eBook - ePub
Air Pollution and Climate Change
The Basics
John K. Pearson, Richard Derwent
This is a test
Share book
- 160 pages
- English
- ePUB (mobile friendly)
- Available on iOS & Android
eBook - ePub
Air Pollution and Climate Change
The Basics
John K. Pearson, Richard Derwent
Book details
Book preview
Table of contents
Citations
About This Book
This book identifies four key forms of air pollution: indoor, urban, regional and global. It discusses how these four types of pollution are manifest in today's society and examines the scientific and policy challenges that stand in the way of progress.
Written in a style that balances scientific underpinnings with accessible language, Pearson and Derwent examine the sources and historical context of air pollutants, before dedicating a chapter to each of the key forms. Armed with these basics, they begin to address the challenges faced by improving indoor, urban and regional air quality, whilst reducing global warming in the years ahead. This leads to a greater understanding of the challenges of global climate change, with new proposals for reducing global warming. However, the authors conclude that it is only when we have a scenario of reforestation combined with reductions in emissions of all greenhouse gases that real progress will be made in the fight against climate change. Then, air pollution will also be consigned to history.
With a foreword written by Professor James Lovelock, this book will be of great interest to students and scholars of climate change and environmental policy, as well as air quality professionals working in this important field.
Frequently asked questions
How do I cancel my subscription?
Can/how do I download books?
At the moment all of our mobile-responsive ePub books are available to download via the app. Most of our PDFs are also available to download and we're working on making the final remaining ones downloadable now. Learn more here.
What is the difference between the pricing plans?
Both plans give you full access to the library and all of Perlegoâs features. The only differences are the price and subscription period: With the annual plan youâll save around 30% compared to 12 months on the monthly plan.
What is Perlego?
We are an online textbook subscription service, where you can get access to an entire online library for less than the price of a single book per month. With over 1 million books across 1000+ topics, weâve got you covered! Learn more here.
Do you support text-to-speech?
Look out for the read-aloud symbol on your next book to see if you can listen to it. The read-aloud tool reads text aloud for you, highlighting the text as it is being read. You can pause it, speed it up and slow it down. Learn more here.
Is Air Pollution and Climate Change an online PDF/ePUB?
Yes, you can access Air Pollution and Climate Change by John K. Pearson, Richard Derwent in PDF and/or ePUB format, as well as other popular books in Technology & Engineering & Environmental Management. We have over one million books available in our catalogue for you to explore.
Information
1
Air pollutants and their sources
DOI: 10.4324/9781003293132-1
Overview
Air pollutants may be present in the atmosphere as gases or particles. Most air pollutants are directly emitted into the atmosphere, but some are formed there by chemical reactions. Air pollutants are transported across regions and countries and may cross national boundaries. In this chapter, we discuss air pollutants, their health impacts and their principal sources. We also highlight the main greenhouse gases and pollutants: carbon dioxide, methane and ozone. While there is much focus on the reduction of the emissions of those particles which can penetrate the lungs, reducing aerosol particles also affects global warming.
Coal and oil combustion are major causes of air pollution problems, followed by road transport using gasoline and diesel fuels. Massive reductions in carbon dioxide and all pollutants will be achieved over the next two decades by transforming power stations and road transport. It is, however, important to consider all sources of pollution, both anthropogenic and natural biogenic, in order to improve air quality.
Earthâs atmosphere contains 78.08% nitrogen (N2), 20.95% oxygen (O2) and 0.93% argon (Ar). The remaining atmospheric constituents are called trace gases and include water vapour (H2O), carbon dioxide (CO2), neon (Ne), helium (He), methane (CH4), krypton (Kr) and nitrous oxide (N2O). Water vapour concentrations are highly variable and average about 1% at the Earthâs surface.
The atmosphere is essential to life on Earth, providing the oxygen we breathe, carbon dioxide for plant growth through photosynthesis, ozone to absorb damaging ultraviolet radiation from the sun and a greenhouse blanket of water vapour and carbon dioxide to maintain the habitable temperatures required to sustain life on Earth.
In addition to the major gases and the trace constituents mentioned above, the atmosphere contains a whole range of atmospheric pollutants which are present in trace amounts and whose levels are highly variable in space and time.
