An atmospheric pollution history for lead–zinc mining from the Ystwyth Valley, Dyfed, mid-Wales, UK as recorded by an upland blanket peat

Abstract

This paper presents records of the atmospheric deposition of lead and zinc close to a former metal mining area as recorded by an upland blanket peat that has accumulated on the northern slopes of the Ystwyth valley, Dyfed, mid-Wales, UK. The research objective was to explore the possibility that the peat contained a geochemical record of the pollution generated by mining activity during the last four millennia. Four monoliths were extracted from the blanket peat to reconstruct the pollution history of lead and zinc mining. Three different geochemical measurement techniques were employed, and five lead and zinc profiles have been reconstructed, two of which are radiocarbon-dated. In the radiocarbon-dated monoliths lead enrichment occurs in the peat during the Roman occupation whilst both lead and zinc concentrations increase from the Mediaeval period until the early part of the 20th century. Similar enrichment of lead and zinc is shown in the remaining profiles. Whilst other possible explanations are discussed, it is argued that the high lead concentrations represent evidence of atmospheric pollution caused by mining. Zinc, however, may have suffered from post-depositional mobility. The results of this suggest that lead is largely rendered immobile in blanket peat and can be used to reconstruct atmospheric pollution histories in former lead mining areas.