Heavy Metals in Some River and Bay Sediments near Swansea

Abstract

RELATIVELY high concentrations of trace metals in plants1 and in coastal waters2 around the Swansea area indicate the need for identifying their possible sources. We have analysed some sediments from the Rivers Neath and Tawe and from the shore of Swansea Bay (Fig. 1). Both rivers are tidal in the sampling localities and material was collected from muddy sediment exposed at approximately half tide levels. The Swansea Bay samples were also obtained from the half tide zone at three localities ranging from the West Pier by the mouth of the River Tawe (South Dock) westwards away from the industrial belt to the University College and Blackpill (Fig. 1). Two samples were taken from the River Neath, one about 1 inch and the other 6 inch beneath the surface. This was repeated at the River Tawe with an additional sample from the surface layer of sediment. The beach samples consisted of a surface layer sample and another 6 inch below from each of the three collecting stations (Fig. 1). Of the 11 samples 6 have more than 70% and 4 more than 43% by weight of material finer than BSS 120 mesh (0.124 mm) and, with one exception (R. Tawe sample 3) less than 12% larger than BSS 40 mesh (approx. 0.4 mm). The grain size distribution is therefore mainly in the silt-clay range (Fig. 2).