Combined magnetic, chemical and morphoscopic analyses on lichens from a complex anthropic context in Rome, Italy

Native and transplanted lichens were analyzed as bioaccumulators of airborne particulate matter (PM) in an eastern district of Rome, Italy, where frequent fraudulent fires are set to recover metals, mostly copper, from waste electrical and electronic equipment (WEEE). The presence of native lichens was scarce, due to the drought of spring-summer 2017, thus, sampling was extended to a neighboring area for toughening the dataset to a similar context. The magnetic analyses revealed intense properties connected to the anthropic complexity of the zone, where industrial, traffic and arson-related dusts are emitted and bio-accumulated. Magnetic and chemical analyses were compared, leading to significant linear correlations between the concentration dependent magnetic parameters (susceptibility, saturation magnetization and saturation remanence) and the concentration of heavy metals, among which copper, chrome, lead and zinc. Moreover, selected magnetic particles were chemically and morphologically characterized by Scanning Electron Microscope and Energy Dispersion System microanalyses. Magnetic particles resulted incorporated into the lichens' tissues and their composition, morphology and grain size strongly supported their anthropogenic, mostly combustion-related, origin. Even if, given the complexity of the area, it was not feasible to fully discriminate the multiple anthropogenic sources, magnetic biomonitoring of lichens, especially when combined with microtextural and compositional analyses, confirmed to be an excellent methodology for a rapid characterization of environmental pollution.