Karst aquifers are very vulnerable to various pollution sources. Among these, landfills can contribute contaminants over long periods. Groundwater quality monitoring is required to assess the impact ...of a landfill leachate on underlying aquifer water or spring discharge. Tracer tests are useful for selecting the location and frequency of sampling. Three landfill sites in karst areas were studied with tracer tests. Additional insight was accomplished by the comparison of the tracer transfer and the breakthrough curves obtained from these tests with the results of two other tracer tests carried out in the same period in karst areas without a landfill. To explain the differences observed, the hypothesis of increased permeability below the landfill due to the presence of inorganic acids in leachates was further tested. The results of detailed, long-term monitoring of contaminated drip water in the Postojna Cave were used to verify the hypothesis. The analysis of the simultaneously increased content of calcium, magnesium, and contaminants in the drip water indicates a direct correlation between limestone dissolution and contaminants. Increased dissolution increases secondary porosity and thus permeability of the vadose zone resulting in higher vulnerability of underlying aquifers and springs in the vicinity landfills.
Postojnska jama (Postojna Cave) is one of the most famous karst caves in the world and has been a well-known tourist attraction for nearly 200 years. It is particularly famous for its unique ...double-track railway. Eight heavy metals - aluminium (Al), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), strontium (Sr), and zinc (Zn) - were determined in dust deposits by ICP-MS in order to assess sources of deposited particles on the cave walls. The samples were collected along the main passage in the cave, at different horizontal and vertical levels, in order to test horizontal homogeneity and study vertical distribution of the particles. It seems that the railway is an important anthropogenic source of particles, reflected in increased concentrations of Cu, Pb, and Zn, as well as of Fe and Mn in dust deposits at individual sampling sites. The maximum concentrations of Cu (217 mu g g-1), Pb (4,940 mu g g-1), and Zn (1,060 mu g g-1) considerably exceeded their natural abundance and were explained by anthropogenic impact. The three heavy metals are markers for vehicles, engine oil and brake wear. On the other hand, mixed sources could prevail for Fe and Mn. The maximum concentrations of Fe (85,900 mu g g-1) and Mn (682 mu g g-1) in dust deposits were similar to the concentrations determined in fragments of the railway tracks (97,100 mu g g-1 for Fe and 821 mu g g-1 for Mn) and were explained by track wear and/or corrosion. In most other parts of the cave, Fe and Mn concentrations were, however, below the concentration of their natural abundance. Al, Sr, and Cr seem to be predominantly of natural origin. They generally exhibited concentrations lower than their natural abundance.
Monitoring of air temperature takes place at five locations in two cave systems. At monitoring location Velika gora (Postojna 1), mean air temperature for the time period 2009–2010 was 11.10 °C. Of ...three monitoring locations Velika gora is situated at the highest absolute height. Mean air temperature in the same period was 10.66 °C in the central part of the Lepe jame cave (Postojna 3) and 10.30 °C in the side passage (Postojna 2). Temperature difference between outside and cave temperature is the highest at Postojna 2 monitoring location, due to the inflow of the air currents from the unknown parts, especially in winter time. Manual temperature measurements (2004–2010) exhibit slight increase of air temperature at Postojna 1 and Postojna 2 monitoring sites. In the Predjama cave system, the air temperature in Velika dvorana is much more stable than in Konjski hlev passage, which is more subject to external influences.
Vertical static pendulums have been installed in mines or caves in Central Europe since 2007. Two-dimensional optical measurement of the tilt of a rock mass and continuous fully digital on-line ...evaluation of results makes possible the detection of a small tilt of the surroundings with a resolution of tens of nanoradians or the deformation of the surroundings in the horizontal plane with resolution of hundreds of nanometres. The paper describes the measurement device and the first results of the measurements in Magdalena Jama, which is part of the Postojna Cave System (Slovenia). The correlation of deformation between distant stations shows the existence of stress variations that are not only of local origin (high floods, local seismicity, and aseismic deformations). The stress field has a wider, and not only regional, character with effects that can be observed very far from the origin.
In three selected drips in the Postojna cave in SWw Slovenia and in the nearby Korentan spring, which in general belongs to the same karst aquifer, the discharge and electrical conductivity were ...measured at 15-minute intervals. Simultaneously, the meteorological parameters in Postojna were measured and the effective infiltration was assessed. The data obtained in the period of one hydrological year, 2003–2004, was compared in order to study the influence of the vadose flow on the characteristics of groundwater flow in a karst system and on the functioning of a karst spring. The highest discharges of the Korentan spring are the result of the inflow of water through a hierarchy of fissures of various permeabilities within the vadose zone, but the contribution of stored water from low-permeability zones is especially important. One of our most significant findings is that in the conditions of high saturation of the vadose zone, the network of small fissures is hydraulically connected, which enables an integral reaction of the system to the pressure pulse induced by infiltrated precipitation. On the other hand, a detailed comparison of effective infiltration and discharge indicates that in dry periods with a lower saturation of the vadose zone, the infiltrated precipitation is mainly stored in the system and only the most permeable fissures enable a rapid transfer of the recharge impulses toward the spring. Data on measured discharge and conductivity were additionally compared in order to study the complex conditions of the actual mass flow of water through the system.Key words: karst aquifer, vadose zone, Postojna Cave, Korentan spring, Slovenia
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