Using calcicolous and corticolous lichens to assess lead and cadmium air pollution of the moroccan atlantic coast safi-essaouira

Abstract

Air pollution by metallic trace elements (MTE) has evolved in recent years in Moroccan cities – especially those with significant industrial activities. Biological tools, especially the use of lichens as a bioindicator of heavy metal air pollution, have been receiving world-wide attention. This study aims to evaluate atmospheric pollution of the Moroccan Atlantic coastline Safi-Essaouira using lichen as monitors of atmospheric metal contamination. Thus, two trace elements (lead and cadmium) were analysed through biomonitoring by two calcicolous lichens, Xanthoria calcicola and Ramalina pollinaria, and two corticoulous lichens, Xanthoria parietina and Ramalina lacera. The results show that the concentrations of the two trace elements in lichen samples were relatively higher in urban and industrial sites than in rural sites. The maximum lead levels were 30.18 mg/kg, 4.36 mg/kg, 9.79 mg/kg and 3.35 mg/kg respectively in Xanthoria calcicola, Ramalina pollinaria, Xanthoria parietina and Ramalina lacera. The maximum cadmium levels were 0.53 mg/kg, 0.19 mg/kg, 0.58 mg/kg and 0.37 mg/kg respectively in Xanthoria calcicola, Ramalina pollinaria, Xanthoria parietina and Ramalina lacera. Three levels of air quality have been deduced in the studied area: poor air quality in the industrial site of Safi city, medium air quality in peri-urban areas, and good air quality in rural sites.