Biological Monitoring of Air Pollutants (Ozone and Nitrogen Dioxide) by Lichen(Lecanora muralis)

Lichens are composite organisms formed by a fungus and a green alga and / or a blue-green bacterium. They are recognized as being very sensitive to atmospheric pollution and respond to factors that influence human and environmental healths. Since 1860، lichen has been identified as a biological indicator to detect air pollution in Great Britain and Europe. Lichens have the high sensitivityto nitrogen dioxide، ozone، fluorine and heavy metals. The purpose of this study was lichen’s chlorophyll changes in contact with different concentrations of O3 and NO2 pollutants in urban environments. Lecanora muralis transported into special bags in contact with O3 gas at concentrations of 30، 100 and 200 ppb and NO2 gas at concentrations 60، 100 and 200 ppb respectively. After one and three hours، they moved to the laboratory. Their chlorophyll (chlorophyll a، b، chlorophyll a + b and the ratio OD435 / OD415) was extracted by immersion of the building 20 mg weight lichens in 10 ml DMSO solution. Data was analysed to evaluate the correlation and changes in amount of pollutants and concentrations of chlorophyll degradation. Destruction of chlorophyll with positive correlation (P <0. 05) In samples exposed to O3 and damage of chlorophyll in contact with NO2 hawith a negative correlation، level P> 0. 05 were observed. This study showed that Lecanora muralis can be used as a biological indicator in monitoring emissions of ozone and NO2 in urban area.