Microplastic Contamination in High-Altitude Andean Lakes: Sources, Distribution, and Environmental Implications

Microplastics (MPs) are widespread environmental contaminants that disperse through aquatic and atmospheric pathways, reaching virtually all Earth ecosystems. In this study, we investigated the abundance and characteristics of MPs in the surface water and sediments of five mountain lakes located at elevations between 3848 and 4245 m above sea level (m.a.s.l.) in the Ecuadorian Andes. A total of nine composite water samples and five sediment samples were collected to assess MP concentrations, size distribution, morphology, and polymer composition. The distribution of MPs within this lacustrine system was assessed, and the potential role of atmospheric transport from the Amazon Basin as a contamination source was evaluated. MP concentrations were 10 ± 5 MP/m³ in water samples and 2838 ± 1489 MP/kg in dry sediment samples. Transparent MPs predominate in water, whereas white particles were the most common MPs in sediment. MP sizes exhibited considerable variation, with larger particles (1800–3400 μm) prevalent in water samples, while sediment samples contained smaller MPs (150–1800 μm). Fibers and films were the dominant morphological types in both matrices. Polymer analysis identified polyethylene (PE) and polypropylene (PP) as the most frequently detected materials. Given the remoteness of the study area, the polymer composition, and the observed particle morphology, it is likely that the sources of MPs are associated with local tourism activities. Additionally, easterly winds from the Amazon region may facilitate long-range atmospheric transport, introducing MPs into these fragile ecosystems. This study highlights the need for further research to identify MP sources, evaluate their ecological impacts in high-altitude environments, and implement monitoring and mitigation strategies to protect these vulnerable aquatic systems.