The environmental legacy of historic Pb-Zn-Ag-Au mining in river basins of the southern edge of the Massif Central (France)

Abstract

The main rivers (Aude, Orb, Herault) that discharge into the Gulf of Lions and the west bank tributaries of the Rhone River including the Gardon have former non-ferrous metal mines in their upper drainage basin. Using unpublished data and data from the literature, this study provides an integrated overview of the contamination of water and sediment along the continent-sea continuum and of its impacts on the biota and on human health. In the upper part of these basins, water and stream sediments are enriched in metal(-loids) compared to median European concentrations. Arsenic is the main contaminant in the rivers Aude and Gardon d'Anduze, Sb in the Orb and Gardon d'Alès, and Tl in the Herault river. A rapid reduction in dissolved and particulate concentrations was systematically observed along the river due to dilution and precipitation. The high concentrations of metal(-loid)s observed suggest that the former mining activity still represents a potential threat for the environment, but the lack of high temporal resolution monitoring, especially during Mediterranean floods, prevents accurate assessment of metal fluxes from these rivers to the Mediterranean Sea. Studies dedicated to the impacts on human health are too rare, given that studies have shown a higher rate of arsenic-specific cancer near Salsigne mine in the Aude River basin and cases of saturnism in children in the upper Herault River basin. These studies underline the need to take environmental health issues into consideration not only in these watersheds but around the entire Mediterranean basin, which harbors numerous metalliferous ores that have been mined for millennia.

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