Etude de la pollution environnementale par les micro- et nanoplastiques : échantillonnage atmosphérique, développement d'un modèle de plastique marqué, interaction avec des organismes vivants

The management and monitoring of plastic waste have become a major issue for our society. However, there is no single optimal method for the effective study and monitoring of plastic pollution. The objective of this thesis work was to explore new approaches to study the occurrences, fate, and behavior of micro- and nanoplastics in the environment. Thee vectors of investigation were combined in this work, including: i) the development of a methodology of sampling and analysis of MPs and NPs from the atmosphere; ii) the development of an environmentally relevant model of MPs and NPs, which could be used for ecotoxicological studies and iii) the study of its interaction with living microorganisms. Environmentally relevant models of micro- and nanoplastics of HDPE were obtained by top-down approach, by exposing bulk polymer material to mechanical grinding. Particles were labelled with background-free persistent luminescent probes such as UCNPs that allows their detection even in thick samples such as in a tissue or a small animal. Further, we used a developed model of plastic to study the interaction mechanism between MPs and green freshwater microalgae Chlorella vulgaris using atomic force microscopy (AFM) nano- and molecular scale experiments. This work revealed that a hydrophobic interaction between algae and microplastics was at the origin of the production of organic matter by algae, and that the latter played an important role in the aggregation phenomena of microalgae and microplastics. Otherwise, MPs and NPs from the atmosphere were collected on areas with different levels of human activity: from an area separated from human activities to a highly industrialized. Investigation of those areas included the collection of meteorological data and sampling of atmospheric samples including aerosols (suspended particles in the atmosphere) and deposition (rain, snow, sleet, etc.). As a result, we proposed a methodology for samples collection, preparation, qualitative and quantitative analysis performed by the combination of analytical methods including μ-FTIR (Fourier transform-infrared microscopy), Py-GC-MS (pyrolysis coupled with gas chromatography and mass spectrometry), DLS (Dynamic Light Scattering), NTA (Nanoparticle Tracking Analysis), etc.