A 300 year history of lead contamination in northern French Alps reconstructed from distant lake sediment records

International audienceLead concentrations and isotopic ratios were measured along two well-dated sediment cores from two distant lakes: Anterne (2100 m a.s.l.) and Le Bourget (270 m a.s.l.), submitted to low and high direct human impact and covering the last 250 and 600 years, respectively. The measurement of lead in old sediment samples (>3000 BP) permits, in using mixing-models, the determination of lead concentration, flux and isotopic composition of purely anthropogenic origin. We thus show that since ca. 1800 AD the regional increase in lead contamination was mostly driven by coal consumption (206Pb/207Pb ∼ 1.17–1.19; 206Pb/204Pb ∼ 18.3–18.6), which peaks around 1915 AD. The increasing usage of leaded gasoline, introduced in the 1920s, was recorded in both lakes by increasing Pb concentrations and decreasing Pb isotope ratios. A peak around 1970 (206Pb/207Pb ∼ 1.13–1.16; 206Pb/204Pb ∼ 17.6–18.0) corresponds to the worldwide recorded leaded gasoline maximum of consumption. The 1973 oil crisis is characterised by a drastic drop of lead fluxes in both lakes (from ∼35 to <20 mg cm−2 yr−1). In the late 1980s, environmental policies made the Lake Anterne flux drop to pre-1900 values (