The terms air pollution and air pollutant have precise meanings. An air pollutant is a substance which when emitted into the atmosphere causes damage to human health or the wider environment. Air pollutants may be present in the atmosphere as gases or particles. Examples of gaseous air pollutants include sulphur dioxide, nitrogen oxides, carbon monoxide, carbon dioxide, methane and other organic compounds. Examples of particulate air pollutants include smoke, smuts, fine particles from traffic and coarse particles such as sea salts and wind-blown dusts.
Here we examine the common air pollutants and describe their sources in the air that we all breathe.
Carbon monoxide (CO)
This compound is formed by incomplete combustion of fuels linked to insufficient oxygen. Outdoors, the main sources are gasoline vehicles and forest fires. In practice, modern gasoline vehicles emit very small amounts of carbon monoxide and this source has become a problem of the past in air quality. Bonfires and forest fires do give rise to high levels of carbon monoxide, but these are usually brought under control quickly. Indoors, carbon monoxide remains a significant problem. These issues are covered in Chapter 3.
Carbon dioxide (CO2)
Atmospheric carbon dioxide concentrations are increasing steadily due to combustion processes linked to oil, gas, coal and wood. This is the most important greenhouse gas associated with global warming and climate change and its control is essential in the years to come. Power stations in Europe are phasing out the use of coal and oil in favour of renewable technologies and motor manufacturers are introducing hybrid and electric vehicles. Both these measures are helping to reduce emissions of this pollutant. However, Asian countries continue to build coal-fired power stations and car ownership is increasing rapidly based on gasoline vehicles, generating huge emissions of carbon dioxide. The challenges to reduce global carbon dioxide emissions are covered in Chapter 6.
Sulphur dioxide (SO2)
Sulphur dioxide, an acidic gas, is associated with the burning of fossil fuels to generate heat and electricity. SO2 is readily transported across international boundaries by wind fields which contributes to the challenge of reducing acid rain and its damaging impacts on soils and surface waters. In general, it is in decline, but countries which rely on power stations burning coal such as China, India, Czech Republic, Poland and Serbia still have substantial SO2 emissions. Low sulphur fuels have also helped Europe to reduce SO2 pollution over the past 30 years.
Nitrogen oxides (NOx)
Nitric oxide (NO) and nitrogen dioxide (NO2) are always found together in the atmosphere and classed as Nitrogen Oxides (NOx = NO + NO2). In developed countries, the largest source of NOx comes from the automotive sector, accounting for about 50%, with power stations contributing about 20%. In previous years, the diesel engine has made the greatest NOx contribution in the automotive sector, but advances in diesel engine technology (for example: de-NOx catalysts) have started to reduce this considerably. Further reductions continue as the diesel engine gives way to electric and hybrid engine technologies. Most pollutant sources emit their NOx as NO which is converted in the atmosphere to the much more harmful NO2 by chemical reactions involving ozone. High levels of NO2 are a major concern in our cities because of health effects, particularly their contribution to excess deaths. These issues are addressed in Chapter 4.
NOx and its compounds are highly reactive in the atmosphere and contribute to acid rain, eutrophication and the formation of fine particles and ground-level ozone. They are readily transported across international boundaries and so impacts are felt across entire regions. Acid rain and eutrophication lead to environmental damage in the form of loss of fish stocks, destruction of sensitive habitats and the loss of biological diversity. Fine particles and ozone cause health effects and ozone damages crops and vegetation. These issues are addressed in Chapter 5.
Volatile organic compounds (VOCs)
Volatile organic compounds (VOCs) comprise the many hundreds to thousands of organic compounds that are present in the atmosphere. They range from simple hydrocarbons (such as alkanes and aromatics) to oxygenates (such as alcohols and ketones). They are pollutants in their own right because some cause cancer, such as benzene, but it is their substantial contribution to ground-level ozone formation which is of greater concern. The sources of VOCs are both man-made (vehicle exhaust, gasoline evaporative emissions and solvents) and biogenic (from trees and plants). Industry has made substantial efforts to reduce VOCs, through the development of three-way catalyst systems and evaporative canisters in gasoline vehicles and solvent reformulation including water-based paints. These issues are discussed in Chapter 5.
