Title: Short-term variability of atmospheric helium revealed through a cryo-enrichment method
Abstract. Tropospheric helium variations are tightly linked to CO2 due to the co-emission of He and CO2 from natural-gasburning. Recently, Birner et al. (2022a) showed that the global consumption of natural gas has measurably increased the He content of theatmosphere. Like CO2, He is also predicted to exhibit complex spatial and temporal variability on shorter timescales, butmeasurements of these short-term variations are lacking. Here, we present the development of an improved gas delivery and purification system for thesemi-continuous mass spectrometric measurement of the atmospheric He-to-nitrogen ratio (He/N2). The method replaces the chemicalgetter used previously by Birner et al. (2021, 2022a) to preconcentrate He in an air stream with a cryogenic trap which can be more simplyregenerated by heating and which improves the precision of the measurement to 22 per meg (i.e., 0.022 ‰) in10 min (1σ). Using this “cryo-enrichment” method, we measured the He/N2 ratios in ambient air at La Jolla (California,USA) over 5 weeks in 2022. During this period, He/N2 was strongly correlated with atmospheric CO2 concentrations, as expectedfrom anthropogenic emissions, with a diurnal cycle of 450–500 per meg (max–min) caused by the sea–land breeze pattern of local winds,which modulates the influence of local pollution sources. more »« less
Birner, Benjamin; Paplawsky, William; Severinghaus, Jeffrey; Keeling, Ralph F.
(, Atmospheric Measurement Techniques)
null
(Ed.)
Abstract. The atmospheric He/N2 ratio is expected to increase due to the emission of He associated with fossil fuels and isexpected to also vary in both space and time due to gravitational separationin the stratosphere. These signals may be useful indicators of fossil fuelexploitation and variability in stratospheric circulation, but directmeasurements of He/N2 ratio are lacking on all timescales. Here wepresent a high-precision custom inlet system for mass spectrometers thatcontinuously stabilizes the flow of gas during sample–standard comparisonand removes all non-noble gases from the gas stream. This enablesunprecedented accuracy in measurement of relative changes in the helium molefraction, which can be directly related to the 4He/N2 ratio usingsupplementary measurements of O2/N2, Ar/N2 and CO2.Repeat measurements of the same combination of high-pressure tanks using ourinlet system achieves a He/N2 reproducibility of∼ 10 per meg (i.e., 0.001 %) in 6–8 h analyses. This compares to interannual changesof gravitational enrichment at ∼ 35 km in the midlatitudestratosphere of order 300–400 per meg and an annual tropospheric increasefrom human fossil fuel activity of less than ∼ 30 per meg yr−1 (bounded by previous work on helium isotopes). The gettering andflow-stabilizing inlet may also be used for the analysis of other noble-gasisotopes and could resolve previously unobserved seasonal cycles inKr/N2 and Xe/N2.
These data were collected on the CCGS (Canadian Coast Guard) Louis St. Laurent during BGOS (Beaufort Gyre Observing System) research cruises in 2012-2014 and 2016-2021 in the Beaufort Sea area. They are underway pCO2 (Partial pressure of carbon dioxide) data collected using an equilibrator-infrared method (SUPER CO2 system from Sunburst Sensors). Ancillary data for calculation of air-sea CO fluxes include temperature, salinity, atmospheric CO2, wind speed, and gas transfer velocity (calculated from Wanninkhof et al. (2009). Fluxes are not corrected for fractional ice-coverage. The specific goal of the study is to continue to operate an Arctic Observing Network (AON) for the measurement of the partial pressure of CO2 (pCO2), pH, and dissolved O2 (DO) focused on the surface waters of the Arctic Ocean (specifically, the Canada Basin). These data were collected on the CCGS (Canadian Coast Guard) Louis St. Laurent during a BGOS (Beaufort Gyre Observing System) research cruise in the Beaufort Sea area. It is underway pCO2 (partial pressure of carbon dioxide) data collected using an equilibrator-infrared method (SUPER CO2 system from Sunburst Sensors). Ancillary data for calculation of air-sea CO2 fluxes include temperature, salinity, atmospheric CO2.
We report on the use of an atmospheric pressure, open-air plasma treatment to remove Li2CO3 species from the surface of garnet-type tantalum-doped lithium lanthanum zirconium oxide (Li6.4La3Zr1.4Ta0.6O12, LLZTO) solid-state electrolyte pellets. The Li2CO3 layer, which we show forms on the surface of garnets within 3 min of exposure to ambient moisture and CO2, increases the interface (surface) resistance of LLZTO. The plasma treatment is carried out entirely in ambient and is enabled by use of a custom-built metal shroud that is placed around the plasma nozzle to prevent moisture and CO2 from reacting with the sample. After the plasma treatment, N2 compressed gas is flowed through the shroud to cool the sample and prevent atmospheric species from reacting with the LLZTO. We demonstrate that this approach is effective for removing the Li2CO3 from the surface of LLZTO. The surface chemistry is characterized with X-ray photoelectron spectroscopy to evaluate the effect of process parameters (plasma exposure time and shroud gas chemistry) on removal of the surface species. We also show that the open-air plasma treatment can significantly reduce the interface resistance. This platform demonstrates a path towards open-air processed solid-state batteries.
