Heavy Metals in Holocene Peats from South West England: Detecting Mining Impacts and Atmospheric Pollution

South west England has a long history of mining and smelting activity, primarily focused upon the exploitation of tin (Sn), copper (Cu) and arsenic (As) in the mineralised zones of the upland areas. Fragmentary archaeological evidence exists for the exploitation of these mineral resources from the mid-Bronze Age onwards (ca. 1000 BC). This paper explores the usefulness of two peatland systems in revealing the history of trace metal pollution associated with this activity in the south west peninsula and further afield. Using quantitative XRF analyses it was possible to reconstruct the pollution histories for the two sites investigated by analysis of Cu, Zn, As and Pb. Results are presented both as element concentration profiles and as enrichment factors using ash content to normalise the data. Tor Royal, a large raised mire on Dartmoor, contained a regional signal suggesting that concentrations of trace metals began to rise following mid-Neolithic (ca. 2500 BC) disturbance activity on the moor. Sustained increases are noted from this period with a definite peak detected in peats dating from the period of Roman occupation (ca. AD 0-400). The Pb profile displays the characteristic industrial revolution increase and recent decline, the result of the decline in British Pb mining, and the use of lead based petrol additives. Crift Down, a small soligenous mire, displays a more local signal of which the most significant features include the high concentrations of lithogenic elements: rubidium (Rb), yttrium (Y) and uranium (U), and metals (Cu and Zn). Qualitative analyses of the sediments using EDMA provides qualified evidence of local Sn extraction and processing operations, known from archaeological excavations, to date from the Medieval period (10th to 14th centuries AD). Regional variations in atmospheric pollution are also recorded, particularly for Pb. The detection of early mineral exploitation in sediments of this kind is an important step in understanding the extent and nature of mining and smelting in the past history of south west England.