A first (small) step towards understanding the ability of biochar to provide information on the environmental availability of potentially toxic elements (PTEs) in atmospheric depositions
(1) Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 11/A, 43124 Parma, Italy, (2) INFN, National Institute of Nuclear Physics, Division of Florence, Via Bruno Rossi, 1, 50019 Sesto Fiorentino, Florence, Italy
The aim of this study is to investigate the ability of two wood-derived biochars to accumulate PTEs from atmospheric deposition, using the lichen Evernia prunastri as a benchmark. The lichen samples were collected in a remote area of the Tuscan-Emilian Apennines. They were first washed with deionized water, loosely wrapped in a 1 mm2 mesh nylon net, and then transplanted for two months (from 10/03 to 10/05/2023) in three different areas, (i) in the University Park of the city of Parma (outdoor exposure), an area affected by the presence of a ring road in its immediate vicinity (approx. 100m), (ii) in a private office of the Bioscience Plexus of the University of Parma (indoor exposure), an area affected by seismic retrofitting of the facilities in the previous weeks, and (iii) in the living room of a private house (indoor exposure) characterized by a modern pellet heating system. In contrast, the two pools of biochar, once purchased, were first sieved separately to obtain a 2-4 mm diameter biochar batch, and then washed with a warm 1M HCl solution. They were then exposed according to lichen methods, areas, and times. Samples were analyzed using accelerator-based nuclear analytical techniques, such as ion beam analysis (IBA), for elemental analysis. Two IBA techniques, PIXE (Particle Induced X-ray Emission) and EBS (Elastic Backscattering Spectrometry) were used, with protons (beam energy of 3 MeV, beam spot size of 1 mm) in external beam mode. Using these techniques, the samples were analyzed in a rapid and non-destructive way. Several elements (Mg, Al, Si, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr and Pb) were identified in the analyzed samples with detection limits down to the ppm range. Reference standard materials such as NIST 1573A (tomato leaves), NIST 1547 (peach leaves) and NIST 1515 (apple leaves) were also analyzed for quality assurance purposes and to verify the accuracy of the quantitative results presented here.
Keywords: air pollution, biochar, biomonitoring, Evernia prunastri, indoor biomonitoring, outdoor biomonitoring, lichens
