Lichen diversity and bioaccumulation of heavy metals in northern Tunisia: a study to evaluate environmental pollution

This study focused on the diversity of lichens present in selected regions of northern Tunisia and assessed their resistance to atmospheric pollution. Twenty-five species of lichen were identified, divided into 13 families and 17 different genera. The results show that the Cladoniaceae and Parmeliaceae families predominate. Foliose and complex lichens are the most abundant. The main objective of this study was to examine, via atomic absorption spectrometry, the bioaccumulation of heavy metals (lead, zinc, copper, and cadmium) in the lichens Cladonia rangiformis, Flavoparmelia caperata, Parmotrema perlatum, and Evernia prunastri, which were selected due to the presence of similar lichens at the sites. The results showed high accumulations of lead, copper, and zinc at all stations (Nefza, Babouche, Oued Zen) characterized by intense road traffic and/or industrial activity, while cadmium levels were low at all stations. Flavoparmelia caperata proved to be a species tolerant of metal stress, making it a promising candidate for air quality biomonitoring programs aimed at assessing air pollution (17.53 mg/g DW of Pb and 89.8 mg/g DW of Zn in Nefza, and 2.36 mg/g DW of Cd and 10.13 mg/g DW of Cu in Oued Zen). These results highlight the importance of lichens as biological indicators for assessing pollution, the need to carefully monitor heavy metal concentrations in urban environments, and to provide future projects with funding for their potential transplantation to polluted.