Magnetic and chemical biomonitoring with lichens and vascular plants for the preservation of cultural heritage: A case study at two museums in a megacity (Buenos Aires, Argentina)

: Magnetic and chemical biomonitoring was applied at Museo Nacional de Bellas Artes and Museo Histórico Nacional, two museums facing busy roads in Buenos Aires, Argentina. Plant leaves (Jacaranda mimosifolia and Fraxinus americana) and lichens (Evernia prunastri) were sampled and transplanted, respectively, from November 2022 to March 2023 for assessing the diffusion of vehicular metallic particulate matter (PM) and potentially toxic elements (PTEs) inside the museum's halls. The magnetic properties of leaves and lichens, deduced from magnetic susceptibility values, hysteresis parameters and first-order reversal curve (FORC) diagrams, were compared to the concentration of PTEs (Al, Ba, Cd, Cr, Cu, Fe, Mn, Sb and Zn), showing that most of outdoor metallic PM was sourced from vehicular brake abrasion and did not bioaccumulate inside the museums. Lichens confirmed to be reliable biomonitors of airborne PM. PTEs were accumulated in higher concentration by J. mimosifolia with respect to F. americana leaves, thus providing more efficient and sustainable nature-based solutions for the preventive conservation of cultural heritage.