Assessing the Impact of Microplastic Pollution on Freshwater Ecosystems: A Case Study of River Ecosystems in Southeast Asia
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Background: Microplastic pollution is an emerging environmental concern in freshwater ecosystems, particularly in regions affected by rapid urbanization, untreated wastewater discharge, weak solid-waste management, and increasing plastic consumption. Rivers in Pakistan are vulnerable because they serve as essential water resources while also receiving domestic and industrial waste. Objective: This study assessed microplastic contamination in selected freshwater river systems in Punjab, Pakistan, by evaluating waterborne concentration, particle morphology, polymer type, sediment presence, and ingestion in freshwater fish. Methods: A cross-sectional environmental monitoring study with laboratory-based analysis was conducted in upstream, midstream, and downstream sections of selected rivers. Water, sediment, and fish samples were collected and processed using filtration, density separation, organic matter digestion, stereomicroscopic examination, and Fourier Transform Infrared Spectroscopy for polymer confirmation. Results: Microplastics were detected across the studied river compartments. Waterborne concentrations increased from 120 particles/m³ upstream to 340 particles/m³ midstream and 620 particles/m³ downstream, representing a 5.17-fold downstream increase compared with upstream sections. Fibers were the dominant morphology, accounting for 55% of particles, followed by fragments at 35% and beads/others at 10%. Polyethylene, polypropylene, and polyethylene terephthalate were identified. Fish samples contained 3 to 12 microplastic particles. Conclusion: Microplastic contamination was present in river water, sediments, and fish, with the highest burden in downstream zones. These findings support the need for improved wastewater treatment, plastic-waste control, routine river monitoring, and larger standardized studies.
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