Assessing air pollution removal by urban tree species in Chulalongkorn University Centenary Park

Abstract

Nowadays, urban populations are growing rapidly leading to urbanization that can increase air pollution emission such as Nitrogen dioxide (NO₂). Some studies have suggested that urban greening could contribute to air pollution reduction in two ways; through leaf stomata uptake of gaseous pollutants and leaf interception of particulate matter. This study has studied air pollution absorbed through leaf stomata uptake, nitrogen dioxide (NO₂), in 4 species of urban trees that planted in Chulalongkorn University Centenary Park (CU 100 Park) includes: Lagerstroemia floribunda (Crepe Myrtle), Afzelia xylocarpa (Black rosewood), Homalium tomentosum (Vent.) Benth (Moulmein lancewood) and Bauhinia purpurea (Orchid Tree). The objective of this study is to estimate the air pollution removal and to compare the air pollution removal between wet and dry season of the four species. We estimated air pollution removal rate by measure stomatal conductance (gs) and environmental factors to calculated NO₂ flux in wet and dry season and to find relationships with environmental factors. We found that NO₂ flux of all species had no difference between wet and dry season (p-value equals 0.08-0.16). The highest NO₂ flux is occurred in Afzelia xylocarpa (Black rosewood). In dry season, linear relationships between wind speed affect to NO2 flux of Afzelia xylocarpa and Lagerstroemia floribunda while, in wet season wind speed were not affected. Therefore, the information from this study can be used to help planners better design and manage urban trees to improve air quality in parks.