Integration of In Situ Experiments and Numerical Simulations to Reveal the Physicochemical Circumstances of Organic and Inorganic Precipitation at a Thermal Spring

Abstract

Organic and inorganic precipitates are both characteristic in the active hypogenic karst area of Buda Thermal Karst in Hungary. As an active system, it is a good natural laboratory to study ongoing precipitation processes. Because of anthropogenic influence and the complexity of spring environments, it is challenging to reveal all the governing factors in the process of precipitation. In situ experiments, i.e. artificially controlled natural systems simplify the complexity by adding, excluding or stabilizing influencing parameters during the experiment. CO 2 degassing drives changes in the physicochemical parameters of spring waters from the discharge along their flow path. The rate and spatial extension of these changes depend on local hydrogeological, geological, climatic, topographical etc. factors, affecting precipitation processes. In this study, two one-day-long in situ experiments were executed to examine the physicochemical parameter changes of thermal water in a tunnel. The integration of the results with reactive transport models revealed the physicochemical processes of ingassing and degassing and predicted CaCO 3 precipitation along the flow path. Small-scale roughness of the channel surface seemed to further influence pH and concentration of HCO 3 −. After 6 weeks of thermal water flowing, organic precipitate (biofilm) formed close to the discharge and then, with a sharp change, inorganic precipitate (calcite) dominates a bit further from the discharge. In situ experiments and connected numerical simulations revealed the role of CO 2 degassing and calcite precipitation in the changes of physicochemical parameters, but organic precipitates also have to be considered near the discharge.

INVESTIGATION OF A FLOWSTONE-LIKE HISTORICAL INDOOR-TRAVERTINE (RUDAS SPA, BUDAPEST, HUNGARY) USING THE 14C “BOMB-PEAK”

“…Recently, carbonate precipitation still occurs in active thermal springs and spas of the Gellért Hill area (cf. Virág et al 2013aVirág et al , 2013bKovács-Bodor et al 2018.…”

Szemelvények az elmúlt két évtized ELTE-n végzett, medenceléptékű hidrogeológiai kutatásaiból

“…E folyamatok és a ha tásukra kialakuló jelenségek rendkívül szerteágazóak az ásvány-és szénhidrogéntelepek képződésétől a barlangok kialakulá sán, biogeokémiai kiválásokon, ökoszisztémákon és a geo termális jelenségeken át egészen a tektonikai mozgásokig (pl. TÓTH 1999, INGEBRITSEN et al 2006, KLIMCHOUK 2007, TÓTH 2009a, ERŐSS et al 2012a, Kovács-BODOR et al 2018. Ez egyúttal felkínálja a felszín alatti víz-és fluidumáramlások közvetett, az általuk okozott földtani és környeze ti jelensé gek megértésén alapuló kutatási lehetőségét.…”