Spatiotemporal distribution and characteristics of microplastics across environmental matrices associated with a...

This study investigated microplastic contamination in water, air, and soil within a municipal waste disposal site in Nakhon Si Thammarat, Thailand, during the dry and rainy seasons of 2023. A total of 51 environmental samples were collected, including leachate from treatment ponds, atmospheric total suspended particulates, and soil from both perimeter and internal landfill zones. Microplastics were extracted using organic digestion (H₂O₂/FeSO₄) and density separation (ZnCl₂), followed by identification and characterization using stereomicroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS), and micro-Fourier transform infrared spectroscopy. The results showed that microplastic concentrations were higher in the primary leachate pond than in the final treatment pond. In the atmosphere, the active disposal area exhibited the highest levels of both total suspended particulates and microplastics compared to other sampling locations. Soil samples showed substantial contamination, particularly within active and legacy landfill zones, where elevated concentrations were observed. Seasonal variation was observed, with higher mean microplastic concentrations in wastewater and air during the dry season, while soil samples exhibited location-dependent patterns. Fragments were the dominant morphology across all environmental matrices (43-90%). The predominant colors were black and brown, while other colors were present in smaller proportions. A total of 16 polymer types were identified, with polyethylene, polypropylene, polyurethane, and polystyrene being the most common. SEM analysis revealed surface degradation features, including fractures and erosion, indicative of environmental weathering processes. These findings highlight municipal waste disposal sites as both significant sources and accumulation zones of microplastics, emphasizing the need for improved waste management strategies to reduce environmental dispersion and potential human exposure.