Groundwater responses to recharge in the Gacka Area, Croatia, as revealed by stable isotopes, tritium, CFCs and noble gases
| Autor: | Liang-Feng Han, Pradeep K. Aggarwal, Tamara Hunjak, Takuya Matsumoto, Zvjezdana Roller-Lutz, Hans Otto Lutz |
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| Rok vydání: | 2017 |
| Předmět: |
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010504 meteorology & atmospheric sciences Croatia 0208 environmental biotechnology Aquifer 02 engineering and technology 01 natural sciences Geochemistry and Petrology Spring (hydrology) environmental tracers 0105 earth and related environmental sciences groundwater dating and mixing Hydrology geography Hydrogeology geography.geographical_feature_category Stable isotope ratio multiple tracer Groundwater recharge karst Karst 020801 environmental engineering Geophysics techniques Groundwater Geology |
| Zdroj: | GEOCHEMICAL JOURNAL. 51:391-407 |
| ISSN: | 1880-5973 0016-7002 |
| DOI: | 10.2343/geochemj.2.0440 |
| Popis: | Due to their extreme anisotropy and heterogeneity, the hydrogeological characterization of karst terrains is notoriously difficult. Approximately 50% of Croatia consist of karst aquifers, in particular the touristically important region along the Adriatic coast. Being an important water reservoir for this area, we have chosen the Gacka area of Croatia as a typical example. We studied the mixing of groundwater and the responses to recharge in several karst springs by using environmental tracers, including stable isotopes in water (O-18, H-2), tritium (H-3), chlorofluorocarbons (CFCs) and noble gases (He-3, He-4, Ne, Ar, Kr, Xe). The variation of the stable isotopic signal (delta O-18 and delta H-2) in the spring discharges provides qualitative information on the mixing of waters with different transit time. Assuming piston flow in the system, the CFC and H-3 data indicate that the waters contain mainly post-1980 recharge. The CFC concentrations in the spring waters were found to be significantly different between wet and dry weather periods. The higher CFC values during the wet weather period indicate that the waters contained some water components that have relatively short mean residence times. An important finding of the study was that the sole application of tritium-helium methods does not permit an accurate age determination. This is due to mass exchange between liquid and gaseous phases occurring in karst aquifer systems particularly in dry weather periods. During such a dry weather period, more space in the karst groundwater system is not filled with water compared with a wet weather period. It is shown in this study, however, that the combined use of stable isotopes (O-18, H-2), tritium, CFCs and noble gases is able to account for groundwater mixing and responses to recharge in this specific scenario. Compared to single-tracer studies, multi-tracer techniques will allow a much better understanding and characterization of these systems. This information is vital for the assessment of resources and potential contamination of the groundwater in this special environment. |
| Databáze: | OpenAIRE |
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