On Kranjsko polje in central Slovenia, carbonate conglomerates have been dated to several Pleistocene glacial phases by relative dating based on the morphostratigrafic mapping and borehole data, and ...by paleomagnetic and 10Be analyses. To define how the age of conglomerates determines the geomorphological characteristics of karst surface features, morphometrical and distributive spatial analyses of dolines were performed on three test sites including old, middle, and young Pleistocene conglomerates. As dolines on conglomerates are covered by a thick soil cover and show a strong human influence, the ground penetrating radar (GPR) method was first applied to select dolines appropriate for further morphometrical and distributive analyses. A considerable modification of natural morphology was revealed for cultivated dolines, excluding this type of depression from spatial analyses. Input parameters for spatial analyses (doline rim and deepest point) were manually extracted from the 1 × 1 m grid digital elevation model (DEM) originating from the high-resolution LiDAR (Light Detection and Ranging) data. Basic geomorphological characteristics, namely circularity index, planar size, depth, and density index of dolines were calculated for each relative age of conglomerates, and common characteristics were determined from these data to establish a general surface typology for a particular conglomerate. The obtained surface typologies were spatially extrapolated to the wider conglomerate area in central Slovenia to test the existent geological dating. Spatial analyses generally confirmed previous dating, while in four areas the geomorphological characteristics of dolines did not correspond to the existing dating and require further revision and modification. Doline populations exhibit specific and common morphometrical and distributive characteristics on conglomerates of a particular age and can be a reliable and fast indicator for their dating.
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Ground penetrating radar (GPR) using a special unshielded 50 MHz Rough Terrain Antenna (RTA) in combination with a shielded 250 MHz antenna was used to study the capability of this geophysical method ...for detecting cave sediments. Allochthonous cave sediments found in the study area of Lanski vrh (W Slovenia) are now exposed on the karst surface in the so-called “unroofed caves” due to a general lowering of the surface (denudation of carbonate rocks) and can provide valuable evidence of the karst development. In the first phase, GPR profiles were measured at three test locations, where cave sediments are clearly evident on the surface and appear with flowstone. It turned out that cave sediments are clearly visible on GPR radargrams as areas of strong signal attenuation. Based on this finding, GPR profiling was used in several other places where direct indicators of unroofed caves or other indicators for speleogenesis are not present due to strong surface reshaping. The influence of various field conditions, especially water content, on GPR measurements was also analysed by comparing radargrams measured in various field conditions. Further mineralogical-geochemical analyses were conducted to better understand the factors that influence the attenuation in the area of cave sediments. Samples of cave sediments and soils on carbonate rocks (rendzina) were taken for X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses to compare the mineral and geochemical compositions of both sediments. Results show that cave sediments contain higher amounts of clay minerals and iron/aluminium oxides/hydroxides which, in addition to the thickness of cave sediments, can play an important role in the depth of penetration. Differences in the mineral composition also lead to water retention in cave sediments even through dry periods which additionally contribute to increased attenuation with respect to surrounding soils. The GPR method has proven to be reliable for locating areas of cave sediments at the surface and to determine their spatial extent, which is very important in delineating the geometry of unroofed cave systems. GPR thus proved to be a very valuable method in supporting geological and geomorphological mapping for a more comprehensive recognition of unroofed cave systems. These are important for understanding karstification and speleogenetic processes that influenced the formation of former underground caves and can help us reconstruct the direction of former underground water flows.
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The S-19 Cave was with its explored depth of 177 m one of the most important caves of the Mt. Kanin massif, but after its discovery in 1974, a huge snow avalanche protection dyke was constructed ...across the cave entrance. To excavate the buried cave, the accurate location of the cave had to be determined first. Since the entrance coordinates were incorrect and no markers were available, application of geophysical techniques was necessary to do this. A Ground Penetrating Radar (GPR) with special 50 MHz rough terrain antennas was selected as the single suitable geophysical method for the given conditions where thick debris overlay a rugged limestone surface. Nevertheless, it was not possible to directly detect the relatively narrow cave entrance itself due to data resolution limits. However, a historical photo of the area showed that the cave entrance was located in a local depression, which therefore represented the main target of the GPR survey. Seven GPR profiles were measured across the rough and steep surface causing difficulties in traversing the area with sensitive research equipment. In all recorded radargrams a small depression was clearly imaged under debris, and recognized as a topographic feature with the cave entrance. Based on the GPR data interpretation, the exact location for digging was determined and the thickness of debris assessed at 6.5–7 m. A massive excavation by a dredger resulted in a successful opening of the cave entrance, confirming both its geophysically determined location and its estimated depth. The application of an advanced geophysical method was therefore proven successful in providing a solution to this specific case in karst exploration and an important cave was saved.
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Karst as an extremely complex and heterogeneous system, that presents a great challenge for the ground penetrating radar (GPR). However, properly planed GPR surveys can provide additional information ...about the shallow subsurface, where most karst processes take place. Due to the specific nature of the karst terrain, the introductory part presents some obstacles and adaptive approaches to karst research. An analysis of the published literature revealed that the GPR is most commonly used for detecting caves and subsidence areas and for preventing collapses in urban areas and for construction interventions. This is followed by exploration of karst aquifers, epikarst and quarry research. Some non-established applications are also presented, such as the use of a georadar in exploration of unroofed caves and cave sediments. The main purpose of this article is to demonstrate and evaluate the possibilities of using a georadar in different karst environments, to encourage its use in some new applications, and to emphasize the necessity of an interdisciplinary approach in such studies.
•Determination of peat stratigraphy, peat thickness and basin morphology.•Comparison of geophysical and conventional approaches in peatland environment.•3D model was created from GPR data to ...visualize the morphology.•Peatland formed from four smaller lakes which were later joined in one lake.
Owing to their anoxic environment, peatlands play an important role in the preservation of records documenting past atmospheric depositions. To determine past records, data on peat stratigraphy and bog development are needed. Ground penetrating radar (GPR) was used to determine the peat thickness and morphology of the Šijec bog on the Pokljuka plateau in Slovenia, which will serve as a basis for further geochemical studies. Information on the stratigraphy below the peat/clay boundary was acquired by applying electrical resistivity tomography (ERT). The GPR results reveal four depressions within the peat bog, which are separated by elevated ridges. Within the depressions the peat reaches a depth of 6–9 m. The edges of the bog are flat, with peat thickness ranging from 2 to 4 m. The reach of the GPR was complemented with manual peat probing. A comparison of the depths obtained using GPR and the peat probe reveals that the results of both methods correspond well in most locations. The ERT indicated similar peat depths; peat responds with high electrical resistivity. In contrast, clayey sediments with low resistivity are found below the peat. The peat depressions are underlain with larger clayey depressions reaching more than 20 m in thickness and represent lake sediments. The complementary geophysical methods proved to be an efficient approach with which we can delineate the peat morphology and the underlying stratigraphy. Both indicate bog formation from a lake with four deeper depressions, that are separated by glacial deposits. The results presented here show the potential for geophysical methods to infer formational processes in peatlands, showing the presence of a series of isolated basins that later coalesced into a single peat landform. This interpretation is consistent with previous conceptual models from studies in boreal regions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fluvial sediment samples (river bottom sediment, suspended sediment and active floodplain/overbank) were collected in 2 baseline stations of the Transnational Monitoring Network for each of the 12 ...countries in the Danube Basin Region: Austria, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Hungary, Republic of Moldavia, Montenegro, Romania, Republic of Serbia, Slovakia and Slovenia, according to a harmonized methodology. The sediment samples were analyzed for selected hazardous substances (HSs): 8 metals, 8 polycyclic aromatic hydrocarbons (PAHs) and 6 pesticides in an accredited laboratory selected as reference laboratory, as well as in national laboratories. Risk ratios were computed in order to compare the results to the Environmental Quality Standards listed in the European Directives, to the national threshold values in the Danube Basin, and to other available international European and American quality standards, and the risk ratios were classified as background, alert and intervention values for readily evaluation. Results show widespread metal(oid) (As, Cd, Cu, Hg, Pb, and Zn) contamination in the Danube Basin, most often associated with historic mining. Concentration values of Ni and Cr exceeding the thresholds are caused by the geological background (ultrabasic and metamorphic rocks in Bosnia and Herzegovina, Republic of Serbia and Romania). Concentration values higher than the thresholds for some of the PAHs (e.g. Fluoranthene) and sometimes for Total PAHs were also noted almost in every countries, caused by industrial activities, wastewater discharges or navigation on the Danube River. Pesticides were below the detection limit or below the legislative intervention thresholds at all national baseline sampling sites.
The bare karst surface in the southeastern part of Krk Island (Croatia) is characterized by different surface karst features, such as valley-like shallow linear depressions and partially or fully ...sediment-filled depressions of various shapes and sizes. They were noticed due to locally increased thickness of sediment and enhanced vegetation but had not yet been systematically studied and defined. Considering only the geometry of the investigated surface features and the rare traces of cave environments detected by field surveys, it was unclear which processes (surface karstification and/or speleogenesis) contributed most to their formation. The low-frequency ground penetrating radar (GPR) method using a special 50MHz RTA antenna was applied to study and describe these karst features. Three study sites were chosen and 5km of GPR profiles were positioned to include various surface features. The results obtained from the GPR investigation lead to the following conclusions: (1) an increased thickness of sediment was detected in all the investigated depressions indicating their considerable depth; (2) areas between different depressions expressed as attenuated zones in GPR images reveal their interconnection; (3) transitions between surface and underground features are characterized by a collapsed passage visible in the GPR data; and (4) an underground continuation of surface valley-like depressions was detected, proving the speleogenetic origin of such features. Subsurface information obtained using GPR indicates that the valley-like depressions, irregular depressions completely or partially filled with sediment, and some dolines are associated with a nearly 4km-long unroofed cave and developed as a result of karst denudation. In the regional context, these results suggest long-lasting karstification processes in the area, in contrast to the pre-karstic fluvial phase previously assumed to have occurred here. This research is the first application of the GPR method to survey unroofed caves worldwide and the first detailed study of such karst features in Croatia. The low-frequency GPR proved to be an efficient method not only for detecting underground continuations but also for distinguishing and identifying surface features and transition zones between surface and subsurface segments of unroofed caves and can therefore be used for recognizing similar geomorphological features.
