engleski

Study of 2H and 18O isotopes as a basis for characterization of a coastal karstic aquifer

Karst encompasses about 50% of the Croatian land territory. The major part of the Croatian karst belongs to the Dinaric Karst and is found at the Adriatic Sea coastline. Carbonate aquifers are the primary source of freshwater in those areas and their protection is of the highest priority. Karst aquifers are sensitive to pollution since pollutants easily enter the groundwater channel system without prior self-purification process that is characteristic for other types of the aquifers. Once pollutants enter the karstic underground they spread through the aquifer very quickly. Therefore, a thorough knowledge of the karst aquifer is essential for a timely and appropriate reaction to possible pollution incidents. Complexity of the karst landforms and groundwater networks requires implementation of a standard hydrogeological monitoring as well as unconventional methods of investigation. Analysis of stable water isotopes 2H and 18O proved to be helpful complementing method to a standard hydrogeological karst studies. We present the results of a two-year systematic analysis of the stable isotope composition of the coastal karst spring Dobrica in the Bakar Bay and rain water collected in the hinterland of the spring. Dobrica is one of the springs under supervision from the local water supply company but it is rarely in use due to sea water intrusions related to rainfall regimes, recharge conditions and sea tides. Occasional contaminations by saline seawater require additional research to better understand Dobrica’s functioning mechanisms. Spring water samples were collected on a weekly basis and rain samples were collected once a month. The stable isotope composition of the karst groundwater was modelled using Gaussian mixture modelling, time series analysis and autoregressive integrated moving average modelling. The main results of the study are: winter precipitation dominates the spring’s recharge, presence of a multiple water masses in the system, mean residence time up to one year and lower mean recharge elevation in comparison to bordering Rječina River catchment.

coastal environmental physics ; coastal karstic aquifer ; stable isotopes ; statistical modelling

nije evidentirano