Impact of water exhaled out by visitors in show caves: a case study from the Moravian Karst (Czech Republic).

The anthropogenic impact of the water and CO2 exhaled by visitors was studied in the show caves of the Moravian Karst (Czech Republic), especially in the Balcarka and Výpustek Caves. Two alternative models based on (1) the known/presumed composition of the breathed air and physical activity of visitors and (2) the detailed monitoring microclimatic data were proposed. The CO2 fluxes of 2.4 × 10-4 and (2.0-3.9) × 10-4 mol person-1 s-1 and the water vapor fluxes of (3.2-8.9) × 10-3 and (0.6-1.2) × 10-2 g person-1 s-1 were found for a slightly increased physical load. The total attendance and cave tour duration were the main driving factors. For the available data on attendance and accessibility periods, the total mass of water vapor exhaled by visitors in all show caves in the Moravian Karst was estimated between 9.6 × 106 and 4.3 × 108 g with significant seasonality. According to the geochemical model, this mass of water is capable of dissolving 1280 to 59,038 g of calcite, assuming a mean winter and summer CO2 concentration in the cave air of 1000 and 3000 ppmv. The larger extent of water condensation can lead to the so-called condensation corrosion, whereas the lower extent of condensation probably causes a recrystallization of calcite on the surface of speleothems and rocks.

Historical ferrous slag induces modern environmental problems in the Moravian Karst (Czech Republic).

Ferrous slag produced by a historic smelter is washed from a slagheap and transported by a creek through a cave system. Slag filling cave spaces, abrasion of cave walls / calcite speleothems, and contamination of the aquatic environment with heavy metals and other toxic components are concerns. We characterize the slag in its deposition site, map its transport through the cave system, characterize the effect of slag transport, and evaluate the risks to both cave and aqueous environments. The study was based on chemical and phase analysis supported laboratory experiments and geochemical modeling. The slag in the slagheap was dominated by amorphous glass phase (66 to 99 wt%) with mean composition of 49.8 ± 2.8 wt% SiO2, 29.9 ± 1.6 wt% CaO, 13.4 ± 1.2 wt% Al2O3, 2.7 ± 0.3 wt% K2O, and 1.2 ± 0.1 wt% MgO. Minerals such as melilite, plagioclase, anorthite, and wollastonite / pseudowollastonite with lower amounts of quartz, cristobalite, and calcite were detected. Slag enriches the cave environment with Se, As, W, Y, U, Be, Cs, Sc, Cd, Hf, Ba, Th, Cr, Zr, Zn, and V. However, only Zr, V, Co, and As exceed the specified limits for soils (US EPA and EU limits). The dissolution lifetime of a 1 mm3 volume of slag was estimated to be 27,000 years, whereas the mean residence time of the slag in the cave is much shorter, defined by a flood frequency of ca. 47 years. Consequently, the extent of slag weathering and contamination of cave environment by slag weathering products is small under given conditions. However, slag enriched in U and Th can increase radon production as a result of alpha decay. The slag has an abrasive effect on surrounding rocks and disintegrated slag can contaminate calcite speleothems.

Arsenic speciation in aerosols of a respiratory therapeutic cave: A first approach to study arsenicals in ultrafine particles.

Arsenic is ubiquitous in the environment and of special concern due to its varying toxicity depending on the chemical form present. Less is known about arsenic in air, especially about organoarsenicals, their sources and fate. There is also a lack of knowledge regarding arsenic in airborne nanoparticles that are critical for understanding with respect to human health effects due to their size. Here we show results from an arsenic speciation analysis in size-resolved airborne particles with aerodynamic diameters down to 15 nm. Analysis of aerosols from a respiratory therapeutic cave showed temporarily higher concentrations of trimethylarsine oxide than inorganic arsenic and substantial amounts of organoarsenicals, especially in smaller particles. Our method provides guidance for future studies investigating arsenicals in ultrafine particles and their health implications. Furthermore, the method developed can be used to widely monitor particle-bound organoarsenicals to fully understand the importance of As biovolatilization in the environment.

Anthropogenic CO2-flux into cave atmosphere and its environmental impact: A case study in the Císarská Cave (Moravian Karst, Czech Republic).

The evolution of CO2 levels was studied in the ventilated and unventilated Nagel Dome chamber (the Císarská Cave) with- and without human presence. Based on a simplified dynamic model and CO2/Rn data (222Rn considered as a conservative tracer), two types of CO2-fluxes into the chamber were distinguished: (1) the natural input of (2-4) x 10(-6) m3 s(-1), corresponding to a flux of (8.5-17) x 10(-10) m3 m(-2) s(-1) and (2) an anthropogenic input of (0.6-2.5) x 10(-4) m3 s(-1), corresponding to an average partial flux of (4.8-7.7) x 10(-6) m3 s(-1) person(-1). The chamber ventilation rates were calculated in the range from 0.033 to 0.155 h(-1). Comparison of the chamber CO2-levels with chamber dripwater chemistry indicates that the peak CO2-concentrations during stay of persons (log p(CO2) approximately -2.97, -2.89, and -2.83) do not reach the theoretical values at which dripwater carbonate species and air CO2 are at equilibrium (log p(CO2[DW]) approximately -2.76 to -2.79). This means that CO2-degassing of the dripwaters will continue, increasing supersaturation with respect to calcite (dripwater saturation index defined as SI(calcite) = a(Ca2+)a(CO3(2-))/10(-8.4) varied in the range from 0.76 to 0.86). The p(CO2[DW]) values, however, would easily be exceeded if the period of person stay in the chamber had been slightly extended (from 2.85 to 4 h under given conditions). In such case, the dripwater CO2-degassing would be inverted into CO2-dissolution and dripwater supersaturation would decrease. Achieving the threshold values at which water become aggressive to calcite (log p(CO2[EK]) approximately -1.99, -2.02, and -1.84) would require extreme conditions, e.g., simultaneous presence of 100 persons in the cave chamber for 14 h. The study should contribute to a better preservation of cave environment.

Environmentally acceptable effect of hydrogen peroxide on cave "lamp-flora", calcite speleothems and limestones.

Mosses, algae, and cyanobacteria (lamp-flora) colonize illuminated areas in show caves. This biota is commonly removed by a sodium hypochlorite solution. Because chlorine and other deleterious compounds are released into a cave environment during lamp-flora cleansing, hydrogen peroxide was tested as an alternative agent. In a multidisciplinary study conducted in the Kateinská Cave (Moravian Karst, Czech Republic), 12 algae- and cyanobacteria taxons and 19 moss taxons were detected. The threshold hydrogen peroxide concentration for the destruction of this lamp-flora was found to be 15 vol.%. Based on laboratory experiments in stirred batch reactors, the dissolution rates of limestones and calcite speleothems in water were determined as 3.77 x 10-3 and 1.81 x 10-3 mol m-2 h-1, respectively. In the 15% peroxide solution, the limestone and speleothem dissolution rates were one order of magnitude higher, 2.00 x 10-2 and 2.21 x 10-2 mol m-2 h-1, respectively. So, the peroxide solution was recognised to attack carbonates somewhat more aggressively than karst water. In order to prevent the potential corrosion of limestone and speleothems, the reaching of preliminary peroxide saturation with respect to calcite is recommended, for example, by adding of few limestone fragments into the solution at least 10 h prior to its application.