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Article

Tracing Source Pollution in Soils Using Cadmium and Lead Isotopes

C. Cloquet,*^†^‡ J. Carignan,^† G. Libourel,^†^§ T. Sterckeman, and E. Perdrix

CRPG-CNRS, 15 Rue Notre Dame des Pauvres, BP 20, 54501 Vandoeuvre-ls-Nancy, France, GEOTOP-UQAM-McGill, C.P. 8888, succ. centre ville, Montreal, Canada, H3C 3P8, INPL-ENSG, BP 40, 54501 Vandoeuvre-ls-Nancy, France, INPL-ENSAIA, BP 172, F-54505 Vandoeuvre-ls-Nancy, France, and Dpartement de Chimie-Environnement, Ecole des Mines de Douai, BP 838, F-59508 Douai Cedex, France

Environ. Sci. Technol., 2006, 40 (8), pp 2525–2530

DOI: 10.1021/es052232+

Publication Date (Web): March 22, 2006

Corresponding author phone: +1 514 987 3000 x5662; fax: +1 514 987 3635; e-mail: cloquet.christophe@courrier.uqam.ca

†

CRPG-CNRS.

‡

GEOTOP-UQAM-McGill.

INPL-ENSG.

INPL-ENSAIA.

Ecole des Mines de Douai.

Abstract

Tracing the source of heavy metals in the environment is of key importance for our understanding of their pollution and natural cycles in the surface Earth reservoirs. Up to now, most exclusively Pb isotopes were used to effectively trace metal pollution sources in the environment. Here we report systematic variations of Cd isotope ratios measured in polluted topsoils surrounding a Pb−Zn refinery plant in northern France. Fractionated Cd was measured in soil samples surrounding the refinery, and this fractionation can be attributed to the refining processes. Despite the Cd isotopic ratios being precisely measured, the obtained uncertainties are still large compared to the total isotopic variation. Nevertheless, for the first time, Cd isotopically fractionated by industrial processes may be traced in the environment. On the same samples, Pb isotope systematics suggested that materials actually used by the refinery were not the major source of Pb in soils, probably because refined ore origins changed over the 100 years of operation. On the other hand, Cd isotopes and concentrations measured in topsoils allowed identification of three main origins (industrial dust and slag and agriculture), assuming that all Cd ores are not fractionated, as suggested by terrestrial rocks so far analyzed, and calculation of their relative contributions for each sampling point. Understanding that this refinery context was an ideal situation for such a study, our results lead to the possibility of tracing sources of anthropogenic Cd and better constrain mixing processes, fluxes, transport, and phasing out of industrial input in nature.

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