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[Fizinfo] Atomki-szeminárium

Chronological Thread 
  • From: Máté Zoltán <mate AT>
  • To: Fizinfo <fizinfo AT>
  • Subject: [Fizinfo] Atomki-szeminárium
  • Date: Wed, 4 Feb 2015 17:43:22 +0100 (CET)
  • Authentication-results: (amavisd-new); dkim=pass (2048-bit key)

Az MTA Atommagkutató Intézet előadótermében
(Debrecen, Bem tér 18/c. 12. ép. III. em.)
2015. február 10-én, KEDDEN 11:00-kor

(US Geological Survey Groundwater Dating Laborator)

Exploring Hydrofluorocarbons as Groundwater Age Tracers

címmel előadást tart.

Az előadás előtt 10:30-tól tea, vendégeket szívesen látunk.

Máté Zoltán

Groundwater dating tracers are an essential tool for analyzing hydrologic
conditions in groundwater systems. Commonly used tracers for dating
post-1940s groundwater include sulfur hexafluoride (SF6), chlorofluorocarbons
(CFCs), 3H-3He, and other isotopic tracers (85Kr, delta2H and delta18O
isotopes, etc.). Each tracer carries a corresponding set of advantages and
limitations imposed by field, analytical, and interpretive methods.
Increasing the number available tracers is appealing, particularly if they
possess inert chemical properties and unique temporal emission histories from
other tracers.

Among the likely candidates identified are HCFC-22 and HFC-134a. Both
compounds have unique atmospheric histories and chemical properties compared
to other tracers, making them appealing for inclusion lumped parameter mixing
models and in situations where SF6 or the CFCs are present in elevated
concentrations from non-atmospheric sources such that they cannot be used for
dating purposes. To measure these compounds we developed an analytical method
that uses an atomic emission detector (GC-AED) in place of an ECD. In
contrast to the ECD, the AED is a universally sensitive, highly linear,
elementally specific detector, with sensitivities reaching into the low
pico-gram range. The GC-AED system is capable of detecting concentrations
cca. 200 fM (HCFC-22) and cca. 100 fM (HFC-134a), corresponding to piston
flow ages of 54 and 18 yr, respectively, with a typical uncertainty of cca. 1
yr. Comparisons between H(C)FCs, CFCS, and SF6 typically show broad
disagreement between traditional dating methods and the H(C)FCs, indicating
they are generally subject to loss processes, and may not be suitable for use
as groundwater age tracers.
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