Cd, Cu, Pb and Zn concentrations in atmospheric wet deposition at a coastal station in Western Europe

Bulk rainfalls were sampled during ten months in the Eastern Channel ( Northern France). Chloride and sodium are the heavily loaded major ions in wet deposition, indicating a high influence of seasalt. However, the presence of heavy metals is independent of seasalt emissions and various anthropogenic sources should have an impact on their atmospheric concentrations. The comparison between heavy metals concentrations, always ranked as [Zn] much greater than [ Pb]>[Cu] much greater than [Cd], with other values obtained during the same period on European coastal or on urban sites, confirms that our western European station is in a semi-rural area where no local source strongly influences the abundance of atmospheric heavy metals. This semi-rural site could be disturbed by medium and/or long range transport episodes. The observation of literature data confirms a decrease of Cd, Cu and Pb concentrations in rain waters from the beginning of the nineties. On the other hand, no sharp evolution has been observed for zinc concentrations. The structuring of data by clustering has permitted to extract five clusters, including four different types of origins. Two marine clusters, with relatively low levels of heavy metals, are opposite to three other clusters with higher heavy metal levels and a more important impact of continental polluted sources. In 47% of cases, the heavy metals collected at Cap Gris-Nez could originate from British Islands or north western Europe. Heavy metals fluxes show that this rural coastal European site has a level of contamination higher than those measured in remote area. The wet depositions of heavy metals to the English channel and the southern bight of the north sea are not negligible in the evaluation of global fluxes for this area, representing from 20 to 70% of the total input ( riverine, direct and atmospheric inputs).