Introduction

1.1 THE ENVIRONMENT

The environment is the sum total of human surroundings consisting of the atmosphere, the hydrosphere, the lithosphere and the biota. Human beings are totally dependent on the environment for life itself. The atmosphere provides us with the air we breathe, the hydrosphere provides the water we drink and the soil of the lithosphere provides us with the vegetables that we eat. In addition, the environment provides us with the raw materials to fulfill our other needs: the construction of housing, the production of the numerous consumer goods, etc. In view of these important functions it is imperative that we maintain the environment in as pristine a state as is possible. Fouling of the environment by the products of our industrial society (i.e. pollution) can have many harmful consequences, damage to human health being of greatest concern.

In addition to the outdoor environment, increasing concern is being expressed about the exposure of individuals to harmful pollutants within the indoor environment, both at home and at work. Levels of harmful pollutants can often be higher indoors than outdoors, and this is especially true of the workplace where workers can be exposed to fairly high levels of toxic substances. Occupational health, occupational medicine, and industrial hygiene are subjects that deal with exposure at the workplace.

Pollution is mainly, although not exclusively, chemical in nature. The job of the environmental analyst is therefore of great importance to society. Ultimately, it is the environmental analyst who keeps us informed about the quality of our environment and alerts us to any major pollution incidents which may warrant our concern and response.

1.1.1 Biogeochemical Cycles

The different components of the biosphere and their interactions are illustrated in Figure 1.1. The biosphere is that part of the environment where life exists. It consists of the hydrosphere (oceans, rivers, lakes), the lower part of the atmosphere, the upper layer of the lithosphere (soil) and all life forms. The concept of the biosphere was first introduced by the Russian scientist Vladimir Vernadsky (1863–1945) as the "sphere of living organisms distribution". Vernadsky was among the first to recognise the important role played by living organisms in various interactions within the biosphere, and he established the first-ever biogeochemical laboratory specifically dedicated to the study of these interactions. He expounded his theories in an aptly entitled book, "Biosphere", published in 1926.

The various spheres act as reservoirs of environmental constituents and they are closely linked through various physical, chemical and biological processes; there is constant exchange of material between them. Chemical substances can move through the biosphere from one reservoir to another, and this transport of constituents is described in terms of a biogeochemical cycle. Biogeochemical cycles of many elements are closely linked to the hydrological cycle, The hydrological cycle acts as a vehicle for moving water soluble nutrients and pollutants through the environment. If all the components of the cycle are identified and the amounts and rates of material transfer quantified, the term budget is used. Both beneficial nutrients and harmful pollutants are transported through biogeochemical cycles with far-reaching consequences. The more commonly discussed biogeochemical cycles are those of important macronutrients such as carbon, sulfur, nitrogen and phosphorus, but, in principle, a biogeochemical cycle could be drawn up for any substance. The cycle is usually illustrated as a series of compartments (reservoirs) and pathways between them. Each reservoir can be viewed in terms of a box model shown in Figure 1.2.

If the input into a reservoir equals the output, the system is said to be in a steady state. The residence time, τ, is defined as:

τ = Amount of substance in the reservoir (mass)/ Flux (mass/time)

Flux is the rate of transfer through the reservoir (i.e. the rate of input or output). If the input exceeds the output, there will be an increase in the amount of substance in the reservoir. There are many examples of the build-up of pollution in environmental systems since pollutants are often added at rates greater than the rates of natural processes that act to remove them from the system. On the other hand, if the output is greater than the input, the amount of substance in a reservoir will decrease. An example of this is the depletion of natural resources.

It is debatable whether, in the absence of human activities, natural systems would tend towards some sort of steady-state or equilibrium. Natural systems are dynamic, and both natural and human-induced disturbances lead to change, albeit over different time scales. Natural changes to biogeochemical cycles generally take place over geological time scales, and for millennia these cycles have maintained the delicate balance of nature conducive to life. However, since the industrial revolution, and especially over the last 40 years, human activities have caused significant perturbations to these cycles. The effects of these disruptions are already becoming apparent, and are likely to become even more severe in the coming millennium. Serious environmental problems that have been caused by disruptions of biogeochemical cycles include: global warming, acid rain, depletion of the ozone layer, bioaccumulation of toxic wastes and decline in freshwater resources. Modelling of biogeochemical cycles is becoming increasingly important in understanding, and predicting, human impacts on the environment, and the possibility of using biogeochemical cycles to solve environmental problems, so-called biogeochemical engineering, has recently been recognised.

Some of the major human impacts on biogeochemical cycles are given in Table 1.1.

The extent of human impacts on biogeochemical cycles can be illustrated by comparing the contribution of anthropogenic emissions to the atmosphere with natural emissions (Table 1.2). For some toxic substances the contribution of industrial emissions is even more striking: the ratio of anthropogenic to natural emissions to the environment is 3:1 for arsenic, 5:1 for cadmium, 10:1 for mercury and 28:1 for lead.

1.1.2 Environmental Pollution

Pollution is commonly defined as the addition of a substance by human activity to the environment which can cause injury to human health or damage to natural ecosystems. This definition excludes "natural pollution", although natural processes can also release harmful substances into the environment. There are different categories of pollution: chemical, physical, radioactive, biological and aesthetic. This book is concerned primarily with chemical pollutants and their determination in environmental matrices.

Most substances that are considered as pollutants are actually natural constituents of the environment, albeit at...