Preliminary study on the distribution and risk assessments of microplastic pollution in surface water in Chengdu, China

Microplastics have emerged as a significant global environmental issue that has garnered considerable attention from both the public and governmental bodies. In this study, microplastics (0.02-5.0 mm) in the surface water of the Minjiang River and Tuojiang River valleys in Chengdu were quantitatively characterized and analyzed using micro-infrared spectroscopy. Key metrics such as the pollution load index, polymer risk, and potential ecological risk index were calculated to evaluate and analyze the risks associated with microplastics. The results indicated that the concentrations of microplastics in the study area's surface water ranged from 5.0 to 18.2 items/L. Additionally, the microplastic content in the Tuojiang River valley was higher than that in the Minjiang River valley. Microplastics were predominantly transparent or yellow, primarily occurring as granules, fragments, and fibers, with sizes mainly below 1000 μm. In 2021, the predominant types were polyethylene terephthalate (34.2%) and polyethylene (20.7%). In 2023, polyamide (32.8%) and polyethylene (19.5%) became the predominant types, indicating a significant shift in the composition. The contamination risk of microplastics was significantly influenced by the type of polymer. These findings provided a theoretical foundation for the detection and risk assessment of microplastics in surface waters within the Chengdu region.