Ancient copper and lead pollution records from a raised bog complex in Central Wales,UK

This paper presents records of metal deposition as preserved by a peatland which has accumulated in the lowland coastal zone at Borth, near Aberystwyth, Ceredigion, mid-Wales, U.K. The research objective was to explore the origins and history of metal mining and (or) metallurgy by reconstructing a geochemical record of copper, lead and zinc pollution for the last four millennia. Two cores were extracted from Borth Bog, one from the raised ombrotrophic part of the bog and another from a minerotrophic part of Borth Bog close to the ancient copper workings at Llancynfelin. Although peat stratigraphy and nutrient status have influenced the geochemical record, the results suggest that an early phase of copper and lead pollution occurred at Llancynfelin whilst lead enrichment occurred in the peat core taken close to the centre of Borth Bog during the Bronze Age and the Roman occupation. Therefore the origins of copper and lead mining and metallurgy possibly extend back to the Bronze Age in central Wales. No record of historical pollution exists at either site. The results of this study also provide further evidence that lead and copper are immobile in ombrotrophic peat and that pollution records can be elucidated from minerotrophic peat. Zinc, however, may have suffered from post-depositional mobility.