Stable isotopes as potential tracers in fluid transport through micropores
Abstract
In order to test the hypothesis that natural abundances of light element stable isotopes may help understand how fluids might migrate through micropores, a lab based study was undertaken. In this study, water samples were stored in plastic vials with caps that appeared to have small pores that enabled liquid water to diffuse at a very slow rate. Samples were analyzed for stable oxygen and hydrogen isotope ratios over a period of months and years. The data showed the same effects observed previously by other researchers in evaporation experiments with no condensation (Cappa et al 2005, 2007). Normally evaporation is treated as a combination of equilibrium and kinetic process. The equilibrium is assumed to take place between liquid and vapor in a microlayer at the water -air interface. Kinetic effects are attributed to differences in diffusional velocities of lighter and heavier isotopes. In the experiments conducted in this study, obviously there is no condensation and unlikely a microlayer where equilibrium is likely to exist. Moreover the system studied also approximates to a perfect "closed system. Therefore, Fick's Law of diffusion under a unidirectional diffusion model will be attempted to explain the observed behavior. It is suggested that this study provides a fundamental science approach and has relevance, for fluid migration (e.g. water, carbon dioxide, methane etc.) from geoenergy development activities through the critical zone.
References: Cappa, C. D., Drisdell, W. S., Smith, J. D., Saykally, R. J., & Cohen, R. C. (2005). Isotope fractionation of water during evaporation without condensation. Journal of Physical Chemistry B, 109(51), 24391-24400. https://doi.org/10.1021/jp0539066 Cappa, C. D., Smith, J. D., Drisdell, W. S., Saykally, R. J., & Cohen, R. C. (2007). Interpreting the H/D isotope fractionation of liquid water during evaporation without condensation. Journal of Physical Chemistry C, 111(19), 7011-7020. https://doi.org/10.1021/jp065095r Kim, K., & Lee, X. (2011). Isotopic enrichment of liquid water during evaporation from water surfaces. Journal of Hydrology, 399(3-4), 364-375. https://doi.org/10.1016/j.jhydrol.2011.01.008- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H51J1623Y
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 1803 Anthropogenic effects;
- HYDROLOGY;
- 1829 Groundwater hydrology;
- HYDROLOGY;
- 1875 Vadose zone;
- HYDROLOGY