Abstract Volcanic ash clouds potentially cause damage to aircraft engines. Especially, glassy materials contained in volcanic ash could cause a serious damage. After the 1970s, incidents of ash-related aircraft damage rapidly increased. A significant example is the incident that engines of Boeing 747 was shut down when it flew in a volcanic ash cloud from Mt. Galunggung, Indonesia in 1982. The pilot was unconscious of the ash cloud. In order to prevent such incidents, a world-wide volcanic advisory system was developed. This system has nine Volcanic Ash Advisory Centers (VAACs) in the world and each VAAC monitors volcanic eruptions and provides information concerning the forecasting of movement of volcanic ash clouds over its responsible region. The Tokyo VAAC is in charge of the East Asia and the Northwest Pacific region. The prediction of ash dispersal is calculated using numerical models, however, the precision tends to be overestimation. This could result in excessive regulation of aviation and unnecessary enormous economic loss. Although Japan is a volcanic country, there is no combination system of in-situ monitoring and aviation management which Europe already has. Disaster Prevention Research Institute of Kyoto University has started airborne ash measurement study for Mt. Sakurajima in cooperation with European scientists, aiming at the establishment of a monitoring and prediction system for assisting reasonable aviation management.

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Abstract In various hazards caused by volcanic eruptions, tephra particles (including volcanic ash and lapilli) transported by atmosphere affect widespread areas distant from the volcano. To provide information about predicted ash fall quantity and lapilli fall area for residents, the Japan Meteorological Agency (JMA) renewed the Volcanic Ash Fall Forecast (VAFF) in March 2015. Focusing on relatively large ash and lapilli particles, the VAFFs have operationally used short-term falling simulations based on the JMA Regional Atmospheric Transport Model (JMA-RATM). In this article, grain-size distribution and settling velocity of tephra which have an especially large impact on the accuracy of the fall simulations are described. We show an example of the RATM simulation for the 2011 eruption of Shinmoe-dake volcano and discuss the future work on the modeling and predicting of tephra transport.

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Abstract This paper reviews health hazards caused by volcanic aerosols such as fine volcanic ash and acid mist formed from volcanic gases. Volcanic ash, which is defined as tephra or pyroclastic particles smaller than 2 mm, spreads over a wide area during explosive volcanic eruptions. A certain fraction of fine volcanic ash is classified as PM_2.5 and thus has potential to cause health problems. Volcanic gases also have adverse effects on human health. In particular, sulfur dioxide injected into the stratosphere during a large scale eruption produces massive amounts of sulfuric acid aerosols to cause severe environmental stress on a global scale and possibly increase excess mortality due to cardiopulmonary diseases. This paper describes fundamental properties of volcanic ash and gases from the view point of health effects. This paper also outlines some historical records of volcanic eruptions to show relationships between observed volcanic ash/gas concentrations and resultant health problems. Some fundamental issues are then discussed with the aim of promoting interdisciplinary collaboration to study volcanic aerosols.

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Abstract Volcanic eruptions have wide variety of styles, magnitude, and intensity. The products are also diverse in terms of chemistry, mineralogy, and granulometry. Here the relationship between eruption styles and products is summarized in terms of macroscopic flow and microstructure of magma. The eruption style strongly depends on the degassing history of ascending magma in conduit from depths. The conduit flow depends deeply on the physical properties, especially viscosity, of magma consisting of silicate melt, crystals, and gas that can change largely during eruption. Thus continuous monitoring of volcanic products is fundamental for further understanding and forecast of eruption, and are to some extent successful in obtaining time series data of mass ashfall rate and petrological characteristics.

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Abstract Recently, the importance of electrostatic charging state to particle deposition in the human airways has been suggested. In this study, we developed a measurement method of electrostatic charging state of individual ambient aerosol particles using Kelvin probe force microscopy (KPFM). For KPFM substrates, glass plates were more suitable than PTFE or polycarbonate filters. We collected charged polystyrene latex standard particles with the number of elementary charges between 4 to 11 on the glass plate, and measured the topography and the surface potential using KPFM. The difference in surface potential between the particle top and the glass substrate surface was determined as the particle surface potential. The particle surface potential for positively charged particle was＋50 mV and that for negatively charged particle was approximately－45 mV. For the ambient aerosol particles, the surface potential ranged from－56.6 mV to＋156.7 mV, indicating that the number of elementary charges of ambient aerosol particles analyzed in this study was more than 4. Sequential analysis of KPFM followed by SEM/EDX for a single aerosol particle would be useful to find the relationship between the surface potential and chemical composition of individual particles.

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Abstract Airborne culturable microbial concentration was measured during spring (April-May) and fall-winter (September-December) in 2011, using commercial aerobic count plates (Sanita-kun Aerobic Counts). Mean microbial concentration was significantly lower in spring than in fall and winter. During a 5-day-long dust event, microbial concentration had a correlation (R²＝0.71) with number concentration of coarse particles (＞2 μm). However, the ratio of microbial to particle number concentrations differs in another dust event, and statistical analysis using data throughout the sampling period yielded no significant correlation between them. Appearance of colonies on the count plates suggests that Bacillus was abundant in spring. The difference in microbial concentration between seasons can possibly be attributed to the difference in microbial species. The statistical analysis revealed that, among meteorological elements, temperature (positive), solar insolation (negative), and wind speed (positive) are influential to microbial concentration. The meteorological elements during several hours before the sampling also have significant correlations with microbial concentration. Rainfall apparently has conflicting effects to microbial concentration, thus should be evaluated case by case.

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