Chlorine isotopes as environmental tracers in Columbia River basalt groundwaters

Conference · Thu Mar 01 00:00:00 EST 1984

OSTI ID:5750590

Graham, D L; Gifford, S; Bentley, H

Chlorine-36 analyses were performed on 21 groundwater samples collected from six boreholes penetrating the Saddle Mountains, Wanapum, and Grande Ronde Formations of the Columbia River basalts. These samples were collected from depths of 136 to 1353 m below land surface and represent waters from both sedimentary interbeds and basalt flow top aquifers. Measured levels of /sup 36/Cl (atoms/L x 10/sup -7/) ranged from 3 to 26 and /sup 36/Cl/Cl ratios ranged from 7 to 1130 (x 10/sup 15/). The highest /sup 36/Cl ratios were interpreted as modern input of /sup 36/Cl and are two to three times that predicted for this latitude. Analyses of stable chlorine isotopes were performed on 14 samples form 7 boreholes penetrating the Wanapum and Grande Ronde Formations. Ratios of /sup 37/Cl//sup 35/Cl range from +0.46% (accuracy to two decimal points) relative to Standard Mean Ocean Chloride (SMOC). Negative delta/sup 37/Cl values were associated with the lowest groundwater chloride concentrations. Chlorine isotopic information was used to arrive at a groundwater flow model suggesting that recharge is occurring in the western portion of the Hanford Site with shallow circulation through the Saddle Mountains and Wanapum Basalts, and upward flow from the Grande Ronde Basalts to the Wanapum Basalts to the east of the Reference Repository location. In addition to meteoric chloride, a second chloride source was hypothesized. Two explanations are proposed which account for this source of chloride: (1) chloride previously dissolved and transported into the basalt groundwaters from an external source and/or (2) chloride leached from the host rock. The low /sup 36/Cl concentration associated with this second source of chloride implies a very long residence time. One sample from the deep Grande Ronde indicates a groundwater age in excess of 300,000 yr. 11 refs., 7 figs., 2 tabs.

• Research Organization: Rockwell International Corp., Richland, WA (USA). Rockwell Hanford Operations; Hydro Geo Chem., Inc., Tucson, AZ (USA)
• DOE Contract Number: AC06-77RL01030
• OSTI ID: 5750590
• Report Number(s): RHO-BW-SA-372P; CONF-850170-2; ON: DE85011392
• Resource Relation: Conference: 17. International Association of Hydrologists international congress, Tucson, AZ, USA, 7 Jan 1985; Other Information: Portions of this document are illegible in microfiche products
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CHLORINE 35
ISOTOPE RATIO
CHLORINE 36
CHLORINE 37
GROUND WATER
FLOW MODELS
AGE ESTIMATION
BASALT
EXPERIMENTAL DATA
HYDROLOGY
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHLORINE ISOTOPES
DATA
ELECTRON CAPTURE RADIOISOTOPES
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
INFORMATION
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL MODELS
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
OXYGEN COMPOUNDS
RADIOISOTOPES
ROCKS
STABLE ISOTOPES
VOLCANIC ROCKS
WATER
YEARS LIVING RADIOISOTOPES
580100* - Geology & Hydrology- (-1989)
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