Jafarova, Mehriban, Grifoni, Lisa, Renzi, Monia, Bentivoglio, Tecla, Anselmi, Serena, Winkler, Aldo, Di Lella, Luigi Antonello, Spagnuolo, Lilla, Aherne, Julian, and Loppi, Stefano
Simple Summary: This research investigated the presence of atmospheric microplastics, including those originating from tyre wear, in urban parks and rural roadside areas (Siena, Italy). We used the leaflets of the commonly found higher plant, Robinia pseudoacacia L. (black locust), as a novel biomonitor of atmospheric microplastic deposition. In the study, we observed that rural roadside locations had high concentration of tyre wear particles, whereas urban parks situated more than 500 m away from busy roads exhibited no detectable levels of tyre wear particles. In contrast, the number of plastic microfibres was significantly greater in urban parks, given their central city locations. The results suggest a substantial daily deposition of microplastics, potentially leading to human exposure in both residential and rural areas. In situations where human habitation is in proximity to roads, there is a heightened risk of exposure to tyre wear particles from road surfaces. Our results suggest that Robinia pseudoacacia L., with its widespread availability, waxy coating, and high surface-to-mass ratio, as well as ease of surface area determination for estimating deposition rates, can serve as a valuable resource for investigating the deposition of airborne microplastics including tyre wear particles. Here we investigate the suitability of Robinia pseudoacacia L. (black locust) leaflets as a novel biomonitor of airborne microplastics (MPs) including tyre wear particles (TWPs). Leaflets were collected from rural roadside locations (ROs, n = 5) and urban parks (UPs, n = 5) in Siena, Italy. MPs were removed by washing, identified by stereomicroscope, and analysed for polymer type by Fourier transform infrared spectroscopy. Daily MP deposition was estimated from leaf area. The mass magnetic susceptibility and the bioaccumulation of traffic-related potentially toxic elements (PTEs) were also analysed. The total number of MPs at ROs was significantly higher at 2962, dominated by TWPs, compared with 193 in UPs, where TWPs were not found. In contrast, total microfibres were significantly higher in UPs compared with ROs (185 vs. 86). Daily MP deposition was estimated to range from 4.2 to 5.1 MPs/m2/d across UPs and 29.9–457.6 MPs/m2/d across ROs. The polymer types at ROs were dominated by rubber (80%) from TWPs, followed by 15% polyamide (PA) and 5% polysulfone (PES), while in UPs the proportion of PES (44%) was higher than PA (22%) and polyacrylonitrile (11%). The mean mass magnetic susceptibility, a proxy of the bioaccumulation of traffic-related metallic particles, was higher at ROs (0.62 ± 0.01 10–8 m3/kg) than at UPs (–0.50 ± 0.03 10–8 m3/kg). The content of PTEs was similar across sites, except for significantly higher concentrations of Sb, a tracer of vehicle brake wear, at ROs (0.308 ± 0.008 µg/g) compared with UPs (0.054 ± 0.006 µg/g). Our results suggest that the waxy leaflets and easy determination of surface area make Robinia an effective biomonitor for airborne MPs including TWPs. [ABSTRACT FROM AUTHOR]