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

Abstract

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.