In-situ analysis of the gas-emissions of the Eastern Carpathians (Romania) using the Multi-Gas instrument

The Multi-Gas instrument is an important tool for the investigations and monitoring of volcanic systems world- wide, because it can be easily placed on a volcano and can provide real-time data on the compositional changes of the fluids that are released (Aiuppa et al., 2005, Shinohara et al., 2005). We used a specially designed Multi-Gas to gather in situ compositional information about low-temperature, CO2-rich gases, emerging from different manifestations like dry gas emissions (mofettes), bubbling pools and springs. The instrument is equipped with two IR sensors for CO2 (0-100%) and CH4 (0-7%) and one electrochemical sensor for H2S (0-200 ppm). The Multi-Gas was used during several field surveys between September-November 2018 across the Eastern Carpathians area, where a total of 69 gas emissions were investigated for their CO2, CH4 and H2S concentrations. Concentrations of the different gas-species varied according to the geological context. The CO2 concentrations varied between 0.96 and 98.08 %. The highest values were measured in the the volcanic area of Ciomadul, the youngest volcano of the Eastern Carpathians (32 kyr, Harangi et al., 2015), characterized by high CO2 gas output up to 8700 t/year (Kis et al., 2017). High values were measured also in the thrusted and folded area of the Carpathian Flysch and, suggesting the tectonic control over the appearance of the gas emissions. The CH4 concentrations ranged between 0.21 and 6.76% and were higher at hydrocarbon-prone areas, such as the sedimentary deposits of the Transylvanian Basin and Carpathian Flysch. In these cases the CO2 concentrations were low (up to 4.6%). The concentrations of H2S were higher at the volcanic area of Ciomadul, reaching values above the detection limit (∼200 ppm). The Multi-Gas proved to be useful tool in the in-situ investigation of cold gas emissions of the Eastern Carpathians, being efficient especially for the measurement of the H2S concentrations that are very sensitive for oxidation processes. This research belongs to the scientific project supported by the OTKA, K116528 (Hungarian National Re- search Fund), the EU and Hungary, co-[U+FB01]nanced by the European Regional Development Fund in the project GINOP-2.3.2-15-2016-00009 ‘ICER’, New York Hungarian Scientific Society and the Deep Carbon Observatory. Aiuppa, A., Federico, C., Giudice, G., Gurrieri, S. 2005, Chemical mapping of fumarolic field: La Fossa Crater, Vulcano Island (AeolianIslands, Italy), Geophysical Research Letters, Vol. 32, LI3309 Harangi, Sz., Lukács, R., Schmitt, A.K., Dunkl, I., Molnár, K., Kiss, B., Seghedi, I., Á. Novothny, Molnár, M. 2015, Constraints on the timing of Quaternary volcanism and duration of magma residence at Ciomadul volcano, east-central Europe, from combined U-Th/He and U-Th zircon geochronology, Journal of Volcanology and Geothermal Research, 301, 66-80 Kis B.M. , Ionescu, A., Cardellini, C., Harangi, Sz., Baciu, C., Caracausi,C. & Viveiros, F. 2017, Quan- tification of carbon dioxide emissions of Ciomadul, the youngest volcano of the Carpathian-Pannonian Region (Eastern-Central Europe, Romania), Journal of Volcanology and Geothermal Research, 341, 119–130 Shinohara, H. 2005, A new technique to estimate volcanic gas composition: plume measurements with a portable multi-sensorsystem, Journal of Volcanology and Geothermal Research, 143, 319– 333