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Nunzia Voltattorni, Istituto Nazionale di Geofisica e Vulcanologia (Italy)
Daniele Cinti, Istituto Nazionale di Geofisica e Vulcanologia (Italy)
Luca Pizzino, Istituto Nazionale di Geofisica e Vulcanologia (Italy)
Fedora Quattrocchi, Istituto Nazionale di Geofisica e Vulcanologia (Italy)
Alessandra Sciarra, Istituto Nazionale di Geofisica e Vulcanologia (Italy)
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The near-surface leakage processes can provide opportunities for the study and prediction of the possible consequences of gas leakage from geological sequestration sites of anthropogenic CO2 (i.e., the return to surface potentially causing localised environmental problems). Natural CO2 occurrences are common across Italy and their distribution is mostly controlled and associated to Tyrrhenian volcanism. Different examples of natural CO2 accumulation and leakage have been studied in order to better understand near-surface processes, to assess potential impacts on ecosystems (on a scale not easily replicated experimentally) and to develop new monitoring systems to detect in real time increases in CO2 escaping along vertical migration pathways. These include a comparison among different Italian geological scenarios characterised by: i) CO2-rich waters both at depth and in springs. This is the case of Telese area (Southern Italy), one of the most seismically active segments of the Southern Apennine belt. Geochemical surveys in this area, has revealed the presence of high CO2 content in ground-water. Carbon isotopic analysis of CO2 revealed its deep origin probably caused by the presence of a cooling magmatic intrusion inside the carbonatic basement.; ii) dry CO2 gas vents at Tor Caldara area (Latium, Central Italy), a natural reserve pertaining to the "Ardea Basin" fault system, where CO2 flux distribution is controlled by preferential migration pathways such as fault and fracture networks, as well as at the Solfatara crater (Phlegraean Fields, Southern Italy), an ancient Roman spa, 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 CO2 a day. Volcanic-hydrothermal activity characterises also Panarea island (Aeolian islands, Southern Italy). Submarine gas emissions have chemically modified seawater causing a strong modification of the marine ecosystem. All of the collected gases are CO2-dominant (maximum value: 98.43 vol. %).
All these sites are CO2-leaking and they represent natural laboratories for the direct study of the micro and macro scale migration of gas. The shallow subsurface may be the last barrier before CO2 escape to the atmosphere. A detailed understanding of gas migration in this environment is therefore important to assess risk to human health and the environment.
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