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  • 1
    Online Resource
    Online Resource
    A three‐dimensional synthesis study of δ 18 O in atmospheric CO 2 : 1. Surface fluxes
    American Geophysical Union (AGU) ; 1997
    In:  Journal of Geophysical Research: Atmospheres Vol. 102, No. D5 ( 1997-03-20), p. 5857-5872
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 102, No. D5 ( 1997-03-20), p. 5857-5872
    Abstract: The isotope 18 O in CO 2 is of particular interest in studying the global carbon cycle because it is sensitive to the processes by which the global land biosphere absorbs and respires CO 2 . Carbon dioxide and water exchange isotopically both in leaves and in soils, and the 18 O character of atmospheric CO 2 is strongly influenced by the land biota, which should constrain the gross primary productivity and total respiration of land ecosystems. In this study we calculate the global surface fluxes of 18 O for vegetation and soils using the SiB2 biosphere model coupled with the Colorado State University general circulation model. This approach makes it possible to use physiological variables that are consistently weighted by the carbon assimilation rate and integrated through the vegetation canopy. We also calculate the air‐sea exchange of 18 O and the isotopic character of fossil emissions and biomass burning. Global mean values of the isotopic exchange with each reservoir are used to close the global budget of 18 O in CO 2 . Our results confirm the fact that the land biota exert a dominant control on the δ 18 O of the atmospheric reservoir. At the global scale, exchange with the canopy produces an isotopic enrichment of CO 2 , whereas exchange with soils has the opposite effect.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/96JD02360
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1997
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  • 2
    Online Resource
    Online Resource
    A three‐dimensional synthesis study of δ 18 O in atmospheric CO 2 : 2. Simulations with the TM2 transport model
    American Geophysical Union (AGU) ; 1997
    In:  Journal of Geophysical Research: Atmospheres Vol. 102, No. D5 ( 1997-03-20), p. 5873-5883
    Details
    In: Journal of Geophysical Research: Atmospheres, American Geophysical Union (AGU), Vol. 102, No. D5 ( 1997-03-20), p. 5873-5883
    Abstract: In this study, using a three‐dimensional (3‐D) tracer modeling approach, we simulate the δ 18 O of atmospheric CO 2 . In the atmospheric transport model TM2 we prescribe the surface fluxes of 18 O due to vegetation and soils, ocean exchange, fossil emissions, and biomass burning. The model simulations are first discussed for each reservoir separately, then all the reservoirs are combined to allow a comparison with the atmospheric δ 18 O measurements made by the National Oceanic and Atmospheric Administration‐University of Colorado, Scripps Institution of Oceanography‐Centrum Voor Isotopen Onderzoek (United States‐Netherlands) and Commonwealth Scientific and Industrial Research Organisation (Australia) air sampling programs. Insights into the latitudinal differences and into the seasonal cycle of δ 18 O in CO 2 are gained by looking at the contribution of each source. The isotopic exchange with soils induces a large isotopic depletion over the northern hemisphere continents, which overcomes the concurrent effect of isotopic enrichment due to leaf exchange. Compared to the land biota, the ocean fluxes and the anthropogenic CO 2 source have a relatively minor influence. The shape of the latitudinal profile in δ 18 O appears determined primarily by the respiration of the land biota, which balances photosynthetic uptake over the course of a year. Additional information on the phasing of the terrestrial carbon exchange comes from the seasonal cycle of δ 18 O at high northern latitudes.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/96JD02361
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 1997
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    detail.hit.zdb_id: 161667-5
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  • 3
    Online Resource
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    Total energy expenditure assessed by salivary doubly labelled water analysis and its relevance for short‐term energy balance in humans
    Wiley ; 2016
    In:  Rapid Communications in Mass Spectrometry Vol. 30, No. 1 ( 2016-01-15), p. 143-150
    Details
    In: Rapid Communications in Mass Spectrometry, Wiley, Vol. 30, No. 1 ( 2016-01-15), p. 143-150
    Abstract: The doubly labelled water (DLW) method is a stable isotopic technique for measuring total energy expenditure (TEE). Saliva is the easiest sampling fluid for assessing isotopic enrichments, but blood is considered superior because of its rapid exchange with body water. Therefore, we compared a large range of isotopic enrichments in saliva and blood, and related TEE in subjects with their ad libitum total energy intake (TEI). The relevance of these parameters to body weight and fat change over an 8‐day interval was also assessed. Methods Thirty subjects underwent DLW analysis over either 8 or 14 days, during which time initial and final blood and saliva enrichments were compared. TEI was assessed by dieticians over the 8‐day period only. Isotope ratio mass spectrometry was used for the measurement of δ 2 H and δ 18 O values. Results No discrepancies were observed between sampling fluids over a wide range of enrichments. During the 8‐day period, average TEI exceeded TEE by ~5% or less. Using saliva as sampling fluid, TEI and TEI‐TEE, but not TEE, were positively correlated to body weight change. TEI‐TEE and physical activity EE (AEE), but not TEI, correlated, respectively, positively and negatively to changes in fat mass. Conclusions The DLW method in humans can be reliably applied using saliva as sampling fluid. TEI‐TEE as well as AEE contributes significantly to changes in fat mass over an 8‐day period. Copyright © 2015 John Wiley & Sons, Ltd.
