Spatial Variability, Sources, and Atmospheric Deposition of Microplastics in Seasonal Snowpacks of the Pakistani Himalaya

Microplastics (MPs) in high-altitude and ecologically sensitive areas in Pakistan remain unknown and have become a pervasive global issue. This study investigated the occurrence, potential sources, and spatial variability of microplastics across the high-altitude Galiyat region, with emphasis on quantifying their distribution patterns and identifying factors influencing deposition within this mountainous environment. A total of 72 snow samples were collected from 12 different locations (12 × 3) and analyzed for MPs within an analytical size range of about 300 to 5000 µm, with a lower detection limit of 50 µm. The results show that MP abundance (MPs/L) in 2023 ranged from 89 to 265 (average 161 ± 0.58) and from 52 to 265 (average 134 ± 57.36) in 2024, using means of triplicate field samples and reflecting spatial variability among replicates. The highest MP concentration (MPs/L) was at Ayubia Track, with 265 counts in both years, dominated by polyvinyl acetate (PVAc), while the lowest MPs were 89 and 52 at Khanspur and Barra Gali in 2023 and 2024, respectively. By comparison, the present result was lower than Alps (Europe) as 1760 MPs/L and higher than the Tibetan region with <10 MPs/L. At low altitudes, the spatial distribution of polyisobutylene (PIB) and PVA was the dominant type, constituting more than 33% in 2023 and 50% in 2024 of the total MPs, while PPS, PET, PES, and PL made up less than 9% in both sampling years. Based on morphological characteristics, fiber and transparent MPs were dominant at 30% in 2023 and 31% in 2024, followed by black MPs, i.e., 24% in 2023 and 23% in 2024, and red MPs were 8% in both years. Results indicated that MP pollution in remote areas varied from region to region and by proximity to human activities in high-altitude remote areas. This study provides the first multi-year (2023–2024) quantitative assessment of MPs abundance, morphology, and polymer composition in seasonal snowpack of the Galiyat region, addressing a critical research gap in the Pakistani Himalaya. The MPs in high-altitude snow highlight ecological implications and the role of human and atmospheric activities in disseminating MPs while stressing the need to limit plastic product usage in remote and sensitive areas to protect the integrity and vulnerability of the mountain ecosystem, contributing to Sustainable Development Goals (SDGs 6, 12, 13, and 15).