HR: 0830h
AN: A31D-0067    [PDF]
TI: Preparation of Gravimetric Standards for Measurements of Atmospheric O2/N2 Ratio and Reevaluation of Atmospheric O2 Concentration
AU: * Tohjima, Y
EM: tohjima@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506 Japan
AB: Great concern has been increased about the measurements of the variations in atmospheric O2 concentration because they give us crucial information about the carbon cycle. The changes in the atmospheric O2 concentration are usually reported as relative deviations of O2/N2 ratio from a reference gas. However, there is no reference gas of which absolute O2 concentration is determined at ppm level. Therefore each laboratory uses ambient air filled into cylinders or flasks as own reference gases. In this study, gravimetric mixtures containing natural levels of CO2, Ar, O2 and N2 gases were prepared in 10-L high-pressure aluminum cylinders to develop absolute scale for the O2 measurements. The mole fractions of individual components, calculated from the weights determined by a highly precise balance, were compared with analyzed values of CO2, Ar, and (O2+Ar)/N2. The precision of the gravmimetric O2 concentration was estimated to be about 3 ppm from the 14 gravimetric mixtures. The gravimetric O2 scale was applied to the atmospheric O2 measurements from air samples collected at Hateruma Island. The results showed that the annual mean in 2001 was by about 70 ppm lower than the global mean O2 concentration reported by Machta and Hughes (1970).
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 1610 Atmosphere (0315, 0325)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting