Assessment of the PCDD/F fate from MSWI residue used in road construction in France

MSWI fly ash is susceptible to contain high amount of polychlorinated dibenzo-dioxins and polychlorinated dibenzo-furans. However, the use of MSWI residue for road construction started in France at a period when MSWI Bottom Ash and MSWI fly ash were not separated. From four old road sites, MSWI residue, road soils, reference soils and geo-textiles were sampled and their PCDD/F contents were analyzed. MSWI residue show a great heterogeneity but also high amounts of PCDD/F (142960 ng ITEQ kg-1 dm). Soils underlying the road show less heterogeneity and PCDD/F contents between 0.57 and 7.23 ng I-TEQ kg-1 dm, lower than ordinary soils. Moreover, the specific analysis of the 17 toxic PCDD/F congeners (notably the 2,3,7,8-TetraCDD) indicates the very low harmfulness of road soils. The study also allows to assert the relation between the MSWI residue particle size and the PCDD/F content

Modelling of long-term dynamic leaching tests applied to solidified/stabilised waste

International audienceThe paper aims at simulating the closed-system dynamic leaching of a cement-based monolith containing lead with the numerical reactive transport code HYTEC in a 3D-cylindrical geometry. The model considers, simultaneously, the chemical evolution of pore water, the progression of mineralogical alteration fronts, and the concomitant release of elements from the S/S waste. In good agreement with the experiment, element releases were found to be mainly controlled by either diffusion (Na, K, and, to a lesser extent, Cl), by surface dissolution (Ca, Si) or by a mixed evolution (Pb, SO4). All of the calculated mineralogical transformations take place in a thin layer beyond the monolith surface. Consequently, modelling of Ca, Si and SO4 releases was quite sensitive to the node size of the simulation grid and was improved by taking into account the increase of porosity and effective diffusion coefficient due to mineral dissolution in the leached layer. In agreement with experimental results, the deepest front corresponds under closed-system conditions to portlandite dissolution and calcium silicate hydrates CSH 1.8 transformation into CSH of lower Ca/Si ratio. A second, distinct and intermediate, front is made by ettringite dissolution. The network of CSH is globally preserved in the leached layer, complete dissolution occurring over a very small thickness only. Finally, hydrotalcite precipitation in the leached layer is expected by modelling due to pH drop

Assessment of long term mining waste behavior by a dynamic leaching test : application to contrasted physico-chemical conditions

International audienceMining activity has generated large amounts of mining wastes abandoned on the site after extraction, concentration or metallurgic processes. In this study assessment of the long term behaviour of mining wastes has been performed by the realisation of a dynamic leaching test performed with a Soxhlet device on mining wastes from two contrasted sites : Bentaillou and Saint-Salvy from south-west France. Sphalerite and galena are the source of heavy metals, (Zn, Cd and Pb) in both sites. Pyrite and pyrrothite are the main potential acid source in Saint-Salvy and Bentaillou respectively. Although both wastes display high contents of carbonate minerals associated to the metal bearing phases, their composition is different, calcite for Bentaillou and siderite for Saint-Salvy allowing different minerals transformations and drainage mining water compositions. Due to different impoundment type, dumps for Bentaillou and a dam for Saint-Salvy, oxidation reactions are favoured in the former compared to the latter. Waste drainage waters generated in situ display lower pH, Eh and higher Fe and heavy metals in drainage waters from Saint-Salvy compared to those from Bentaillou. The leaching experiments lasted 62 days and 84 days for Bentaillou sample and Saint-Salvy sample respectively corresponding to an equivalent time of 288 and 183 years respectively calculated from pluviometry in situ. During the experiment, the amounts of elements released was higher for Saint-Salvy sample ( 0.2 % of Zn, and Pb and 1,4 % of Cd) than for the Bentaillou one ( 9.7 % of Zn, and 0.15 % of Pb and 46 % of Cd). The comparison of experimental leaching results with site data on waste drainage waters demonstrated the validity of laboratory results under oxidic conditions at Bentaillou while the duration experimentally estimated for total sulphide oxidation overestimates the time calculated from the sulfate flow in field drainage waters under reducing conditions at Saint-Salv

Evaluation du comportement à long terme des déchets miniers par un essai de lessivage dynamique : application à différentes conditions physico-chimiques

National audienceLes différents processus de l'industrie minière tels que la prospection, l'extraction et le traitement génèrent d'importantes quantités de déchets miniers enrichis en métaux toxiques tels que Hg, As, Pb, Cd. Ils constituent des sources potentielles de contamination métallique pour les différents compartiments de l'environnement (sols, eaux superficielles et souterraines, atmosphère). L'évaluation du comportement à long terme des déchets miniers reste un défi pour les chercheurs. En effet, au delà des analyses de concentration totale en contaminant c'est leur mobilité qui doit être évaluée pour estimer leur impact potentiel sur l'environnement et aussi pour répondre aux questions d'aménagement des sites miniers et de gestion des déchets

MSWI bottom ash used as basement at two pilot-scale roads: Comparison of leachate chemistry and reactive transport modeling

