Mass transfer between a multicomponent trapped gas phase and a mobile water phase: Experiment and theory

Abstract

[1] Gas tracer experiments were carried out in dynamically compressed sediments to investigate the mass transfer between a trapped multicomponent gas phase and a mobile water phase. The saturation state of the column was characterized by three independent methods: (1) by gravimetric measurements, (2) by bromide tracer tests, and (3) by hydraulic conductivity measurements. For inverse modeling a new kinetic model was developed allowing volume change of the entrapped gas. The new kinetic model consistently explains oxygen elution curves, the time evolution of the integral gas saturation, and integral hydraulic conductivity. The sensitivity of three different velocity-dependent mass transfer correlations to the dissolution process was investigated: (1) a classical square-root, single-sphere correlation, Sh $ Pe 0.5 , (2) a multisphere correlation, Sh $ Pe n (n = 0.5-1.0), and (3) an empirical correlation, Sh $ Pe 0.8 . It was found that all correlations yield nearly the same elution curves for 10 gas tracer experiments with three different two-component gas phases: O 2 /He, O 2 /N 2 , and O 2 /Ar and for different flow velocities ranging from 5 to 20 m d À1 . For all gas tracer experiments a distinct minimum of the longitudinal dispersivity was found during gas dissolution, i.e., in the unsaturated state. For the saturated state we found that the experimental values could be described by Saffman's theory:D p / Pe ln (Pe) with a normalized mean square root error of 6%.Citation: Geistlinger, H., A. Beckmann, and D. Lazik (2005), Mass transfer between a multicomponent trapped gas phase and a mobile water phase: Experiment and theory, Water Resour. Res., 41, W11408,

Spatial and temporal variability of dissolved nitrous oxide in near‐surface groundwater and bubble‐mediated mass transfer to the unsaturated zone

“…We note that the increase of the N 2 O partial pressure due to the curved interface will have some effect on dissolution kinetics as we have shown in Geistlinger et al (2005), but it is of minor importance for the acceleration of the BMT.…”

“…Assuming a homogeneous distribution of entrapped air bubbles by an increasing GWL, a typical mean grain diameter for Fuhrberg sands of ≈ 0.3 mm, and a typical gas saturation of ≈ 10%, one can calculate the mean bubble distance of ≈ 1 mm and hence a relaxation time of ≈ 30 min (for details and references see Geistlinger et al, 2005). If one compares this time scale of BMT with the typical time scale of GWL fluctuation of ≈ 14 d, it is obvious that the O 2 concentration in the water phase is always in local equilibrium with the gas phase of the gas bubbles.…”

“…Assuming that the specific gas-water interface is composed by spherical gas bubbles and using the standard formula to estimate it (Eq. 6 in Geistlinger et al, 2005), one obtains:…”

“…In the following, we refer to it as bubble-mediated mass transfer (BMT). There exists only a few papers that develop models which are able to include the BMT; however, all of them have certain limitations (Visser et al, 2008;Amos and Mayer, 2006;Geistlinger et al, 2005;Williams and Oostrom, 2000).…”

On the role of caprock and fracture zones in dispersing gas plumes in the subsurface

“…In the more general situation in which the travel time of gas across the pores is comparable to or longer than the dissolution time, less gas is dissolved and the gas plume will travel further before it is dissolved into the water [cf. Geistlinger et al, 2005].…”