Chemistry Reference
In-Depth Information
Chapter 3: Chemistry and the Environment
JOHN V. HOLDER
1 Introduction
the toxicology, metabolism and biogeochemical
cycling of environmental contaminants and pollu-
tants are being elucidated.
It is logical, therefore, for a book on sustainable
chemistry to begin by looking at the natural chem-
istry of the environment and how this is being
affected by the perturbations introduced by humans,
which may lead to unsustainable situations locally or
globally.
This chapter will attempt briefly to summarise the
current position in what is a large and complex field.
The chemistry of the natural environment will be
introduced and the sources and causes of pollution
will be reviewed, together with some of the toxi-
cological and other environmental impacts. The
importance of chemical speciation on the biogeo-
chemical cycling of anthropogenic chemicals will be
highlighted.
'There is a sufficiency in the world for man's need
but not for man's greed.'
Mahatma Gandhi (1869-1948)
To fulfil its part in sustainable World development,
chemistry is changing. This 'greening' of chemistry
involves two main thrusts. First, production, use and
disposal of hazardous chemicals is being reduced
and, where possible, eliminated. This must, however,
be achieved while maintaining or improving the
quality of human life, the natural environment and
industrial competitiveness. Second, the environ-
mental impact of anthropogenic chemicals is being
studied so that it may be better understood, moni-
tored and controlled.
More specifically, chemistry can contribute to:
• Understanding and reducing the enhanced green-
house effect
• Understanding the role of chlorofluorocarbons
and other materials that affect the ozone layer and
finding alternatives
• Understanding and reducing the effects of volatile
organic compounds that contribute to low-level
photochemical smog
• Understanding and minimising the effects of acidic
pollutants such as sulfur dioxide and nitrogen
oxides
• Finding alternatives to non-renewable energy
resources such as oil, gas and coal
• Contributing to waste minimisation and improved
waste treatment and disposal
• Understanding the effects of toxic materials on
both humans and the environment and finding
alternatives
• Improving current chemical processes
2 Chemistry of the Atmosphere
2.1 Structure of the atmosphere
'The most alarming of all man's assaults upon the
environment is the contamination of air, earth,
rivers and sea . . . this pollution is for the most part
irrecoverable.'
Rachel Carson (1907-1964)
The Earth's atmosphere is layered, forming con-
centric spheres of markedly differing properties
(Fig. 3.1). As the smallest of Earth's compartments,
the atmosphere provides the smallest reservoir and
hence the most susceptible to pollution. This pollu-
tion affects principally the lowest two layers. From
the Earth's surface to a height of 8-15 km is the tro-
posphere. This is thinnest at the poles and thickest
at the equator and shows seasonal variations. It is
well mixed: vertically by solar-powered convection
and horizontally by the Earth's rotation (Coriolis
force). Mixing ensures that species exhibiting long
lifetimes (Table 3.1) are uniformly distributed
around the globe.
Research is continuing to support these goals. New
synthetic pathways are being developed using
renewable feedstocks, alternative reaction condi-
tions, solvents and catalysts to increase energy and
atom efficiency and to reduce waste. Simultaneously
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