The structure of this book

In the following chapters we describe how components of the Earth's chemical systems operate. Chapter 2 is a 'toolbox' of fundamental concepts underpinning environmental chemistry. We do not expect all readers will need to pick up these 'tools', but they are available for those who need them. The emphasis in each of the following chapters is different, reflecting the wide range of chemical compositions and rates of reactions that occur in near-surface Earth environments. The modern atmosphere (see Chapter 3), where rates of reaction are rapid, is strongly influenced by human activities both at ground level, and way up in the stratosphere. In terrestrial environments (see Chapters 4 & 5), a huge range of solid and fluid processes interact. The emphasis here is on weathering processes and their influence on the chemical composition of sediments, soils and continental surface waters. Human influence in the contamination of soils and natural waters is also a strong theme. Terrestrial weathering links through to the oceans (see Chapter 6) as the major input of constituents to seawater. It soon becomes clear, however, that the chemical composition of this vast water reservoir is controlled by a host of other physical, biological and chemical processes. Chapter 7 examines environmental chemistry on a global scale, integrating information from earlier chapters and, in particular, focusing on the influence of humans on global chemical processes. The short-term carbon and sulphur cycles are examples of natural chemical cycles perturbed by human activities. Persistent organic pollutants (POPs) are used as examples of exotic chemicals that persist for years to decades in soils or sediments and for several days in the atmosphere. Their persistence has allowed them to be transported globally, often impacting environments remote from their place of manufacture and use. In all of these chapters we have chosen subjects and case studies that demonstrate the chemical principles involved. To help clarify our main themes we provide information boxes that describe, in simple terms, some of the laws, assumptions and techniques used by chemists.

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