A Quantitative Assessment of Particulate Matter and Metallic Elements on Leaf Surfaces of Pinus koraiensis, Quercus acutissima, and Quercus serrata

The atmospheric particulate matter (PM) is a concern for public health. Metallic elements in PM can also cause serious health problems, even though metals contribute a small portion to the total mass of PM. Trees have the potential to reduce PM by adsorbing particles on leaf surfaces. We investigated the capacity of trees to capture PM and metal elements on leaf surfaces at the Seoul National University Forest in Mt. Taehwa, South Korea in 2021. Pinus koraiensis, Quercus acutissima, and Quercus serrata leaves were cut, and the PM on leaves was collected by immersing the leaves in deionized water for 1 min (WC: water cleaned) followed by ultrasonic cleaning for 3 and 10 min (UC: ultrasonic cleaned) for oak and pine leaves, respectively. The mass of PM was measured, and the concentrations of metallic elements were measured using ICP-MS. During the severe Asian spring dust in May 2021, 9.1, 14.4, and 3.8 g cm-2 of PMWC (water cleaned PM) were collected on the leaves of P. koraiensis, Q. acutissima and Q. serrata, respectively, whereas 16.7, 7.4, and 1.1 g cm-2 of PMUC (ultrasonic cleaned PM) were collected on those, respectively. The results suggested that ~70% of total PM captured on oak leaf surfaces can be washed by rainfall, and that large PM (e.g., PM10) can be strongly adsorbed on the leaves of P. koraiensis during spring Asian dust. The mass of the elements in PM was in the following order: Ca> K> Zn> Fe> Mg> Al> Mn> Na> Ba> Pb> Sr> Cu> Ni> As> V> Cr> Co> Cd>Be. In general, the mass of metallic elements was larger on the leaves of pine than those of oak trees, indicating that the mass of elements can be dependent not only on atmospheric events (e.g. the period without rains) and the intensity of Asian dust, but also on tree species. The results could be used to select and manage tree species to remove PM in the atmosphere, as Korea Forest Service proposes the expansion of urban forests as a forest management strategy.