A show cave management: Anthropogenic CO2 in atmosphere of Výpustek Cave (Moravian Karst, Czech Republic)

Anthropogenic impact on CO2 levels was studied in the Bear Chamber of the Výpustek Cave, a show cave in the Moravian Karst (Czech Republic), during a period of active ventilation and enhanced attendance. The study showed that the natural CO2 levels were controlled by (i) the natural CO2 influxes from soils/epikarst (up to ∼5.64 × 10−2 mol s−1); and, (ii) the advective CO2 fluxes out of cave atmosphere (up to 4.66 × 10−2 mol s−1). During visitor presence, the anthropogenic CO2 flux into the chamber reached up to ∼0.13 mol s−1 and exceeded all other CO2 fluxes. The reachable anthropogenic steady states at sufficient duration of stay (up to 2.65 × 10−1 mol m−3) could exceed the natural CO2 levels by factor of more than nine based on the number of visitors. Recession analysis of anthropogenic pulses showed that intervals between individual visitor groups would have to be up to ∼6 h long if the cave environment has to return to natural conditions. As such pauses between individual tours are hardly realizable, a risk analysis was conducted to find the consequences of breaking natural conditions. It showed that the condition under which dripwater becomes aggressive to calcite (i.e., the point when PCO2 in cave atmosphere exceeds the hypothetical CO2 concentrations in epikarst that has participated on the water formation, PCO2(H) = 10−1.56) is potentially reachable under extreme conditions only (enormous visitor stay period and visitor number). In case of condensed water, however, any increase in CO2 concentration will cause an increase of water aggressiveness to calcite. Therefore, in the periods and sites of enhanced condensation, it is important to strive for preservation of natural conditions.