Trace metals from historical mining sites and past metallurgical activity remain bioavailable to wildlife today.

11 pagesInternational audienceThroughout history, ancient human societies exploited mineral resources all over the world, even in areas that are now protected and considered to be relatively pristine. Here, we show that past mining still has an impact on wildlife in some French protected areas. We measured cadmium, copper, lead, and zinc concentrations in topsoils and wood mouse kidneys from sites located in the Cévennes and the Morvan. The maximum levels of metals in these topsoils are one or two orders of magnitude greater than their commonly reported mean values in European topsoils. The transfer to biota was effective, as the lead concentration (and to a lesser extent, cadmium) in wood mouse kidneys increased with soil concentration, unlike copper and zinc, providing direct evidence that lead emitted in the environment several centuries ago is still bioavailable to free-ranging mammals. The negative correlation between kidney lead concentration and animal body condition suggests that historical mining activity may continue to play a role in the complex relationships between trace metal pollution and body indices. Ancient mining sites could therefore be used to assess the long-term fate of trace metals in soils and the subsequent risks to human health and the environment. The first evidence of extractive metallurgy dates from the 6 th millennium BC in the Near East 1,2. Since then, mining and smelting activities have developed almost everywhere that humans have settled 3,4 , resulting in the emission of unexpectedly large amounts of metals into the environment, e.g., during the Roman Empire 5,6. Deleterious consequences on human health were observed as early as the 1 st century BC, with Lucretius, for instance, pointing out "the ill effects in the miners' complexions" and writing "How deadly are the exhalations of gold mines!" (De natura rerum, 4, 808 7). Negative impacts of mining and smelting activities on animals and the environment were also recognized long ago. During the 1 st century BC, Vitruvius wrote that springs coming from mining areas were very harmful (De Architectura, 8, 5 8), while Pliny the Elder, during the 1 st century AD, noticed how silver mine emissions affect all animals (Naturalis Historia, 33, 31 9). With geographical shifts of human settlements over time, some mining and/or smelting sites may have vanished from collective memory 10-12. For instance, in the Morvan and Cévennes massifs (France), the older sites remain difficult to identify in the field, particularly in forested areas. Because of their outstanding landscapes and biodiversity, both the Morvan and the Cévennes are recognized as nature parks, considered to be pristine areas, relatively free from anthropogenic impact. These areas have nonetheless experienced several phases of mining and smelting, starting as early as the Bronze Age for the Morvan 13-15 and at least from the Iron Age for the Cévennes 16