International audienceThe recycling of municipal solid waste incineration bottom ash as aggregates for road basement requires assessing the long-term evolution of leachate chemistry. The Dåva (Sweden) and Hérouville (France) pilot-scale roads were monitored during 6 and 10 years, respectively. Calculated saturation indices were combined to batch test modeling to set a simplified geochemical model of the bottom ash materials. A common reactive transport model was then applied to both sites. At Hérouville, pH and the concentration of most elements quickly drop during the first two years to reach a set of minimum values over 10 years. The decrease is less pronounced at Dåva. The evolutions of pH and major element concentrations are fairly well related to the following pH-buffering sequence: portlandite, C-S-H phases or pseudo-wollastonite and, finally, calcite in equilibrium with atmospheric CO2. Al(OH)3, barite, ettringite and monohydrocalcite may also control leachate chemistry. Cu release is correctly modeled by DOM complexation and tenorite equilibrium. Temperature has no significant effect on the modeling of leachate chemistry in the range 5-30 C, except at high pH. Effects at road edges and roadside slopes are important for the release of the less reactive elements and, possibly, for carbonation processes

The GeDSeT project: constitution of a decision support tool (DST) for the management and material recovery of waterways sediments in Belgium and Northern France

International audienceThe European InterReg IV GeDSeT project (2008-2011) is a contribution to a sustainable management of waterways sediments, in order to develop good practice in a perspective of water resource protection and of the development of regional fluvial transport. Waterways sediments are a major environmental issue in the Walloon region of Belgium - Northern France trans-boundary region for several reasons, all of them resulting from the dense habitat, industrial pattern and waterways network, and of a long industrial history. Sediments affect water resources quality, through pollution, and availability, through flooding. Sediment dredging allows the development of environmentally-friendly regional fluvial transport, but also generates important waste deposits. Therefore material recovery for reuse in buildings or infrastructure is a key issue, as it allows a reduction of waste and limits the need for natural resources for the same use. In order to address waterways sediments management in a global way, the GeDSeT project intends to capitalise know-how regarding the criteria to take into account for a sustainable management, and to include them in a decision support methodology applicable to the transboundary context. Such decision support aims at developing good practice in a perspective of water resource management and development of regional fluvial transport. Relevant criteria include: - criteria evaluating the physical and chemical characteristics of the sediments to be dredged, and their level of contamination, - costs of dredging operations and benefits with respect to improved waterways, - potential material value and costs of sediment treatment for material recovery versus costs of sediment deposit management. The decision support methodology will rely in part on previous BRGM and European experience in the development of an environmentally extended, physical, quasi-dynamic input-output model for waste management. Experience from other specific DSTs on sediments will be valorised with the project partners. Potential recovery of secondary resources from dredged sediment will be addressed through a review and economic evaluation of available technologies, technical and economical constraints, side effects on the uses of recovered products, and a global balance of the environmental costs and benefits. Social and employment impacts, as well as land use issues in this densely populated area will be fully acknowledged as primary decision-support criteria. The expected benefit of the project comprises also the transboundary comparison of specific situations and methods, issued from a different history.Le projet InterReg IV GeDSeT (2008-2011) est une contribution à une gestion globale durable des sédiments des voies d’eau, au développement du transport régional fluvial et de bonnes pratiques pour la protection des ressources en eau et de l’espace urbain.Les sédiments des voies d’eau sont un enjeu majeur en Europe, et particulièrement dans la région transfrontalière Belgique Wallonie – Nord de la France pour plusieurs raisons, toutes liées à la densité de l’habitat, du tissu industriel passé et présent, et du réseau de voies d’eau. Non seulement les sédiments affectent la navigabilité, mais aussi la qualité des ressources en eau, par la pollution, et la gestion des inondations. Le curage régulier des sédiments permet le développement d’un transport régional fluvial éco-favorable, mais génère d’importants volumes de déchets potentiels. La réutilisation des sédiments pour la construction ou les infrastructures est donc un enjeu clé, en combinant réduction des déchets et des besoins en ressources naturelles pour le même usage.Afin de prendre en compte la problématique des sédiments fluviaux dans sa globalité, le projet GeDSeT va capitaliser l’état de l’art sur les critères pertinents pour une gestion durable, et les incorporer dans une méthodologie d’aide à la décision applicable au contexte transfrontalier. Cette méthodologie vise à développer des bonnes pratiques en harmonie avec la gestion des ressources en eau, et le développement du transport fluvial régional

Evaluation de l'impact des PCDD/PCDF contenus dans les MIOM utilisés dans les structures routières

National audienceEn vue de l'évaluation de l'impact des PolyChloroDibenzo-para-Dioxines (PCDD) et des PolyChloroDibenzoFurannes (PCDF) contenus dans les MIOM utilisés en technique routièren sur les sols sous-jacents aux structures routières, l'INERIS a réalisé des auscultations de chaussées de conception récente en collaboration avec EUROVIA, et de conception ancienne en collaboration avec le Laboratoire Central des Ponts et Chaussées. Les résultats ont montré que pour les chaussées de conception récente (entre 2 et 7 ans), les teneurs en PCDD/PCDF dans les MIOM sont faibles. Elles sont comprises entre 7,20 et 20 ng I-TEQ/kg. Pour chaque site, les MIOM peuvent contenir des teneurs en PCDD/PCDF similaires ou présentent une légère hétérogénéité

Préparation et analyse des végétaux consommés par l’Homme dans le contexte des sites et sols pollués

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