Comparative microbiological, chemical, and radiological assessment of the sacred spring and immersion pool at the Pergamene Asklepieion

Abstract

Water sources associated with ancient healing centres were historically believed to possess therapeutic properties, yet their physicochemical, microbiological, and radiological characteristics remain insufficiently documented. In this study, the Sacred Spring and the adjacent Roman-period Immersion Pool at the Pergamene Asklepieion (Bergama, Türkiye) were investigated through a comprehensive integrated assessment. Water samples were collected during two critical hydrological periods (Autumn 2024 and Spring 2025) to evaluate seasonal variability and environmental influences on water quality as part of a pilot initiative for long-term monitoring. Arsenic and selected elemental concentrations were determined using ICP-MS, while microbiological quality was assessed based on ISO standards for Escherichia coli , total coliforms, intestinal enterococci, and total viable counts. To evaluate radiological characteristics, radon (Rn-222) and total alpha activity were measured in the water. Main findings revealed a significant seasonal increase in arsenic concentrations in both water sources, with the Immersion Pool reaching 9.49 ppb in Spring 2025, closely approaching the World Health Organization (WHO) guideline value of 10 ppb. While major ions exhibited similar distributions, microbiological analyses indicated a clear distinction: the Sacred Spring remained free of fecal indicators ( E. coli and intestinal enterococci) across both seasons, suggesting a well-protected groundwater source. In contrast, the Immersion Pool showed elevated microbial loads, including detectable E. coli in spring, reflecting higher environmental exposure. Radiological measurements demonstrated that both gross alpha activity (0.010–0.022 Bq/L) and radon concentrations (1.02–5.95 Bq/L) remained consistently below the WHO screening level (0.1 Bq/L) and the EPA regulatory limit (11 Bq/L for radon), indicating no regulatory concern under current conditions. Overall, this research highlights clear differences between the protected Sacred Spring and the environmentally vulnerable Immersion Pool. While the sacred spring maintains a stable profile, the findings establish an essential baseline for the preservation of historical water systems. This study serves as a foundation for future longitudinal research aimed at developing predictive models for the sustainable management of ancient healing waters under changing environmental and climatic conditions. These findings lay groundwork for ongoing monitoring of such heritage waters, stressing the need to safeguard their health and cultural roles amid shifting conditions.