Spatial patterns and short-term deposition of atmospheric microplastics in an urban environment

Atmospheric deposition is an important and newly recognised pathway for microplastics (MPs), influencing their transportation and distribution both on land and in aquatic environments. However, MP pollution in the air remains relatively understudied compared to aquatic environments, particularly in developing regions such as Southern Africa. Despite the growing body of literature on MPs in Southern Africa, studies investigating atmospheric MP deposition, short-term variability, and links with meteorological conditions remain limited. This study investigates the occurrence and characteristics of atmospheric MP deposition and their relationship with meteorological factors within an urban town in the Albany thicket biome of South Africa, using weekly sampling over a six-week period across three sites associated with different land-use types. MP deposition fluxes were found to be significantly different between study sites, with an average of 86.5 ± 10.4 particles/m²/day. The highest deposition fluxes were recorded at S2, located in a peri-urban area (178.1 ± 69.2 particles/m²/day) ~ 4.5 km from the town center, while the lowest were observed at S3, ~ 10 km outside the town in a semi-natural area (24.7 ± 8.2 particles/m²/day). Around 30.2% of MPs identified had particle sizes between ≥ 250 and < 500 μm. The dominant colour was transparent/clear (46.6%) and the prevalent shape was fibre/filament (95.5%). FTIR-ATR analysis revealed that polyethylene terephthalate (PET) was the predominant polymer type (42.5%). Microplastic deposition fluxes at S1 (urban area) showed a positive correlation with rainfall, suggesting that rainfall likely influences local MP deposition dynamics at this site. Microplastic deposition fluxes in the town are likely influenced by a combination of local pollution sources, including sewage seepage, poor waste disposal, wastewater management, and textile-related activities. These findings demonstrate clear spatial variation in atmospheric MP deposition linked to land use and local anthropogenic activities, emphasising the importance of atmospheric pathways in regional plastic pollution cycling. The study highlights an urgent need to incorporate atmospheric MPs into environmental monitoring and waste management policies, particularly in urbanising regions of Southern Africa where regulatory frameworks and baseline datasets are still emerging.