[H-GG03] Dialogues on natural resources and environment between earth and social sciences

[HGG03-P01] Preliminary results of the spatial resolution of atmospheric particulate matter in Toyama prefecture: A comparison of biomagnetic monitoring and road traffic.

*Kenta Ueki¹, Kazuo Kawasaki¹ (1.University of Toyama)

Keywords:Environmental magnetism, Atmospheric particulate matter, Human activities, Toyama

Biomagnetic monitoring techniques have been used to investigate, the spatial distribution of atmospheric particulate matter in Toyama prefecture. Environmental magnetic studies are reported for the dust deposited on Japanese flowering cherries (Prunus subgenus Cerasus) at 65 sites in Toyama prefecture in 2024. Three to four leaves were collected from each cherry at a height of about 2 meters from the ground, and the collected leaves were directly placed into 7 cm³ non-magnetic plastic cubes for room-temperature magnetic analyses. Additionally, the materials on about ten leaves’ surfaces were wiped off using quartz wool with ethanol and analyzed by low-temperature magnetic experiments. Both room-temperature and low-temperature magnetic analyses indicated the presence of measurable magnetic particles on the leaves at each site. Furthermore, the major magnetic minerals in the samples were single-domain partially oxidized magnetite and/or maghemite, and the magnetic mineralogy is likely consistent throughout the study area. Higher saturation isothermal remanent magnetization (SIRM) intensities were observed in urban areas, particularly in the northern part of Toyama City and the Shinminato area in Imizu City, than in rural or mountainous areas, indicating that magnetic minerals in the dust on the leaves predominantly originated from local activities rather than Asian dust via long-range transportation. The traffic volume within a certain radius of each site was estimated using the KDDI Location Analyzer. The observed SIRM intensities show a positive correlation with traffic volumes, and a higher correlation is observed when the radius is set to between 500 and 600 meters. However, there are some sites where the SIRM intensities do not correspond proportionally with traffic volume, suggesting the effect of local sources other than traffic, such as thermal power plants. These results indicate that local anthropogenic activities are major sources of magnetic minerals in atmospheric particulate matter in Toyama prefecture.