Luigi Antonello Di Lella

This study investigated the suitability of X-ray fluorescence (XRF) analysis for routine multi-elemental composition analysis, checking its analytical capabilities by measuring a wide array of certified reference materials of soil and plant origin. A portable XRF analyzer was used to evaluate 32 soil and 12 plant standard materials, using both the Soil and Geochem mode, with sequential beams, allowing the detection of a wide range of elements. Recovery rates were calculated by comparing XRF measurements with certified values, and their correlations were verified through the Spearman coefficient. The results demonstrated the reliability of XRF measurements for soil samples, with a large number of elements showing a good or very good recovery and strong correlations with certified values. For plant samples, XRF largely overestimated the certified values, but the strong statistically significant correlations for almost all tested elements allowed us to correct this systematic bias, using the reported median value for dividing the value obtained via XRF. The Geochem mode emerged as more reliable for a larger number of elements. It was concluded that XRF may be a suitable alternative to ICP-MS in routine multi-elemental composition analysis.

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 aim of this study was to investigate the ability of biochar amendment to reduce the availability of Pb in the soil and its uptake in lettuce (Lactuca sativa L. var. adela). Seedlings of lettuce were cultivated in Pb-contaminated soils, both with and without 5% biochar (w/w), as well as in a simplified soilless system (hydroponics) at the ecologically relevant Pb concentration of 100 µM, both with and without 1% biochar. Soils amended with biochar resulted in a ca. 50% reduction of the extractable (bioavailable) fraction of Pb, limiting the accumulation of this toxic element in the leaves of lettuce by ca. 50%. A similar behavior was observed for lettuce plants grown hydroponically, even with a much higher reduction of Pb uptake (ca. 80%). Increased cation exchange capacity and pH were likely the main factors limiting the bioavailability of Pb in the soil. Complexation with functional groups and precipitation/co-precipitation both on the biochar surface and in soil aggregates were likely the main mechanisms immobilizing this element.

The aim of this study was to provide, for the first time, data on the concentration of potentially toxic elements (PTEs) in soils and bulbs of elephant garlic (Allium ampeloprasum L.) cultivated in Valdichiana, a traditional agricultural area of Tuscany, Italy. Bulbs of elephant garlic and soil samples were collected in four cultivation fields and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) to determine the concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, Sb, Tl, U, V, Zn. The concentrations of these PTEs in bulbs and cultivation soils were used to calculate geochemical, ecological and health risk indices. The results of this study suggest that, although bulbs of elephant garlic from the Valdichiana area may present slightly high concentrations of Cd, Ni and Pb, the associated health risk based on the daily intake is absolutely negligible. Cultivation soils had somewhat high Cu concentrations probably due to the diffuse use of Cu-based products in agriculture, but showed overall a very low ecological risk.