Trace element and Pb isotope variability during rainy events in the NW Mediterranean: constraints on anthropogenic and natural sources

Rain samples collected over the period 1995–1999 on the French Mediterranean coast have been analyzed for their trace elements and Pb isotopic compositions, both in the dissolved and particulate loads. Our results show that metal Enrichment Factors (EF) relative to Upper Erodable Crust are high for Cu, Pb, Zn and Cd and comparable to values reported about 10 years ago for North Western Mediterranean rains. Overall unradiogenic Pb isotopic compositions indicate the still visible influence of French gasoline lead on both dissolved and particulate loads. This influence is also seen on aerosols, although more variable. The examination of air mass trajectories allows us to distinguih the Pb isotopic signatures of main sources, in particular Marseille/North Italy/North Africa. Rains collected and analyzed sequentially show intra-rain variations for metal contents, metal EF and Pb isotopes, which may also be related to the main paths and altitudes of the air masses. Metal EFs and Pb isotopic data on rains from Southern France in the late 1990s are similar to recent data published on French aerosols or sediments, which are interpreted as reflecting the phasing out of leaded gasoline in the atmosphere.