Informace o publikaci
Does external wind impact the speleothem growth in cave?
| Název česky | Ovlivňuje venkovní vítr růst speleotém v jeskyni? |
|---|---|
| Autoři | |
| Rok publikování | 2013 |
| Druh | Konferenční abstrakty |
| Fakulta / Pracoviště MU | |
| Citace | |
| Popis | Carbon dioxide is a key component controlling the karst processes like limestone dissolution and calcite speleothem growth. Principally, driving forces of the latter process are given by the difference between (1) CO2 partial pressure in soils/epikarst (PCO2(soil/epikarst)) and (2) CO2 partial pressure in a cave atmosphere (PCO2(cave)). Low PCO2(cave) supports dripwaters degassing and enhancing the driving forces of speleothem growth (Bourges et al. 2001). The instantaneous PCO2(cave) represents a steady state, at which the total CO2-flux into a cave is balanced by the CO2-flux out from the cave (Faimon et al. 2006). The cave input flux includes (1) natural fluxes, e.g., diffusion fluxes from soil/epikarst or the fluxes derived from dripwater degassing (Bourges et al. 2001) and (2) an anthropogenic flux, i.e., the flux stemming from a human respiration (Faimon et al. 2006). The output flux is controlled by ventilation (Fig. 1). Based on the former facts, it may be deduced that cave ventilation participates on the spelothem growth. The ventilation rate is given by the cave geometry and the differences in densities between the cave air and external air (de Freitas et al. 1982). In general, air density is function of many variables, temperature from which is the most significant. Therefore, the airflow driving forces may be expressed by the temperature differences DT = Texterior – Tcave (Faimon et al. 2012). A specific role in cave airflow plays external wind. The wind is generally believed to participate on cave airflows (e.g. de Freitas et al. 1982; Pflitsch and Piasecki 2003; Kowalczk and Froelich 2010). The impact of external wind was studied in the dynamic Císařská Cave (Moravian Karst). Time series of cave airflow and external wind were measured at the cave lower entrance with time steps of 10 seconds. Correlation analysis of the signals showed only weak positive correlation (correlation coefficient of 0.2, significant at confidence level ?=0.05), which indicates very slight dependence between cave airflow and external wind, if any. Cross correlation does not confirmed any time shift between the both signals. The spectral analysis showed inconsistent oscillations with the periods ranging from 8.8 to 15.8 minutes at cave airflow and from 10.3 to 23.1 minutes at external wind. Therefore, it may be conclude that this case study does not confirm a direct impact of external wind on cave airflow. For a definite „verdict“, however, additional studies are necessary. |