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Dam operation changed the transport patterns of microplastics - from a global perspective
Summary
Researchers analyzed data from 517 sampling sites near dams worldwide to understand how dam operations affect microplastic transport in rivers. They found that reservoirs behind dams accumulate higher abundances and more diverse types of microplastics compared to upstream and downstream areas, essentially acting as traps. Seasonal dam operations, particularly during wet seasons, can flush accumulated microplastics downstream into sediments, altering pollution distribution patterns.
The global proliferation of dams has raised concerns about their environmental impact, yet their role in microplastic transport in rivers remains unclear. Our study integrated existing data on the distribution characteristics of microplastics from 517 sampling sites within 100 km of dams to understand the influence of dam operations on the microplastic transport process in rivers. Results demonstrated that microplastics exhibited a higher abundance and diversity in reservoirs than in the upstream and downstream areas. Upstream microplastic levels negatively correlated with distance from the dam, while downstream sediment showed increased microplastic accumulation during wet seasons. Fibrous microplastics were the most prevalent in both water and sediment, with their abundance decling with distance from the dam, both in the sediment upstream of the dam and in the water downstream of the dam. Microplastic communities were compositionally similar across regions within the same environmental component. The conditional fragmentation models indicated significant microplastic fragmentation downstream of the dam. Our results enhance our understanding of the environmental behavior and migration process of microplastics in dammed rivers, and provide valuable reference for an accurate prediction of microplastic transport fluxes and the development of microplastic pollution mitigation technology.