Lisa Grifoni

Wood vinegar (WV), a by-product of woody biomass pyrolysis, is increasingly used in agriculture as a sustainable biostimulant, although its effects on plant stress resistance and underlying mechanisms remain poorly understood. Recent studies propose that WV may act through a eustress-based mechanism, defined as a mild and controlled stress that activates adaptive physiological responses and enhances plant performance without causing structural or metabolic damage. This study investigated the physiological and biochemical effects of WV on strawberry plants grown under three water-deficit stress levels [no stress (NS), moderate stress (MS), and high stress (HS)] and treated with WV either via fertigation (0.5% v/v, WV₁) or foliar spray (0.2% v/v, WV₂). Gas exchange parameters (A, g_sw, E, Ci, WUE), total chlorophyll content, and nutrient balance ratios (Fe/Mn and K/Ca) were measured after a three-month growth period. PERMANOVA revealed significant effects of both WV and water-deficit stress, as well as their interaction, on most parameters. Under NS and MS conditions, WV reduced A, gsw, E, and Ci while increasing WUE, indicating enhanced water-use efficiency and improved physiological adjustment to water limitation. Chlorophyll content remained stable, demonstrating preserved photosynthetic integrity. Nutrient ratios further supported a controlled ion rebalancing associated with adaptive stress responses under NS and MS, whereas HS conditions indicated the onset of distress. Overall, the data demonstrate that WV enhances plant stress resistance primarily by inducing eustress-mediated physiological regulation rather than by directly stimulating growth.

Interest in using lichens and mosses to monitor airborne microplastics is growing, but few studies have thoroughly compared their effectiveness as biomonitors. Here, we directly compare the ability of lichen and moss transplants collected from a rural area to accumulate microfibers (MFs) and Potentially Toxic Elements (PTEs) under the same deployment conditions. Transplants (n = 60; triplicates for both lichen and moss) were co-deployed on tree branches across a range of urban exposure sites (e.g., commercial and residential areas and urban parks) for 77 days in Siena, Italy. The results showed that both biomonitors accumulated similar amounts of MFs, in terms of counts and on a mass basis, but when expressed on a surface area basis, lichens showed significantly higher values. Irrespective of the metric, lichen and moss MF accumulation data were strongly correlated. In contrast, there was no correlation between MFs and PTEs, suggesting that their sources were different. MFs accumulated by lichen and moss transplants were dominated by polyethylene terephthalate (PET) and polypropylene polymers, suggesting that the main source of airborne MFs is synthetic textiles. Our results suggest that both lichen and moss transplants can be effectively used as low-cost monitors of atmospheric MFs in urban areas in support of the sustainable development goal of clean air.

Monitoring atmospheric pollution in urban areas is challenging because pollutant deposition occurs at short distances, requiring a large amount of sampling and analysis to characterize it. Ecological indicators can help overcome this problem, allowing us to select sites with the highest deposition of pollutants from the atmosphere. Nevertheless, a major gap is the temporal characterization of the accumulation rate of magnetic particles in ecological indicators, which is critical to understand if the bioaccumulation process is linear or if saturation occurs. To overcome this problem, Parmotrema perlatum lichens were magnetically and chemically studied in a pollution gradient over space and time. Lichen transplants were exposed over 18 weeks to a high-traffic road. Results show that magnetic properties and element composition reflected both distance from the road (nonlinear decrease of up to 100 m from source) and exposure time (increasingly linearly over the entire study period with eightfold increments), showing that up to 18 weeks, the accumulation rate remained constant over time, with no saturation occurring. Chemical analysis showed a strong linear relationship between the accumulation of zinc (Zn), antimony (Sb), manganese (Mn), copper (Cu) chromium (Cr) and magnetic susceptibility. Magnetization acquisition curves reveal a time-dependent low-coercivity component, interpreted as mainly related to nonexhaust, mostly brake abrasion particle emissions. It is concluded that the magnetic properties of lichen transplants can be used in urban environments to characterize the spatial and temporal patterns of the deposition of pollution metallic particles from the atmosphere.

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.

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.