Instigated by relatively high cave-air CO2 concentrations in Modrič Cave (Croatia) recorded for the purpose of speleothem-based paleoclimate research, we established preliminary monitoring of radon ...(222Rn) concentrations within the cave for a 4.5-year period (2018–2022). As radioactive geogenic gas, radon, which often correlates with cave-air CO2 concentrations, presents a potential health hazard in cases of longer exposure time in high concentration conditions. Since the Modrič Cave is open to tourists and long-term scientific research has been performed within, a safety assessment for radon concentrations was essential. The integrated measurements of radon concentrations were performed by passive LR115 detectors that were exposed from three to six months at eight sites within the cave. Preliminary results showed seasonal variations of radon concentrations (0.08–13.6 kBq/m3) governed by the cave ventilation patterns, but superimposed on this, cave morphology and bedrock architecture control the radon variations on finer spatial scale. The 3-months average 222Rn concentration of up to 13.6 kBq/m3 during summer in one of the cave passages is among the highest measured seasonal averaged radon concentrations in Croatian caves, but maximum concentrations were even higher. Based on obtained results and calculations, potential negative health effects of radon exposure for cave visitors, guides and scientists were assessed and the results showed values of exposure to be below recommended levels. Calculated worst-case scenario for cave guides (most affected by radon and its progeny) revealed that they would receive dose slightly below the occupational dose limit of 20 mSv/y (19.0 ± 5.2 mSv/y) in the touristic part of the cave and significantly higher doses (34.1 ± 9.2 mSv/y) in the non-touristic part of the cave. To detect precise spatio-temporal radon concentration variations (up to diurnal scale) we recently established continuous radon measurements. This will enable detection of possibly health threatening short-term peaks in radon concentration and consequently further improve cave management.
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Extreme heterogeneity of karst systems makes them very challenging to study. Various processes within the system affect its global response, usually measured at karst springs. Research conducted in ...caves provides a unique opportunity for in situ analysis of separate processes in karst underground. The aim of the present study was to research the water and air dynamics within a deep karst system. Air and water basic physical parameters across the Lukina jama–Trojama cave system (−1,431 m) were continuously monitored during a 1‐year period. Recorded hydrograph of the siphon lake at the bottom of the cave was used to interpret the characteristics of an unexplored phreatic/epiphreatic conduit network. Water origin in the siphon was determined based on temperature and electrical conductivity. Air temperature and humidity monitoring revealed a strong inflow of air of sub‐zero temperature into the upper portion of the cave during winter. Cave passage morphology was interpreted as the main determinant of air dynamics, which caused ice to accumulate extensively in the upper portions of the cave and caused the temperature on the top of the homothermic zone to be significantly below the mean outside temperature. Air dynamics also lowered the temperature of water flowing through the cave vadose zone and feeding the phreatic zone of the massif. The pronounced temperature difference between the phreatic zone and the top of the homothermic zone probably contributed to the thermal gradient observed in the cave, which is steeper than in ice‐free caves in the area. Our results enabled the development of a conceptual model that describes coupling between air and water dynamics in the cave system and its surroundings.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In limestone caves, environmental processes often cause alterations of human or animal skeletal remains, complicating classical analytical methods. Exemplary, a proximal femoral skeletal fragment, ...enclosed by a thick layer of speleothemic calcite deposits, was discovered during the exploration of the Bedara cave in Žumberak, Croatia. An examination without removal of the surrounding mineral deposits, possibly leading to damage of the specimen, was, therefore, desirable.
We describe and discuss the applied techniques, including clinical computed tomography, virtual cleaning by a specially developed segmentation protocol using an open-source DICOM viewer, and virtual visualisation and dimensioning using computer-aided design software, so that this “hidden” specimen could be non-invasively examined in great detail. We also report on the circumstances and origin of the find, the results of radiocarbon dating, and its anatomical and taxonomic identification, according to which, the bone fragment belonged to a wild boar (
Sus scrofa
) from the timeframe of the Middle Eneolithic Retz-Gajary culture in the region (4,781 ± 35 years before present). This study provides a reference for future paleontological and anthropological analyses, seeking to unlock the enormous potential of anatomical studies of comparable skeletal remains that are either petrified or enclosed in speleothemic deposits.
Sjeverni Velebit hrvatski je biser koji u kontekstu obrazovanja 21. stoljeća, zaštite
prirode, suočavanja s ugrožavanjem prirode i klimatskim promjenama može postati
europski značajan edukativni ...centar. Osim vrednovanja, zaštite prirode i doprinosa
obrazovanju, ovaj pristup može otvoriti nova radna mjesta te podići kvalitetu života
lokalne zajednice. Pri tome se povezuju različiti sadržaji – obrazovni, znanstveni, kulturni,
športski, zdravstveni i dr.
Suvremeno znanstveno (STEM) obrazovanje temeljeno na značajnoj georaznolikosti
i bioraznolikosti može se u obliku programa ponuditi dionicima obrazovnoga sustava.
Krški fenomeni Nacionalnog parka Sjeverni Velebit, posebice njegove duboke jame, jedna
su od tema koja ima velike znanstveno-istraživačke i edukativne izazove.
