ANALYSIS OF NOBLE-GASES IN WATER USING A QUADRUPOLE MASS-SPECTROMETERIN STATIC-MODE

A quadrupole-based mass spectrometer used in static mode has been empl oyed to determine noble gas concentrations of water samples by isotope dilution. Water samples are degassed and spiked with minor isotopes o f each noble gas. After separation of the various gas components, the isotopic ratios are measured in the mass spectrometer. Because a spike is added to each sample, the recovery of each gas component does not have to be quantitative. Equilibration temperatures are calculated fro m the gas concentrations, based on noble gas solubility data. An accur acy of +/-1 degrees C, from the air equilibration temperature, is atta inable for air-saturated water samples prepared under controlled condi tions in the laboratory. The method has been applied to groundwaters f rom the London Basin Chalk aquifer. The noble-gas-derived temperatures are consistent with climatic conditions prevailing at the periods of recharge. (C) 1997 Elsevier Science Ltd. All rights reserved.