Laboratory Assessment for Determining Microplastics in Freshwater Systems—Characterization and Identification along the Somesul Mic River

Abstract

Microplastics (MPs) pollution has become a persisting problem over the last decades and is a critical issue for environmental protection and human health. In this context, scientific data able to reveal MPs presence and improve the characterization and identification of this pollution via different systems are valuable. The aim of this paper is to assess available techniques for determining MPs in real freshwater samples and subsequently to highlight the occurrence and type of MPs in the study case area (Somesul Mic River). The MPs sampling was performed from fresh water and sediment using planktonic nets and sieves with different mesh sizes (from 20 to 500 µm). Using both classical microscopic techniques as well as scanning electron microscopy (SEM), large (1–5 mm) and small (1 µm to 1 mm) MPs were observed in the shape of fibers, fragments, foam, foils and spheres in various colors (red, green, blue, purple, pink, white, black, transparent, and opaque). Raman and FT-IR spectroscopic methods were used for MPs identification. The presence of polyethylene (PE), polypropylene (PP), and polystyrene (PS) was registered for all sampling points. The MPs laboratory investigations have raised some issues regarding the identification of MPs particles smaller than 500 µm, these being characterized especially under microscope. Some small MPs particles were identified using micro-Raman spectroscopy that highlighted the same type of polymers. No differences were registered between the sampling points due to the widespread presence of MPs. The sediment samples presented a greater abundance as compared to the water samples. Overall, it is necessary to continue the optimization of MPs separation protocol and identification according to the complexity of samples, mainly due to the limitation and lack of spectral databases.