The effect of air pollution from nitrogen dioxide (NO2) on epiphytic lichens in Seville, Spain

The effect of air pollution from nitrogen dioxide (NO₂) on the epiphytic lichens of the city of Seville (Spain) has been studied. Indices of air purity (IAP) were calculated, based on the lichen flora ofMelia azedarach L. present at 25 stations distributed through the city. The arrangement and classification of the stations by principal component analysis and cluster analysis, respectively, enabled the study area to be zoned into four zones of air purity. Accordingly, the zonal map of air purity for the city of Seville yields a gradient of air purity that is very steep from the centre to the outskirts. The dependence of 77.6% of IAP variability with NO₂ pollution levels detected with air emission sensors distributed through the city suggests the relationship between NO₂ levels and zones of air purity.