REE characteristics and Pb, Sr and Nd isotopic compositions of steel plant emissions

摘要

A comprehensive Pb-Sr-Nd isotope and REE tracer study of atmospheric trace metal pollution by a steel plant situated to the north of the urban communities of Strasbourg (France) and Kehl (Germany) has been performed using tree barks as biomonitors. The Pb-206/Pb-207 and Pb-208/Pb-207 isotopic ratios of the steel plant's filter dust are similar to values found in dust of waste incinerators. The Sr-87/Sr-86 ratio is similar to present-day ratios of Phanerozoic or Precambrian granitic rocks. The Nd-143/Nd-144 isotopic composition is very low and corresponds to an epsilon(Nd) value of -17.5. Such a low value is characteristic of old Precambrian granitic rocks and banded iron formations. Thus, this low eNd value might point to the origin of the iron necessary for the steel production. The fact, that this isotopic composition does not occur in crustal rocks of Western Central Europe makes the Nd isotope ratio a powerful tool to trace steel plants atmospheric emissions. The rare earth element (REE) distribution pattern of the steel plant's filter dust shows very specific fractionations like La and Nd enrichments which are traceable in tree barks over a distance of 4 km. The Pb, Sr and Nd isotope ratios not only enable the steel plant's emissions to be traced in a north-easterly direction, along the principal wind pathway but also enables the interference of this emission at 4 km NE from the steel plant with another atmospheric component originating from the Strasbourg Rhine harbour to be identified. (c) 2006 Elsevier B.V. All rights reserved.