PhD defense Amélie Humbrecht

The fate of contaminants of emerging concern is one of the major scientific issues related to the characterisation of surface ecosystem quality and dynamics. According to recent literature, small-scale hydrosystems have been found to be particularly sensitive to new persistent organic pollutants (POPs), such as pharmaceutical products (PPs). The behaviour of PPs within the particulate matrix as it is transferred through hydrosystems, and their fate in the water-sediment continuum, are still poorly understood. However, this knowledge is necessary in order to accurately quantify mass balances and identify and quantify rates of PPs contamination in terrestrial and aquatic ecosystems. Understanding the behaviour of PPs in the water-sediment continuum is important for 1/ determining the nature of the reactive matrices likely to carry PPs 2/ understanding the role played by environmental factors, such as physico-chemical conditions, in the diagenesis of sedimentary organic matter (a matrix with a known affinity for PPs) and 3/ evaluating the stability or potential reversibility of PPs being trapped in the particulate phase. In this context, building on results collected since 2017 about the transfer of particulate and aqueous phases through the Egoutier catchment (Semoy, Loiret, France), this PhD work aims to determine the behaviour of PPs in the water-sediment continuum of the Beulie pond, and more particularly to characterise the parameters and mechanisms that influence the fate of PPs in surface environments. This will be achieved through a combined field and laboratory approach, analysing targeted PPs in particulate and aqueous phases. The role of organic matter will be given particular consideration. The study aims to determine the spatial response of PPs at the scale of the Beulie pond, understand the behaviour of PPs within surface sediments collected at the pond’s water/sediment interface with regard to the composition, typology, and reactivity of sedimentary organic matter, and identify the mechanisms and kinetics of PPs’ sorption to the particulate phase through batch experiments with an evaluation of the potential reversibility of trapping.