A Urban Geochemical Background Database for Contaminated Land Management
Résumé
In February 2007, new approaches of management were proposed by the French Ministry for Sustainable development to the various actors of the set of themes "Potentially contaminated land". These approaches describe the whole of the stages of management of a (potentially) contaminated site: the diagnosis to identify and locate pollution, the installation of the management plan to set objectives of rehabilitation, the residual risks assessment, the (Media Quality Assessment (MQA) (Interpretation de l'Etat des Milieux (IEM)) While these approaches are conducted, the interpretation of the data collected from the field necessarily causes the comparison of the analyses and measurements with reference values. Thus, the approach of MQA is based on the risk management policy conducted by the public authorities for the French population. It results in comparing the state of the investigated mediums with: * Natural environment close to the zone of investigation; * Regulatory management values set by the public authorities. Indeed, the public authorities fix sanitary values which regulate air quality as well as water and food. Therefore, these values naturally serve as references within the framework of the studies undertaken on the (potentially) contaminated sites. However, the soil is not the object of a specific regulation and no regulatory value of reference exists in France for this medium. A soil is considered free from pollution since its characteristics are coherent with the local natural geochemical background. This is why, the approach results in comparing the state of the investigated soil with the state of the natural soils close to the zone of investigation. With this intention, the knowledge of the natural geochemical background, in particular of the local geochemical anomalies, is essential. Moreover, the characterization of pollution is important to distinguish if it implies the site or not. However, the industrial sites are more often gathered in industrial and urban areas where an anthropic geochemical background is superimposed at the natural geochemical background. It then becomes necessary to compare data collected on the investigated site with this anthropized pedological and geochemical background. In order to support the various actors implied in the management of (potentially) contaminated land, it was thus proposed to carry out a database of analyses of soils from urban and industrialized environment on the whole of the French national territory. The project "Diagnoses of the soils in the places hosting children or teenagers" implemented by the French ministry for Sustainable development, was the occasion of launching an operation of sampling and analyses of urban soils at the level of the national territory. The collection of analyses during this operation constitutes the heart of the project "Urban Geochemical Background Database (Fond Géochimique Urbain - FGU) conducted by BRGM and funded by ADEME. Soils are analyzed for metallic trace elements, mercury, cyanides, phenol index, HC C10-C40, PAH, PCB an PCDD/PCDF. This presentation points out the conditions of realization of this task and described the difficulties encountered.