Contamination de sols par des éléments traces métalliques en zone méditerranéenne côtière : études de leur mobilité et du transfert à la phytocénose.

Les objectifs de cette thèse ont été de contribuer à l'évaluation des niveaux de contamination en éléments traces métalliques et métalloïdes (ETMM) des sols du site de l'ancienne fonderie de plomb de l'Escalette (sud-est de Marseille), d'en approcher les processus de transport et transfert dans l'environnement en particulier leurs mobilités dans le sol et leurs transferts aux plantes. La contribution à l'établissement d'une cartographie de la contamination sur un périmètre plus vaste que celui de l'usine (zone des Calanques) a permis de mettre clairement en évidence l'impact de cette dernière. Sur le site industriel, les formes et niveaux de contamination des sols diffèrent d'une zone à l'autre. Les sols formés en surface des crassiers se caractérisent par leurs fortes teneurs en Cu, Zn et Pb, dont les fractions mobilisables sont notables (2 à 30%), l'influence des scories est nette. Les sols prélevés à proximité de la cheminée présentent les plus fortes contaminations en Pb, Sb et As, avec de 10 à 30% de fractions mobilisables. Cette contamination est liée aux émissions anciennes via la cheminée rampante mais aussi à la dégradation de cette dernière. Le potentiel de libération des éléments As et Sb des sols de ces 2 zones conduirait à leurs stockages dans des décharges pour déchets dangereux. Les essais de solubilisation en milieu acide ont mis en évidence des risques pour la santé par ingestion concernant Pb et As. Les zones en proche périphérie de l'usine sont moins impactées mais sont néanmoins considérées comme fortement contaminées. G. alypum et R. officinalis, présentes sur le site, sont tolérantes aux ETMM et peuvent les accumuler.The overall objective of this thesis was to contribute to the assessment of the level of contamination by trace metals and metalloids (TMM) on the site of Escalette (a former lead smelter in southeastern Marseille). The study of TMM transfer and transport processes on this site, taking into account their mobility in the soil and their transfer to plants, was a specific objective. The mapping of TMM contamination in an extended area around the factory site (on Calanques zone) has clearly highlighted the impact of the former industry. So, on the Escalette site, forms and levels of soil contamination differ from one area to another. Soils formed on the surface of the slag deposits are characterized by high levels of Cu, Zn and Pb, whose mobilizable fractions are significant (2-30%), showing a clear influence of slag. Soils collected near a chimney creeping uphill the slope, present the highest contamination levels in Pb, Sb and As, with from 10 to 30 % of mobilizable fractions. This contamination is linked to emissions through the damaged chimney but also to the degradation of this latter. The potential release of As and Sb from the soils of these two areas requires that these soils must be disposed of in landfills for hazardous wastes and their solubilization in acid medium have highlighted the health risks by ingestion for Pb and As. On areas in near periphery of the smelter, soils are less affected but must be still considered heavily contaminated. G. alypum and R. officinalis were observed on the site. They are tolerant and can accumulate TMM. Concentrations in roots were significantly correlated with the concentrations in soils, except for Cu

N2O emissions from oil palm on mineral soils: measurements and modelling challenges

In oil palm plantations, addition of nitrogen (N) via legume cover crops and fertilisers is a common practice to achieve the yield potential of the crop. It is associated with effects on climate change through emissions of N2O (Choo et al., 2011). As oil palm is the most rapidly expanding tropical perennial crop, and is expected to keep expanding in the next decades (Corley, 2009), this raises environmental concerns.We reviewed the available measurements for N2O and other N fluxes in oil palm plantations on mineral soils (Pardon et al., 2016). We saw that direct N2O emissions were the most uncertain N flux, ranging from 0.01 to 7.3 kg N ha-1 yr-1, with a tendency to be higher during the immature phase, to decrease with the age of palms and to be higher in poorly drained soils (Ishizuka et al., 2005; Banabas, 2007). However, only very few measurements were available on mineral soils, and data is still lacking to better understand the potential effects of spatial heterogeneity in plantations (soil properties, soil cover) and management practices (e.g. fertiliser application timing, splitting, placement). Indirect N2O emissions were related to emissions of NH3 and NO3- which were particularly high during the immature phase when the N inputs are high while the palms are still young. We compared 11 existing models and 25 sub-models to simulate oil palm N budget and losses, among which 8, 9 and 8 sub-models were specific to N2O emissions, NH3 volatilisation, and NO3- losses through leaching and runoff; respectively (Pardon et al., under review). We saw that direct N2O emissions estimates were some of the most variable across models, ranging from 0.3 to 7 kg N ha-1 yr-1 (Mosier et al., 1998; Bouwman et al., 2002b; IPCC 2006, from Eggleston et al., 2006; Crutzen et al., 2008; Meier et al., 2012; APSIM from Huth et al., 2014 ; Shcherbak et al., 2014). The main influential factors on direct N2O emissions were the rate of mineral fertiliser applied and the emission factors of the models. The models accounting for felled palms decomposition, empty fruit bunches applications, and biological N fixation also estimated a peak of N2O emissions during the immature phase. Therefore direct and indirect emissions of N2O in oil palm plantations seemed not to be negligible in terms of environmental effect, with ranges of 11 to 2,425 and 79 to 2,443 kg CO2e ha-1 yr-1 for measured and modelled values; respectively (assuming a global warming potential of 298 for N2O). However, in order to be able to adapt management practices to mitigate these emissions, knowledge is still lacking to better understand the potential effects of spatial heterogeneity and management practices on direct and indirect N2O emissions The main modelling challenges are to model the impact of management practices, taking into account the soil N dynamics and residues decomposition, and this over the whole cycle

Trace metal and metalloid contamination levels in soils and in two native plant species of a former industrial site: Evaluation of the phytostabilization potential

International audienceThis study aimed at identifying the extent and type of contamination of a former lead smelting site in the area of Marseille, France, dating from the industrial revolution, and to evaluate environmental hazards and opportunities for phytoremediation, a promising sustainable technology. Amongst the native plants growing in this semiarid shrub ecosystem, two perennials Globularia alypum L. and Rosmarinus officinalis L were selected. Twenty-one soil/plant couples were collected and seventeen additional soil samples were added to better characterize the soil pollution of the area. A multi-contamination by Pb, As, Sb, Zn, Cu was demonstrated, with huge variations within the contamination levels. The soils highest concentrations were encountered along the horizontal chimney and on the slag heaps area. However, both sites differed from each other. The former was characterized by the highest Pb, As and Sb concentrations that could reach 130, 7.0 and 9.0 g kg(-1) respectively, the latter, by high Cu, Fe, Mn, S concentrations, even if it was also heavily contaminated by Pb and Zn. G. alypum and R. officinalis were shown to be metal-tolerant and to accumulate trace metals and As. Due to the low bioconcentration and translocation factors determined, both species may not be used for phytoextraction, but seem to be good candidates for phytostabilization. (C) 2013 Elsevier B.V. All rights reserved