The Cryogenic Enrichment System in Chromatographic Analysis of Noble Gases in Groundwater
J. Najman and I. Śliwka
Institute of Nuclear Physics, Polish Academy of Sciences, E. Radzikowskiego 152, 31-342 Kraków, Poland
Received: July 20, 2015; In final form: July 18, 2016
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The concentration of helium in groundwater may be a good environmental tracer for groundwater dating in hydrogeology. In this work, we present a chromatographic method for simultaneous analysis of helium, neon, and argon in groundwater from a single groundwater sample. Proper use of environmental tracers for dating purposes requires the knowledge of the recharge temperature of the system and the excess air. Both parameters can be determined by measuring the concentration of argon and neon in groundwater. The lowest helium concentration in groundwater is 4.8×10-8 cm3STP/gH2O at sea level and temperature 10°C. In view of the deficiency of a suitable detector with a limit of detection for helium at the level of 4.8×10-8 cm3STP/gH2O, the application of the enrichment method is necessary. In this work, the cryogenic method of enrichment with activated charcoal at abated pressure conditions was applied. Helium, neon and argon are analyzed on two gas chromatographs equipped with capillary and packed columns (filled with molecular sieve 5A and activated charcoal) and three thermo-conductive detectors. The chromatographic method was applied to groundwater dating from Kraków and Żarnowiec aquifers. The levels of detection for measurement systems for the tested compounds are: 1.9×10-8 cm3STP/cm3 for neon, 3.1×10-6 cm3STP/cm3 for argon, and 1.2×10-8 cm3STP/cm3 for helium.

DOI: 10.12693/APhysPolA.130.737
PACS numbers: 68.43.-h, 07.20.Mc, 92.40.Kf, 92.40.-t