Heavy metals in the waters of the Nant-y-Fendrod: change in pollution levels and dynamics associated with the redevelopment of the Lower Swansea Valley, South Wales, UK.

Approximately 240 years (c. 1720-1960) as a world centre for the metal smelting industry left the Lower Swansea Valley as a derelict urban landscape with severe Cu, Zn, Pb, Cd and Ni and metal contamination. Using analysis of archival water quality and discharge records, this paper assesses changes in river pollution over the period 1966-1999 for the Nant-y-Fendrod stream. The marked reduction in metal pollution levels over the period can be linked to the cessation of remaining metal smelting activity and to the rehabilitation and redevelopment measures and their timing. Pollution, both in the past and currently, is shown to be episodic rather than continuous and relationships of high pollution levels to antecedent weather, season, discharge and hydrograph position are explored. Some of the highest levels were recorded during redevelopment itself. Prospects for metal pollution episodes in the Nant-y-Fendrod with further redevelopment in the Lower Swansea Valley in the future are briefly discussed.