| Abstract
| - Numerous palaeo metallurgical sites (n = 70) characterizedby slag presenting a homogeneous typology have beenreported on the Mont-Lozère Massif (Southern France).These activities took place in the medieval period. The silicatedslag matrix comprises mainly Pb (25%), Sb (0.4%), andseveral thousand parts per million of As, Cu, and Zn. Soilsamples were collected in and around two sites, tounderstand the dispersion mechanism affecting the slagtailings through use of metal concentrations and lead isotopiccompositions. The majority of polluted soil samples showhigh enrichment factors (EF) for Pb and Sb, slightly lower EFsfor Cu, and much lower EFs for As and Zn. We showthat this “old” metal pollution was physically dispersed,through erosion of workshop soils and slag tailings, in arestricted area (ca. 200 m down slope form the site). Thereis no evidence for massive leaching of slag metals bysoil waters, except for Zn. Thus, the pollution is mainly dueto the metal-making process, i.e., smoke-fallout, piecesof ore, the crackling of smelting ore outside the oven duringreduction, and charcoal, etc. The lead isotopic compositionsof the soils define a binary mixing trend between localgranite or background soil and slag (which represent theworkshop soil). Simple mass balance equations usingeither Pb isotopes or Pb concentrations suggest that between40 and 100% of the total Pb in soils comes from theMedieval workshop pollution, leaving any later pollutionnegligible. The large number of sites on the Mont-Lozèremeans this medieval pollution is significant and poses a realenvironmental risk.
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