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Extreme fractionation of gases caused by formation of clathrate hydrates in Vostok Antarctic Ice
Author(s) -
Ikeda Tomoko,
Fukazawa Hiroshi,
Mae Shinji,
Pepin Laurence,
Duval Paul,
Champag Bernard,
Lipenkov Volodya Ya.,
Hondoh Takeo
Publication year - 1999
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1998gl900220
Subject(s) - clathrate hydrate , atmospheric pressure , geology , hydrostatic equilibrium , fractionation , dissociation (chemistry) , hydrostatic pressure , raman spectroscopy , mineralogy , analytical chemistry (journal) , chemistry , hydrate , environmental chemistry , thermodynamics , oceanography , physics , organic chemistry , quantum mechanics , optics
Atmospheric gases are trapped in ice sheets. These gases stored in air‐bubbles at shallower depth are gradually transformed into clathrate hydrates below the depth where the hydrostatic pressure exceeds the dissociation pressure of the clathrate hydrates. We measured Raman spectra of air‐bubbles and clathrate hydrates in Vostok Antarctic ice cores in order to determine the fractionation effects on the concentrations of gases during their transition process. The results showed variations of the N 2 /O 2 ratios with depth. The average N 2 /O 2 ratio in the air‐bubbles increases from the atmospheric value at the beginning of the transition to 11.7 at the end. The average N 2 /O 2 ratio for the clathrate hydrates is 2.0 at the beginning, and asymptotically approaches the atmospheric value. This fractionation is attributed to faster diffusion of O 2 than N 2 through the ice lattice.