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

The chemical properties of the atmospheric deposition and soil solution were monitored in a deciduous secondary forest in Kumagaya, Saitama Prefecture, Japan, from June 2000 to July 2001. Mt. Oyama, a volcano in Miyakejima Island, became active at the end of June 2000 and has been emitting volcanic fumes with a large amount of sulfur dioxide (SO2) since the end of August 2000, while no fall of volcanic ash occurred in the Kanto District. Therefore, we aimed at analyzing the effect of the fumes from Mt. Oyama on the chemical properties of the atmospheric deposition and soil solution in Kumagaya, focusing on the behavior of sulfate (SO4 2−). The equivalent ratio of non-seasalt SO4 2−} (nss-SO4 2−) to nitrate (NO3 2−) and also nss-SO4 2− to total anions in atmospheric deposition evidently increased, especially from August to December 2000, compared to the period from June to July 2000. On the other hand, the changes in the SO4 2− concentration in the soil solution appeared to be relatively stable but were delayed in the case of atmospheric deposition. The delay was ascribed to the adsorption of SO4 2− on the surface of soil particles, and Oll ligand exchange associated with the adsorption.