Emerging organic contaminants in springs of the highly karstified Dinaric region.

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.

Groundwater level and electrical conductivity datasets acquired within pumping tests on Ilovik Island in Croatia.

The small karst island of Ilovik is the most southern of inhabited islands in the Croatian part of the Adriatic Sea. During summer tourist season the number of inhabitants increases significantly, and securing the additional freshwater quantities was needed. Given the hydrogeological and geomorphological setting of the island, possibility of brackish groundwater exploitation was considered. Hence, borehole drilling accompanied with pumping tests at three specified locations was carried out. During the pumping tests in two campaigns, groundwater level was measured manually every 2 hours in boreholes, while groundwater electric conductivity and temperature were periodically measured in situ. The sea level was observed at the reference point located near port. Given dataset consists of electrical conductivity, temperature, groundwater and seawater levels. The research article connected with these data (Terzic et al., 2020) provides hydrogeological interpretation of brackish groundwater lens on small karst island.