Air Pollution Tolerance Index (APTI) and carbon sequestration of selected trees and shrubs for urban development in Akure Ondo State, Southwest Nigeria

Abstract

Urban green space is a collection of trees and shrubs growing in urban area. Green plants are well known for their abilities to reduce air and noise pollution. It is important that plants used for the development of urban landscaping must be tolerant to air pollutants. There must be some criteria to select tolerant plants for urban landscaping design and for that two indices viz. Air Pollution Tolerance Index (APTI) and carbon sequestration can be a good tool. Thus this study was carried out to assess the efficiency of urban trees (Tabebuia rosea, Polyalthia longifolia, Delonix regia and Raphia farinifera) and shrubs (Ficus spp) to tolerate air pollution and potential for carbon sequestration in Akure, Ondo State, Nigeria in 2015. The sites were sampled from Akure City Major Road, from Oloko Junction to Oba-Ile. The plant species identified at the sample area were Ficus spp, Tabebuia rosea, Polyalthia longifolia, Delonix regia and Raphia farinifera. The assessment of the ascorbic acid, pH, relative water content and total chlorophyll content of the leaves of the identified plant species was done to determine the APTI. The APTI of the plant ranged from 5.11 to 9.31 with Tabebuia rosea having the highest value which indicates it's high tolerance of air pollutants from the assessment and Raffia farinifera with the lowest value and least tolerant. The biomass of the trees species were estimated for the quantification of the amount of carbon sequestered and the absorbed CO2 in the plant. Tabebuia rosea also had the highest carbon sequestered (10,074 kg) and Delonix regia having the lowest of 4,702.50 kg.