Spatiotemporal variation of microplastics along the long-distance raw water pipeline

Raw water pipelines are considered a significant pathway for human exposure to microplastics (MPs, <5 mm) in surface water. However, there is currently very limited information on the longitudinal distribution characteristics of microplastics in raw water pipelines. This study assessed the abundance and distribution characteristics of microplastics in surface water from two different water sources in Jiangsu Province during different seasons. The correlation between conventional water quality indicators and microplastics was also explored. Specifically, the longitudinal variation of microplastics in raw water pipelines was investigated. Results showed that microplastics were detected in both basins during different seasons. In Basin 1, the abundance of MPs ranged from 34 ± 1 to 58 ± 2 n/L in March and from 3 ± 1 to 6.7 ± 4 n/L in June. In Basin 2, the abundance ranged from 6.5 ± 1 to 14 ± 1 n/L in March and from 2 ± 1 to 7.7 ± 1 n/L in June. The abundance of microplastics showed a decreasing trend along the pipeline. Polymethyl methacrylate (PMMA) was the main polymer type detected in both basins. Polyethylene terephthalate (PE) and polyurethane (PU) showed higher removal rates in the pipeline due to their higher density. The predominant size ranges of microplastics in the raw water were 10-50 μm and 50-100 μm. Additionally, the average particle size of MPs increased with the transportation distance, likely due to microbial colonization. This study is the first comprehensive investigation of the distribution characteristics of microplastics in raw water pipeline systems. The removal of microplastics in raw water pipelines contributes significantly to the elimination of microplastics at the source. This research helps to fill the knowledge gap regarding the fate of microplastics in raw water pipeline systems.