A metrological approach to improve accuracy and reliability of ammonia measurements in ambient air

Pogány, Andrea; Balslev-Harder, David; Braban, Christine F.; Cassidy, Nathan; Ebert, Volker; Ferracci, Valerio; Hieta, Tuomas; Leuenberger, Daiana; Martin, Nicholas A.; Pascale, Céline; Peltola, Jari; Persijn, Stefan; Tiebe, Carlo; Twigg, Marsailidh; Vaittinen, Olavi; Wijk, Janneke van; Wirtz, Klaus; Niederhauser, Bernhard

doi:10.1088/0957-0233/27/11/115012

Cited by 24 publications

(27 citation statements)

References 34 publications

(48 reference statements)

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“…This has been evidenced by Yokohata et al (1985) for CCl 4 and CH 3 CCl 3 in very dry mixtures (i.e. likely less than 750 nmol mol −1 of water vapour), who also experimentally showed that adding water vapour to the cylinder annulled this adsorption, water vapour being an excellent competitor for adsorption sites on a metal surface (Vaittinen et al, 2013;Pogàny et al, 2016).…”

Section: Cryo-fillingmentioning

confidence: 84%

Dynamic–gravimetric preparation of metrologically traceable primary calibration standards for halogenated greenhouse gases

et al. 2018

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Abstract. For many years, the comparability of measurements obtained with various instruments within a global-scale air quality monitoring network has been ensured by anchoring all results to a unique suite of reference gas mixtures, also called a “primary calibration scale”. Such suites of reference gas mixtures are usually prepared and then stored over decades in pressurised cylinders by a designated laboratory. For the halogenated gases which have been measured over the last 40 years, this anchoring method is highly relevant as measurement reproducibility is currently much better (< 1 %, k = 2 or 95 % confidence interval) than the expanded uncertainty of a reference gas mixture (usually > 2 %). Meanwhile, newly emitted halogenated gases are already measured in the atmosphere at pmol mol−1 levels, while still lacking an established reference standard. For compounds prone to adsorption on material surfaces, it is difficult to evaluate mixture stability and thus variations in the molar fractions over time in cylinders at pmol mol−1 levels. To support atmospheric monitoring of halogenated gases, we create new primary calibration scales for SF6 (sulfur hexafluoride), HFC-125 (pentafluoroethane), HFO-1234yf (or HFC-1234yf, 2,3,3,3-tetrafluoroprop-1-ene), HCFC-132b (1,2-dichloro-1,1-difluoroethane) and CFC-13 (chlorotrifluoromethane). The preparation method, newly applied to halocarbons, is dynamic and gravimetric: it is based on the permeation principle followed by dynamic dilution and cryo-filling of the mixture in cylinders. The obtained METAS-2017 primary calibration scales are made of 11 cylinders containing these five substances at near-ambient and slightly varying molar fractions. Each prepared molar fraction is traceable to the realisation of SI units (International System of Units) and is assigned an uncertainty estimate following international guidelines (JCGM, 2008), ranging from 0.6 % for SF6 to 1.3 % (k = 2) for all other substances. The smallest uncertainty obtained for SF6 is mostly explained by the high substance purity level in the permeator and the low SF6 contamination of the matrix gas. The measured internal consistency of the suite ranges from 0.23 % for SF6 to 1.1 % for HFO-1234yf (k=1). The expanded uncertainty after verification (i.e. measurement of the cylinders vs. each others) ranges from 1 to 2 % (k = 2). This work combines the advantages of SI-traceable reference gas mixture preparation with a calibration scale system for its use as anchor by a monitoring network. Such a combined system supports maximising compatibility within the network while linking all reference values to the SI and assigning carefully estimated uncertainties. For SF6, comparison of the METAS-2017 calibration scale with the scale prepared by SIO (Scripps Institution of Oceanography, SIO-05) shows excellent concordance, the ratio METAS-2017 / SIO-05 being 1.002. For HFC-125, the METAS-2017 calibration scale is measured as 7 % lower than SIO-14; for HFO-1234yf, it is 9 % lower than Empa-2013. No other scale for HCFC-132b was available for comparison. Finally, for CFC-13 the METAS-2017 primary calibration scale is 5 % higher than the interim calibration scale (Interim-98) that was in use within the Advanced Global Atmospheric Gases Experiment (AGAGE) network before adopting the scale established in the present work.

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Section: Cryo-fillingmentioning

confidence: 84%

Dynamic–gravimetric preparation of metrologically traceable primary calibration standards for halogenated greenhouse gases

et al. 2018

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“…This is much better than the expanded uncertainty of reference gas mixtures, estimated to be on the order of 2 to 4 % for SIO standards (Scripps Institution of Oceanography, e.g. Prinn et al, 2000), 0.3 to 3 % for NIST (National Institute of Standard and Technology, Rhoderick et al, 2015) and 0.6 to < 2 % for NOAA (Hall et al, 2007;Montzka et al, 2015;Lim et al, 2017), as examples. Given this technical state of the art, monitoring networks have developed a so-called "primary calibration scale" system, in which all stations of a specific network are anchored to the same suite of primary reference gas mixtures with a calibration chain as short as possible.…”

