In recent years, it has been reported that microplastics have been detected in various environmental media and in the human body. Atmospheric microplastics (AMPs) are attracting attention as it has been pointed out that air inhalation is the most common route of ingestion into the body. However, to date, there has been no research on AMPs in forest areas either in Japan or abroad, and it was unclear how much AMPs are captured by forest canopies and how they are captured.

　The research group collected leaves of Quercus serrata, a major deciduous broad-leaved tree, from June to August 2022 in a forest on the Nishi-Ikuta Campus of Japan Women's University (Kawasaki City, Kanagawa Prefecture). We developed a new analytical method for AMPs captured on leaves and investigated the mechanism of AMPs capture.

　As a result, AMPs were found to be strongly adsorbed to the epicuticular wax on the leaf surface (a coating structure composed of saturated and unsaturated fatty acids on the leaf surface). It was found that AMPs trapped on the leaf surface could not be completely removed by leaf washing with ultrapure water or ultrasonic cleaning, but could be properly recovered using an alkaline reagent.

　As a result, it was estimated that the entire Japanese Quercus forest (approximately 32,500 km2) captures approximately 420 trillion AMPs in its canopy annually. In addition, urban forests such as street trees and park forests may reduce the risk of AMPs inhalation for humans. It has been shown that there is a possibility that there is an accumulation of

　In the future, it will be necessary to investigate the amount and impact of microplastics on the forest floor and soil, clarify the ability of various tree species to capture AMPs on their leaves, and establish efficient microplastic air pollution countermeasures.

Paper information:[Environmental Chemistry Letters] Alkaline extraction yields a higher number of microplastics in forest canopy leaves: implication for microplastic storage