Paper Title
An Assessment of Air Pollution Tolerance Capability of Common Trees in Chiang Mai city, Thailand

Abstract
Vegetation is highly recognized as an alternative method for removing pollutants mainly through deposition, absorption, and accumulation processes, moreover, they can clean air by providing oxygen to the atmosphere. In this study, seven common tree species in Chiang Mai city were selected for evaluating air pollution tolerance index (APTI). Four important biochemical parameters including ascorbic acid content (AA), total chlorophyll content (TCh), leaf extract pH (LEpH), and leaf relative water content percentage were computed together to calculate the air pollution tolerance index. The study was conducted comparatively in two different seasons, i.e. in the month of October 2016, the highest peak of rain and humidity, and in the March, 2017 the dry and polluted season. Mangifera indica was found to be tolerant, Ficus religiosa, and Butea monosperma were found to be moderately tolerant, while Polyalthia longifolia, Lagestroemia speciosa, and Plumeria rubra were recognized as intermediately tolerant tree species, moreover, Alstonia scholaris was recorded as a sensitive tree species. The results were further statistically analyzed by using t-test showed that at 95% confidence level, there were no significant differences between the means of two seasonal groups of the air pollution tolerance index (APTI) value and biochemical parameters. Index Terms - Air pollution tolerance index, Biochemical parameters, Chiang Mai, Tolerant trees.