Successive and automated stable isotope analysis of CO , CH and N O paving the way for unmanned aerial vehicle-based sampling.

RATIONALE

Measurement of greenhouse gas (GHG) concentrations and isotopic compositions in the atmosphere is a valuable tool for predicting their sources and sinks, and ultimately how they affect Earth's climate. Easy access to unmanned aerial vehicles (UAVs) has opened up new opportunities for remote gas sampling and provides logistical and economic opportunities to improve GHG measurements.

METHODS

This study presents synchronized gas chromatography/isotope ratio mass spectrometry (GC/IRMS) methods for the analysis of atmospheric gas samples (20-mL  glass vessels) to determine the stable isotope ratios and concentrations of CO , CH and N O. To our knowledge there is no comprehensive GC/IRMS setup for successive measurement of CO , CH and N O analysis meshed with a UAV-based sampling system. The systems were built using off-the-shelf instruments augmented with minor modifications.

RESULTS

The precision of working gas standards achieved for δ C and δ O values of CO was 0.2‰ and 0.3‰, respectively. The mid-term precision for δ C and δ N values of CH and N O working gas standards was 0.4‰ and 0.3‰, respectively. Injection quantities of working gas standards indicated a relative standard deviation of 1%, 5% and 5% for CO , CH and N O, respectively. Measurements of atmospheric air samples demonstrated a standard deviation of 0.3‰ and 0.4‰ for the δ C and δ O values, respectively, of CO , 0.5‰ for the δ C value of CH and 0.3‰ for the δ N value of N O.

CONCLUSIONS

Results from internal calibration and field sample analysis, as well as comparisons with similar measurement techniques, suggest that the method is applicable for the stable isotope analysis of these three important GHGs. In contrast to previously reported findings, the presented method enables successive analysis of all three GHGs from a single ambient atmospheric gas sample.