Field Degassing as a New Sampling Method for 14 C Analyses in Old Groundwater

Radiocarbon ( 14 C) activity in groundwater can be used to determine subsurface residence time up to ∼40 kyr, providing crucial information on dynamic properties of groundwater and on paleoclimate. However, commonly applied sampling methods for dissolved inorganic carbon (DIC- 14 C) are prone to low level of modern atmospheric contamination, resulting in underestimation of groundwater ages that cluster around 30–40 kyr. We extract CO 2 gas from groundwater using a device originally developed for studies of noble gas radionuclides. Carbon is collected in the gas phase, eliminating the possibility of fostering microbial activities and aqueous chemical reactions during sample storage. This method collects CO 2 - 14 C and radiokrypton ( 81 Kr and 85 Kr) samples simultaneously. The presence of any shorter-lived 85 Kr is used to evaluate the degree of atmospheric contamination during sampling or mixing of young groundwater. Most groundwater samples showed lower CO 2 - 14 C activities than those of DIC- 14 C, presumably due to the absence of atmospheric contamination. Samples with 81 Kr age exceeding 150 kyr have no detectable CO 2 - 14 C except where mixing sources of young groundwater is suspected. These field data serve as confirmations for the reliability of the newly presented sample collection and CO 2 - 14 C method, and for the outstanding roles of radiokrypton isotopes in characterizing old groundwater

Contamination · Dissolved organic carbon · Groundwater · Isotope · Isotopes of carbon · Radiocarbon dating · Radionuclide · Total organic carbon · Chemistry · Environmental Science · Geology and Paleoclimatology Research · Groundwater and Isotope Geochemistry · Hydrocarbon exploration and reservoir analysis · Environmental Chemistry · Geology

• A Simple Co 2 Extraction Method for Radiocarbon Analyses of Dissolved Inorganic Carbon in Water Samples Without a Carrier Gas

  Open Access•Hiroshi A Takahashi, Hiroko Handa et al.•Radiocarbon•2021

  Incluir item

• Comparison of 14 C Collected by Precipitation and Gas-Strip Methods for Dating Groundwater

  Open Access•Kotaro Nakata, Takuma Hasegawa et al.•Radiocarbon•2016

  Incluir item

• Rehovot Radiocarbon Measurements I

  Open Access•I Carmi, Y Noter et al.•Radiocarbon•1971

  Incluir item

• A Gas Ion Source for Radiocarbon Measurements at 200 kV

  Open Access•M Ruff, L Wacker et al.•Radiocarbon•2007

  Incluir item

• On-line Radiocarbon Measurements of Small Samples Using Elemental Analyzer and Micadas Gas Ion Source

  Open Access•M Ruff, S Fahrni et al.•Radiocarbon•2010

  Incluir item

• Optical Detection of Radiocarbon Dioxide

  Iacopo Galli, S Bartalini et al.•Radiocarbon•2013

  Incluir item

• Radiocarbon Variability in Groundwater in an Extremely Arid Zone—The Arava Valley, Israel

  Open Access•Avihu Burg, Michael Zilberbrand et al.•Radiocarbon•2013

  Incluir item

• Rehovot Radiocarbon Measurements III

  Open Access•Israel Carmi•Radiocarbon•1987

  Incluir item