Long-range transportation and deposition of chemical substances over the Northern Japan Alps mountainous area

The chemical compositions in the snow layers of vertical snow samples collected from six sites in the central mountainous area, Japan, during early spring 2004 were analyzed to investigate the long-range transportation of chemical substances from the Asian continent to the high mountainous areas in Japan. These sites included Iou-zen, at 800 m above mean sea level (AMSL) and in closest proximity to the Sea of Japan: Kongoudou-zan, at 1300 m; Nishi-Hodaka-dake, the Northern Japan Alps at 2200 m; Hachimori-yama, at 2100 m; Kiriga-mine, at 2000 m; and Yatsuga-take, the most inlying site, at 2200 m. The concentration of anthropogenic components in the snow such as non-sea-salt (nss-) SO₄^2-and NO₃^-range from nearly 0 to more than 100 μeq/L. The nss-SO₄^2-/NO₃^-(S/N) ratio in snow typically ranges from 0.3 to 6.3. A considerable number of samples had higher S/N ratios than those found in Tokyo, Japan, at approximately 1.6, whereas some samples had a much higher ratio of approximately 4–6, which is more similar to values found in Beijing, China, at approximately 3.2. The vertical profile pattern variations of chemical components in the snow layers were found to correspond roughly. For example, the concentrations of nss-SO₄^2-in snow was found to reduce exponentially with increasing distance from the Sea of Japan to the Japan Alps, although the value decreased sharply at three sites located monsoon-leeward of the Japan Alps. This suggests that the anthropogenic components transported from the Asian continent with the monsoon were gradually removed from air and deposited in the snow cover as the air masses passed over the Northern Japan Alps.