Individual VOCs such as benzene remain a concern because they can cause cancers. The issue of benzene as an air pollutant is now largely associated with cigarette smoking, particularly indoor air quality, as examined in Chapter 3.
Methane (CH4)
Methane is the largest constituent of natural gas which is a widely used fossil fuel in power stations for generating electricity, in industry for the manufacture of fertilisers and in the home for heating and cooking. Methane is emitted in large quantities by agriculture, particularly rice paddies and by animals, notably cattle. There are important natural methane sources including tropical wetlands, bogs and marshes. It is the second most important man-made greenhouse gas after carbon dioxide and is discussed in detail in Chapter 6.
Ozone (O3)
There are no important direct emissions of ozone into the atmosphere and all the ozone present there has been formed by atmospheric chemical reactions. In the upper atmosphere, the so-called stratosphere, ozone acts as a sunscreen and filters out the harmful ultra-violet radiation from the sun. This is the stratospheric ozone layer which is essential to all life as we know it. In the lower atmosphere, particularly that portion closest to the ground, ozone is a man-made pollutant causing health effects and damage to crops and vegetation.
At ground level, ozone is a secondary pollutant formed by sunlight-driven chemical reactions involving VOCs and NOx precursors and is transported across international boundaries by wind fields. As such, it is being addressed by all countries, which continue to reduce these two main precursor pollutants. Both chemical reactivity and meteorology are the key factors in ground-level ozone formation and mathematical models are used to predict the optimum strategy for ozone reduction in any region, as seen in Chapters 5 and 7. It is interesting to note that isoprene is one of the most reactive VOCs in ozone formation and is a major component of natural biogenic VOC emissions from trees. Strategies to control ozone formation have to take into account both man-made and biogenic VOCs in any particular region, together with NOx emissions. It has become recognised that the formation of ozone across Europe and large parts of North America are now NOx-limited and, consequently, further NOx emission reductions will have the greater impact on reducing ozone levels compared with VOC reductions.
Ozone is also a man-made greenhouse gas, being the third in importance after carbon dioxide and methane. Global ozone levels are controlled by the emissions of methane, carbon monoxide, oxides of nitrogen and VOCs. Its role as a greenhouse gas is discussed in Chapter 6.
Particles
The term âparticlesâ refers to the complex mixture of solid or liquid material that is finely dispersed in the atmosphere. It may be termed particulate matter, suspended particulate matter, aerosol or aerosol particles. Most recently, concerns have been raised about the coarse particles of size less than 10 microns in diameter (the so-called PM10) and the fine particles of size less than 2.5 microns (PM2.5). There is much current debate in the health-effects community concerning where, in terms of particle size, the toxicity resides. While this has not yet been satisfactorily resolved, it is clear that particles can be extremely damaging to human health. Smoke from wildfires, for example, can cause large increases in respiratory emergencies and hospital admissions. Open agricultural burning is an important seasonal source of particles.
PM2.5 can be classed as primary, such as those from the tail pipe of the diesel engine, secondary inorganic aerosol (ammonium sulphates and nitrates) formed by the atmospheric chemical reactions of SO2, NOx and NH3 and secondary organic aerosol formed by the atmospheric reactions of VOCs. Over the past decade, diesel engine exhaust particle emissions have been reduced by new diesel engine technology and the steady decline in emissions of sulphur dioxide and nitrogen oxides has reduced the formation of secondary inorganic particles. Road vehicles, whether petrol, diesel or electric passenger cars or whether buses and coaches, light- or heavy-goods vehicles, cause particle emissions through brake, tyre and road surface wear. Strategies for improvement of particle air quality need to consider non-exhaust vehicle emissions. The subject of secondary organic aerosols remains a key challenge. Particles and their health effects are important issues for urban air quality (Chapter 4) and regional air quality (Chapter 5).
Particles play an important role in climate processes. They scatter incoming solar radiation and control the formation of clouds and rainfall. Particles, thereby, exert a cooling influence on global climate and have, to a considerable extent, offset the global warming from the greenhouse gases. Their role ...