Plastic pollution is a worldwide environmental issue, which affects all natural habitats via the global network of land, rivers, lakes, seas and oceans and atmospheric transport and deposition. Although the sources, size, fluxes, behaviour and effects of plastic pollution in freshwater ecosystems are poorly quantified, it is generally accepted that once present in the aquatic system, plastic particles contaminate shoreline habitats, the water column and the river benthos, with the highest concentration measured in the latter. Recent works indicate that rivers may function as (temporary) sinks for land-based plastic pollution and a potential source of its future remobilization. PLASTIC0PYR project responds to the challenge of making tourism compatible with the conservation and improvement of mountain freshwater ecosystems. The general objective of the project is to propose solutions to reduce in a sustainable way the accumulation of plastics in the mountain ecosystems and their subsequent transport to the sea. The project is developing unique protocols to be applied in 3-4 natural areas located in the Pyrenees of Catalonia, Andorra and France that show different levels of human impact (ski resorts, national parks...). Different river environment compartments are sampled to quantify the abundance of plastic particles in the riparian area, water column, benthic area (sediments and biofilm), fishes and atmosphere (rain and dry deposition). With the results, we are going to be able to identify the most impacted areas, the transport and storage areas across the headstream and observe if exists a link between microplastic abundance and the health of the river system. Our efforts will help to improve the plastic waste management by involving different stakeholders (scientific, governments, citizens...).