Assessment of tree species resistance to air pollution around a metal-scrap recycling factory using air pollution tolerance index and anticipated performance index

Air pollution is one of the major global tribulations in many developing cities around the world. This study evaluates pollution resistance of Terminalia catappa, Anacardium occidentale and Tectona grandis growing around a metal scrap-recycling factory in Osun state, Nigeria using air pollution tolerance index (APTI) and anticipated performance index (API) with the view of recommending the species for greenbelt development in urban spaces. Biochemical parameters such as ascorbic acid, total chlorophyll content, foliar extract pH and relative water content were analyzed in fresh leaves harvested from the tree species growing around the metal-scrap recycling factory (ES) and a relatively unpolluted control site (CS). APTI and API were obtained from the results of biochemical variables. The results showed that biochemical parameters (ascorbic acid, total chlorophyll, foliar extract pH and relative water content) and APTI varied significantly (p<0.05) among tree species and between the sites. The order of APTI varied as T. catappa (15.66) > A. occidentale (13.53) > T. grandis (13.17) with plants having a higher index at CS than at ES. All three-tree species showed intermediate tolerance but T. catappa and A. occidentale were assessed as good performers while T. grandis performed moderately in polluted sites. The study recommended T. catappa and A. occidentale over T. grandis for use in developing greenbelts in urban centres especially in highly polluted areas, such as the vicinity of factories