Autochamber-based CH4 fluxes and δ13C values measured with a Tunable Infrared Laser Direct Absorption Spectrometer (TILDAS, Aerodyne Research Inc.); and ancillary data, including CO2 fluxes (measured with a LGR Greenhouse Gas Analyzer), temperatures, atmospheric pressure, and photosynthetically active radiation (PAR). In addition to the data published here, data from 2011 is also available in the supplementary files to McCalley et al. (2014) under the Source data to Fig. 1 link. METHODS: Methane fluxes were measured using a system of 8 automatic gas-sampling chambers made of transparent Lexan (n=3 each in the palsa and bog habitats, and n=2 in the fen habitat). Chambers were initially installed in the three habitat types at Stordalen Mire in 2001 (Bäckstrand et al., 2008) and the chamber lids were replaced in 2011 with the current design, similar to that described by Bubier et al 2003. Chambers cover an area of 0.2 m2 (45 cm x 45 cm), with a height ranging from 15-75 cm depending on habitat vegetation. At the Palsa and bog site the chamber base is flush with the ground and the chamber lid (15 cm in height) lifts clear of the base between closures. At the fen site the chamber base is raised 50–60 cm on lexon skirts to accommodate large stature vegetation. The chambers are instrumented with thermocouples measuring air and surface ground temperature, and water table depth and thaw depth are measured manually 3–5 times per week. The chambers are connected to the gas analysis system, located in an adjacent temperature-controlled cabin, by 3/8” Dekoron tubing through which air is circulated at approximately 2.5 L min-1. Each chamber lid is closed once every 3 hours for a period of 8 min, with a 5 min flush period before and after lid closure. We measured methane concentration using a Tunable Infrared Laser Direct Absorption Spectrometers (TILDAS, Aerodyne Research Inc.) connected to the main chamber circulation using ¼” Dekoron tubing (McCalley et al 2014). Calibrations were done every 90 min using 3 calibration gases spanning the observed concentration range (1.8–10 ppm). For each autochamber closure we calculated flux using a method consistent with that detailed by Bäckstrand et al 2008 for CO2 and total hydrocarbons, using a linear regression of changing headspace CH4 concentration over a period of 2.5 min. Eight 2.5 min regressions were calculated, staggered by 15 sec, and the most linear fit (highest r2) was then used to calculate flux. Daily average flux for each chamber was used to calculate daily flux and standard error for each cover type. References: Bäckstrand, K., Crill, P. M., Mastepanov, M., Christensen, T. R. & Bastviken, D. Total hydrocarbon flux dynamics at a subarctic mire in northern Sweden. Journal of Geophysical Research 113, (2008). Bubier, J. L., Crill, P. M., Mosedale, A., Frolking, S. & Linder, E. Peatland responses to varying interannual moisture conditions as measured by automatic CO2 chambers. Global Biogeochemical Cycles 17, (2003). McCalley, C.K., B.J. Woodcroft, S.B. Hodgkins, R.A. Wehr, E-H. Kim, R. Mondav, P.M. Crill, J.P. Chanton, V.I. Rich, G.W. Tyson, S.R. Saleska (2014), Methane dynamics regulated by microbial community response to permafrost thaw, Nature, 514:478-481, doi:10.1038/nature13798. FILES: Files are named with the year or date range, followed by a suffix indicating data resolution: *_CH4output_clean_ckm.txt - Individual measurements of CH4 fluxes (CH4Flux), CO2 fluxes (CO2flux; for select years), and δ13C signature of emitted CH4 (Flux13CH4) for each chamber closure. CH4FluxRsq is the R2 value of the linear fit used to calculate CH4 flux, CO2Rsq is the R2 value of the linear fit used to calculate CO2 flux, and Flux13CH4_stdev is the standard deviation of the δ13C signature (standard deviation of the intercept of the Keeling plot). *_DailyCH4output_ckm.txt - Daily average CH4 fluxes (CH4Flux) and δ13C values (13CH4), grouped by site: Palsa, Bog, Fen, and Chamber 9 (bog/fen transition); along with standard deviations (stdev) and standard errors (se) of the flux or δ13C for each site type. For the Palsa, Bog, and Fen sites, these averages are calculated by chamber (n=3 for Palsa and Bog, n=2 for Fen), so each chamber's daily average is calculated, and then a daily average for that site is calculated as the average of the chambers. For Chamber 9 (bog/fen intermediate; n=1 chamber), averages are calculated by day as there are no chamber replicates. MEASUREMENT UNITS (same for both file types): CH4 flux: mg CH4 m−2 hr−1 CO2 flux: mg C m−2 h−1 δ13C: ‰ Temperature: °C Air pressure: mbar PAR: µmol photons m−2 s−1 FUNDING: This research is a contribution of the EMERGE Biology Integration Institute, funded by the National Science Foundation, Biology Integration Institutes Program, Award # 2022070.We thank the Swedish Polar Research Secretariat and SITES for the support of the work done at the Abisko Scientific Research Station. SITES is supported by the Swedish Research Council's grant 4.3-2021-00164.This study was also funded by the Genomic Science Program of the United States Department of Energy Office of Biological and Environmental Research, grant #s DE-SC0004632, DE-SC0010580, and DE-SC0016440.Autochamber measurements between 2013 and 2017 were supported by a grant from the US National Science Foundation MacroSystems program (NSF EF 1241037, PI Varner).
