Environmental magnetism of roadside soil contamination in the restricted bijyodaira area of Mt. Tateyama, Toyama, Japan

Environmental magnetic techniques have been shown to be highly useful for investigating roadside pollution in Europe, North America and Asia. However, no studies have reported such magnetic monitoring in Japan. Here we report environmental magnetic results along the Tateyama-Kurobe Alpine route at the Bijyodaira area of Mt. Tateyama in Toyama, which is part of the Special Protection Zone of the Chubu Sangaku National Park. In-field susceptibility measurements from 17 sites (297 points) as well as in-laboratory susceptibility measurements from six sites (75 surface and auger core soil samples) show higher susceptibilities near the roadside and a positive correlation between the susceptibility and heavy metal contents. Also, the concentration of the magnetic minerals and associated heavy metals near the surface shows less vertical downward migration of these materials below 15 cm from surface. Rock magnetic analyses indicate that: (a) the major magnetic minerals are pseudosingle- and multi-domain magnetite and/or titanomagnetite; (b) the closer the road side, the more anthropogenic magnetite is present; and (c) most pollutants derived from the vehicles are deposited within a few metre distances from the road through the area. Overall, the results show that environmental magnetic techniques are suitable for studying pollution associated with vehicle traffic elsewhere in Japan.