KW_chemistry_isotopes

Chemistry and Isotope Data Sample Collection: Water samples were collected from approximately 100 feet (30 meters) below the water table using either a 4 foot or 6 foot long stainless-steel bailers with an inner diameter of 0.5 in. Samples for anion concentration measurements were poured into 60 ml polypropylene bottles through 0.45mm pore-diameter filter. Raw (unfiltered, unpreserved) samples for oxygen-18 and deuterium isotope analyses were stored in 30 ml glass bottles. Sample Analyses: The concentrations of sulfate (SO42-), chloride (Cl-), and fluoride (F-) in samples collected until October 2003 were determined with a Dionex DX-300 ion chromatograph, and since October 2003 with a Dionex ICS-2000 ion chromatograph at the U.S. Geological Survey laboratories in Menlo Park, California, with analytical errors better than 3%. Concentrations of fluoride were usually at or below the analytical detection limit. Total alkalinity was determined on stored samples by titrating ten milliliters of sample with 0.05 N sulfuric acid to the bicarbonate end-point. The analytical error in the determined alkalinity concentrations is approximately 5%. Starting in March 2018, alkalinity has been determined in the field using a portable titrator. Oxygen-18 and deuterium isotope analyses were stored in 30 ml glass bottles and analyzed at the USGS laboratories in Reston, Virginia. Analysis of oxygen isotopes was according to the methods of Epstein and Mayeda [1953] with a precision of ±0.1°, and the hydrogen isotopes were analyzed according to the method described in Kendall and Coplen [1985] and Coplen et al. [1991] with a precision of ±1.5°. References Coplen, T. B., J. D. Wildman, and J. Chen, Improvements in the gaseous hydrogen-water equilibration technique for hydrogen isotope ratio analysis, Anal. Chem., 63, 910– 912, 1991. doi:10.1021/ac00009a014. Epstein, S., and T. Mayeda, Variation of 18O content of waters from natural sources, Geochim. Cosmochim. Acta, 4, 213– 224, 1953, doi: 10.1016/0016-7037(53)90051-9. Kendall, C., and T. B. Coplen, Multi sample conversion of water to hydrogen by zinc for stable isotope determination, Anal. Chem., 57, 1437-1440, 1985, doi: 10.1021/ac00284a058. Database Contents The data file (KW_chemistry_isotopes.csv) contains the anion concentrations and the water isotope data for water samples from the deep well. The entries in the data file appear in the following columns: A. Sample name B. Date sample was collected C. Alkalinity (milligrams per liter as bicarbonate) D. Fluoride concentration (milligrams per liter) E. Chloride concentration (milligrams per liter) F. Sulfate concentration (milligrams per liter) H. Hydrogen isotope value (per mil) I. Oxygen isotope value (per mil)

[
  "010:12"
]

[
  "geospatial"
]