STUDY OF NATURAL CO_2 EMISSIONS IN DIFFERENT ITALIAN GEOLOGICAL SCENARIOS

摘要

Natural gas emissions represent extremely attractive surrogates for the study of CO_2-effects both on the environment and human life. Three Italian case histories demonstrate the possible co-existence of CO_2 natural emissions and people since Roman times. The Solfatara crater (Phlegraean fields caldera, Southern Italy) is an ancient Roman spa. The area is characterized by intense and diffuse fumarole and hydrothermal activity. Soil gas flux measurements show that the entire area discharges between 1200 and 1500 tons of CO_2 a day. In proximity of Panarea island (Aeolian islands, Southern Italy), a huge submarine volcanic-hydrothermal gas burst occurred in November, 2002. The submarine gas emissions locally modified seawater pH (from 8.0 to 5.0) and Eh (from +80 mV to -200 mV), causing a strong modification of the marine ecosystem. Collected data suggest an intriguing correlation between the gas/water vent location/evolution and the main local and regional faults. CO_2 degassing also characterizes the Telese area (Southern Italy), one of the most seismically active segments of the southern Apennine belt with the occurrence of five large destructive earthquakes in the last 500 years. Geochemical surveys in this area reveal the presence of high CO_2 content in ground-water. Carbon isotopic analysis of CO_2 reveal its deep origin, probably caused by the presence of a cooling magmatic intrusion inside the carbonate basement. All the above mentioned areas are constantly monitored since they are densely populated. Although natural phenomena are not always predictable, local people have nevertheless learnt to manage and, in some case, exploit these phenomena, suggesting significant human adaptability even in extreme situations.