Physicochemical Stability of Freshly Extracted Techirghiol Sapropelic Mud During Atmospheric Exposure: Implications for Lakeside Balneotherapy

Freshly extracted Techirghiol sapropelic mud is used in lakeside balneotherapy, where atmospheric exposure may alter its physicochemical characteristics. This study investigated compositional changes during prolonged air exposure, accounting for the influence of dehydration on reported concentrations. Sapropelic sediment homogenized with native lake water was maintained in open containers at approximately 20 °C for 144 h. Moisture, volatile and mineral fractions, organic constituents, organic carbon and nitrogen, and sulfide fractions were assessed at baseline and at 24 h intervals, while individual mineral constituents were evaluated through 72 h. Temporal changes were analyzed descriptively, and concentrations reported on a wet-mass basis were additionally normalized to dry matter using the corresponding moisture measurements. Moisture decreased from 71.24% to 29.11%, accompanied by crust formation, cracking, and loss of homogeneity. Mineral residue increased from 20.36% to 62.45% on a wet-mass basis. Although the wet-mass volatile fraction remained near 8.40%, its calculated dry-mass proportion decreased from 29.21% to 11.85%. Total H2S decreased from 0.1257% to 0.0493%, and the ether-extractable fraction from 1.61% to 0.74%, corresponding to wet-mass reductions of 60.8% and 54.0%, respectively. The corresponding reductions in calculated dry-mass concentrations were 84.1% and 81.3%, respectively. Individual mineral constituents showed comparatively small concentration changes through 72 h. Atmospheric exposure was associated with dehydration and differential compositional changes in Techirghiol mud. Dry-mass normalization revealed changes obscured by wet-mass reporting. Exposure duration and hydration state are relevant variables for physicochemical characterization and handling; these findings do not establish changes in therapeutic efficacy or a maximum permissible exposure time.