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http://hdl.handle.net/10136/501
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| Title: | Dispersion induced advection of an isotope ratio |
| Authors: | Wolff, Mark R. |
| Issue Date: | 26-Aug-2009 |
| Abstract: | In hydrologic investigations, knowledge of the groundwater age can be valuable in better understanding the hydrologic system and its properties. Isotopic dating is a commonly used method of determining groundwater age. In using isotopic dating it is frequently assumed that the common isotope, of the isotopic ratio, remains constant in concentration over the domain of the area under investigation. What effect does constant spatial variability of the concentration of the common isotope have upon the isotopic ratio and inferences that might be drawn from that ratio?
An equation to describe one-dimensional groundwater transport of an isotope in terms of a ratio between rare and common isotopes of an element is developed in this paper. This description of the transport process differs from others in that an additional term to account for the effects of spatial variation in the common isotope concentration upon the effective advective velocity of the system, termed dispersion induced advection, is introduced. The effects upon isotopic transport of a dispersion induced advection term sufficiently large to change the effective advective velocity by more than 10 percent are examined using analytical and numerical techniques. Analytical results indicate that when significant dispersion induced advection is present, the spatial distribution of a isotopic ratio is effected. Numerical results indicate the difficulty in the selection of the appropriate realistic boundary and initial conditions to simulate the effects of dispersion induced advection.
The implication of these findings suggest that prior to the modeling of isotopic transport in terms of a ratio, careful examination of all isotopic data for a spatial common isotope concentration gradient is required. In the presence of such a concentration gradient, both components of the isotopic ratio should be modeled separately. |
| URI: | http://hdl.handle.net/10136/501 |
| Appears in Collections: | Independent Studies
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| Wolff, Mark R..pdf | | 3218Kb | Adobe PDF | View/Open |
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