Mofettes in Slovenske gorice, Slovenia

Abstract

Natural CO2 Springs and groundwater rich in free gas in Slovenia occur mainly in the Slovenske gorice hills. Within the frame of fieldwork performed in 2014-2015 we investigated 11 springs: Ihovska slatina, Ivanjševska slatina, Lokavska slatina, Polička slatina, Radvenska slatina, Mofette Rihtarovci, mofettes Stavešinske Slepiče, and Strmec, Ujterska slatina, Verjanska slatina and Zekš. The diameter of five uncaptured springs can exceed 4 m, with depression depths of 2 m, but most are smaller. We elaborated bathymetric 3D models of these spring areas, marked degassing locations in a plan view, and evaluated the gas flux according to a subjective, visual five-level scale. We also measured physicochemical parameters of the water. The observed phenomena were classified among mofettes and mineral waters. Two are wet mofettes (Polička slatina and Slepiče) and three dry mofettes (Rihtarovci, Strmec, mofette at Lokavska slatina). These constantly emit cold CO2, hold acid surface or meteoric water, and bare soil or changed Vegetation may also be present. Mineral water consisting of more than 1 g/l of total dissolved solids surfaces at Ihovska, Ivanjševska and Radvenska slatina, and Zekš. It is rich in free CO2, having a flux intensity of 2-4. Verjanska slatina and Ujterska slatina are neither mofettes nor mineral waters. The first, like most others, may be a slatina, having more than 250 mg/l of free CO2 (CO2)g. We found no connection between the depth of the springs and the intensity of gas emissions.