Atmospheric microplastic accumulation in Ramalina celastri (Sprengel) Krog & Swinscow Thalli: a transplant study across different levels of urbanization

Lichens are widely recognized as bioindicators of atmospheric pollution, but studies on their role in monitoring microplastic (MP) deposition remain scarce. This study investigates MP accumulation in natural populations of Ramalina celastri across an urbanization gradient in Luján, Argentina, marking the first report for this species. MP concentrations ranged from 16.54 ± 3.59 MPs g^–1 in baseline sites to significantly higher levels in urban zones. Fragments showed a stronger association with urbanised areas compared with fibres. Unlike larger urban centers, no significant trend was observed in MP size with urbanization, likely due to Lujan’s small size, facilitating unrestricted MP movement. Comparisons with global studies revealed consistent patterns of increased MP accumulation near anthropogenic sources, while unique findings highlight the potential of R. celastri as a bioindicator in diverse environments. These results emphasize the influence of urbanization on MP deposition and suggest localized sources as key contributors to fragments, advancing our understanding of MP dynamics. This work underscores the need for standardized methodologies to enhance comparability in future research on terrestrial MP pollution.