Chemical and ecotoxicological assessment of microplastics and emerging risks in the coastal environments

In recent decades, global plastics production and consumption have continued to increase. Although many policy strategies on waste prevention and recycling have been implemented, much of the plastic waste is dispersed in nature. In general, the presence of waste in the aquatic environment is a serious environmental problem, well known as marine waste, and is responsible for environmental, economic, health and aesthetic problems at the ocean and regional level and the dominant category of waste is plastics. Due to their chemical persistence, buoyancy and increased sources, plastic objects and their fragments (known as "microplastics" (MPLs) and "nanoplastics" (NPLs)) are omnipresent in the marine environment, especially in closed basins such as the Mediterranean Sea. Nowadays, given the increasing levels of plastic pollution in marine environments, MPL/NPL are considered emerging pollutants that can pose a serious threat to marine ecology and human health. Despite constant scientific progress, large gaps in knowledge about the fate, distribution, behaviour and effects of MPLs/NPLs have not yet been filled. \nIn this context, this thesis aimed to expand knowledge on plastic pollution in coastal environments. In particular, the first part of the study focused on the river transport of plastics and the fate and behaviour of MPLs/NPLs in estuaries and coastal waters. The results of one year of visual observations of floating anthropogenic macro-litters (> 2.5 cm) of the Llobregat and Besòs Rivers showed that the Barcelona metropolitan area contributes substantially to marine pollution. Large quantities of plastic (mainly single-use goods) were transported from these rivers to the western Mediterranean Sea. Given the significant contribution of plastic waste from rivers, valuable information can be obtained by assessing the spatial distribution of MPLs/NPLs in estuarine environments. To perform these studies, several analytical techniques based on mass spectrometry (MALDI-TOF/MS, DART-MS, and LC-APPI-HRMS) were compared for the quantitative analysis of MPLs/NPLs in water samples. The best results in terms of sensitivity were obtained with dimensional exclusion-LC coupled with APPI-QExactive. Consequently, a new LC-HRMS method was optimized, validated and finally applied to assess the presence of PS in natural water samples from the Ebro Delta (Catalonia, Spain). The results reported the highest concentrations along the river near urban areas and in the bay where important commercial fishing activities are established. In addition to plastic pollution, estuaries can be highly contaminated with persistent organic pollutants, especially from wastewater. Since MPLs may also be responsible for the transport and distribution of pollutants, the absorption behaviour of MPLs with perfluoroalkylated substances (PFASs) in freshwater and seawater has been assessed. An increase in adsorption capacity was observed in this order PS>PS-COOH>PE. \nAs demonstrated by these results, the plastic pollution of coastal ecosystems, from macro to nano, is a real problem that can lead to serious damage to both nature and society. To protect the coastal environment, its productivity and humans, it is necessary to assess the ecotoxicological impacts on marine organisms and human health. In this regard, a new digestion approach has been developed to determine the presence of MPLs in the gastrointestinal tracts of a sentinel species in the Western Mediterranean. The high frequency of plastics and the types of polymers reported in this study confirmed the negative impacts of local fishing gear. Although the ingestion of MPLs by marine organisms is a widely recognised effect of marine plastic waste, very limited data are available on the impact of MPLs, and especially NPLs, on human health. Therefore, cytotoxic effects at the cellular level after exposure to moderate concentrations of PS and PE particles of nanometric size have been assessed. Significant results were reported only at high concentrations of PS. \nIn conclusion, the work presented in this thesis has successfully filled some of the various gaps in knowledge about plastic pollution and its effects. In the future, further tools should be promoted to facilitate the overall analysis of smaller MPLs, including NPLs.