Supervisors info:
Αριάδνη Αργυράκη, Καθηγήτρια, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Summary:
Considering the estimated maximum 300k Tn of microplastics (MPs) released yearly in the EU and the scarcity of systematic surveys for MPs, monitoring and managing their potential risks poses notable challenges to researchers and governments worldwide. Primarily owing to their small size and complex composition, the lack of standardization on methodologies for sampling & analysis, reporting units, and QA/QC procedures, present significant challenges for synthesizing research findings, interpreting data, and drawing meaningful conclusions. Furthermore, up to now the focus of research has been mostly on developing methods to estimate the amount and type of MPs in the marine environment. Standardized protocols for the recovery and characterization of MPs in soils are still under investigation, although it has been established that they are characterized by elevated adsorption capacity as the result of their large specific surface area; thus, they adsorb typical soil contaminants such as metals and metalloids, promoting their dispersion in the environment. In this study, soil samples were selected from the systematic soil dataset of the Attica region in Greece, taken at depths of 0-20 cm and 20-40 cm. Spiking experiments were conducted using a composite mixture of soil collected at natural forest sites and blank samples spiked with cryomilled polymers. Various techniques and reagents were tested to enhance recovery and facilitate characterization. Different reagents were compared regarding their effectiveness on the degradation of organic particles, including Strand solution (0.67 mol/L NaClO, 0.45 mol/L KOH), KOH (2.6%), H2O2 (30%), and one using porcine pancreatic enzymes. Mineral particle removal involved density separation with supersaturated NaCl and ZnCl2 solutions, followed by filtration to retain MPs. A multimethod approach for identifying and characterizing MPs included analysis with an optical microscope, FTIR, and Raman spectroscopy for evaluating the MP recoveries based on different treatments. All pre-treatment methods successfully reduced certain organic matter aggregates, and both chlorine solutions were effective in extracting lighter plastic particles like polyethylene (PE) and polystyrene (PS). Notably, despite their higher density, PVC, PET, and tire particles were still recovered from both density solutions through observations using an optical microscope. However, the KOH and Strand solutions were unable to decompose organic aggregates. It is crucial to continue the experimental process by utilizing FTIR analysis for either natural or anthropogenic organic polymer counting, in order to apply the recovery methods to soil samples with unknown microplastic contamination
Keywords:
Microplastics (MPs), Contamination, Characterization methods, Density separation
