Le Prix de thèse de la FERED récompense de jeunes docteur.e.s du site académique alsacien, auteurs de thèses remarquables en sciences de l’environnement et de la durabilité.
Plus d'information: https://fered.unistra.fr/evenements/evenements-en-cours/prix-de-these
Le Dr. Tobias Junginger est distingué en 2023 par ce prix pour ses travaux de recherche conduits dans sa thèse intitulée "Transport and degradation of urban biocides from facades towards groundwater" / "Transport et dégradation des biocides urbains des façades vers l'eau souterraine'. Cette thèse était encadrée par le Dr. Gwenael Imfeld et le Pr. Sylvain Payraudeau.
Le résumé de la thèse en anglais, est le suivant:
Abstract:
Urban biocides are used in facade materials like paint and render to prevent growth of algae and fungi. Biocides are released with wind driven rain and contaminate surface water, soil and groundwater with potential ecotoxicological effects to the ecosystem. The general goal of this thesis is to improve the understanding of reactive transport of urban biocides from their sources (construction materials/ facades) to receiving compartments (surface water, soil, and groundwater). The overall approach relies on concentration measurements of biocides and transformation products, compound-specific isotope analysis and reactive transport modelling from the laboratory (e.g., single reaction in microcosms) to the district scale (transport, retention and reaction occurring simultaneously). We first examined degradation pathways and mechanisms of the biocide terbutryn during photodegradation, abiotic hydrolysis and biodegradation under controlled laboratory conditions, using multi-element compound specific isotope analysis and transformation product measurements. We further developed a framework to use compound specific isotope analysis for urban biocides under environmental conditions, discussing its potential and limitations. By using an integrative approach, from laboratory microcosm experiments to field scale experiments for short-term (e.g., days to months) to long-term assessments (e.g., several years), we show that solar irradiation and the volume of facade runoff are the main hydroclimatic variables responsible for the release of transformation products of terbutryn from facades and provide estimates of the contribution of TPs in facade leachate over several years. Additionally, we were able to evaluate the reactive transport of urban biocides through typical urban surfaces, proofing that permeable pavement and gravel drainage are potential hot spots for biocide entry towards groundwater, while vegetated surfaces act largely as a sink with high biocide retention potential. On the district scale, we provided estimates of biocide fluxes under sustainable stormwater management practice. The results indicate high infiltration of biocides close to facades, while only small proportions of biocides reach the stormwater retention facilities resulting in risk of deterioration of groundwater quality. Overall, this thesis underscores environmental risks associated with urban biocides worldwide but also discusses alternative approaches with biocide-free materials and therefore paves the way towards a biocide-free city.