ABSTRACT
Particulate matter concentrations (PM10, PM2.5, PM1) and microclimatic parameters (air temperature, CO2) were monitored in the Skocjan Caves (Slovenia). The effects of tourist visits on the PM concentrations and the cave's microclimate are immediate and direct, but these values normalise relatively quickly. The results showed seasonal, diurnal, and spatial differences in all parameters studied. Due to the higher number of visitors, their influence on the cave's microclimate and PM10 and PM2.5 concentrations is greater in summer than in winter. The measured PM1 levels depend on the ventilation in the cave, as air transport plays an important role in their introduction into the cave. PM consists of minerals of natural origin resulting from the re-suspension of cave sediments due to strong air currents generated by the opening of the doors to tourists and their walks. The second most common influence is the anthropogenic phases originating from maintenance work in the cave, electronic devices, cave lighting and emissions from outside the cave (aerosols from the polluted Reka River, industry, traffic, gypsum waste disposal). In order to upgrade the sustainable use of the UNESCO-listed Skocjan Caves for tourism, we propose regular monitoring of PM and a detailed characterization of individual PMs and their sources, in addition to monitoring of the cave's microclimate and biology.
ABSTRACT
Historical air temperatures at three karst caves in Slovenia have been compared to current data time series. In Postojnska Jama (PJ), the most visited show cave in Slovenia, the significant temperature difference between historical and modern measurements at the Pulpito site relates to the months April to November. Mean monthly temperatures measured at the Sepolcro site (PJ) in the modern period (2016-2019) are year round significantly higher than in the historical period (1935-1937). The temperature increase over the last 85 years in PJ is attributed to outside temperature rise and additional heat input from visitors, especially for Sepolcro site. A comparison of current (2017-2019) and historical (1956-1957) temperature data in touristically poorly visited Predjama Cave shows lower increase as in PJ and is completely related to outside cave conditions. In the case of Skocjanske Jame (Tiha Jama), air temperature has not significantly increased since the historical 1928 measurements because the monitoring site looks to be morphologically isolated from significant impacts of outside climate and visitors. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s42452-021-04881-1.
ABSTRACT
In the caves, the formation of cave minerals is a consequence of a variety of chemical reactions, some of them also due to human activity. There are many caves in Slovenia, but sulphate minerals are not very often reported and analysed. In this study, the presence of sulphate minerals is detected by SEM/EDS analysis of speleothems from Crna Jama, a cave near Kocevje (southern Slovenia). The cave is characterised by its dark, almost black colour on cave walls, floor and speleothems. Anthropogenic influence in the cave is still visible, including the remains of a fireplace, some inscriptions on the walls and wooden containers. The analyses of some of the black-coated speleothems reveal the presence of calcium sulphate, confirmed by XRD as gypsum. Gypsum crystals are around 50 µm in size, and they occur in thin crusts. Additionally, some rare authigenic baryte crystals a few micrometres in size are detected. The sulphates δ34S value in gypsum found on dark coloured speleothems is + 10.4 Vienna Canyon Diablo Troilite (VCDT), while the sulphate δ34S of the bedrock is + 8.6 VCDT. The more likely source of sulphate ions is thus biomass burning rather than bedrock. Also, bedrock and biomass ash are a very probable source of calcium and barium. The highly probable pyrogenous origin of sulphates draws attention to human impact on cave mineralogy.
Subject(s)
Caves/chemistry , Environmental Pollutants/analysis , Sulfates/analysis , Microscopy, Electron, Scanning , Minerals/analysis , Powder Diffraction , Slovenia , Spectrometry, X-Ray Emission , X-Ray DiffractionABSTRACT
Micro-scale observations in karst caves help to identify different processes that shaped local morphology. Scanning electron microscopy/energy-dispersive X-ray spectroscopy inspection of speleothems from two karst caves in Slovenia, Predjama and Crna Jama, confirmed the presence of sub-angular to sub-rounded detrital fragments of clay minerals, feldspars, quartz, Fe-oxides/hydroxides, rutile and Nb-rutile, xenotime, kassite, allanite, fluorapatite, epidote, ilmenite, monazite, sphene, and zircon, between 2 and 50 µm across. These occur in porous layers separating calcite laminae in the clayey coating on the layer below the surface of the speleothems, and are also incorporated within actual crystals. It is likely that they are derived from the weathered rocks of the Eocene flysch. Probably they were first transported into the caves by floodwaters forming cave sediments. Later, depending upon the climate conditions, they were moved by air currents or by water to the surface of active speleothems. They might also be redeposited from overlying soils enriched with wind-transported minerals from the flysch, or from higher passages filled with weathered flysch sediment, by drip water percolating through the fissured limestone. As some of the identified minerals are carriers of rare earth elements, Ti and Zr, their presence could affect any palaeoclimatic interpretations that are based upon the geochemical composition of the speleothems.
