The master's thesis examines the impact of organic acids (oxalic, gluconic, citric and malic acid) on five types of carbonate rocks significant to Slovenia's cultural heritage (Unified Lipica limestone, grey Lesno Brdo limestone, lithothamnian limestone, Škofja Loka conglomerate and Sedovec sandstone). The rocks were exposed to acid solutions of varying concentrations (0.1%, 1%, and 5%) over a period of 28 days. Measurements of pH values and solution conductivity enabled the monitoring of chemical reactions, while X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) revealed mineralogical and microstructural changes. The results show that low acid concentrations (0.1%) generally do not cause significant changes, except in the case of oxalic acid, where insoluble calcium oxalates form, maintaining a low pH value in the solution. Higher concentrations (1% and 5%) result in more intense reactions, such as rock dissolution, CO₂ release, and the formation of calcium salts, with citric acid particularly standing out due to extensive calcium citrate production. The most susceptible rocks to dissolution were Sedovec sandstone and lithothamnian limestone, attributed to their higher porosity and specific surface area. Škofja Loka conglomerate, with its heterogeneous composition and uneven texture, dissolves selectively. The pH values of the solutions generally increased as the reactions progressed, except with oxalic acid, where insoluble oxalates preserved the acidity. The conductivity of the solutions depended on the type of acid, as each released specific amounts of ions. Due to complex reactions, the conductivity of solutions varies differently, necessitating further research. This research highlights the importance of understanding the effects of organic acids on rocks, as these interactions are crucial for preserving Slovenia's cultural heritage, where carbonate rocks are often exposed to natural biological influences from microorganisms
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