Visualization of Artificially Deposited Submicron-sized Aerosol Particles on the Surfaces of Leaves and Needles in Trees

Abstract

To understand the effect of aerosols on the growth and physiological conditions of trees in forests, it is important to know the state of aerosols that are deposited on the surface of the leaves or needles. In this study, we developed methods of visualization of submicron-sized aerosols that were artificially deposited from the gas-phase or liquid phase onto tree leaves or needles in trees. Firstly, we used field-emission scanning electron microscopy (FE-SEM) to observe black carbon (BC) particles that were artificially sprayed onto the leaves or needles. The distribution of BC particles deposited on the leaves and needles were distinguished based on the size and morphological features of the particles. The distribution and agglomerates size of BC particles differed between two spraying methods of BC particles employed. Secondly, we tried to visualize gold (Au) particles that were artificially sprayed onto the leaves using energy dispersive X-ray spectrometry (EDX) coupled to FE-SEM. We detected the Au particles based on the characteristic X-ray spectrum, which was secondarily generated from the Au particles. In contrast to the case of BC particles, the Au particles did not form agglomerates and were uniformly distributed on the leaf surfaces. The present results show that our methods provide useful information of adsorption and/or behavior of fine particles at the submicron level on the surface of the leaves.

Visualization and Localization of Submicron-Sized Ammonium Sulfate Particles on Needles of Japanese Larch (Larix kaempferi) and Japanese Cedar (Cryptomeria japonica) and Leaves of Japanese Beech (Fagus crenata) and Japanese Chinquapin (Castanopsis sieboldii) after Artificial Exposure

“…We previously conducted an exposure experiment on leaf and needle surfaces to submicron-sized black carbon (BC) particles to clarify the effects of BC particles on forest trees species [13][14][15]. We also developed a visualization method to determine the deposition and localization of submicron-sized BC particles on tree leaves and needles using field-emission scanning electron microscopy (FE-SEM) [13]. Our findings revealed that (1) carbon-based particles were aggregated on leaves, and (2) carbon-based particles were deposited on the sparse waxy structural area in Cryptomeria japonica [14].…”