Microplastic pollution in the Tagus River: Distribution and abundance from the the river mouth to the Portuguese border

In recent years, there has been increasing research on microplastics (MP) due to their impact on the environment, biota and human health. However, studies have addressed predominantly marine and coastal areas, and studies in inland waters are limited. In this work, we assess for the first time the presence of MP in the Portuguese stretch of the Tagus River, an ecological and economically important Iberian river. Surface water samples were collected with a 150 µm net at 5 stations and sediment samples were collected on shore near the waterline at 30 stations, in December 2020. Extraction of MP included digestion and density separation. Fibres were not considered. MP were found at all stations, with average concentrations of 0.54 ± 0.5 MP/m3 in water, and 10.9 ± 4.7 MP/kg in sediment samples. MP concentrations in water were higher in the estuary (1.3 MP/m3), and lowest at the most upstream point (0.2 MP/m3). Sediment samples from midstream presented highest concentrations of MP (20.1 MP/kg), while the lowest concentration was registered in the estuary (2.71 MP/kg). Overall, MP sizes ranged between 0.1 and 0.5 mm. In water samples, films were the most common type, followed by fragments, and the predominant colours were green and transparent, while in sediments, the most abundant typology were filaments followed by fragments, and the colours transparent, followed by blue. Common polymers were Low-Density Polyethylene (30.6 Also see: https://micro2024.sciencesconf.org/559706/document