Estimation of groundwater velocities from Yucca Flat to the Amargosa Desert using geochemistry and environmental isotopes Page: 30 of 61
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Evolve ER-6-1 to Amargosa Tracer Well #2. This scenario produced five possible chemical
models. Four of the models produced a 813C value 0.4 %o less than the measured 813C value of
Amargosa Tracer Well #2 and a 14C travel time of 445 yrs. One simulation produced a 813C value
0.5 %o more than the measured 813C value; however, this simulation produced a negative 14C travel
time. All five models dissolved dolomite and gypsum with variations between calcite dissolution
and precipitation, Ca- and Mg-montmorillonite precipitation, and release of Na into solution by
Ca/Na exchange (Table 19).
TABLE 19. NETPATH SIMULATION RESULTS FOR GROUNDWATER CHEMICAL EVOLUTION
SCENARIO FROM ER-6-1 TO AMARGOSA TRACER WELL #2.
Parameter Model 1 Model 2 Model 3 Model 4 Model 5
Difference in 613C (%o) -0.4 -0.4 0.5 -0.4 -0.4
14C Travel Time (yrs) 445 445 -1,928 445 445
Calcite (mmoles)* 0.5 0.5 -1.3 - -
Dolomite (mmoles)* 0.3 0.3 1.2 0.5 0.5
Gypsum (mmoles)* 0.4 0.4 0.4 0.4 0.4
Ca-Montmorillonite (mmoles)* - -5.3 - - -3.9
Mg-Montmorillonite (mmoles)* - - -5.3 -1.4 -1.4
Ca/Na Exchange (mmoles)t 0.9 - - 0.7 -
*For minerals, negative number indicates precipitation, positive number indicates dissolution.
tFor exchange, negative number indicates Ca released into solution, positive number indicates Na released into solution.
Evolve UE-1q to Amargosa Tracer Well #2. This scenario produced five possible chemical
models but only one model with a 813C value within 1.0 %o of the measured 613C value of Amargosa
Tracer Well #2. This model produced a 813C value 0.4 %o more than the measured 813C value but
a negative 14C travel time (Table 20). The simulation precipitated 1.9 mmoles of calcite, dissolved
1.8 mmoles of dolomite and 0.5 mmoles of gypsum, and precipitated 9.4 mmoles of
Mg-montmorillonite.
TABLE 20. NETPATH SIMULATION RESULTS FOR GROUNDWATER CHEMICAL EVOLUTION
SCENARIO FROM UE-lq TO AMARGOSA TRACER WELL #2.
Parameter Model 1
Difference in 813C (%o) 0.4
14C Travel Time (yrs) -756
Calcite (mmoles)* -1.9
Dolomite (mmoles)* 1.8
Gypsum (mmoles)* 0.5
Ca-Montmorillonite (mmoles)*
Mg-Montmorillonite (mmoles)* -9.4
Ca/Na Exchange (mmoles)t -
*For minerals, negative number indicates precipitation, positive number indicates dissolution.
tFor exchange, negative number indicates Ca released into solution, positive number indicates Na released into solution.21
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Hershey, Ronald L. & Acheampong, Steve Y. Estimation of groundwater velocities from Yucca Flat to the Amargosa Desert using geochemistry and environmental isotopes, report, June 1, 1997; Reno, Nevada. (https://digital.library.unt.edu/ark:/67531/metadc691859/m1/30/: accessed April 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.