Biomonitoring of volcanogenic fluoride, Furnas Caldera, Sمo Miguel, Azores

High levels of fluoride have been recorded in the ground waters of Furnas Caldera. To investigate the source of this, lichens were collected from the area and used as biomonitors. From the analysis of these samples, it is shown that fluoride enriched volcanic gases are rising along fault zones and being released through the soil, and this is considered to be the most likely source of the fluoride in the ground waters.