Dating young groundwater with sulfur hexafluoride: Natural and anthropogenic sources of sulfur hexafluoride

Abstract

Abstract. Sulfur hexafluoride (SF6) is primarily of anthropogenic origin but also occurs naturally. The troposphere concentration of SF 6 has increased from a steady state value of 0.054 _+ 0.009 to more than 4 parts per trillion volume during the past 40 years. An analytical procedure was developed for measuring concentrations of SF 6 to less than 0.01 fmol/L in water. Groundwater can be dated with SF 6 if it is in equilibrium with atmospheric SF 6 at the time of recharge and does not contain significant SF 6 from other sources. The dating range of SF 6 is currently 0 to 30 years. The tracer was successfully used to date shallow groundwater of the Atlantic Coastal Plain sand aquifers of the United States and springs issuing near the top of the Blue Ridge Mountains of Virginia. Significant concentrations of naturally occurring SF 6 were found in some igneous, volcanic, and sedimentary rocks and in some hydrothermal fluids.

Residence time, mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone

“…Lag times may be observed and are mostly dependant on gas solubility, diffusion coefficients and soil water content (Cook and Herczeg, 2000;Heaton and Vogel, 1981) and geology (Cook et al, 1995;Cook et al, 2006). In addition, contamination problems may occur in presence of individual sewage treatment plants and tips (Archbold et al, 2012;Hohener et al, 2003) or gardening activities (Busenberg and Plummer, 2000;Spurlock et al, 2000). Within the Bonifacio aquifer, the presence of a thick UZ (with variable thickness, see Table 1) as well as the presence of some individual sewage treatment plants and gardening activities may probably modify groundwater residence time in some places.…”

Assessing the applicability of global CFC and SF6 input functions to groundwater dating in the UK

“…Chlorofluorocarbons (CFCs) and sulphur hexafluoride (SF 6 ) are increasingly being used to date recent groundwater components (Busenberg and Plummer, 1992;Cook et al 1996;Oster et al, 1996: Busenberg andPlummer, 2000). Their use in this role depends critically on the input function, i.e.…”

Development of an in situ sampler of submarine springs for the analysis of CFCs and SF6

“…Tritium ( 3 H) has been employed to estimate the groundwater residence time up to 60 years, but it is now less useful because of its decline to pre-1950 levels in precipitation. Recently, chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF 6 ) have been successfully used to estimate the residence time of young continental groundwater (Busenberg and Plummer, 2000;Bauer et al, 2001;IAEA, 2006). We used these tracers in our investigation.…”