Temporal patterns of the wet deposition of Zn, Cu, Ni, Cd and Pb: The Arcachon Lagoon (France)

We report here the first data set on wet deposition of heavy metals in the southwestern French coastal zone. In this region, there are two major sensi tive coastal ecosystems: the Gironde Estuary and the Arcachon Lagoon. Chemi cal analyses of heavy metals were carried out by ICP-MS. Annual mean concen trations of the dissolved fraction in precipitation were 0.2, 3.4, 4.3, 8.1 and 30 mu g L-1 for Cd, Ni, Cu, Pb and Zn, respectively. In terms of annua l fluxes, these numbers are of the same order of magnitude as the fluxes me asured in southeastern France, but are higher than those measured in wester n Brittany. When extrapolated to the entire Bay of Biscay, the annual wet d issolved fluxes of Cd, Ni, Cu, Pb and Zn are respectively 7, 110, 140 340 a nd 1440 t yr(-1). According to available data in the literature, the region al Cd, Cu, Pb and Zn atmospheric fluxes for the Bay of Biscay are of the sa me order of magnitude as riverine inputs (Loire and Gironde). On a daily or weekly time scale, we observed a strong variability of elemental fluxes: u p to 20% of the annual dissolved flux may occur in a rain event shorter tha n 3.5 days. Although elements display generally parallel variations with ti me, they sometimes follow independent behaviours (e.g. Pb and Cd), suggesti ng that they may derive from different geographical and/or pollution source s.