Groundwater data and age information from samples collected in Minnesota, 1996-1997

Groundwater age distributions and susceptibility to natural and anthropogenic contaminants were assessed for selected wells across Minnesota. The data provide information to understand how long it will take to observe groundwater quality improvements from best management practices implemented at land surface to reduce losses of nitrate (and other chemicals) from agricultural practices. A total of 13 age estimates were done on samples collected from 8 wells between July 1996 and May 1997. Groundwater ages were estimated from dissolved gas (argon and nitrogen) and environmental tracer data (tritium, chlorofluorocarbons, and tritiogenic helium-3) from field samples using the equations available in TracerLPM (an Excel® workbook for interpreting groundwater age distributions from environmental tracer data) and DGMETA (an Excel® workbook for dissolved gas modeling and environmental tracer analysis); groundwater age estimates are reported in Table_1_Age_Information.txt. DGMETA was used to compute optimal water temperature and excess air that explain the measured dissolved gases (argon and nitrogen) in a sample; condensed results are reported in Table_1_Age_Information.txt and these results are reported in detail in Table_2_Dissolved_Gases.txt. These values were then used to convert the raw measured concentrations of chlorofluorocarbons into a form appropriate for age dating analysis, the dry air mixing ratio of chlorofluorocarbons; these results are reported in Table_3_Computed_Tracer_Concentrations.txt. Table_4_Additional_Helium.txt reports calculated concentrations of tritiogenic helium that were used in groundwater age calculations and the measured concentrations used in those calculations. Table_5_Site_And_Background_Information.txt reports additional site information and field parameters. In addition to these five tables, two ancillary tables are included to provide more detailed information about the fields and the abbreviations used in tables 1-5. A readme file is provided that describes each table in more detail and processes to use the data in this data release to view age distributions in TracerLPM and to set up TracerLPM to run scenarios for other chemicals of interest.

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