Carbon forms in formation waters from the Pannonian Basin, Hungary

The amount of carbon in organic, inorganic and gas (CH4 and CO2) components, and the concentration of dissolved organics like humic substances, short-chain aliphatic acid anions (acetate and propionate), PAHs, phenols volatile with water vapor, alkylphenols, benzene, alkylbenzenes and oil were determined in groups of formation waters from different depths and locations in two adjacent subbasins located in the central part of the Pannonian Basin (southeast Hungary). The proportions of inorganic, organic and gas carbon to total carbon content of water, and the proportion of carbon content in the identified organic compounds to TOC were calculated. These proportions are characteristic of the location of water-bearing formations. The more aromatic character of organic matter together with the high ammonium and low iodide concentrations suggest a more terrestrial sedimentation in the Szeged area than in the Körös area, where the more aliphatic character with low ammonium and high iodide concentrations indicate a more aquatic paleoenvironment. In the Körös area, formation waters are highly depleted in 13C in the whole studied depth interval, compared to the Szeged area. The high negative δ13C values of bicarbonate may be attributed to depletion of 13C in the sediment organic matter of aquatic origin, depletion of 13C in the atmospheric and soil CO2 during the infiltration period before the last glacial, and a longer residence time of water.