    Type of Medium: Online Resource
    ISSN: 0951-4198 , 1097-0231
    URL: Issue
    URL: Article
    DOI: 10.1002/rcm.v30.1
    DOI: 10.1002/rcm.7412
    Language: English
    Publisher: Wiley
    Publication Date: 2016
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  • 4
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    Comprehensive inter‐laboratory calibration of reference materials for δ 18 O versus VSMOW using various on‐line high‐temperature conversion techniques
    Wiley ; 2009
    In:  Rapid Communications in Mass Spectrometry Vol. 23, No. 7 ( 2009-04-15), p. 999-1019
    Details
    In: Rapid Communications in Mass Spectrometry, Wiley, Vol. 23, No. 7 ( 2009-04-15), p. 999-1019
    Abstract: Internationally distributed organic and inorganic oxygen isotopic reference materials have been calibrated by six laboratories carrying out more than 5300 measurements using a variety of high‐temperature conversion techniques (HTC) a in an evaluation sponsored by the International Union of Pure and Applied Chemistry (IUPAC). To aid in the calibration of these reference materials, which span more than 125‰, an artificially enriched reference water ( δ 18 O of +78.91‰) and two barium sulfates (one depleted and one enriched in 18 O) were prepared and calibrated relative to VSMOW2 b and SLAP reference waters. These materials were used to calibrate the other isotopic reference materials in this study, which yielded: Reference material δ 18 O and estimated combined uncertainty c IAEA‐602 benzoic acid +71.28 ± 0.36‰ USGS35 sodium nitrate +56.81 ± 0.31‰ IAEA‐NO‐3 potassium nitrate +25.32 ± 0.29‰ IAEA‐601 benzoic acid +23.14 ± 0.19‰ IAEA‐SO‐5 barium sulfate +12.13 ± 0.33‰ NBS 127 barium sulfate +8.59 ± 0.26‰ VSMOW2 water 0‰ IAEA‐600 caffeine −3.48 ± 0.53‰ IAEA‐SO‐6 barium sulfate −11.35 ± 0.31‰ USGS34 potassium nitrate −27.78 ± 0.37‰ SLAP water −55.5‰ The seemingly large estimated combined uncertainties arise from differences in instrumentation and methodology and difficulty in accounting for all measurement bias. They are composed of the 3‐fold standard errors directly calculated from the measurements and provision for systematic errors discussed in this paper. A primary conclusion of this study is that nitrate samples analyzed for δ 18 O should be analyzed with internationally distributed isotopic nitrates, and likewise for sulfates and organics. Authors reporting relative differences of oxygen‐isotope ratios ( δ 18 O) of nitrates, sulfates, or organic material should explicitly state in their reports the δ 18 O values of two or more internationally distributed nitrates (USGS34, IAEA‐NO‐3, and USGS35), sulfates (IAEA‐SO‐5, IAEA‐SO‐6, and NBS 127), or organic material (IAEA‐601 benzoic acid, IAEA‐602 benzoic acid, and IAEA‐600 caffeine), as appropriate to the material being analyzed, had these reference materials been analyzed with unknowns. This procedure ensures that readers will be able to normalize the δ 18 O values at a later time should it become necessary. The high‐temperature reduction technique for analyzing δ 18 O and δ 2 H is not as widely applicable as the well‐established combustion technique for carbon and nitrogen stable isotope determination. To obtain the most reliable stable isotope data, materials should be treated in an identical fashion; within the same sequence of analyses, samples should be compared with working reference materials that are as similar in nature and in isotopic composition as feasible. Copyright © 2009 John Wiley & Sons, Ltd.
