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Reliable determination of oxygen and hydrogen isotope ratios in atmospheric water vapour adsorbed on 3A molecular sieve
Author(s) -
Han LiangFeng,
Gröning Manfred,
Aggarwal Pradeep,
Helliker Brent R.
Publication year - 2006
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2772
Subject(s) - chemistry , water vapor , molecular sieve , adsorption , nitrogen , volume (thermodynamics) , hydrogen , analytical chemistry (journal) , precipitation , oxygen 18 , isotope , environmental chemistry , isotopes of oxygen , nuclear chemistry , meteorology , physics , organic chemistry , quantum mechanics
The isotope ratio of atmospheric water vapour is determined by wide‐ranging feedback effects from the isotope ratio of water in biological water pools, soil surface horizons, open water bodies and precipitation. Accurate determination of atmospheric water vapour isotope ratios is important for a broad range of research areas from leaf‐scale to global‐scale isotope studies. In spite of the importance of stable isotopic measurements of atmospheric water vapour, there is a paucity of published data available, largely because of the requirement for liquid nitrogen or dry ice for quantitative trapping of water vapour. We report results from a non‐cryogenic method for quantitatively trapping atmospheric water vapour using 3A molecular sieve, although water is removed from the column using standard cryogenic methods. The molecular sieve column was conditioned with water of a known isotope ratio to ‘set’ the background signature of the molecular sieve. Two separate prototypes were developed, one for large collection volumes (3 mL) and one for small collection volumes (90 µL). Atmospheric water vapour was adsorbed to the column by pulling air through the column for several days to reach the desired final volume. Water was recovered from the column by baking at 250 °C in a dry helium or nitrogen air stream and cryogenically trapped. For the large‐volume apparatus, the recovered water differed from water that was simultaneously trapped by liquid nitrogen (the experimental control) by 2.6‰ with a standard deviation (SD) of 1.5‰ for δ 2 H and by 0.3‰ with a SD of 0.2‰ for δ 18 O. Water‐vapour recovery was not satisfactory for the small volume apparatus. Copyright © 2006 John Wiley & Sons, Ltd.