[A-CC32] 雪氷学

[ACC32-07] Preliminarily environmental magnetic results from a 2024 snow pit in the Midagahara area of Mt. Tateyama, Toyama, Japan

*川崎 一雄¹、高木 泰成¹、堀 雅裕¹、杉浦 幸之助¹、谷川 朋範²、西村 基志³、青木 輝夫⁴ (1.富山大学、2.気象庁気象研究所、3.信州大学、4.国立極地研究所)

キーワード：環境磁気学、雪、大気粒子状物質、立山

Atmospheric pollution often contains measurable magnetic minerals and environmental magnetic monitoring techniques have been shown to be rapid and cost-effective in investigating the spatial distribution of atmospheric particulate matter. Although snowpack is widely used in anthropogenic pollution studies, only a few studies using packed snow have been reported for magnetic monitoring. Environmental magnetic studies are reported on the Midagahara area of Mt. Tateyama in Toyama. Snow pit observations were made on a site ~600 m from the Tateyama Kurobe sightseeing Alpine route on 16-17 April 2024. One obscure dust layer, likely caused by Asian dust events, is recognized by in-situ snow observation. The snow depth at the study site was about 312 cm. 124 samples were collected from the top to bottom of the pit wall using 7 cm³ non-magnetic plastic cubes. The snow samples melted to water at room temperature and then solidified using a superabsorbent polymer. Rock magnetic measurements indicate that the major magnetic mineral in the snow is maghemite, and its composition is nearly the same throughout the snow wall except for the uppermost parts where the major magnetic mineral is partially oxidized magnetite. A comparison of saturation isothermal remanent magnetization (SIRM) intensities and snow grain shape indicates negligible vertical transportation of the magnetic minerals. Therefore, the magnetic minerals are likely preserved sequentially in the snow layers. Although higher SIRM intensities are sporadically observed in the snow pit wall, significantly higher SIRM intensities are observed at the top and bottom of the wall. Based on the relationship between high SIRM intensities and dust concentrations, rock magnetic properties, and the locations of samples, the observed magnetic minerals in the snow wall are likely derived from different sources, including Asian dust and background soils. The results show that environmental magnetic methods using a superabsorbent polymer could effectively monitor atmospheric particulate matter in mountain areas.