    Type of Medium: Online Resource
    ISSN: 0951-4198 , 1097-0231
    URL: Issue
    URL: Article
    DOI: 10.1002/rcm.v23:7
    DOI: 10.1002/rcm.3958
    Language: English
    Publisher: Wiley
    Publication Date: 2009
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  • 5
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    Minimum requirements for publishing hydrogen, carbon, nitrogen, oxygen and sulfur stable-isotope delta results (IUPAC Technical Report)
    Walter de Gruyter GmbH ; 2022
    In:  Pure and Applied Chemistry Vol. 94, No. 11-12 ( 2022-12-16), p. 1249-1255
    Details
    In: Pure and Applied Chemistry, Walter de Gruyter GmbH, Vol. 94, No. 11-12 ( 2022-12-16), p. 1249-1255
    Abstract: Stable hydrogen, carbon, nitrogen, oxygen and sulfur (HCNOS) isotope compositions expressed as isotope-delta values are typically reported relative to international standards such as Vienna Standard Mean Ocean Water (VSMOW), Vienna Peedee belemnite (VPDB) or Vienna Cañon Diablo Troilite (VCDT). These international standards are chosen by convention and the calibration methods used to realise them in practice undergo occasional changes. To ensure longevity and reusability of published data, a comprehensive description of (1) analytical procedure, (2) traceability, (3) data processing, and (4) uncertainty evaluation is required. Following earlier International Union of Pure and Applied Chemistry documents on terminology and notations, this paper proposes minimum requirements for publishing HCNOS stable-isotope delta results. Each of the requirements are presented with illustrative examples.
    Type of Medium: Online Resource
    ISSN: 0033-4545 , 1365-3075
    URL: Article
    DOI: 10.1515/pac-2021-1108
    RVK:
    VA 6665
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2022
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  • 6
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    Simultaneous measurement of 〈i〉δ〈/i〉〈sup〉13〈/sup〉C, 〈i〉δ〈/i〉〈sup〉18〈/sup〉O and 〈i〉δ〈/i〉〈sup〉17〈/sup〉O of atmospheric CO〈sub〉2〈/sub〉 – performance assessment of a dual-laser absorption spectrometer
    Copernicus GmbH ; 2021
    In:  Atmospheric Measurement Techniques Vol. 14, No. 6 ( 2021-06-09), p. 4279-4304
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 14, No. 6 ( 2021-06-09), p. 4279-4304
    Abstract: Abstract. Using laser absorption spectrometry for the measurement of stable isotopes of atmospheric CO2 instead of the traditional isotope ratio mass spectrometry method decreases sample preparation time significantly, and uncertainties in the measurement accuracy due to CO2 extraction and isobaric interferences are avoided. In this study we present the measurement performance of a new dual-laser instrument developed for the simultaneous measurement of the δ13C, δ18O and δ17O of atmospheric CO2 in discrete air samples, referred to as the Stable Isotopes of CO2 Absorption Spectrometer (SICAS). We compare two different calibration methods: the ratio method, based on the measured isotope ratio and a CO2 mole fraction dependency correction, and the isotopologue method, based on measured isotopologue abundances. Calibration with the ratio method and isotopologue method is based on three different assigned whole-air references calibrated on the VPDB (Vienna Pee Dee Belemnite) and the WMO 2007 (World Meteorological Organization) scale for their stable isotope compositions and their CO2 mole fractions, respectively. An additional quality control tank is included in both methods to follow long-term instrument performance. Measurements of the quality control tank show that the measurement precision and accuracy of both calibration methods is of similar quality for δ13C and δ18O measurements. During one specific measurement period the precision and accuracy of the quality control tank reach WMO compatibility requirements, being 0.01 ‰ for δ13C and 0.05 ‰ for δ18O. Uncertainty contributions of the scale uncertainties of the reference gases add another 0.03 ‰ and 0.05 ‰ to the combined uncertainty of the sample measurements. Hence, reaching WMO compatibility for sample measurements on the SICAS requires reduction of the scale uncertainty of the reference gases used for calibration. An intercomparison of flask samples over a wide range of CO2 mole fractions has been conducted with the Max Planck Institute for Biogeochemistry, resulting in a mean residual of 0.01 ‰ and −0.01 ‰ and a standard deviation of 0.05 ‰ and 0.07 ‰ for the δ13C measurements calibrated using the ratio method and the isotopologue method, respectively. The δ18O could not be compared due to depletion of the δ18O signal in our sample flasks because of storage times being too long. Finally, we evaluate the potential of our Δ17O measurements as a tracer for gross primary production by vegetation through photosynthesis. Here, a measurement precision of 〈0.01 ‰ would be a prerequisite for capturing seasonal variations in the Δ17O signal. Lowest standard errors for the δ17O and Δ17O of the ratio method and the isotopologue method are 0.02 ‰ and 0.02 ‰ and 0.01 ‰ and 0.02 ‰, respectively. The accuracy results show consequently results that are too enriched for both the δ17O and Δ17O measurements for both methods. This is probably due to the fact that two of our reference gases were not measured directly but were determined indirectly. The ratio method shows residuals ranging from 0.06 ‰ to 0.08 ‰ and from 0.06 ‰ to 0.1 ‰ for the δ17O and Δ17O results, respectively. The isotopologue method shows residuals ranging from 0.04 ‰ to 0.1 ‰ and from 0.05 ‰ to 0.13 ‰ for the δ17O and Δ17O results, respectively. Direct determination of the δ17O of all reference gases would improve the accuracy of the δ17O and thereby of the Δ17O measurements.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    URL: Article
