Estelle Camizuli lors de l’échantillonnage dans le Morvan
L’article “Impact of historical mining assessed in soils by kinetic extraction and lead isotopic ratios.” par Camizuli, E., Monna, F., Bermond, A., Manouchehri, N., Besançon, S., Losno, R., van Oort, F., Labanowski, J., Pereira, A., Chateau, C., Alibert, P. est maintenant publié chez Science of the Total Environment. 472, 425-436 [pdf].
Estelle Camizuli (estelle.camizuli@u-bourgogne.fr) a étudié le devenir des métaux présents dans des sols pollués par des activités métallurgiques anciennes. La quantité totale de métal contenue dans un sol ne fournit que peu d’informations sur ses capacités de transfert vers les plantes et les animaux. Pourtant le devenir de ces métaux est une question de première importance pour une gestion de l’environnement sur le long terme. Estelle a donc appliqué une lourde procédure chimique basée sur l’extraction cinétique. Le constat est plutôt rassurant, tout au moins dans le Morvan: les métaux présents dans les sols pollués par nos prédécesseurs sont piégés et ne devraient pas affecter de façon trop drastique la faune et la flore.
Abstract: The aim of this study is to estimate the long-term behaviour of tracemetals, in two soils differently impacted by past mining. Topsoils from two 1 km2 zones in the forested Morvan massif (France) were sampled to assess the spatial distribution of Cd, Cu, Pb and Zn. The first zone had been contaminated by historical mining. As expected, it exhibits higher trace-metal levels and greater spatial heterogeneity than the second non-contaminated zone, supposed to represent the local background.One soil profile fromeach zonewas investigated in detail to estimate metal behaviour, and hence, bioavailability. Kinetic extractions were performed using EDTA on three samples: the A horizon from both soil profiles and the B horizon from the contaminated soil. For all three samples, kinetic extractions can be modelled by two first-order reactions. Similar kinetic behaviour was observed for all metals, but more metal was extracted from the contaminated A horizon than from the B horizon. More surprising is the general predominance of the residual fraction over the “labile” and “less labile” pools. Past anthropogenic in-puts may have percolated over time through the soil profiles because of acidic pH conditions. Stable organo- metallic complexes may also have been formed over time, reducing metal availability. These processes are not mutually exclusive. After kinetic extraction, the lead isotopic compositions of the samples exhibited different signatures, related to contamination history and intrinsic soil parameters. However, no variation in lead signature was observed during the extraction experiment, demonstrating that the “labile” and “less labile” lead pools do not differ in terms of origin. Even if trace metals resulting from past mining and metallurgy persist in soils long after these activities have ceased, kinetic extractions suggest that metals, at least for these particular forest soils, do not represent a threat for biota.
Ce travail a été réalisé dans le cadre d’un programme de recherche co-financé par le Fonds Européen de Développement Régional (FEDER), le Conseil Régional de Bourgogne, l’Université de Bourgogne, le Parc national des Cévennes, l’Unité Mixte de Recherche 5594 ARTéHIS, le Ministère de l’Education Nationale, de l’Enseignement Supérieur et de la Recherche, le Centre Archéologique Européen du Mont Beuvray. Il est soutenu activement par le Parc naturel régional du Morvan.