Quantifying the potential contribution of urban trees to particulate matters removal: A study in Chattogram city, Bangladesh

Abstract

Urban trees have capacity to reduce atmospheric particulate matters (PM) concentration through deposition on leaves. However, we have very limited studies on the contribution of urban trees toward removal of PM in Bangladesh. In this study, conducted in Chattogram City Corporation (CCC), Bangladesh, we aimed to i) quantify the ambient atmospheric PM (PM2.5 and PM0.50), ii) quantify deposition of PM by urban trees, and iii) find out variation of PM with respect to common tree species, height of trees (low: 2.0–3.5 m and mid: 3.5–4.5 m), leaf traits (shape, surface), and seasons. Monthly air PM concentrations were measured from September 2020 to April 2021 in six sites (viz. roadside, residential, industrial, commercial, medical, and park area) in CCC. For measuring PM deposition, we collected 128 sample leaves from eight randomly selected trees of eight tree species in every month from study sites. At roadside, where relative greenspace was lowest, the atmospheric PM concentration was the highest. Conversely, where relative greenspace was higher (e. g. residence and park), the PM concentration was the lowest. In winter season (December–February), both ambient PM concentrations and deposition on leaves were the highest. Psidium guajava had significantly (p < 0.05) higher PM deposition than other tree species at both height levels. Deposition of PM was highest in trees with oblong and ovate-shaped, and rough-surfaced leaves at lower height, and therefore, recommendation is made to plant trees with these attributes in urban areas.