Heavy Metal Content of Some Rivers and Lakes in Wales

Abstract

WELSH rivers and lakes are remarkably free from domestic and industrial pollutants, but because of the presence of mineral deposits and the remains of mining activities, they are likely to have small but significant concentrations of heavy metals that may cause severe deterioration of the water quality. For example, the presence of lead, zinc and copper in some Welsh streams causes a high mortality rate in fish and other living populations of these streams^1–5, and the heavy metals carried to the sea by Welsh rivers are the primary source of these metals in Cardigan Bay⁶. But since the cessation of mining activities in the early part of this century, it has been reported that some rivers have shown some degree of recovery from the effects of lead pollution^7,8. Only limited information is available concerning the heavy metals in Welsh rivers, and most of this is not entirely reliable as an indicator of the present level of metals in the water. Here we report an investigation of the heavy metal content of rivers and lakes in Wales carried out from September 1970 to October 1971. The River Dee and its tributaries were examined between July 1968 and April 1969. Samples were taken from the positions shown in Fig. 1 at monthly intervals. Seven trace metals and the major ions were determined. The trace metals were separated by chelating resins and analysed using pulse polarography⁹ or atomic absorption spectrophotometry.