Effect of volcanic fumes from Mt. Oyama, Miyakejima Island, on atmospheric deposition, soil solution, and soil properties in Kumagaya, Central Japan

Abstract

Mt. Oyama, a volcano in Miyakejima Island, became active at the end of June 2000 and began emitting volcanic fumes with a high amount of sulfur dioxide (SO₂) at the end of August 2000. Emission of volcanic fumes was still observed in August 2002. We aimed at analyzing the soil properties in Kumagaya in relation to the effect of the volcanic fumes from Mt. Oyama. A soil survey was conducted in a deciduous secondary forest in Kumagaya, Saitama Prefecture, Japan in September 2001, and the physical and chemical properties of the soil were analyzed. The soil in the research plot consisted of volcanic ash soil. However, the properties were markedly different between the topsoil and subsoil. For example, the base saturation values in the A and Bwl horizons were very low, 1.7 and 0.85%, respectively, while the value in the Bw2 horizon was 29%. The soils in the A and Bw1 horizons displayed a considerable anion exchange capacity (AEC) under the field conditions, and the amount of exchangeable sulfate (SO₄ ²⁻) accounted for 37% of the AEC in the A horizon. The AEC of the A horizon was considered to have brought about a delay in the changes in the SO₄ ²⁻ concentration in the soil solution at the depth of 10 cm compared to the changes in the SO₄ ²⁻ concentration in the throughfall (TF). One of the major features of the soil in the research plot was that it had already adsorbed a large amount of SO₄ ²⁻ compared with the annual deposition load of SO₄ ²⁻ from the atmosphere; the ratio of the adsorbed SO₄ ²⁻ pool to the annual SO₄ ²⁻ deposition was approximately 60 in the Bw1 horizon. Therefore, the volcanic fumes with a high amount of SO₂ from Mt. Oyama were considered to have exerted a negligible effect on the soil properties in the research plot, whereas the fumes affected the properties of atmospheric deposition and upper soil solution in the research plot.

Key Words:

• Mt. Oyama (Miyakejima Island)
• soil property
• sulfate
• sulfur dioxide
• volcanic ash soil