Résumé
Recent shells from the centre of the coastal lagoon at Thau, S France, show lower Pb concentrations than shells from the lagoon edge. Using isotopic ratios, it is shown that the recent lagoon shells are influenced by anthropogenic input from the harbour and road traffic though the degree of anthropogenic influence varies with location. Shells dating back to the bronze age have much lower Pb concentrations than the recent shells. Shells dating back to the Roman empire have similar Pb concentrations to the recent shells from the centre of the lagoon. The isotopic composition of the Pb in the shells dating back to the Roman Empire indicate anthropogenic inputs.