Occurrence, stability and source identification of small size microplastics in the Jiayan reservoir, China

Microplastics (MPs) in terrestrial aquatic ecosystems has received increasing attention. However, its footprints in reservoirs are poorly documented compared to those in rivers and lakes, especially for small-sized microplastics (<300 mu m, SMPs). This study investigated the whole size spectrum of MPs contamination, classified by shape and polymer type, in surface waters and sediments at the Jiayan reservoir, one of the cascade reservoirs in the Upper Yangtze River in western China. High concentrations of MPs were detected in all surface water and sediment samples. The MPs abundances ranged from 1.10 x 10(4) to 6.17 x 10(4) items/m(3) (average 2.75 x 10(4) +/- 2.33 x 10(4) items/m(3)) in the surface water and 2.60 x 10(3) to 1.57 x 10(4) items/kg (average 6.90 x 10(3) +/- 5.96 x 10(3) items/kg) in the sediment. The SMPs accounted for 80% of the total MPs particles, and were dominated by polyethylene (PE) fragment. Small-sized PE was the main contributor to the high abundance of MPs in the Jiayan reservoir. Neglecting SMPs not only leads to an underestimation of the degree of risk, but also causes misjudgment of the major morphology, components, and sources. The conditional fragmentation model analysis showed the stability of MPs increased from the fibers to fragments and fibers tend to disintegrate into smaller particles. Agricultural activities and atmospheric deposition were the main sources of MPs in the Jiayan reservoir. This study indicates that the reservoirs are presumably hotspots for MPs accumulation, and the fate of SMPs in the cascade reservoirs deserves more attention for further studies. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigated the contamination of microplastics in a reservoir in western China, revealing high concentrations of MPs in both surface water and sediment, with small-sized polyethylene fragments being the main contributor. The sources of MPs in the reservoir were found to be agricultural activities and atmospheric deposition. The study highlights the importance of studying the fate of small-sized microplastics in reservoirs for better understanding and management of microplastic pollution.