Abstract
Abstract. Atmospheric trace gases such as dihydrogen (H2),
carbon monoxide (CO) and methane (CH4) play important roles in
microbial metabolism and biogeochemical cycles. Analysis of these gases at
trace levels requires reliable storage of discrete samples of low volume.
While commercial sampling vials such as Exetainers® have been
tested for CH4 and other greenhouse gases, no information on reliable
storage is available for H2 and CO. We show that vials sealed with
butyl rubber stoppers are not suitable for storing H2 and CO due to
release of these gases from rubber material. Treating butyl septa with NaOH
reduced trace-gas release, but contamination was still substantial, with
H2 and CO mixing ratios in air samples increasing by a factor of 3 and
10 after 30 d of storage in conventional 12 mL Exetainers. All tested
materials showed a near-linear increase in H2 and CO mixing ratios,
indicating a zero-order reaction and material degradation as the underlying
cause. Among the rubber materials tested, silicone showed the lowest
potential for H2 and CO release. We thus propose modifying Exetainers
by closing them with a silicone plug to minimise contamination and sealing
them with a stainless-steel bolt and O-ring as a secondary diffusion barrier
for long-term storage. Such modified Exetainers exhibited stable mixing
ratios of H2 and CH4 exceeding 60 d of storage at atmospheric
and elevated (10 ppm) mixing ratios. The increase of CO was still
measurable but was 9 times lower than in conventional Exetainers with
treated septa; this can be corrected for due to its linearity by storing a
standard gas alongside the samples. The proposed modification is
inexpensive, scalable and robust, and thus it enables reliable storage of large
numbers of low-volume gas samples from remote field locations.
Funder
National Health and Medical Research Council
Australian Research Council
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
Cited by
6 articles.
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