A Paleorecord of Atmospheric Lead Deposition in France

A paleorecord of atmospheric lead deposition in France.

New data from “La Godivelle” peat bog (Puy de Dôme)

François De Vleeschouwer1,5,*, Nadine Mattielli2, Virginie Renson3, Gaël Le Roux4, Nathalie Fagel1

1Clays, Geochemistry and Sedimentary Environments Research Unit, Department of Geology, University of Liège, Allée du 6 Août, B18, Sart Tilman, 4000 Liège, BELGIUM.

2Isotopes, Petrology and Environment Research Unit, Département des Science de la Terre et de l’Environnement, Université Libre de Bruxelles, BELGIUM

3Earth System Science, Department of Geology, Vrije Universiteit Brussel, BELGIUM

4EcoLab/Campus Ensat, Avenue de l’Agrobiopole, Castanet-Tolosan, FRANCE

5From March 2010, at: Department of Ecology and Environmental Science, Umeå University, SWEDEN

Lead pollution history over Central France was reconstructed for the last ca. 2000 years using the elemental and Pb isotopic geochemistry applied on a 210Pb- and 14C-dated peat core from “La Godivelle”, Puy de Dôme (France). The whole core displays lead content data well above the natural background (ca. 17μg/g-1 in the Upper Continental Crust), giving evidences for anthropogenic activities in this area back to the Roman Period and possibly earlier. Most of the historical interpretation is based on Pb concentration and Pb isotopes, the other chemical elements (Zn, Cu, Ni) being considered secondary and possibly mobile in the peat column. During the Late Roman Period, lead enrichment factors (Pb E.F., normalized with Ti) show values up to 20 and decrease later on towards 4-5. Similarly, 206Pb/207Pb values decrease from 1.174 to 1.188. The medieval period displays low Pb E.F. values (1-5) and high 206Pb/207Pb values (1.17-1.19). During the industrial revolution (18th-19th centuries), Pb E.F. increase drastically (up to 45) while 206Pb/207Pb decreases towards 1.16. During the last century, leaded gasoline greatly contributed to fingerprint the Pb isotopic signature. The post 80’s decrease of Pb E.F. related to the introduction of unleaded gasoline is relatively well recorded. However, the parallel decrease in the 206Pb/207Pb data is not clearly recorded, suggesting a local (so far not identified) source influencing the recent lead isotopic signature. The results will be compared to local/regional past and present lead emitters in order to tackle the possible lead source in Massif Central since the Roman Period.