Assessment of Air Pollution Tolerance Index of some Tree Species along Osogbo-Iwo Expressway in Osun State, Nigeria

Abstract

Air pollution tolerance index (APTI) can be used to evaluate the extent of air pollution in an environment. Thus this study aims to evaluate the APTI for Tectona grandis, Dacryodes edulis, Gmelina aborea, Terminalia cattapa, Elaies guineensis and Irvingia gabonesis by determining the physiological and biochemical parameters of leaves, sampled from Oba hills forest reserve and Osogbo-Iwo expressway in Osun state. Irvingia gabonesis showed the lowest APTI of 9.96 and 5.24 for experimental and control sites, while Terminalia cattapa and Gmelina aborea showed the highest APTI of 14.52 and 17.27, respectively for experimental and control sites. Dacryodes edulis, Gmelina aborea and Elaeis guineensis APTI increases from experimental site to control site while Terminalia cattapa, Tectona grandis and Irvingia gabonesis showed decrease in APTI values from experimental site to control site. All the trees used in this study showed APTI value below 16 in the experimental site and there was no correlation between relative water content, ascorbic acid content, pH and total chlorophyll when compared to APTI obtained for these tree species (R² = 0.3131, 0.0033, 0.0004, 0.4058). These show that all the trees used in this study are sensitive to gaseous pollutants from vehicular movement and thus can act as bio-indicators of air pollution on this route.