•Unroofed caves proved using low-frequency GPR with 50MHz RTA antenna.•Surface and near surface segments of unroofed caves were detected and interpreted using GPR.•Transition zones between surface and underground features were identified and defined on the basis of the GPR image.•A conceptual model of karst denudation and development of unroofed caves in the study area is proposed.
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The paper presents the results of granulometrical, geochemical and mineralogical characterisation of sediments underlying the Velenje lignite seam as drilled through the P-9k/92 borehole in the ...central part of the Pliocene intermontane Velenje Basin. This study of differently lithified sediments/sedimentary rocks is based on analyses of 32 samples from 21 core intervals at the depth of 562.6–580.0 m (end of the borehole). Grain size was analysed on 12 samples, 24 samples were investigated geochemically, while mineral composition was obtained with X-ray diffraction (XRD) on 23 samples, and optical microscopy was performed on 7 samples. Granulometry of very low lithified samples revealed that they are mostly clayey silts (>85 % of the silt fraction), only two are silty sands and one is pebbly/rubbly sandstone. Well-lithified clastics are all sandstones cemented by calcite, siderite and/or marcasite. Geochemical analysis indicated that most samples are SiO2 + Al2O3 rich (>60–80 %). Some sediments, mostly at the base of the profile, are enriched in Fe2O3 and inorganic C both indicating the presence of siderite. At the top of the profile, thin limestone and gravelly sandstone beds contain a high CaO content and have high loss on ignition (LOI). Qualitative XRD analysis and microscopy showed that all clastic sediments consist of quartz, kaolinite and muscovite/illite. Feldspars occur sporadically, mainly in sands and sandstones. Gypsum was found in some samples of siltstones. Pyrite occurs only in a sample of limestone at the top of the profile. Also marcasite was found only in one sample.
The contamination of soil and water bodies with mercury from anthropogenic sources such as mining and industry activities causes negative effect for living organisms due to the process of ...bioaccumulation and biomagnification through the food chain. Therefore, the need for remediation of contaminated areas is extremely necessary and very desirable when it is cost-effective by using low-cost sorbents. This paper compares the sorption abilities of natural and iron-modified zeolite towards Hg(II) ions from aqueous solutions. The influence of pH, solid/liquid ratio (S/L), contact time, and initial concentration on the sorption efficiency onto both zeolites was investigated. At the optimal pH = 2 and S/L = 10, the maximum amount of sorbed Hg(II) is 0.28 mmol/g on the natural zeolite and 0.54 mmol/g on the iron-modified zeolite. It was found that rate-controlling step in mass transfer is intraparticle diffusion accompanied by film diffusion. Ion exchange as a main mechanism, accompanied with surface complexation and co-precipitation were included in the Hg(II) sorption onto both zeolite samples. This is confirmed by the determination of the amount of sorbed Hg(II) and the amount of released exchangeable cations from the zeolite structure as well as by the scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDS) of saturated zeolite samples. In a wide pH range, 4.01 ≤ pH ≤ 11.08, the leaching of Hg(II) was observed in the amount of only 0.28–0.78% from natural zeolite and 0.07–0.51% from iron-modified zeolite indicating that both zeolites could be used for remediation purposes while the results suggest that modification significantly improves the sorption properties of zeolite.
The EU Water Framework Directive requires the monitoring and evaluation of surface water sediment quality based on the assessment of risk posed by contamination on the biotic receptors. Fluvial ...sediments are important receptors of hazardous substances (HSs) pollution from the upstream catchment areas in the Danube River Basin (DRB). For the development of systematic sediment quality monitoring and evaluation, the Drava River region on the border of Hungary and Croatia was selected as a test area representative of lowland hydromorphological conditions. Overbank (floodplain) sediments and river bottom sediments (stream sediments) were sampled at two depths at 9 locations in the test area. Eight heavy metal(oid)s were analyzed As, Cd, Cr, Cu, Hg, Ni, and Zn as hazardous substances. The sediment quality assessment was carried out according to the 2013/39/EU Directive and EU Water Framework Directive standards. Most of the analysed HS concentrations in river bottom sediment and overbank (floodplain) sediments fall within the limits of environmental quality standards (EQS). Results show that there is no significant differences in metal(oid) HS concentrations among the various sediment types and between shallow (0-5cm) and deeper (stream sediment: 5-10cm; floodplain sediment: 40-50cm) sediment which suggests that the large lowland Drava River fluvial system is an extensive single fluvial system with homogeneous distribution of sediments and the associated contaminants. Specifically, the studied sediments in the tributaries of the Drava River do not seem to be contaminated with metal(oid) hazardous substances but at certain sites concentrations are elevated above the environmental limit values, especially for As and Zn, and to lesser extent for Cr. The data analysis techniques used enabled the identification of sites with anthropogenic pollution and the recognition of regional pattern in HSs distribution.
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