Severinghaus, Jeffrey P
(, U.S. Antarctic Program (USAP) Data Center)
These data cover the penultimate glacial period (MIS 6) and parts of MIS5, in Allan Hills ice. The d18Oatm data are useful for dating the core, and the 15N is useful for inferring firn thickness. Importantly, the data have only been corrected for gas loss using published methods (i.e. Baggenstos et al. 2017), but not for recently recognized (and unpublished) effects of declining contemporary atmospheric O2/N2 due to fossil fuel burning. These changes unfortunately affect the La Jolla Air standard gas O2/N2 ratio that is used in our lab to make the measurements. Users of this data are encouraged to contact Jeff Severinghaus for help in making these novel corrections to the standard gas.
Birner, Benjamin, Morgan, Eric, and Keeling, Ralph F. Short-term variability of atmospheric helium revealed through a cryo-enrichment method. Retrieved from https://par.nsf.gov/biblio/10485565. Atmospheric Measurement Techniques 16.6 Web. doi:10.5194/amt-16-1551-2023.
Birner, Benjamin, Morgan, Eric, & Keeling, Ralph F. Short-term variability of atmospheric helium revealed through a cryo-enrichment method. Atmospheric Measurement Techniques, 16 (6). Retrieved from https://par.nsf.gov/biblio/10485565. https://doi.org/10.5194/amt-16-1551-2023
Birner, Benjamin, Morgan, Eric, and Keeling, Ralph F.
"Short-term variability of atmospheric helium revealed through a cryo-enrichment method". Atmospheric Measurement Techniques 16 (6). Country unknown/Code not available: Copernicus. https://doi.org/10.5194/amt-16-1551-2023.https://par.nsf.gov/biblio/10485565.
@article{osti_10485565,
place = {Country unknown/Code not available},
title = {Short-term variability of atmospheric helium revealed through a cryo-enrichment method},
url = {https://par.nsf.gov/biblio/10485565},
DOI = {10.5194/amt-16-1551-2023},
abstractNote = {Abstract. Tropospheric helium variations are tightly linked to CO2 due to the co-emission of He and CO2 from natural-gasburning. Recently, Birner et al. (2022a) showed that the global consumption of natural gas has measurably increased the He content of theatmosphere. Like CO2, He is also predicted to exhibit complex spatial and temporal variability on shorter timescales, butmeasurements of these short-term variations are lacking. Here, we present the development of an improved gas delivery and purification system for thesemi-continuous mass spectrometric measurement of the atmospheric He-to-nitrogen ratio (He/N2). The method replaces the chemicalgetter used previously by Birner et al. (2021, 2022a) to preconcentrate He in an air stream with a cryogenic trap which can be more simplyregenerated by heating and which improves the precision of the measurement to 22 per meg (i.e., 0.022 ‰) in10 min (1σ). Using this “cryo-enrichment” method, we measured the He/N2 ratios in ambient air at La Jolla (California,USA) over 5 weeks in 2022. During this period, He/N2 was strongly correlated with atmospheric CO2 concentrations, as expectedfrom anthropogenic emissions, with a diurnal cycle of 450–500 per meg (max–min) caused by the sea–land breeze pattern of local winds,which modulates the influence of local pollution sources.},
journal = {Atmospheric Measurement Techniques},
volume = {16},
number = {6},
publisher = {Copernicus},
author = {Birner, Benjamin and Morgan, Eric and Keeling, Ralph F.},
editor = {Chen, Huilin}
}
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