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Validation of sediment granulometry as a key factor in microplastic accumulation: Comparative analysis between the Tena and Pano rivers, ecuadorian Amazon

2026
Mishell Cabrera, Bryan Valencia, David Portillo, Julieth Chancay, Pedro Cadena, Paola Soto

Summary

Scientists studying two rivers in the Ecuadorian Amazon found that microplastic pollution tends to build up more in muddy, fine-grained sediment than in sandy areas—meaning the type of riverbed soil matters just as much as pollution levels when measuring contamination. This is important because it means future water and sediment testing needs to account for soil texture to get accurate readings of plastic pollution, which ultimately affects the fish and water sources people rely on in these regions.

Study Type Environmental

Microplastic (MPs) abundances are often used as pollution indicators, yet neglecting sedimentary processes may bias their estimation. This study examines the relationship between sediment granulometry and MPs accumulation in two rivers of the Ecuadorian Amazon. Six zones were selected in the Tena River and twelve in the Pano River using the Van Zuidam slope classification (<8°). After a single strong rainfall, 30 sediment samples were collected in the Tena and 60 in the Pano. MPs were quantified from 2.5 g of sediment per sample, while granulometry was determined by sieving 100 g into seven fractions (>2 mm to <63 μm). In total, 564 MPs were recorded in the Tena and 567 in the Pano river. A significant positive correlation was found between MPs and muds content in both rivers (Tena: r = 0.46, p = 0.009; Pano: r = 0.40, p = 0.00244). Results demonstrate that granulometry strongly influences MPs accumulation and must be reported to avoid biased estimates.

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