A centrifugal ice microtome for measurements of atmospheric CO2 on air trapped in polar ice cores

[摘要] For atmospheric CO₂ reconstructions using ice cores, the technique torelease the trapped air from the ice samples is essential for the precisionand accuracy of the measurements. We present here a new dry extractiontechnique in combination with a new gas analytical system that together showsignificant improvements with respect to current systems. Ice samples(3–15 g) are pulverised using a novel centrifugal ice microtome (CIM) byshaving the ice in a cooled vacuum chamber (−27 °C) in which nofriction occurs due to the use of magnetic bearings. Both, the shavingprinciple of the CIM and the use of magnetic bearings have not been appliedso far in this field. Shaving the ice samples produces finer ice powder andreleases a minimum of 90% of the trapped air compared to50%–70% when needle crushing is employed. In addition, thefriction-free motion with an optimized design to reduce contaminations of theinner surfaces of the device result in a reduced system offset of about2.0 ppmv compared to 4.9 ppmv. The gas analytical part shows ahigher precision than the corresponding part of our previous system by a factor of two, andall processes except the loading and cleaning of the CIM now runautomatically. Compared to our previous system, the complete system shows a 3times better measurement reproducibility of about 1.1 ppmv(1 σ) which is similar to the best reproducibility of other systemsapplied in this field. With this high reproducibility, no replicatemeasurements are required anymore for most future measurement campaignsresulting in a possible output of 12–20 measurements per day compared to amaximum of 6 with other systems.

[学科分类] 几何与拓扑