PS 16-154 - A quantitative assessment of atmospheric PM and metallic elements on leaf surfaces of Pinus koraiensis, Quercus acutissima, and Quercus serrata

Background/Question/Methods

The atmospheric particulate matter (PM) is a concern for public health. Metallic elements in PM can cause fatal illness although metals contribute a small portion to the total mass of PM. Trees can remove PM by adsorbing the particles on leaf surfaces. We investigated the capacity of trees to capture PM and metallic elements on leaf surfaces at the Taehwa Research Forest near Seoul, South Korea. Pinus koraiensis, Quercus acutissima, and Quercus serrata leaves were taken six times from February to November in 2021. The PM on leaves was desorbed 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.

Results/Conclusions

On average, 9.6, 13.2, and 6.0 μg cm^-2 of PM_WC (water cleaned PM) were collected from the leaves of P. koraiensis, Q. acutissima, and Q. serrata, respectively, whereas 9.1, 6.7, and 3.0 μg cm^-2 of PM_UC (ultrasonic cleaned PM) were collected from those, respectively. The results suggested that PM captured on oak leaf surfaces could be easily washed off by rainfall compared to that on pine leaf surfaces. The amount of the elements in PM per unit area of a leaf (nmols cm^-2) was in the following order: Ca > K > Zn > Fe > Mg > Al > Mn > Na > Ba > Pb > Sr > Cu > Ni > As > V > Cr > Co > Cd >Be. Enrichment factors of Cd, Pb, Ni, Cu, As, Zn, and Co were higher than those of the other metallic elements, suggesting that they were derived from anthropogenic activities. The results strongly indicate that the amount of the elements adsorbed on tree leaves can be dependent not only on atmospheric events (e.g., the period without rains), but also on tree species.