Emerging organic contaminants (EOCs) have become of increasing interest due to concerns about their impact on humans and the wider environment. Karst aquifers are globally widespread, providing critical water supplies and sustaining rivers and ecosystems, and are particularly susceptible to pollution. However, EOC distributions in karst remain quite poorly understood. This study looks at the occurrence of EOCs in the Croatian karst, which is an example of the "classical" karst, a highly developed type of karst that occurs throughout the Dinaric region of Europe. Samples were collected from 17 karst springs and one karst lake used for water supply in Croatia during two sampling campaigns. From a screen of 740 compounds, a total of 65 compounds were detected. EOC compounds from the pharmaceutical (n = 26) and agrochemical groups (n = 26) were the most frequently detected, while industrials and artificial sweeteners had the highest concentrations (range 8-440 ng/L). The number of detected compounds and the frequency of detection demonstrate the vulnerability of karst to EOC pollution. Concentrations of 5 compounds (acesulfame, sucralose, perfluorobutane sulfonate, emamectin B1b, and triphenyl phosphate) exceeded EU standards and occurred at concentrations that are likely to be harmful to ecosystems. Overall, most detections were at low concentrations (50 % <1 ng/L). This may be due to high dilution within the exceptionally large springs of the Classical karst, or due to relatively few pollution sources within the catchments. Nevertheless, EOC fluxes are considerable (10 to 10⁶ ng/s) due to the high discharge of the springs. Temporal differences were observed, but without a clear pattern, reflecting the highly variable nature of karst springs that occurs over both seasonal and short-term timescales. This research is one of a handful of regional EOC investigations in karst groundwater, and the first regional study in the Dinaric karst. It demonstrates the need for more frequent and extensive sampling of EOCs in karst to protect human health and the environment.

The Mediterranean freshwater resources, mostly represented by groundwater, are under increasing pressure due to natural and anthropogenic factors. In this study, we investigated possible negative effects of climate change and land-use practices on water quality and availability from five springs in the karstic catchments in southern Croatia. The investigated springs are used in the regional public water supply system. Firstly, we employed hydrogeochemical field and laboratory analyses to detect possible traces of anthropogenic activity originating from specific land use. Additionally, we performed hydrological and climate modeling to detect changes in the air temperature, precipitation, and runoff. In particular, we used three regional climate models (Aladin, RegCM3, and Promes). The results estimated an increase in the mean annual air temperature, changes in the precipitation patterns, and reductions in runoff in the study area. Hydrochemical analyses showed standard ion concentrations for karst groundwaters, elevated sulfates due to evaporite deposits in the hinterland, surprisingly low nitrate levels which disproved expected agricultural pollution, and high microbiological activity. Significant water losses are expected in the near future which require immediate attention in order to develop adaptation strategies that focus on sustainable utilization and resilience of freshwater resources. This paper was based on the Interreg Central Europe PROLINE-CE project research in the South Dalmatia.

The occurrence of emerging organic contaminants (EOCs) was investigated in vulnerable Dinaric karst catchment of Jadro and Žrnovnica springs in Croatia, under varying flow conditions and across three different water resource types (groundwater, springs, and surface water). The maximal EOCs concentration in both springs were observed following autumn recharge events, while during peak discharge no detection above the limits of detection (LOD) was recorded due to dilution process. Contrarily to springs, groundwater from deep borehole exhibited highest total EOCs concentration under low flow conditions, underscoring the considerable karst aquifer vulnerability and its oligotrophic nature. The peak EOCs concentration in karstic Cetina River coincided with the river's lowest discharge. The highest mass flux of 1013 g/day was determined for very mobile pharmaceutical metformin detected in Cetina. The presence of potentially persistent to very persistent compounds, like DEET and 1H-benzotriazole, which exhibited highest detection frequencies across all sampling sites, was observed in association with varying hydrological conditions. Hypotheses regarding the occurrence of identified EOCs include surface contamination infiltrating directly through ponors and highly karstified areas, potential persistence in the epikarst and aquifer matrix, and site-specific contamination sources for compounds such as 1H-benzotriazole, gabapentin, and ketoprofen found in groundwater. To evaluate the risk of inadvertent human exposure to EOCs across various age groups, we utilized measured spring concentrations and calculated drinking water equivalent levels (DWEL), which ranged from 1.4 μg/L for cotinine to 503 mg/L for sucralose, both detected in Jadro spring. Although EOCs concentrations in ng/L are unlikely to pose a significant risk to healthy population, long-term exposure to EOCs mixture remains unknown. Given scarcity of research on EOCs in karst environments on both global and national levels, our study enhances comprehension of their occurrence and behaviour across different karst water resources that hold crucial importance for drinking water supply in regions like Dinarides.