TY - THES

T1 - Hydrochemical Characterisation of Groundwater Systems in Upper Austria

AU - Hartl, Irene

N1 - no embargo

PY - 2018

Y1 - 2018

N2 - The North Alpine Foreland Basin in Upper Austria holds a manifold geogene potential. Shallow sedimentary aquifers are used for water supply, whereas Jurassic Carbonates (Malm) and Oligocene Linz Sands bear thermal waters utilised as a source of energy and for balneological purposes. Additionally, hydrocarbons are recovered from different stratigraphic horizons and gases are stored, respectively. In order to characterise different aquifers in this region and to identify zones of potential mixing between deep geothermal and shallow meteoric groundwater, water samples from different aquifers were investigated. The analytical programme consisted of measurements of the hydrochemical composition, the stable isotopic composition of the water, an investigation of the gas content coupled with a determination of the isotopic signature of these gases. Moreover, 14C and 13C contents of selected water samples were measured. In total, 32 waters were sampled from two springs and one well in the Bohemian Massif, Quaternary deposits (2 samples), Ottnangian sediments south of the Bohemian Massif outcrop (Ottnangian Sandstone: 10 samples; Ottnangian Schlier: 6 samples; Atzbach Sands: 3 samples), Linz Sands (4 samples), Rupelian Sands (1 sample) and from Malmian Carbonates (3 samples). Based on the measured parameters, the water samples can be categorised into four different groups: Group I contains waters from the Bohemian Massif and one sample from the Atzbach Sands which is characterised by a low mineralisation and presumably recharged from the Bohemian Massif. The total mineralisation of the Ca-Mg-HCO3-type waters ranges between 55-222 mg/l. The samples summarised in Group II are of the same type as Group I, however, their amount of total dissolved solids is increased (204-507 mg/l). Variations in the measured ion contents of this group are probably caused by facial differences and anthropogenic influences. The samples of Group III are characterised by cation exchange and assigned as Na-HCO3-type. The dissolved mineral content ranges between 395-436 mg/l, similar to the waters of Group II. The samples from Group III show higher water temperatures and lower contents in 14C, though. Moreover, stable isotope measurements imply an entry into the aquifer during a glacial period. These characteristics could indicate a mixture with Malmian thermal water. The ion concentration of Na-HCO3-(Cl) waters assigned to Group IV varies between 961-1409 mg/l (Malm) and 526-648 mg/l (Linz Sands, Rupelian), respectively. One water sample of this group originates from a shallow well in Andorf. The stable isotope values of the waters suggest a Pleistocene infiltration into the aquifer. The observed mixture with thermal waters in Andorf shows that the existing thermal aquifer model needs to be revised. The analysed gas samples contain traces of methane in the Innviertel Group (Group II and III) and Linz Sands (Group III). The thermal water samples and the water in Andorf are characterised by significantly higher amounts of methane (Group IV). Additionally, higher hydrocarbons were detected in four water samples. The isotopic signatures suggest a biogenic origin of the methane of shallow strata whereas the Malmian gases are composed of a mixture between thermogenic and biogenic natural gas. Upper Austria as well as Bavaria could serve as provenance areas for these thermogenic hydrocarbons.

AB - The North Alpine Foreland Basin in Upper Austria holds a manifold geogene potential. Shallow sedimentary aquifers are used for water supply, whereas Jurassic Carbonates (Malm) and Oligocene Linz Sands bear thermal waters utilised as a source of energy and for balneological purposes. Additionally, hydrocarbons are recovered from different stratigraphic horizons and gases are stored, respectively. In order to characterise different aquifers in this region and to identify zones of potential mixing between deep geothermal and shallow meteoric groundwater, water samples from different aquifers were investigated. The analytical programme consisted of measurements of the hydrochemical composition, the stable isotopic composition of the water, an investigation of the gas content coupled with a determination of the isotopic signature of these gases. Moreover, 14C and 13C contents of selected water samples were measured. In total, 32 waters were sampled from two springs and one well in the Bohemian Massif, Quaternary deposits (2 samples), Ottnangian sediments south of the Bohemian Massif outcrop (Ottnangian Sandstone: 10 samples; Ottnangian Schlier: 6 samples; Atzbach Sands: 3 samples), Linz Sands (4 samples), Rupelian Sands (1 sample) and from Malmian Carbonates (3 samples). Based on the measured parameters, the water samples can be categorised into four different groups: Group I contains waters from the Bohemian Massif and one sample from the Atzbach Sands which is characterised by a low mineralisation and presumably recharged from the Bohemian Massif. The total mineralisation of the Ca-Mg-HCO3-type waters ranges between 55-222 mg/l. The samples summarised in Group II are of the same type as Group I, however, their amount of total dissolved solids is increased (204-507 mg/l). Variations in the measured ion contents of this group are probably caused by facial differences and anthropogenic influences. The samples of Group III are characterised by cation exchange and assigned as Na-HCO3-type. The dissolved mineral content ranges between 395-436 mg/l, similar to the waters of Group II. The samples from Group III show higher water temperatures and lower contents in 14C, though. Moreover, stable isotope measurements imply an entry into the aquifer during a glacial period. These characteristics could indicate a mixture with Malmian thermal water. The ion concentration of Na-HCO3-(Cl) waters assigned to Group IV varies between 961-1409 mg/l (Malm) and 526-648 mg/l (Linz Sands, Rupelian), respectively. One water sample of this group originates from a shallow well in Andorf. The stable isotope values of the waters suggest a Pleistocene infiltration into the aquifer. The observed mixture with thermal waters in Andorf shows that the existing thermal aquifer model needs to be revised. The analysed gas samples contain traces of methane in the Innviertel Group (Group II and III) and Linz Sands (Group III). The thermal water samples and the water in Andorf are characterised by significantly higher amounts of methane (Group IV). Additionally, higher hydrocarbons were detected in four water samples. The isotopic signatures suggest a biogenic origin of the methane of shallow strata whereas the Malmian gases are composed of a mixture between thermogenic and biogenic natural gas. Upper Austria as well as Bavaria could serve as provenance areas for these thermogenic hydrocarbons.

KW - Hydrochemie

KW - Nordalpines Vorlandbecken

KW - Oberösterreich

KW - meteorisches Wasser

KW - Thermalwasser

KW - Erdgas

KW - Hydrochemistry

KW - North Alpine Foreland Basin

KW - Upper Austria

KW - Meteoric Water

KW - Thermal Water

KW - Natural Gas

M3 - Master's Thesis

ER -