Introduction

ROY M. HARRISON

School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK

1.1 WHAT IS POLLUTION SCIENCE?

There are various definitions for environmental pollution, all of which contain two key components. The first is that pollution involves some kind of change to the environment. The most obvious kinds of changes are the addition of man-made chemicals that do not occur naturally. Equally important, however, can be the additions of chemicals which do occur naturally in the environment, provided the resultant concentration meets the second criterion. This criterion is that for the phenomenon to be described as pollution, then the perturbation suffered by the environment must in some way be harmful. Not all pollution phenomena are the results of chemicals in the environment. Other important forms of pollution include thermal pollution, an example of which is the discharge of relatively warm power station cooling waters into coastal seas where they can lead to a significant change in the ecology of aquatic organisms. A further example is that of light pollution, caused by the massive amount of urban street lighting, which has a deleterious effect on the environment through obscuring our view of stars in the nighttime sky. Noise pollution has important aesthetic impacts through causing widespread annoyance, but is increasingly suspected of causing adverse effects on health.

This book concerns itself almost exclusively with chemical pollution. It considers the environment as a set of compartments that is familiar to us from our everyday existence. Therefore, separate chapters deal with the atmosphere, the world's waters, and soils and the solid earth. While such a subdivision is convenient in that pollutants behave very differently in each of these media, it is of course not the full story. The atmosphere is very mobile and many pollutants have lifetimes in the atmosphere of only hours or days, although some remain for much longer. Pollutants in the aquatic environment, unless rapidly biodegraded, will often be present for days or weeks, and persistent pollutants for many years. In soils and sediments, however, pollutants can remain relatively immobile for tens or hundreds of years. The rates of mixing are also very different. An atmospheric pollutant with a lifetime of more than a year will become globally mixed, whereas the same degree of mixing throughout the oceans will take centuries and throughout the solid earth will never occur unless there are pathways through water and air. Exchange processes between these major environmental compartments can be very important. Thus, for example, the largest inputs of some pollutants to the North Sea arise through deposition from the atmosphere. There are other examples where pollutants discharged to the sea can become suspended in sea spray and lead to contamination of bot