Diverse and detailed data show that climate has always been in a state of change. Climate is driven by radiation energy from the Sun, and for this reason we begin by presenting the basic physics of thermal radiation. Next we will look at the origin of climate and describe some of the many factors that are responsible for natural climate variation. Finally, we will examine natural and anthropogenic factors that are known to have driven climate change since 1750 AD, and some possible climate futures will be discussed. One of the main challenges for the next generation of chemists will be to solve the issues described here that link chemistry, energy, and environment.

Evidence for long-term climate variation can be found in the glacial ice of Antarctica and Greenland, and in deep-sea sediments containing shells from plankton. These records are interpreted by examining changes in the abundance of naturally occurring stable isotopes, for example, oxygen isotopes in water in the ice or in the carbonates of sediments, and sulfur isotopes in pyrite and calcium sulfate in shallow-water sediments. Long-term climate changes are correlated with changes in the Sun-Earth geometry as a consequence of the interaction of the Earth with the Sun and its planets.

Industrial chemicals may be broadly classified as commodity chemicals (see Table 8.1) and specialty chemicals (Table 9.1). The two classes are not exact, but they may be characterized as bulk chemicals (produced in large volume) and fine chemicals (produced in low volume), respectively.

The most important specialty chemicals are listed in Table 9.1. The list is in decreasing order of mass fraction per year, around 2009. An assessment of the actual values is difficult because (1) the delimitation of each group depends on the source of the data, and (2) whereas most data are well known for the United States and the European Union, they are less precise for developing countries. A global production rate of 1 Tg/a corresponds to an average consumption rate of 150 g/a per human being.

The environmental problems that have driven the development of environmental chemistry are associated with the production of goods that we would not want to do without. Industrial production has been built up sequentially: each advance builds on what has come before. One may therefore expect that environmental problems, documented with help from analytical chemistry and spectroscopy, can be solved using the same empirical process. Many compounds either have been phased out or are the subject of regulation. One example is the chlorofluorocarbons described in Chapter 4; another is the pesticides listed in Table 9.2. By the end of the 20th century, useful alternatives had been found for tetraethyl lead, an antiknock additive in gasoline, and its use has been banned (an example of the toxicity of lead can be found in Section 1.3c). The field of environmental chemistry is changing as its focus moves from one pollutant to the next.

Since ancient times, humanity has wanted to understand the Earth. This desire has driven the development of modern physics, chemistry, geology, and biology.

Section 1.1 gives a brief survey of the present understanding of the formation of the Earth. This knowledge is based on observations of electromagnetic radiation coming from space, as well as direct observations of the Sun, the Earth, the Moon, a few planets, comets, and various meteorites found on the surface of the Earth.

In the remaining part of Chapter 1 we discuss classical results dealing with the form of the Earth, including its surface and internal structure, how its tremendous age was determined, and the important role that life has played in the development of our present environment.

Origin of the Earth

A study of environmental chemistry would not be complete without a description of the origin of the Earth and its relation to the rest of the universe. This section describes the materials of which the Earth is made, and how and why these elements are distributed among the various spheres of the Earth.

Introduction

The environment is in a constant state of change. In order to describe this adequately, this chapter reviews environmental dynamics, the unification of fluid dynamics, chemical thermodynamics, and chemical kinetics.

An important goal of environmental chemistry is to model Nature, including predicting the fate of a given chemical species, whether of natural or anthropogenic origin. The purpose of this chapter is to establish the nomenclature used in the book and to present fundamental concepts and expressions. It is particularly important to derive the explicit time dependence of the relevant physical quantities. In separate sections of this introduction, we first describe and define a few basic concepts, and then introduce important concepts for the time dependence of concentration, field, and transport.

Basic concepts

System and phase

The concepts of system, surroundings, and phase used in thermodynamics are the cornerstones of any environmental investigation. A system is the part of the world that has been chosen as the subject of study; it may contain matter, in which case it also contains energy. Everything else is said to belong to the surroundings. The separating boundary may be real or imaginary, but must be defined before the study begins. Depending on the properties of the boundary, one can define three types of system. An open system is one that can exchange substance and energy (work, heat, radiation) with the surroundings. A closed system cannot exchange substance with the surroundings, and an isolated system can exchange neither substance nor energy with the surroundings. Except in the last case, the surroundings enter the physical description, because they must have certain properties as sources or sinks for the exchanged physical quantities.