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Theses

Développement d’indicateurs chimiques et biologiques pour l’évaluation des risques environnementaux des sites et sols contaminés.

Abstract : In the context of the sustainable management of polluted sites and soils, the overall objective of this thesis was to improve environmental (ERA) and human health (HHRA) risk assessments.Threshold guide values (TGV) were determined ex situ in the land snail for metal(loid)s, polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs) as well as global indicators, such as ex situ indices of sum of excess transfer (GSET) and ecotoxicological risk (GERITOXE). These indicators were applied to 68 various contaminated soils and showed that it is not necessarily the most contaminated soils that present the highest risk. In addition, it was highlighted that excess metal(loid) transfers to snail are, unlike non-anomalous transfers from the soil geochemical background, more influenced by the total concentration than by the physico-chemical properties of the soils. Beyond these influences, the question also arose of the influence of site specificities on the bioavailability of contaminants to the snail. This was investigated in an inter-laboratory test leading to the standardization of the in situ and ex situ approaches (ISO 24032). It was evidenced that transfers are generally higher ex situ than in situ, except for few metals (e.g., Cd and Mo). This enable to discern the respective interests of in situ and ex situ ERA methods and the answers obtained according to scientific questions and management perspectives. The relationships between bioavailable concentrations and specific ecotoxicological effects for the snail were studied at different levels of organization (life history traits and genomic stability) to refine the interpretation of the global indicators developed. The relevance of the coupling of the micronucleus assay with the random amplification technique of polymorphic DNA for the assessment of genotoxicity in hemocytes was demonstrated. The study of telomere dynamics in the land snail has been developed and has revealed novel patterns. A strong telomere attrition during growth from the juvenile to the sub-adult stage was characterized, followed by a maintenance of telomere length during adult life. Although genotoxic damage has been identified and associated with health alterations to snails exposed to metal- and PAH-contaminated soils, their telomeres are not shortened in hemocytes. In the context of the applicability of the One health initiative to the management of polluted sites and soils considering both human and environmental health, the study of exposures with the relationships between bioaccessibility to humans and bioavailability to the snails of As, Cd and Pb in contaminated soils revealed strong convergences. Concerning the links between risk levels, it was shown that soils identified as "at risk" for human health could present a low or even absence of transfer of contaminants to snails and therefore an absence of environmental risk, offering alternative management perspectives.In conclusion, the results obtained pave the way towards the research of fundamental relationships between environmental and toxicological bioavailability at different levels of biological organization and the identification of the respective interests of field and laboratory approaches in risk assessments in relation to management issues. Approaches to combine environmental and health assessment methodologies are proposed in the aim to better manage environmental pollutions. Finally, the indicators developed within the framework of this thesis strengthen the positioning of targeted chemical and biological characterization tools at the site scale.
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Maxime Louzon. Développement d’indicateurs chimiques et biologiques pour l’évaluation des risques environnementaux des sites et sols contaminés.. Sciences agricoles. Université Bourgogne Franche-Comté, 2020. Français. ⟨NNT : 2020UBFCD040⟩. ⟨tel-03270909⟩

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