Preparation of gravimetric standards for measurements of atmospheric oxygen and reevaluation of atmospheric oxygen concentration

作者：Yasunori Tohjima, Toshinobu Machida, Tomonori Watai, Isao Akama, Taketo Amari, Yasushi Moriwaki · 发表于：Journal of Geophysical Research Atmospheres · 年份：2005 · DOI：10.1029/2004jd005595 · 被引用次数：94 · 研究领域：Atmospheric and Environmental Gas Dynamics、Atmospheric Ozone and Climate、Atmospheric chemistry and aerosols

Fourteen standard mixtures composed of ambient levels of CO 2 , Ar, O 2 , and N 2 have been prepared in 10‐L high‐pressure aluminum cylinders by a gravimetric technique for atmospheric O 2 measurements. A highly precise balance with a precision of 2.5 mg is used to determine the masses of individual components in the cylinders. To balance the buoyant forces on both sides of the balance beam during weighing the gravimetric standard cylinder, a same sized cylinder is placed on a pan on the opposite side of the beam. In addition, the cylinders of the gravimetric standards and a tare cylinder are alternately weighed to compensate for the drift of the zero‐point of the balance. To determine the mole fractions accurately, the mass of each component is corrected for the buoyancy changes caused by the expansion of the cylinder, and the molecular masses of the source O 2 and N 2 gases are corrected for their isotopic compositions. The differences in the O 2 mole fractions of the 14 gravimetric standards range about 100 ppm (μmol mol −1 ). The gravimetric mole fractions are compared with the analyzed values of CO 2 , Ar, O 2 + Ar, and (O 2 + Ar)/N 2 . The reproducibility of the gravimetric technique is determined from the standard deviations of the differences between the gravimetric and analyzed values, and is quantified as 15.5 per meg for the O 2 /N 2 ratio and 2.9 ppm for the O 2 mole fraction. The gravimetric scale is applied to the measurements from air samples collected at Hater...