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Vzdolž obale med Izolo in rtičem Ronek se nahaja dvanajst podmorskih kotanj lijakaste oblike, imenovane tudi Žumrove kotanje, v katerih so izviri. Voda v teh kraških podmorskih izvirih ima povišano temperaturo, močno smrdi po žveplu, termomineralna voda s takimi lastnostmi pa je na kopnem Izole poznana že stoletja, kjer so jo tudi izkoriščali za terme. Izviri so vezani na pojavljanje alveolinsko-numulitnih apnencev Izolske antiklinale. V podmorskih izvirih in kopenskem žveplenem izviru smo ob primerjavi z vodo v vrtini, sladkovodnimi izviri, vodotoki in morsko vodo raziskovali fizikalno-kemijske, geokemične in izotopske značilnosti, da bi bolje razumeli njihove značilnosti, izvor vode in razširili poznavanje dinamike podzemnih vod na območju Izole. Trije sklopi vzorčenja so potekali junija in julija 2020, oktobra 2020 in aprila 2021, ko smo vzorcem merili fizikalno-kemijske parametre (T, pH, EC, TDS, ORP, DO) in vodo vzorčili za nadaljnje laboratorijske analize: geokemična sestava (kationi, anioni), izotopska sestava kisika (?18O) in vodika (?2H), totalno alkalnost (TA), izotopska sestava ogljika v raztopljenem anorganskem ogljiku (?13C-DIC), vsebnosti tritija (3H), izotopsko razmerje stroncija (87Sr/86Sr) in izotopska sestava žvepla (?34S-SO4) in kisika (?18O-SO4) v sulfatu. Na podlagi rezultatov analiz smo ugotovili, da ima voda v podmorskih izvirih drugačne geokemične značilnosti kot drugi izviri na kopnem. Prisotnost žvepla je verjetno vezana na prisotnost premoga v Liburnijski formaciji. Izvirska voda se meša z morsko vodo. Pri vzorcih podmorskih izvirov je bilo vzorčenje problematično, saj smo zajeli še dodatno morsko vodo. Ugotovili smo, da je vzorčenje z brizgami uspešnejše od vzorčenja z Niskinom. Poleg prisotnosti morske vode smo ugotovili, da izvire napaja tudi padavinska voda, podzemna voda karbonatnega vodonosnika in žveplena voda. Zaznali smo prisotnost razgradnje organske snovi, ki je lahko posledica pojavljanja premoga, termalne značilnosti pa so verjetno posledica narivne aktivnosti območja. Along the coast between the town of Izola and the nearby Ronek cape, there are twelve funnel-shaped submarine depressions with springs, also called the Žumer depressions (Žumrove kotanje). Water in these submarine karst springs has an elevated temperature and a distinct smell of sulphur. On shore, thermomineral water with such properties has been known in Izola for centuries, where it was also used for thermal baths. The springs pertain to the occurrence of alveolinid-nummulitic limestone of the Izola anticline. We investigated the physico-chemical, geochemical and isotopic characteristics of the submarine springs and the terrestrial sulphur spring in comparison with borehole water, freshwater springs, streams and seawater to better understand their features, the source of water and expand the knowledge of groundwater dynamics in the Izola area. Three sampling sets took place in June and July 2020, October 2020 and April 2021, when physicochemical parameters (T, pH, EC, TDS, ORP, DO) of the samples were measured and water was sampled for further laboratory analysis: geochemical composition (cations, anions), isotopic composition of oxygen (δ18O) and hydrogen (δ2H), total alkalinity (TA), isotopic composition of dissolved inorganic carbon (δ13C-DIC), tritium activity (3H), isotopic ratio of strontium (87Sr/86Sr) and isotopic composition of sulphur (δ34S-SO4 ‰) and oxygen (δ18O-SO4 ‰) in sulphate. Based on the results of the analyses it can be concluded that the water in submarine springs has different geochemical characteristics than water in other terrestrial springs. The presence of sulphur is probably related to the presence of coal in the Liburnian formation. The spring water is mixed with sea water. In the case of submarine spring samples, sampling was problematic, as we captured additional seawater. Syringe sampling was established as more successful than Niskin sampling. In addition to sea water, springs are also fed by rainwater, underground water from the carbonate aquifer, and sulfur-rich water. We detected the presence of decomposition of organic matter, which may be the result of the occurrence of coal. Thermal features of submarine springs are probably the result of the thrusting activity of the area. |
