Dust captured by a canopy and individual leaves of trees in the tropical mixed deciduous forest: Magnitude and influencing factors

Abstract

Forest tree leaves play a significant role in air purification, but forest fires could offset the dust sink role. This study aims to assess the functions of the forest in atmospheric dust sink and source and assess the dust capturing capacity of individual leaves of various tree species in the tropical mixed deciduous forest in the dry season (November 21, 2021, to January 23, 2022), along with its influencing factors—climatic variables, environmental variables, and leaf morphology. The result shows that the downward flux or the forest dust sink role was predominant midday when air–mass turbulence played a role. Nonetheless, net mass PM₁ and PM₁₀ concentration trapped by the forest canopy was low, 0.79 and 2.24 µg m⁻³, respectively. For PM_2.5, forest fires could outrun the PM_2.5 sink role for the entire dry season. Considering the individual tree leave, maximum dust capturing capacities for the forest trees ranged from 0.95 to 5.197 g m⁻². Leaf dust capturing capacity was enhanced under cold and dry weather, strong winds, and for trees with defoliated or irregular shape. Leaf/leaflet enhancing the dust capturing capacity exhibited large size; either thick and leathery texture (Coriaceous) or thin, semi-translucent, membrane-like texture (Membranaceous); indumentum top being short, stiff trichomes (Scabrous); or indumentum bottom surface being densely short, soft trichomes (Tomentose). The various dust capturing dynamics among tree species could benefit dust capturing by the forests in the dry season.