| Abstract | Airborne microplastics (AMPs) have emerged as an important environmental pollutant due to their persistence in the atmosphere and potential risks to human health. Although increasing attention has been given to airborne microplastics worldwide, studies in Thailand remain limited, particularly regarding the combined investigation of airborne concentration, dry deposition, particle characteristics, and temporal variation across different environments. In addition, information on airborne microplastics in Northern Thailand, especially Chiang Mai, is still scarce despite the region experiencing severe seasonal air pollution conditions that may influence microplastic transport and deposition.Therefore, this study investigated airborne microplastics at two university campus environments in Thailand: Asian Institute of Technology (AIT), Pathum Thani, and Chiang Mai Rajabhat University (CMRU), Chiang Mai, focusing on their concentration, size distribution, morphology, and dry deposition behavior. Airborne samples were collected using a high-volume air sampler, while dry deposition samples were obtained through passive sampling. Microplastics were identified and quantified using Nile Red staining combined with fluorescence microscopy. The results showed comparable airborne microplastic concentrations at both sites, with mean values of 14.92 ± 5.10 particles/m³ at AIT and 13.50 ± 2.55 particles/m³ at Chiang Mai. Dry deposition flux at AIT ranged from 11,000 to 38,000 particles/m², with an average of 20,466 ± 6,792 particles/m². At the Chiang Mai site, deposition ranged from 24,921 to 39,921 particles/m², with an average of 31,734 ± 4,360 particles/m². Size distribution analysis revealed that particles in the 10–25 µm range dominated airborne samples, while larger particles (25–50 µm and >50 µm) were more prevalent in deposition samples, reflecting size-dependent transport and settling behavior. Morphological analysis showed that fragments were the dominant shape (>95%) across all samples, indicating that secondary microplastics from the degradation of larger plastic materials are the primary sources.Temporal variability was observed at both sites without a consistent trend, and weak correlations with meteorological parameters suggest that local activities and resuspension processes play a more significant role than atmospheric conditions in controlling AMP levels. Overall, this study highlights the importance of particle size and local environmental factors in governing airborne microplastic dynamics and provides baseline data for future monitoring and risk assessment in Thailand. |
