Long-term continuous monitoring of the dissolved CO₂ performed by using a new device in groundwater of the Mt. Etna (southern Italy)

• Published in: Water research (Oxford) Vol. 45; no. 9; pp. 3005 - 3011
• Main Authors: De Gregorio, Sofia, Camarda, Marco, Longo, Manfredi, Cappuzzo, Santo, Giudice, Gaetano, Gurrieri, Sergio
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-04-2011; Elsevier
• Subjects: air temperature; Applied sciences; Carbon dioxide; Carbon Dioxide - analysis; Carbon Dioxide - chemistry; Devices; Dissolution; drainage; Drainage facilities; Environmental Monitoring - instrumentation; Environmental Monitoring - methods; Exact sciences and technology; Fresh Water - chemistry; Groundwater; Italy; laboratory experimentation; Membranes; Membranes, Artificial; Monitoring; Pollution; Seismic phenomena; volcanic activity; Volcanic Eruptions; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - chemistry; Water treatment and pollution; Italy; Europe; Short term; Natural origin pollution; Polymeric membrane; Carbon compound; Carbon dioxide; Dissolved CO; Long term; Operating conditions; Surveillance; Trend analysis; Geogenic factor; Groundwater monitoring; Gas exchange; Measurement accuracy; Gas—water exchange; Ground water
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2011.03.028

We present a new device for continuous monitoring of the concentration of CO₂ dissolved in water. The device consists of a tube made of a polymeric semi-permeable membrane connected to an infrared gas analyser (IRGA) and a pump. Several laboratory experiments were performed to set the best operating condition and test the accuracy of measurements. We used the device for performing 20 months of continuous monitoring of dissolved CO₂ concentration (DCC) in groundwater within a drainage gallery at Mt. Etna. The monitored groundwater intercepts the Pernicana Fault, along which degassing is observed related to volcano-tectonic activity. The acquired data were compared with continuous and discrete data obtained using existing methods. The measurements of DCC resulted in some period of the year well correlated with air temperature. We also found that long-term trends, as well as short-term variations, are probably linked to the dynamics of volcanic activity and/or perturbations in the local or regional stress fields.