[M-IS11] 山の科学

[MIS11-03] Preliminarily environmental magnetic results from a snow pit in the Midagahara area of Mt. Tateyama, Toyama, Japan.

*川崎 一雄¹、平野 瑠香¹、堀 雅裕¹、杉浦 幸之助¹、谷川 朋範²、庭野 匡思²、足立 光司² (1.富山大学、2.気象庁気象研究所)

キーワード：環境磁気、雪、大気汚染、立山

Atmospheric pollution often contains measurable magnetic minerals and environmental magnetic monitoring techniques have been shown to be rapid and cost-effective methods for investigating spatial distribution of air pollution. Although snowpack acts as a seasonal storage of contaminants and is widely used in anthropogenic pollution studies, only a few studies using packed snow have been reported for magnetic monitoring. Here, environmental magnetic studies are reported for the Midagahara area of Mt. Tateyama in Toyama. Snow pit observations at the Midagahara were made on a site ~600 m away from the Tateyama Kurobe sightseeing Alpine route, the only available road in the area, on 16-17 April 2023. Three dust layers, likely caused by Asian dust events, are recognized by in-situ snow observation. The snow depth at the study site was about 241 cm. 99 samples were collected from the top to bottom of the pit wall using 7 cm³ non-magnetic plastic cubes. The collected snow melted to water at room temperature and then it was solidified using a superabsorbent polymer. Rock magnetic measurements indicate that the major magnetic mineral in the snow is partially oxidized magnetite and its composition is nearly the same throughout the snow wall. In addition, high coercivity magnetic minerals such as hematite are also found at the upper part of the wall. The higher saturation isothermal remanent magnetization (SIRM) intensities are observed mostly at the upper part of the wall, suggesting larger amounts of magnetic minerals at the upper part. The continuous higher SIRM intensities at the upper part are most likely from the snow removal vehicles rather than sporadic supplies of Asian Dust-derived magnetic minerals. The results show that environmental magnetic techniques can be applied to packed snow by using a superabsorbent polymer and this could be an effective method for monitoring pollution in mountain areas.