Section: Introductionmentioning

confidence: 92%

“…Furthermore, based on these measurements and using atmospheric transport modelling, emissions can be quantified ("top-down" estimation, e.g. Prinn et al, 2000;Rigby et al, 2010;Brunner et al, 2017). The comparison of top-down reconstructions with bottom-up inventories shows agreement for some gases but also discrepancies that can be considerable for others (Weiss and Prinn, 2011;Lunt et al, 2015;Hu et al, 2016;Simmonds et al, 2016;Sherry et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…The production of a robust and accurate primary calibration scale at low molar fraction level, which is usually created through a set of reference gas mixtures, is a major task (Prinn et al, 2000;Zhao et al, 1997;Dlugokencky et al, 2005;Zhao and Tans, 2006;Hall et al, 2007). In particular for compounds prone to adsorption on material surfaces, it is difficult to evaluate mixture stability and thus variations of molar fractions over time in cylinders.…”

Section: Introductionmentioning

confidence: 99%

“…We apply a preparation technique combining dynamic gravimetry (ISO 6145-10, 2002) and dynamic dilution (ISO 6145-7, 2009), followed by cryo-filling in cylinders. This is an alternative to the prevailing preparation method for such compounds, which is static gravimetry (Prinn et al, 2000;Hall et al, 2007;Rhoderick et al, 2015;Lim et al, 2017). The produced suite of reference gas mixtures is SI-traceable; i.e.…”

Section: Introductionmentioning

confidence: 99%

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Guillevic¹

2018

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For many years, the comparability of measurements obtained with various instruments within a globalscale air quality monitoring network has been ensured by anchoring all results to a unique suite of reference gas mixtures, also called a "primary calibration scale". Such suites of reference gas mixtures are usually prepared and then stored over decades in pressurised cylinders by a designated laboratory. For the halogenated gases which have been measured over the last 40 years, this anchoring method is highly relevant as measurement reproducibility is currently much better (< 1 %, k = 2 or 95 % confidence interval) than the expanded uncertainty of a reference gas mixture (usually > 2 %). Meanwhile, newly emitted halogenated gases are already measured in the atmosphere at pmol mol −1 levels, while still lacking an established reference standard. For compounds prone to adsorption on material surfaces, it is difficult to evaluate mixture stability and thus variations in the molar fractions over time in cylinders at pmol mol −1 levels.To support atmospheric monitoring of halogenated gases, we create new primary calibration scales for SF 6 (sulfur hexafluoride), HFC-125 (pentafluoroethane), HFO-1234yf (or HFC-1234yf, 2,3,3,3-tetrafluoroprop-1-ene), HCFC-132b (1,2-dichloro-1,1-difluoroethane) and CFC-13 (chlorotrifluoromethane). The preparation method, newly applied to halocarbons, is dynamic and gravimetric: it is based on the permeation principle followed by dynamic dilution and cryofilling of the mixture in cylinders. The obtained METAS-2017 primary calibration scales are made of 11 cylinders containing these five substances at near-ambient and slightly varying molar fractions. Each prepared molar fraction is traceable to the realisation of SI units (International System of Units) and is assigned an uncertainty estimate following international guidelines (JCGM, 2008), ranging from 0.6 % for SF 6 to 1.3 % (k = 2) for all other substances. The smallest uncertainty obtained for SF 6 is mostly explained by the high substance purity level in the permeator and the low SF 6 contamination of the matrix gas. The measured internal consistency of the suite ranges from 0.23 % for SF 6 to 1.1 % for HFO-1234yf (k = 1). The expanded uncertainty after verification (i.e. measurement of the cylinders vs. each others) ranges from 1 to 2 % (k = 2). This work combines the advantages of SI-traceable reference gas mixture preparation with a calibration scale system for its use as anchor by a monitoring network. Such a combined system supports maximising compatibility within the network while linking all reference values to the SI and assigning carefully estimated uncertainties.For SF 6 , comparison of the METAS-2017 calibration scale with the scale prepared by SIO (Scripps Institution of Oceanography, SIO-05) shows excellent concordance, the ratio METAS-2017 / SIO-05 being 1.002. For HFC-125, the METAS-2017 calibration scale is measured as 7 % lower than SIO-14; for HFO-1234yf, it is 9 % lower than Empa-2013. No other scale for HCFC-132b w...

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Effect of moisture on the adsorption of ammonia

et al. 2018

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The effect of moisture on the adsorption of ammonia was systematically studied using different surface materials and humidity levels. The experimental water amount fractions varied between 6 and 18000 µmol mol -1 and the ammonia amount fraction was 400 nmol mol -1 . The investigated materials included plain 316L stainless steel and stainless steel cured with Dursan, SilcoNert 2000 and halocarbon wax coatings. Furthermore, Teflon (PTFE) and polyvinylidene difluoride (PVDF) polymer surfaces were studied. Dynamically diluted ammonia, test tubes prepared with the investigated materials, a commercial ammonia analyzer based on cavity ringdown spectroscopy and a commercial dew point transmitter were employed. The adsorption was assessed quantitatively using continuous flow conditions and real-time monitoring of the adsorption process.The ammonia adsorption was found to increase substantially in dry conditions for all the studied materials except PVDF. The increase was largest for plain stainless steel which was the most adsorbing material. The coatings applied on stainless steel decreased the adsorption significantly in dry conditions. Polymers PVDF and PTFE were the least adsorbing materials. In water amount fractions between 1000 and 10000 µmol mol -1 , the ammonia adsorption was at its lowest. The adsorption increased again above one percent humidity levels.

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A metrological approach to improve accuracy and reliability of ammonia measurements in ambient air

Cited by 24 publications

References 34 publications

Dynamic–gravimetric preparation of metrologically traceable primary calibration standards for halogenated greenhouse gases

Dynamic–gravimetric preparation of metrologically traceable primary calibration standards for halogenated greenhouse gases

Reply to the comments of Reviewer 2

Effect of moisture on the adsorption of ammonia

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