Abstract
Analytical details for 13C and 18O isotope analyses of atmospheric CO2 in large air samples are given.
The large air samples of nominally 300 L were collected during the passenger aircraft-based
atmospheric chemistry research project CARIBIC and analyzed for a large number of trace gases
and isotopic composition. In the laboratory, an ultra-pure and high efficiency extraction system and
high-quality isotope ratio mass spectrometry were used. Because direct comparison with other
laboratories was practically impossible, the extraction and measurement procedures were tested
in considerable detail. Extracted CO2 was measured twice vs. two different working reference CO2
gases of different isotopic composition. The two data sets agree well and their distributions can be
used to evaluate analytical errors due to isotope measurement, ion corrections, internal calibration
consistency, etc. The calibration itself is based on NBS-19 and also verified using isotope analyses on
pure CO2 gases (NIST Reference Materials (RMs) and NARCIS CO2 gases). The major problem
encountered could be attributed to CO2-water exchange in the air sampling cylinders. This exchange
decreased over the years. To exclude artefacts due to such isotopic exchange, the data were filtered to
reject negative d18O(CO2) values. Examples of the results are given
Original language | Undefined/Unknown |
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Pages (from-to) | 822-830 |
Number of pages | 9 |
Journal | Rapid Communications in Mass Spectrometry |
Volume | 23 |
Issue number | 6 |
Publication status | Published - 2009 |