Physicochemical or geochemical

• Horwell, C. J., Sparks, R. S. J., Brewer, T. S., Llewellin, E. W., Williamson, B. J., (2003), The characterisation of respirable volcanic ash from the Soufriere Hills Volcano, Montserrat, with implications for health hazard, Bulletin of Volcanology, 65, 346-362, 10.1007/s00445-002-0266-6