PLASTICS AND BIOPLASTICS IN WATER ECOSYSTEMS

In recent years, plastic has emerged as a major ecological concern due to its widespread presence and environmental persistence within natural ecosystems. Aquatic ecosystems, in particular, are the most severely affected, with unpredictable long-term consequences for biodiversity and human health. Bioplastics have lately gained recognition as environmentally friendly alternatives. However, the behaviour of biodegradable bioplastics in open aquatic ecosystems remains largely unknown. This PhD research programme aimed to comprehensively analyze the extent of plastic and bioplastic pollution in aquatic environments to contribute to their mitigation. Two primary lines of investigation were established: one focusing on plastics and microplastics, and the other on bioplastics. For plastics and microplastics, the primary challenge identified was the lack of standardized methods for sampling, processing, and analysis, complicating the accurate assessment of plastic debris pollution and the data comparison across studies. This PhD programme has the potential to contribute to the standardization of sampling protocols for microplastics through an in-depth study of the benefits and drawbacks of various sampling techniques, whose applicability must be evaluated based on the specific objectives of each study. Additionally, it could contribute to the standardization of processing and analysis protocols by introducing innovative techniques to prevent airborne contamination and to reduce analysis times, especially when investigating the smallest fraction of microplastics. Regarding bioplastics, many challenges remain unresolved when assessing their biodegradability in aquatic environments. Firstly, there is no universally recognized definition of “biodegradability” that specifies the environmental conditions, timescale, and extent of decomposition required. This has led to the development of various standards, each with its own test methodology and range of process parameter values, resulting in highly heterogeneous biodegradation rates for different bioplastic types across different studies. Additionally, these standards do not specify a threshold value that bioplastics must surpass to be classified as “biodegradable”. For the reasons outlined above, it is therefore impossible to definitively determine whether a bioplastic is inherently biodegradable or not. This PhD research programme addressed the debate regarding the biodegradability of bioplastics in aquatic environments, emphasizing the lack of a universally accepted standard to accurately assess their environmental impact.