Samples of sediment material were collected from the River Cynon. The concentrations of heavy metals in the samples were determined by Atomic Absorption Spectroscopy after digestion of the dried sample. A rapid hydrochloric acid/hydrogen peroxide digestion was chosen after a brief comparison with the more traditional nitric/perchloric acid digestion. The results were used in a survey of the heavy metal concentrations over the length of the river and in comparison with surveys of other systems. This showed that while the Cynon contains higher levels of heavy metals than some other similar systems, it is not grossly polluted and contains considerably lower levels of some metals than some mineralised Cornish rivers. Factor analysis of the data showed that one major factor was controlling the heavy metal distribution at each site. Profiles of these factors were generated using target factor analysis.The evidence suggests that the local geology is the main factor near the source of the river with coal based material determining the profile of heavy metals in the lower reaches. Pattern recognition techniques were shown to be capable of classifying the four sites and identifying 'outliers' in the data. Similar sites were found to overlap in the principal component analysis but resolution of these sites was improved by utilising principal components that were less important to the overall classification. Magnesium was identified as the feature with the greatest ability to classify the data. Two similar sites identified in the factor analysis were also shown to be similar by the pattern recognition methods. Other data on the Cynon taken at different times was classified as different from the main data categories thus showing the variation of heavy metal concentration with time.
Networked Digital Library of Theses and Dissertations