Most tolerant roadside tree species for urban settings in humid tropics based on Air Pollution Tolerance Index

Selecting most tolerant roadside trees in different environmental settings help to mitigate air pollution by serving as a sink for gaseous air pollutants and be tolerant for polluted environments. However, in most of the humid tropics, there is no proper mechanism for roadside tree selection in the absence of scientific research. The present study was designed with the objective of assessing Air Pollution Tolerance Index (APTI) of Terminalia catappa (Indian almond), Cassia fistula (Golden shower tree), Pongamia pinnata (Indian beech), Madhuca longifolia (Butter tree) and Peltophorum pterocarpum (Yellow flame tree) using four biochemical parameters; pH, ascorbic acid content, relative water content and total chlorophyll content on leaves. The study was conducted at two environmental settings identified as least polluted and highly polluted in Colombo, Sri Lanka. Environmental settings were identified based on SO2, NO2 and PM (2.5) levels in ambient air. Selected five species with ten replicates from each site were assessed by estimating APTI values. Standard One Way ANOVA followed by Tukey's pairwise comparison was carried out to determine the differences in selected biochemical parameters among five selected roadside tree species at each site. In both sites, highest APTI values were recorded in M. longifolia, followed by P. pterocarpum, T. catappa, C. fistula and P. pinnata.