Publication details
Influence of cave CO2 levels by advective fluxes from epikarst
| Authors | |
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| Year of publication | 2015 |
| Type | Conference abstract |
| MU Faculty or unit | |
| Citation | |
| Description | The dynamic model of cave CO2 level evolution was proposed. Analysis of generally presumed CO2 fluxes from soils/epikarst showed that additional advective fluxes are necessary to reach usual cave CO2 concentrations. Based on CO2 different seasonality, two conceptual models of dynamic caves were distinguished: (1) the caves of geometry A, characterized by a free lower entrance and hidden upper openings, and (2) the caves of geometry B, consisting of free upper entrance and hidden lower openings. It is supposed that all the hidden openings are filled by clastic sediment permeable for air and serve as a channel for advective fluxes of epikarstic CO2. In the caves of geometry A, the reached CO2 levels are usually low during upward airflow (UAF) mode due to low advective flux input from external atmosphere. In contrast, the CO2 levels during downward airflow (DAF) mode are higher by magnitude due to the advective fluxes from epikarst. In the caves of geometry B, the higher concentrations are associated with UAF mode and the lower concentrations are associated with DAF mode. For simulating the spring evolution of cave CO2 concentrations, two-reservoir model was proposed. The model was applied on the cave of geometry A due to its broader incidence world wide. It consists of two reservoir, soils/epikarst and cave, and fluxes among them. At first, only ordinary fluxes were considered: (1) the input diffusive flux from soils/upper epikarst, (2) the input advective flux from external atmosphere, (3) the input flux derived from dripwater degassing, and (4) the output advective flux from the cave. Based on published data, the principally attainable values of input fluxes were chosen as follows: 5.4 × 10-2 mol s-1 for advective flux, 5.8× 10-7 mol m-2 s-1 for the diffusive flux, and 2.5 × 10-7 mol m-2 s-1 for the flux derived from dripwater degassing. Based on CO2 concentration in cave and airflow velocity, the output fluxes reached up to 9.6 mol s-1. Regardless of the UAF and DAF modes, the modeling showed the low values of cave CO2 levels that did not reach common cave CO2 levels. The model expanded by the input advective CO2 flux from epikarst confirmed the hypothesis about that a direct advective CO2 flux from epikarst is necessary for reaching usual maxima of cave CO2 levels. The values of such flux could reach up to 15.5 mol s-1. |