molecule between successive collisions)).
Figure 1.1 Relative size of an aerosol particle (diameter 0.1 µm) compared with a molecule (diameter 0.3 nm).
There are various types of aerosol, which are classified according to physical form and method of generation. The commonly used terms are ‘dust’, ‘fume’, ‘smoke’, ‘fog’ and ‘mist’. Virtually all the major texts on aerosol science contain definitions of the various categories. For example, for Whytlaw-Gray and Patterson (1932):
Dust: ‘Dusts result from natural and mechanical processes of disintegration and dispersion.’
Smoke: ‘If suspended material is the result of combustion or of destructive distillation it is commonly called smoke.’
while more recently, for Kulkarni, Baron and Willeke (2011):
Dust: ‘Solid particles formed by crushing or other mechanical action resulting in physical disintegration of a parent material. These particles have irregular shapes and are larger than about 0.5 µm.’
Smoke: ‘A solid or liquid aerosol, the result of incomplete combustion or condensation of supersaturated vapour. Most smoke particles are submicrometer in size.’
It is clear right from the early literature that dust and smoke are not defined in terms of particle size but in terms of their formation mechanism.
The actual meanings of ‘smoke’ and ‘dust’ have recently been the subject of an appeal at the New South Wales Court of Appeal (East West Airlines Ltd v. Turner, 2010). The New South Wales Dust Diseases Tribunal had previously found in favour of a flight attendant who inhaled smoke in an aircraft. The initial trial judge concluded that ‘In ordinary common parlance, dust encompasses smoke or ash. Dust may need to be distinguished from gas, fume or vapour. The distinction would be that dust comprises particulate matter. Smoke comprises particulate matter and, accordingly, is more comfortably described as dust rather than gas, fume or vapour. I do not consider that there is a distinction between smoke and dust such that smoke cannot be dust. When the particulate matter settled, it would, to most people, be recognised as dust. If, through the microscope or other aid, one could see the particulate matter without the smoky haze, most people would recognise the particulate matter as dust. The dictionary definitions would encompass smoke as dust’.
The Court of Appeal stated:
… His Honour did not find that, as a matter of general principle, ‘smoke’ was a ‘dust’ … This was not a decision as to a point of law but a factual determination. There was ample evidence before his Honour to justify that conclusion.
Various governments worldwide have instigated standards to protect workers from toxic substances in workplaces. For example, the American Conference of Governmental Industrial Hygienists (ACGIH) publishes a list of over 600 chemicals for which ‘threshold limit values’ have been established. Approximately 300 of these are found in workplaces in the form of aerosols. Aerosol science is thus central to the study, characterisation and monitoring of atmospheric environments. Aerosols can cause health problems when deposited on the skin, but generally the most sensitive route of entry into the body is through the respiratory system. Knowledge of the deposition of particulate matter in the human respiratory system is important for dose assessment and the risk analysis of airborne pollutants. The deposition process is controlled by physical characteristics of the inhaled particles and by the physiological factors of the individuals involved. Of the physical factors, particle size and size distribution are among the most important. The same physical properties that govern aerosols in the atmosphere apply within the lungs.
Aerosols in the atmosphere are either primary or secondary in nature. Primary aerosols are atmospheric particles that are emitted or injected directly into the atmosphere, whereas secondary aerosols are atmospheric particles formed by in situ aggregation or nucleation from gas-phase molecules (gas to particle conversion). Particles in the...
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