Assessment of pollution aerosols sources above the Straits of Dover using lead isotope geochemistry

We assess the capability of lead isotopes to study the transport of polluti on aerosols above the Straits of Dover by collecting atmospheric aerosols a bove the Eastern Channel and the Southern Eight of the North Sea. During th e same period, we characterized the lead isotopic signature of the main ind ustrial sources on the French coast near the Straits of Dover. Urban and au tomobile-derived aerosols were also collected. Due to the phasing out of le ad in gasoline, the urban isotopic composition (Pb-206/Pb-207 = 1.158 +/- 0 .003) has become more radiogenic, although it is highly variable. On a regi onal scale, major industrial emissions have a well-defined isotopic composi tion (1.13 < Pb-206/Pb-207 < 1.22), more radiogenic than the petrol-lead si gnature (1.06 < Pb-206/Pb-207 < 1.12). These results together with those me asured near the main coastal highway show that the automobile source has be come a minor component of particulate lead in air. On a local scale, Dunker que, the most urbanized and industrialized area along the Straits of Dover, may transiently control elevated lead concentrations. Except for the occur rence of local and regional range transport episodes, lead concentrations i n the Straits of Dover can be related to remote or semi-remote pollution so urce emissions. Combining air mass retrospective trajectories and related l ead abundances and isotopic compositions, it can be shown that lead aerosol s originating from eastern Europe have an isotopic signature (1.145 < Pb-20 6/Pb-207 < 1.169) different from the isotopic composition of west-European lead aerosols (1.111 < Pb-206/Pb-207 < 1.142). The influence of remote Nort h American sources is suggested, with caution, due to uncertainties in mete orological calculations. (C) 1999 Elsevier Science B.V. All rights reserved .