This study investigated the deposition of airborne microplastics (MPs) in the urban area of Milan across 12 sites and at a background control site (northern Italy) using 3-month transplants of the fruticose lichen species Evernia prunastri (exposed in triplicate). The primary objective was to evaluate the use of lichen transplants for the assessment of MP deposition; as such, the study sites spanned a gradient in vehicular traffic and population density across four concentric land-use zones (i.e., urban parks, centre, semi-periphery, and periphery). A total of 149 MP particles were detected in the exposed lichen samples; 94.6% were classified as fibres and 5.4% as fragments. The control site and urban parks experienced a similar number of MPs per gram of dry lichen (20–26 MP/g), while a higher number of MPs were detected in central and peripheral areas (44–56 MP/g), with a clear increasing gradient from the city centre towards the periphery. We estimated the MP deposition in Milan to be in the range of 43–119 MPs m2/d, indicating that people living in Milan are exposed to airborne MPs, with potential health effects. This study suggests that lichens are suitable biomonitors of airborne MPs under a relatively short exposure of three months in urban environments.

The atmosphere is an important pathway for microplastic (MP) transport; however, observations are limited, as traditional sampling methods are generally labor-intensive. Biological monitors (biomonitors) have been widely used as a simple alternative to determine the abundance or presence of anthropogenic pollutants. Here, we compared the effectiveness of co-located lichen and moss species as biomonitors of the atmospheric deposition of microplastics. Samples of the epiphytic lichen Evernia prunastri and the epigeic moss Pseudoscleropodium purum were collected from five remote areas of central Italy. A total of 154 MPs were found across all samples, 93.5% of which were fibers and 6.5% were fragments. The accumulation of MPs for lichens (range of 8–12 MP/g) was significantly lower than for mosses (12–17 MP/g), which might be related to their structural characteristics or habitat positions (epiphytic versus epigeic). Nonetheless, higher accumulation facilitates analytical determination and provides greater separation from the limit of detection, suggesting that mosses are preferred over lichens for studying the deposition of airborne MPs. This study further suggests that biomonitoring may be an effective tool to assess the spatial distribution of atmospheric microplastics, which is a key requirement for the development of waste mitigation policies.

This study investigated whether moderate soil contamination by Cd and Pb may negatively affect seed germination, photosynthesis and foliar accumulation in the medicinal plant Hypericum perforatum. Seeds were incubated with Cd and Pb solutions of 10 and 100 µM, and two-month-old plants were watered weekly for three weeks with the same solutions. Control samples were treated with deionized water. The percentage of seed germination and seedling length, as well as chlorophyll content, chlorophyll fluorescence and foliar reflectance, were measured, along with the foliar Cd and Pb concentrations. The results indicated that seed germination is not affected, while seedling length is decreased by approximately 81% by high Cd levels. Cadmium was subjected to foliar translocation from the soil depending on the supplied concentration, thus causing reductions in the chlorophyll content (−24%). It is of interest that foliar Cd levels in Cd-treated plants were close to or above the limit for the European Pharmacopoeia. Negative effects of Pb were not detected, but accumulation and blockage of this metal at the root level, although not approached experimentally, cannot be ruled out.