What is the soil capacity for providing obvious karst CO2 concentrations?

Abstract

Soil CO₂ was studied in the Moravian Karst (Czech Republic). It was found that the CO₂ concentration in soil pores depends inversely on pore dimension. The simplified relation between soil drill-hole diameter and measured CO₂ concentration,c_CO2⁰ = (c_{CO2 - b D)/(1+a D)}, was derived (where c_CO2⁰is the CO₂ concentration extrapolated to the drill-hole zero diameter in ppmv, c_CO2 is directly measured CO₂ concentration in ppmv, D is drill-hole diameter in cm, and a, b are parameters in cm^-1 and ppmv cm^-1, respectively). For the diameter lesser than 7 cm and the individual karst soils formed at grass meadow and deciduous forest, the values of a and b parameters ranged from -0.135 to -0.160 cm^-1 and from 88 to 422 ppmv cm^-1, respectively. For the heavy clay soils of coniferous forest, however, no dependence between c_CO2 and D was found. To understand the dependence better, a conceptual model was proposed in terms of concentration gradients and fluxes. The work results re-open the question whether soils are capable to provide the CO₂ concentrations obviously monitored/deduced in karst environment.