Recently, environmental pollution from microplastics (MPs) has become a significant reason for increasing the number of studies to develop analysis methods. The Nile red staining method (NR-S), which is staining polymer particles with Nile red (NR) dye, has been widely used for the analysis of MPs in environmental samples. However, this method has several limitations, as it is difficult to stain MPs covered with organic matter residues. In this study, we modified the NR-S method into an NR plate method (NR-P), where the plate is coated with NR instead of staining MPs directly. The optimum concentration of NR solution was obtained (1000 mg/L), and the effectiveness of the NR-P method for the analysis of MPs was assessed using different types (polypropylene, polyethylene, polyethylene terephthalate, and polystyrene), sizes (100–1000 µm), and shapes (sphere, fiber, film, and flake) of plastic materials. The NR-P method demonstrated improved resolution in the overall types, shapes, and sizes of MPs and was better than the control (without NR plate method) and NR-S method. In particular, the NR-P method can effectively observe MPs covered with organic matter, which was a major limitation of the NR-S method. Finally, MPs in sewage field samples were analyzed by the NR-P method with an accuracy of 78% confirmed by FT-IR. We demonstrated that this method is a convenient and efficient alternative for identifying MPs, even for field samples.

Microplastics (MPs) are plastic particles < 5 mm in diameter, which are detected in air, soil, and water, causing various environmental problems. In total, 37.3% of MPs are generated from point pollution sources and 62.7% from non-point sources; most of the non-point-source MPs are from vehicles tires, road-marking paint, and bitumen used in road pavements. In this study, the concentrations of MPs generated from roads in Goyang city, South Korea, were examined in terms of the drying period (0, 1, 2, or 3 d). Road dust sampling was performed at the kerb and quantitative and qualitative analyses were conducted for each sample. The MP concentrations were 552 (±39) MPs g−1 for a 0 d drying period and 1530 (±602) MPs g−1 for a 3 d drying period, confirming that the MP concentration in road dust increased with the increase in drying period. Among the detected substances, black particles accounted for the highest proportion (72%) and were found to be bitumen and tyre particles. This study also confirmed that the MPs accumulated on roads were washed away when rainfall exceeded a certain amount.

Sewage treatment can remove more than 90% of microplastics, yet large amounts of microplastics are discharged into the ocean. Because microfibers (MFs), primarily generated from the washing of synthetic clothes, are the most abundant type of microplastics among various microplastics detected in the sewage treatment, reducing the amount of MFs entering these treatment plants is necessary. This study aimed to test whether the amount of MFs released from the washing process can be reduced by applying a chitosan pretreatment to the garments before washing. Before the chitosan pretreatment, the polyester clothes released 148 MFs/L, whereas 95% of MFs were reduced after the chitosan pretreatment with 0.7% of chitosan solution. The chitosan pretreatment was applied to other types of garments, such as polyamide and acrylic garments, by treating them with 0.7% of chitosan solution; subsequently, MFs reduced by 48% and 49%, respectively. A morphology analysis conducted after washing revealed that chitosan coating on the polyamide and acrylic were more damaged than on polyester, suggesting that the binding strength of polyamide and acrylic with chitosan was weaker than that of polyester garment. Thus, the results suggested that the chitosan pretreatment might be a promising solution for reducing the amount of MFs generated in the laundering process.