Lead isotopes and elemental composition of Roman fistulae plumbeae aquariae from Conimbriga (Portugal) using Quadrupole ICP-MS

Abstract

Lead metal and lead artefacts were widespread over the Roman world, as consequence of its large use in public buildings, namely as plumbing on hydraulic systems of Roman cities and villae. The determination of Pb isotope ratios combined with minor and trace element contents of such lead artefacts may constitute a powerful tool for provenance studies as well as in the assessment of trade routes during the Roman period. In the present work forty four fistulae plumbeae from the hydraulic systems installed at Conimbriga were analysed using a quadrupole based ICP-MS. The overall results demonstrate the suitableness of this well-established and economic analytical technique involving simple sample preparation and high throughput. Pb isotopic patterns present high scattered distributions which suggest different provenances of the raw material. Ag, As, Bi, Cu, Ni, Sb, and Sn contents were determined in an attempt to identify the type of raw materials and the metallurgical process used to obtain the lead metal. Sn content points to the frequent use of recycled lead. The Pb isotope ratios of samples of lead pipes made with metal probably not recycled indicate the use of raw materials (galena ores) from Sierra Morena mines or desilvered litharge resulting from silver cupellation probably using argentiferous jarosite ores from the Iberian Pyrite Belt (Rio Tinto mines).