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First biomonitoring of micro/nanoplastic pollution in freshwater fish from Yalong River, China: accumulation dynamics, influencing factors and ecological risk
Summary
Scientists studying a major Chinese river found tiny plastic particles (microplastics and even smaller nanoplastics) inside the guts of 31 different fish species, with smaller fish carrying higher concentrations than larger ones. Since these fish are part of the food chain — and sometimes end up on our plates — this pollution matters because it shows how widespread and hard to avoid plastic contamination has become in the water systems that supply our food. While this study didn't directly test human health effects, it adds to growing evidence that plastics are working their way into the animals we eat.
Microplastics (1 μm-5 mm) and nanoplastics (<1 μm) are ubiquitous environmental pollutants with increasingly prominent ecological risks. As key indicator organisms in river ecosystems, fish readily ingest micro/nanoplastics, and the contamination levels in their bodies can directly reflection of plastic pollution in rivers. This study presents the first assessment of micro/nanoplastic pollution in freshwater fish from the Yalong River, an important tributary of Yangtze River. Laser direct infrared imaging spectrometer (LDIR) was used to analyze microplastic in the intestinal contents of 31 fish species,while pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) was applied to detect nanoplastics in five representative species. The results showed that a total of 34 microplastic polymer types were identified in fish, exceeding those in water (21) and sediment (12). Polytetrafluoroethylene (PTFE) was dominant in both water and fish, whereas polyurethane (PU) was predominant in sediment. Microplastic abundance in fish intestines ranged from 29.17 to 6,460.58 items/g (mean 566.79 items/g), and was significantly negatively correlated with fish body size, but not with water layer habitat, flow preference, feeding habits, or trophic level. Smaller microplastics were significantly more abundant than larger ones across water, sediment, and fish. Three shapes (pellet, film, and fiber) were observed, with pellets being the dominant form. Nanoplastics, including polyvinyl chloride (PVC), polyethylene terephthalate (PET), nylon 66 (PA66), polycarbonate (PC), and polystyrene (PS), were detected in five fish species. The polymer hazard risk index (PHI) indicated that ecological risks among species ranged from 40.19 (Level II) to 3,980.18 (Level IV). This study systematically characterizes micro/nanoplastic pollution in representative fish from the Yalong River, providing a scientific basis for ecological risk assessment and future pollution control and conservation.