Influence of volcanic activity on the quality of water collected in roof water catchment systems at Stromboli Island (Italy)

Abstract

With the aim of detailing the interaction between volcanic emissions and water harvesting by Roof Water Catchment Systems (RWCSs), the present work illustrates the results of a study carried out at Stromboli Island, a small but densely populated active volcanic area in the South of Italy. Concentrations of major and trace elements determined in RWCS waters and sediments revealed clear clues of a contamination with gases and suspended particles of volcanic origin, even if the values of those contaminants considered by the World Health Organization as dangerous for human health are always belowtheMaximumAdmitted Concentration (MAC). In particular, cistern water showed a composition similar to local coastal rainwater, with dissolved ions related not only to sea aerosol but also to volcanic gases and ash leaching,with a secondary enrichment in Ca ions due to the interactionwith the limewashed surfaces of both roofs and cisternwalls. The simulation of the potential increase in dissolved chemical species due to volcanic ash deposition on the water catchment surfaces indicates the possible exceedance of the MAC for several species. The symptoms of fluorosis affecting elderly people who were young at the time of the 1930–40 volcanic crisis is a clue of a possible volcanogenic fluorine contamination. On the other way, the simulation of the digestion process on solid volcanogenic particulate ingested with drinkingwater highlighted a potential dramatic increase (orders of magnitudes) of dangerous element concentrations in stomach fluids above theirMACs. Despite the evidence of potential health risks induced by volcanic activity, no anamnesic evidence of related pathologies has been found among Stromboli population. This apparent discrepancy is solved taking into account the positive feedback among the good practice in maintaining clean conditions in the harvested waters and the prevalent fallout of volcanogenic ashes away from the main inhabited areas, favoured by the morphological setting of the island and its wind regime.