GNGTS 2013 - Atti del 32° Convegno Nazionale

phenomena of gases and fluids. Particularly in the first characterized by several point sources of emission of fluids. In addition, along the eastern side of the small hill to the east of this place pool have increased the points of greenhouse gas emissions. Fractures are mostly trending N110-120E and the area is dominated by two main features NW-SE and NE-SW. Also were not observed accumulations of material from surface gravitational movements of recent formation. 24.10.06 The day the area has been the subject of an initial investigation with camera portable thermal, both for carrying out a first thermal relief that identify a favourable area for the installation of a thermal fixing station. On 30 October, the station has been installed TIR Mobile (TITANO: Thermal Infrared Transportable Apparatus for Nearby Observation). The average distance is about 150m field of view which shows an average resolution of pixels of about 15cm. From that date shall be acquired and the control unit of the network TIIMNet 6 images at night. Construction of the gas-line monitoring station (May 16-30 2012, June 1-5, 16-23 2012). The on-line gas monitoring station is localized close to the fumaroles field (100 m). The equip- ment used for on-line monitoring consists of a Quadrupole Mass Spec- trometer (Pfeiffer Omnistar©) for on- line gas analysis, a field computer and a data logger for data storage. Air condition was used to stabilize the temperature of the station and an UPS (Uninterrupted Power Supply) was used for buffering in case of short power cut offs. Silicon tubings, a temperature probe, a gas plastic trap and some additional devices (eg., water trap, connection plastics, metal rings) were also used during the con- struction of the gas line between the station and the bubbling pool. Construction of the gas line: different experimental test Test 1. For the construction of the gas line, a Teflon tube with 6 mm diameter was placed in the main fumaroles (T=114 °C) where gas was discharged. The gas was pumped by a membrane pump located in the monitoring station. Few meters away from the fumaroles, a water trap was installed to condense water vapour, so that only dry gas was admitted to the gas line. Nevertheless, in this test the temperature of the fumaroles was too high and condensation starts already before the water trap and blocked the gas flow. Test 2. In the second test we sampled in a bubbling pool close the main fumaroles. Here we used an inverted gas trap inserted in the pool to collect gas. Gas was pumped by the membrane pump but the problem we had was that the pressure in the gas trap became too low and in this case the gas line was blocked by the rise of mud along the Teflon tube. Test 3. In the third and last test we sampled in a fumaroles situated at a height greater than the other sampling points. This is because its lower temperature allows to have a lower condensation inside the Teflon tube. In fact the best results were obtained by considering this point of sampling. Calibration of the QMS. For quantitative analysis, the QMS was calibrated with air, pure CO 2 , and certified gas mixtures, the composition of which are selected according to the expected nature of gas. With calibration, the measured ion currents are put to a solution matrix with the individual concentrations of the components in the gas to be analyzed to determine sensitivity factors. For calculating the gas concentrations from ion currents, the mass spectrometer Fig. 2 – Quadrupole Mass Spectrometer in the monitoring station. 248 GNGTS 2013 S essione 1.3