Use of lichen species for air pollution biomonitoring: Case of Dar-Chichou forest (Cap-Bon, North-East Tunisia)

In the present work, we investigated the bio-uptake of 4 MTE (Ni, Cd, Pb, Zn) in the thalli of some species of lichens near a road crossing the Dar-Chichou forest (NE- Tunisia). In the absence of previous studies on the lichenic heritage of this forest, the objectives of this work are.first of all to identify for the first time the lichen species present in the forest, to determine the impact of this road pollution on certain physiological parameters of these pioneer species, such as the chlorophyll a and b levels, the content of carotenoids, theperoxidation (H2O2) and the ipoperoxidation (MDA) and on the other hand, to show the bioindicatory and bioaccumulative importance of these lichens in front of certain trace metals (Pb, Cd, Zn and Ni). In this study, 23 lichen species with different thallus was detected. The amounts of MTE in thalli of several lichen species were determined using the flame atomic absorption spectrometry. Significant positive correlations between the production of H2O2 and the MDA content and on the MTE content (Ni, Pb, Zn) indicating a defense against oxidative stress. The presence of Evernia prunastri, Xanthoria parietina, Physcia adscendens and Cladonia stellaris, made it possible to classify the air quality of the Dar-Chichou Forest. P. adscendens present the weakest reaction against oxidative stress (H2O2) and seemed the most resistant compared to the two other species. This study was conducted as part of a comprehensive approach combining chemical and biological parameters to assess the effect of road traffic on air quality. It provides the first database in Tunisia referring to MTE contamination and their probable biological effects. This study fills a necessary gap in the literature.