posted on 2018-01-05, 15:25authored byYeongjun Ryu, Jinho Ahn, Ji-Woong Yang
Atmospheric nitrous
oxide (N2O) is a greenhouse gas
and ozone-depleting substance whose emissions are substantially perturbed
by current human activities. Although air trapped in polar ice cores
can provide direct information about N2O evolution, analytical
precision was not previously sufficient for high temporal resolution
studies. In this work, we present a highly improved analytical technique
with which to study N2O concentrations in ancient-air-trapped
ice cores. We adopt a melt–refreezing method to extract air
and use a gas chromatography–electron capture detector (GC–ECD)
to determine N2O concentrations. The GC conditions are
optimized to improve the sensitivity for detecting N2O.
Retrapped N2O in ice during the extraction procedure is
precisely analyzed and corrected. We confirmed our results using data
from the Styx Glacier ice core in Antarctica by comparing them with
the results of a dry-extraction method. The precision estimated from
the pooled standard deviation of replicated measurements of the Styx
ice core was 1.5 ppb for ∼20 g of ice, a smaller sample of
ice than was used in previous studies, showing a significant improvement
in precision. Our preliminary results from the Styx Glacier ice core
samples have the potential to define small N2O variations
(a few parts per billion) at centennial time scales.