Chemical characters of crater lakes in the Azores and Italy: the anomaly of Lake Albano

Investigations have been carried out on crater lakes in areas of recent volcanism in the Azores and in Italy, with the aim of detecting possible evidence of residual anomalies associated with past volcanic activities; data from crater lakes of Cameroon have been considered for comparison. Among the physical-chemical characters taken into account, the increases of temperature, ammonium and dissolved carbon dioxide with depth are interpreted as providing information about the contribution of endogene fluids to the lake water budgets. The greater extent of such evidence at Lakes Monoun and Nyos (Cameroon) appears associated with the disasters that occurred there during the last decade; some similarities observed at Lake Albano (Italy) suggest a potential instability also for this crater lake.