Aerosol Science (eBook)

Technology and Applications

Ian Colbeck, Mihalis Lazaridis (Herausgeber)

eBook Download: EPUB

2014
John Wiley & Sons (Verlag)
978-1-118-67535-9 (ISBN)

Infos

Aerosols influence many areas of our daily life. They are at the core of
environmental problems such as global warming, photochemical smog and
poor air quality. They can also have diverse effects on human health, where
exposure occurs in both outdoor and indoor environments.

However, aerosols can have beneficial effects too; the delivery of drugs to the
lungs, the delivery of fuels for combustion and the production of nanomaterials
all rely on aerosols. Advances in particle measurement technologies have
made it possible to take advantage of rapid changes in both particle size and
concentration. Likewise, aerosols can now be produced in a controlled fashion.
Reviewing many technological applications together with the current scientific
status of aerosol modelling and measurements, this book includes:

• Satellite aerosol remote sensing
• The effects of aerosols on climate change
• Air pollution and health
• Pharmaceutical aerosols and pulmonary drug delivery
• Bioaerosols and hospital infections
• Particle emissions from vehicles
• The safety of emerging nanomaterials
• Radioactive aerosols: tracers of atmospheric processes

With the importance of this topic brought to the public’s attention after the
eruption of the Icelandic volcano Eyjafjallajökull, this book provides a timely,
concise and accessible overview of the many facets of aerosol science.

Ian Colbeck, University of Essex, UK

Mihalis Lazaridis, Technical University of Crete, Greece

 

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AEROSOL SCIENCE TECHNOLOGY AND APPLICATIONS Aerosols influence many areas of our daily life. They are at the core of environmental problems such as global warming, photochemical smog and poor air quality. They can also have diverse effects on human health, where exposure occurs in both outdoor and indoor environments. However, aerosols can have beneficial effects too; the delivery of drugs to the lungs, the delivery of fuels for combustion and the production of nanomaterials all rely on aerosols. Advances in particle measurement technologies have made it possible to take advantage of rapid changes in both particle size and concentration. Likewise, aerosols can now be produced in a controlled fashion. Reviewing many technological applications together with the current scientific status of aerosol modelling and measurements, this book includes: Satellite aerosol remote sensing The effects of aerosols on climate change Air pollution and health Pharmaceutical aerosols and pulmonary drug delivery Bioaerosols and hospital infections Particle emissions from vehicles The safety of emerging nanomaterials Radioactive aerosols: tracers of atmospheric processes With the importance of this topic brought to the public's attention after the eruption of the Icelandic volcano Eyjafjallaj kull, this book provides a timely, concise and accessible overview of the many facets of aerosol science.

Textauszug

Chapter 1

Introduction

Mihalis Lazaridis1 and Ian Colbeck2

1Department of Environmental Engineering, Technical University of Crete, Greece

2School of Biological Sciences, University of Essex, UK

1.1 Introduction

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...

Produkt-Details

• Erscheint lt. Verlag: 30.1.2014
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Chemie ► Organische Chemie
• Themenwelt: Naturwissenschaften ► Chemie ► Physikalische Chemie
• Themenwelt: Technik
• Schlagworte: Aerosol • aerosol effects on human health • aerosol modeling • aerosols and climate change • aerosol science • Aerosol Science applications • Aerosol Science technology • Bioaerosols • bio-electro spraying • Chemie • Chemistry • Environmental Chemistry • Environmental Science • Environmental Studies • Geo-engineering • health impact of aerosols • health implications of aerosols • Ian Colbeck • Industrial Chemistry • Mihalis Lazaridis • radioactive aerosols • satellite aerosol remote sensing • Technische u. Industrielle Chemie • Umweltchemie • Umweltforschung • Umweltwissenschaften
• ISBN-10: 1-118-67535-5 / 1118675355
• ISBN-13: 978-1-118-67535-9 / 9781118675359