Introduction

The last chapter of our book will describe the use of radioisotopes for assessing the impact of human activities on the environment. The range of opportunities is very extensive as seen by the list of applications in Table 9.1 which is by no means complete. Emphasis will be placed on assessing such impacts using two methods, described here as the mathematical modelling approach and the archival approach.

1. The modelling approach. Due to recent vast increases in the power of computers, applications of mathematical modelling techniques to environmental science are now very widespread and underpin much of our detailed understanding of processes in the oceans, the atmosphere and coastal and terrestrial ecosystems. Since increasing use is being made of numerical models for scientific prediction and environmental management, there is a growing need for independent verification of the model predictions. Tracer techniques are a powerful tool for model validation, as will be demonstrated in several examples.

2. The archival approach. This approach to the study of environmental processes involves using evidence from the past to understand the present and to assess the future. The approach is implemented in two stages. The first stage involves the systematic dating of material which has accumulated layer by layer often over long periods of time. Cores extracted from sediments, ice sheets, old growth trees or massive corals are commonly used. From knowledge of the dates of the samples and their locations in the core, it is possible to calculate the average rate of growth or accumulation.