A pilot investigation of PM10-bound atmospheric microplastics over a protected mangrove ecosystem: Role of land–sea breeze circulation in marine and terrestrial inputs

Atmospheric microplastics (MPs) are an emerging pollutant class with significant ecological implications, particularly in vulnerable ecosystems like mangroves. This pilot study presents the first investigation of PM₁₀-bound MPs over an uninhabited island in the core zone of the Sundarbans Mangrove Ecosystem (SME), India, during a winter 2025 campaign. The study leverages an 8-day stratified sampling design based on land-sea breeze cycles and fog-non-fog episodes, capturing distinct atmospheric dynamics over this ecologically sensitive and anthropogenically isolated site. Using a combination of high-volume air sampling, optical microscopy, and μ-Raman spectroscopy, MPs were characterized by shape, size, color, and polymer composition. The results revealed a mean MPs abundance of 10 ± 6 MPs/100 m, with higher values during foggy land breeze episodes. Fibers were the most prevalent morphotype, and black-colored MPs dominated, suggesting substantial terrestrial contributions, likely from plastic carry bag waste, fishing net degradation, and regional textile activity. In contrast, the sea breeze samples showed a predominance of marine-derived MPs, with polymer profiles indicating inputs from fishing and oceanic MPs reservoirs via bubble-burst mechanisms. Principal Component Analysis (PCA) differentiated between marine and land-based sources, further affirming distinct source-receptor pathways. This pilot study not only establishes a crucial atmospheric MPs baseline for the SME but also underscores the influence of mesoscale meteorological conditions on MPs deposition. The findings emphasize the urgent need for integrating atmospheric MPs into coastal pollution frameworks and for adopting source-specific mitigation strategies in mangrove conservation policy.