Isotopic evidence of spatial magnitude of the Pb deposition near a lead smelter

Abstract
In order to détermine the dry deposition of lead around a Pb-Zn refinery, two cross-sectional sampling experiments, using deposition plates, have been performed on a daiiy basis, ucder representative meteorological situations (north-easterly and south-westerly winds). The amount of lead deposited as well as its isotopic composition (expressed by the ²⁰⁶Pb/ ²⁰⁷Pb ratio) are systematically measured. For a daily production of approximately 670 metric tons of (Pb+Zn) the dry fallout, greater than 1000  g Pb.h ^-1.m ^-2 on the edge of the plant, falls to about 100  g Pb.h ^-1.m ^-2, four kilometres away from the refinery. This value is still ten times higher than th urban background ( <10  g Pb.h ^-1.m ^-2). The spatial extension of the dry deposition plume is evidenced by the evolution of the isotopic signature of the refinery (1.10 < ²⁰⁶Pb/ ²⁰⁷), clearly distinct from the urban backgrounde signature (1.15 < ²⁰⁶Pb/ ²⁰⁷Pb <1.16). As a first estimate, the extension of the deposition plume seems not to be linked to the wind speed. At the opposite, diffuse emissions from slag heaps are related to this parameter.