Dating wine tritium
Sampling for tracers The feasibility of using CFCs as tracers of recent recharge and indicators of ground-water age was first recognized in the 1970s (see Plummer and Busenberg, 1997 and references therein).CFCs have been increasingly used in oceanic studies since the late 1970s as tracers of oceanic circulation, ventilation, and mixing processes.A closed path is established between the well or pump to a valve system that is used to fill glass ampoules with water, creating a headspace with CFC-free, ultra-pure nitrogen gas. Age is determined from CFCs by relating their measured concentrations in ground water back to known historical atmospheric concentrations and/or to calculated concentrations expected in water in equilibrium with air.As with any environmental tracer, age applies to the date of introduction of the chemical substance into the water, and not to the water itself.H), and other chemical and isotopic substances in ground water, can be used to trace the flow of young water (water recharged within the past 50 years) and to determine the time elapsed since recharge.Information about the age of ground water can be used to define recharge rates, refine hydrologic models of ground-water systems, predict contamination potential, and estimate the time needed to flush contaminants from ground-water systems.The detection of chlorofluorocarbons and tritium in ground water provides valuable information that can be used for dating and tracing young ground watertechniques that help water-resources managers develop management strategies for shallow ground-water systems.Young ground water in shallow ground-water systems Young ground water is typically found at depths from 0 to 100 feet in unconsolidated sediments and at depths up to 1000 feet in fractured-rock systems.
The CFC analysis determined that concentrations of CFC-11, CFC-12 and CFC-113 were 493, 203, and 28 pg/kg in the water sample to be dated. B., Busenberg, Eurybiades, Drenkard, Stefan, Schlosser, Peter, and Michel, R. N., Busenberg, Eurybiades, Drenkard, Stefan, Schlosser, Peter, Mc Connell, J. L., Ekwurzel, Brenda, and Weppernig, Ralf, 1998b, Flow of river water into a karstic limestone aquifer, 2.
For this reason, the term age is normally qualified with the word model or apparent, that is, model age or apparent age. USGS scientists have investigated some of the most important factors that can affect CFC concentrations in ground water and the resulting age interpretations (Busenberg and Plummer, 1992; Plummer and others, 1993; Dunkle and others, 1993; Ekwurzel and others, 1994; Cook and others, 1995; Plummer and others 1998a, 1998b; Plummer and Busenberg, 1999).
These include (1) uncertainty of the temperature at the water table during recharge, (2) entrapment of excess air during recharge, (3) uncertainty in recharge elevation, (4) thickness of the unsaturated zone, (5) effect of urban air where CFC values may exceed regional values, (6) contamination from a specific local source, (7) microbial degradation (in anaerobic environments), (8) sorption onto organic and mineral surfaces, and (9) mixing of younger and older water in a well. A., 1998, Chemistry of unsaturated zone gases sampled in open boreholes at the crest of Yucca Mountain, Nevada: Data and basic concepts of chemical and physical processes in the mountain: Water Resources Research, v. For additional information, see or contact: Niel Plummer (email: [email protected]) U.
In the atmosphere, these substances have mixed and spread worldwide.
These atmospheric substances, such as tritium (H) in water vapor from detonation of nuclear bombs in the 1950s and early 1960s,and chlorofluorocarbons (CFCs) from refrigeration and other uses from the 1950s through the 1980s, dissolve in precipitation, become incorporated in the Earths hydrologic cycle, and can be found in ground water that has been recharged within the past 50 years.