Analytical approaches for studying occurrence and fate of environmental micro- and nanoplastics

Plastic pollution is a serious environmental concern. Small plastic fragments, reaching sizes below 5 mm (microplastics, MPs) and 1 μm (nanoplastics, NPs), are transported across the environment and can exert toxic effects. There is a need for analytical approaches allowing for detection, characterization and quantification of plastic particles. The aim of this thesis was to develop such approaches and to apply them in fate studies of micro-and nanoplastics.
Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was applied for studying NPs in untreated wastewater. Py-GC-MS delivers information on polymer chemistry and mass, however, it does not distinguish between different particle sizes. Therefore, the potential of asymmetrical flow-field flow fractionation (AF4) for size-based separation was studied. The two techniques were coupled offline, allowing for size-resolved mass quantification of NPs. An alternative approach was studied, where polymer disintegration is done chemically rather than thermally. This method was adopted to polyethylene furanoate (PEF).
Next, plastic objects were exposed to close-to-environmental conditions in simulated seawater and freshwater. NPs were observed in the whole water column in both systems. After small plastic particles are formed, they can be transported and eventually reach the food net. MPs can be found in all types of food. The highest daily intake was estimated to originate from the most commonly eaten products, such as grains or vegetables, although these food types are rarely examined. Finally, NP behaviour after ingestion was studied by simulating human gastrointestinal tract in vitro. NPs aggregate during digestion. The digestive enzymes play a key role in aggregate formation.