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Noble gas isotopes and lumped parameter model results for environmental tracer based groundwater ages, South Rim Grand Canyon, Arizona, USA

February 5, 2020

This data release documents three Microsoft Excel tables; one contains noble gas isotopic data, one contains data for understanding groundwater ages in the South Rim of the Grand Canyon, and one that describe the data fields. Results described include raw noble gas concentrations, environmental tracer concentrations (tritium, tritiogenic helium-3, sulfur hexafluoride, carbon-14, and chlorofluorocarbons), and mean age and age distribution.

Noble gas isotopes (NobleGas) contain noble gas isotope concentrations measured for South Rim springs. Samples were collected in pinch clousure copper tubes (Weiss, 1968) and analyzed at the University of Utah Dissolved Gas Lab.

Mean age and age distribution results (TracerLPM) contain final models of groundwater age by calibration of lumped parameter models to tracer concentrations (Jurgens and others, 2012). In cases where age was modeled with a binary lumped parameter model (BMM), the mean age was computed from the mean age and fraction of the two components in the mixture. Please see the processing steps below and the main manuscript for additional details on the results presented in this table. Multiple LPMs are provided for a single sample to estimate uncertainty in mean age and age distribution associated with LPM parameter estimates.

Jurgens, B.C., Bohlke, J.K., and Eberts, S.M., 2012, TracerLPM (Version 1): An Excel workbook for interpreting groundwater age distributions from environmental tracer data: U.S. Geological Survey Techniques and Methods Report 4-F3, 60 p., https://pubs.usgs.gov/tm/4-f3/.