Dynamic Olfactometry Measurements of Geothermal Endogenous Gas Emissions

Gaseous emissions which may be of odour impact and interest are not solely derived from industrial processes or agricultural fields, but also from natural sources. Natural odorous gaseous emissions are often present in geothermal areas. In these cases, the inventory and the measurement of the emitted gas flows are not trivial. This work presents the experience of an olfactometric survey conducted in a geothermal-interest area, specifically around Mt. Amiata, Tuscany, Italy. Dynamic olfactometry analyses showed odour concentrations in the order of millions of ouE/m3. While the main constituent of these natural gas emissions was CO2, the very high odour concentration data primarily resulted from the high portion of H2S in these emissions, with detected concentrations ranging from 1,000 to 10,000 ppmv. This not only indicates the presence of odour impact potential but also the high risk for people in the nearby area due to the high concentration of this gas. In parallel with the measurement of representative concentration data of these spot vents, a flexible and innovative approach was established for the measurement of emitted gas flow. The main breakthrough was obtained via the revamping of a balometer, a tool used for the measurement of indoor airflows, in the measurement of the gas flow of large spot vents (i.e. mine gates). Thanks to this stretchy approach, it was possible to estimate the OER of these emissions: the overall OER of all the inventory of the investigated spot vents in the area was impressive, and reached almost 10 million of ouE/s.