Preprints
https://doi.org/10.5194/amt-2020-328
https://doi.org/10.5194/amt-2020-328

  11 Sep 2020

11 Sep 2020

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

An improved method for atmospheric 14CO measurements

Vasilii V. Petrenko1, Andrew M. Smith2, Edward M. Crosier1, Roxana Kazemi1, Philip Place1, Aidan Colton3, Bin Yang2, Quan Hua2, and Lee T. Murray1 Vasilii V. Petrenko et al.
  • 1Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA
  • 2Australian Nuclear Science and Technology Organisation (ANSTO), Locked Bag 2001, Kirrawee DC, NSW 2232, Australia
  • 3NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, Colorado, USA

Abstract. Important uncertainties remain in our understanding of the spatial and temporal variability of atmospheric hydroxyl radical concentration ([OH]). Carbon-14-containing carbon monoxide (14CO) is a useful tracer that can help in the characterization of [OH] variability. Prior measurements of atmospheric 14CO concentration ([14CO] are limited in both their spatial and temporal extent, partly due to the very large air sample volumes that have been required for measurements (500–1000 liters at standard temperature and pressure, L STP) and the difficulty and expense associated with the collection, shipment and processing of such samples. Here we present a new method that reduces the air sample volume requirement to ≈ 90 L STP while allowing for [14CO] measurement uncertainties that are on par with or better than prior work (≈ 3 % or better, 1 σ). The method also for the first time includes accurate characterization of the overall procedural [14CO] blank associated with individual samples, a key improvement over prior atmospheric 14CO work. The method was used to make measurements of [14CO] at the NOAA Mauna Loa Observatory, Hawaii, USA, between November 2017 and November 2018. The measurements show the expected [14CO] seasonal cycle (lowest in summer) and are in good agreement with prior [14CO] results from another low-latitude site in the Northern Hemisphere. The lowest overall [14CO] uncertainties (2.1 %, 1 σ) are achieved for samples that are directly accompanied by procedural blanks and whose mass is increased to ≈ 50 micrograms of carbon (µgC) prior to the 14C measurement via dilution with a high-CO, 14C-depleted gas.

Vasilii V. Petrenko et al.

 
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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Vasilii V. Petrenko et al.

Vasilii V. Petrenko et al.

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Short summary
This paper presents an improved methodology for measurements of atmospheric concentration of carbon-14-containing carbon monoxide (14CO), as well as a 1-year data set that demonstrates the methodology. Atmospheric 14CO concentration measurements are useful for improving the understanding of spatial and temporal variability of hydroxyl radical concentrations. Key improvements over prior methods include a greatly reduced air sample size and accurate procedural blank characterization.