Atmospheric microplastic deposition in high-altitude snowpacks across Türkiye

Microplastic (MP) pollution has been increasingly documented in remote high-altitude environments worldwide, including the European Alps, Himalayas, Andes, and polar snowfields, where atmospheric transport delivers plastic particles even to regions far from emission sources. Despite this growing body of evidence, the occurrence of MPs in the mountainous regions of Türkiye remains unknown. This study presents the first nationwide investigation of MP contamination in alpine snow, conducted across eleven sites, including Mount Ağrı, Süphan, Kaçkar, Erciyes, Uludağ, and Sandras. MPs were detected at all locations, with an average concentration of 286 ± 91 MPs/L with the highest concentration detected at Sandras Mountain (908 MPs/L) and the lowest at Uzundere-Uzunkavak, Erzurum (16 MPs/L). Across the eleven sites, the mean relative shape composition was 71.2 ± 6.1% fibres, 23.8 ± 5.8% fragments, and 5.0 ± 4.5% films (summing to 100% as percentages of all detected MPs). Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), nylon (PA), and polymethyl methacrylate (PMMA) were identified as the primary polymers. Spatial variability suggested both atmospheric deposition and local human activities contributed to contamination. Backward trajectory analysis indicated that microplastic deposition in snow was influenced by both long-range atmospheric transport from Africa and the Mediterranean and short-range local emissions, highlighting the combined impact of transboundary and regional processes on microplastic distribution. These first-season findings provide a preliminary baseline that even isolated alpine snowpacks of Türkiye can receive measurable MP inputs of both regional and long-range origin, highlighting the need for sustained, multi-season monitoring of high-mountain ecosystems within national and transboundary mitigation frameworks.