Carbon and isotopic mass balance models of Oasis Valley-Fortymile Canyon ground water basin, southern Nevada
Environmental isotopes and carbon chemistry provide means of differentiating various recharge areas, flow paths, and ages of ground water in portions of the Nevada Test Site and vicinity. Regional {delta}D/{delta}{sup 18}O trends are offset from the present-day meteoric line by a deuterium depletion of 5 per thousandth, suggesting paleoclimatic changes. Partial pressures of CO{sub 2} and the {sup 18}O and {sup 13}C data indicate solubility and isotopic equilibrium between the gas and water in the soil zone with progressive exchange with underlying ground water in the shallow alluvium of Oasis Valley. Application of a closed system CO{sub 2} model using the EQ3NR/EQ6 reaction path simulator successfully reproduces chemical compositions observed in the alluvium in the Amargosa Desert and in the deep tuff aquifer beneath Pahute Mesa and Yucca Mountain. Initial P/sub CO{sub 2}/ input to the soil zone during recharge was calculated to range from 0.03 to 0.10 atm, which is comparable to measured soil CO{sub 2} pressures in Oasis Valley. Results are compared for {sup 14}C ages using the {delta}{sup 13}C dilution correction and a mass action correction term relating predicted and calculated ionic activity products of CaCO{sub 3}. Results are generally comparable with discrepancies attributed to anomalous {delta}{sup 13}C values.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 60190
- Journal Information:
- Water Resources Research, Vol. 23, Issue 4; Other Information: PBD: Apr 1987
- Country of Publication:
- United States
- Language:
- English
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