title: ³⁹Ar/Ar measurements using ultra-low background proportional counters.
abstract: Age-dating groundwater and seawater using the (39)Ar/Ar ratio is an important tool to understand water mass-flow rates and mean residence time. Low-background proportional counters developed at Pacific Northwest National Laboratory use mixtures of argon and methane as counting gas. We demonstrate sensitivity to (39)Ar by comparing geological (ancient) argon recovered from a carbon dioxide gas well and commercial argon. The demonstrated sensitivity to the (39)Ar/Ar ratio is sufficient to date water masses as old as 1000 years.
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States. Electronic address: jeter@pnnl.gov.
authors.forename: Jeter
authors.initials: J
authors.lastname: Hall
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Craig E
authors.initials: CE
authors.lastname: Aalseth
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Ricco M
authors.initials: RM
authors.lastname: Bonicalzi
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Jill M
authors.initials: JM
authors.lastname: Brandenberger
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Day
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Paul H
authors.initials: PH
authors.lastname: Humble
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Emily K
authors.initials: EK
authors.lastname: Mace
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Panisko
authors.affiliation: Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States.
authors.forename: Allen
authors.initials: A
authors.lastname: Seifert
keywords: (39)Ar; Low level couning; Water age-dating