Northern Velebit is a Croatian pearl which in the context of education in the 21st century, nature protection, confronting the endangerment of nature and climatic changes could become a significant ...European centre. Besides the evaluation, protection of nature and contribution to education from the nursery to lifelong learning, the development in this direction opens new workplaces and raises the quality of life of the local community. The Northern Velebit National Park is a location which in synergy with the infrastructure and logistic elements in Krasno, Otočac and Senj, along with the support of European funds, can develop on contemporary educational concepts of the 21st century. Especially the underground of Velebit, in other words, its numerous speleological phenomena, represent an excellent example of why it is necessary to connect the geological, biological and climatic aspects of the protected location.The high level of unexplored karst phenomena of the Northern Velebit National Parkand the potentials for new discoveries open the possibilities of generating dynamic educational contents which can be supplemented through continuous collaboration with experts. The discovery of something new until then unknown, unusual and unexpected is something which with the corresponding presentation techniques can awaken interest in the natural sciences in pupils and students, in other words, in accordance with the recommendations of the European Commission awaken the interest in the education of science and STEM regions.
We have performed measurements of the cave microclimate, water quality parameters and radon concentration to a depth of -1000 m in Velebita Cave system (Northern Velebit, Croatia). The results were ...analyzed as a function of the cave depth and geomorphological characteristics. Two different air temperature gradients were obtained, which can be attributed to a cave morphology and air circulation in the upper part of the pit. The water quality parameters show that the studied waters are poorly mineralized and are of weakly alkaline type. Water chemistry is probably predominantly controlled by the petrography of the bedrock (limestone) and the cave morphology. Water in the cave is not affected by pollution. The average value of radon concentration is rather low, much lower than in some other Croatian caves.
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Researching the hydrogeological properties of karst systems is very challenging due to their extreme heterogeneity. A grey-box approach in karst research combines the results from classical ...hydrogeological methods with direct observations within the karstic underground, i.e. in the caves. Isotope research has become a widely used method in the investigation of karst systems. The results presented are of a preliminary 2H and 18O stable isotope study of the Northern Velebit karst system (Croatia) employing the grey-box approach. Groundwater samples were collected during two summer expeditions in deep caves within the karst massif. Monthly precipitation samples were also collected (at three locations between approx. 900 m and 1600 m altitude), as well as water samples at some of the most significant springs, i.e. discharge outlets of the system. For a single expedition, the stable isotope composition is almost constant, i.e. the stable isotope measurements are within the measurement error across the complete cave profile. Similar characteristics across different caves during the same year were also noted. Samples of water from the springs were taken during base-flow conditions and they have similar isotopic contents to the cave water. The results obtained indicate that homogenization of the water already occurs within the subsurface epikarst zone above the sampling locations in the caves, but a future extended sampling campaign during variable hydrologic conditions is needed to confirm this. The final research goal is to establish a conceptual grey-box model for the functioning of this complex hydrogeological system.
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The aim of this study is to detect proxies from speleothems that are suitable for geochemical and paleoenvironmental research in Croatian karst (Dinaric karst and isolated karst of the Pannonian ...basin). The main subject is elemental composition and mineralogy of speleothems from various sites in Croatian karst and whether the different climatic, geological and hydrological characteristics of those karst regions affect elemental and mineralogical characteristics of speleothems in order to design and plan future research. Total of 37 speleothem samples from 32 caves in different geological, geomorphological and climatic zones of Croatian karst were collected. In all samples concentration of 30 elements was determined by ICP-MS and mineral composition was analyzed by XRD. In 82% of studied samples calcite is the only mineral identified. Minor minerals detected are: quartz, dolomite, muscovite/illite, chlorite and plagioclase. Besides the most abundant calcium, the elements with the highest concentrations (>500mg/kg) are: Al, Fe, Si and Mg. Elements with the lowest concentrations recorded (<1mg/kg) are: Be, Cd, Tl, W, Bi, U, As and Co. Besides Cd, other heavy metals used as anthropogenic contamination indicators have very low concentrations (<10mg/kg). Statistical relationships between elements were established. A boxplot statistical method showed that largest numbers of anomalies are present in all three samples from Lukina jama located on Northern Velebit Mountain, where a whole series of elements, including many heavy metals, show extreme values (Pb, Cu, Zn, Mn, Ni, Cr, Co, Ba, K, Mg, Li, Be, Al, U, Si, Ti, W, Fe, As). Factor analysis showed that anomalies of element concentrations in most cases can be explained by local mineralogical conditions. This study will significantly contribute the knowledge about elemental and mineralogical composition of speleothems in Croatia, which are mostly determined by geogene influence.
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•We assessed geochemistry and mineralogy of speleothems from Croatian karst.•Analyses were performed using ICP-MS and XRD and evaluated by statistical methods.•Calcite is the only identified mineral in 83.8% of studied speleothem samples.•Most heavy metals used as contamination indicators show very low concentrations.•Anomalies of element concentrations can be mostly explained by local mineralogy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
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