    DOI: 10.5194/amt-14-4279-2021
    DOI: 10.5194/amt-14-4279-2021-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2021
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  • 7
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    Near-real-time CO 2 fluxes from CarbonTracker Europe for high-resolution atmospheric modeling
    Copernicus GmbH ; 2023
    In:  Earth System Science Data Vol. 15, No. 2 ( 2023-02-06), p. 579-605
    Details
    In: Earth System Science Data, Copernicus GmbH, Vol. 15, No. 2 ( 2023-02-06), p. 579-605
    Abstract: Abstract. We present the CarbonTracker Europe High-Resolution (CTE-HR) system that estimates carbon dioxide (CO2) exchange over Europe at high resolution (0.1 × 0.2∘) and in near real time (about 2 months' latency). It includes a dynamic anthropogenic emission model, which uses easily available statistics on economic activity, energy use, and weather to generate anthropogenic emissions with dynamic time profiles at high spatial and temporal resolution (0.1×0.2∘, hourly). Hourly net ecosystem productivity (NEP) calculated by the Simple Biosphere model Version 4 (SiB4) is driven by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5th Generation (ERA5) dataset. This NEP is downscaled to 0.1×0.2∘ using the high-resolution Coordination of Information on the Environment (CORINE) land-cover map and combined with the Global Fire Assimilation System (GFAS) fire emissions to create terrestrial carbon fluxes. Ocean CO2 fluxes are included in our product, based on Jena CarboScope ocean CO2 fluxes, which are downscaled using wind speed and temperature. Jointly, these flux estimates enable modeling of atmospheric CO2 mole fractions over Europe. We assess the skill of the CTE-HR CO2 fluxes (a) to reproduce observed anomalies in biospheric fluxes and atmospheric CO2 mole fractions during the 2018 European drought, (b) to capture the reduction of anthropogenic emissions due to COVID-19 lockdowns, (c) to match mole fraction observations at Integrated Carbon Observation System (ICOS) sites across Europe after atmospheric transport with the Transport Model, version 5 (TM5) and the Stochastic Time-Inverted Lagrangian Transport (STILT), driven by ECMWF-IFS, and (d) to capture the magnitude and variability of measured CO2 fluxes in the city center of Amsterdam (the Netherlands). We show that CTE-HR fluxes reproduce large-scale flux anomalies reported in previous studies for both biospheric fluxes (drought of 2018) and anthropogenic emissions (COVID-19 pandemic in 2020). After applying transport of emitted CO2, the CTE-HR fluxes have lower median root mean square errors (RMSEs) relative to mole fraction observations than fluxes from a non-informed flux estimate, in which biosphere fluxes are scaled to match the global growth rate of CO2 (poor person's inversion). RMSEs are close to those of the reanalysis with the CTE data assimilation system. This is encouraging given that CTE-HR fluxes did not profit from the weekly assimilation of CO2 observations as in CTE. We furthermore compare CO2 concentration observations at the Dutch Lutjewad coastal tower with high-resolution STILT transport to show that the high-resolution fluxes manifest variability due to different emission sectors in summer and winter. Interestingly, in periods where synoptic-scale transport variability dominates CO2 concentration variations, the CTE-HR fluxes perform similarly to low-resolution fluxes (5–10× coarsened). The remaining 10 % of the simulated CO2 mole fraction differs by 〉2 ppm between the low-resolution and high-resolution flux representation and is clearly associated with coherent structures (“plumes”) originating from emission hotspots such as power plants. We therefore note that the added resolution of our product will matter most for very specific locations and times when used for atmospheric CO2 modeling. Finally, in a densely populated region like the Amsterdam city center, our modeled fluxes underestimate the magnitude of measured eddy covariance fluxes but capture their substantial diurnal variations in summertime and wintertime well. We conclude that our product is a promising tool for modeling the European carbon budget at a high resolution in near real time. The fluxes are freely available from the ICOS Carbon Portal (CC-BY-4.0) to be used for near-real-time monitoring and modeling, for example, as an a priori flux product in a CO2 data assimilation system. The data are available at https://doi.org/10.18160/20Z1-AYJ2 (van der Woude, 2022a).
    Type of Medium: Online Resource
    ISSN: 1866-3516
    URL: Article
    DOI: 10.5194/essd-15-579-2023
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
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  • 8
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    Standard atomic weights of the elements 2021 (IUPAC Technical Report)
    Walter de Gruyter GmbH ; 2022
    In:  Pure and Applied Chemistry Vol. 94, No. 5 ( 2022-05-25), p. 573-600
    Details
    In: Pure and Applied Chemistry, Walter de Gruyter GmbH, Vol. 94, No. 5 ( 2022-05-25), p. 573-600
    Abstract: Following the reviews of atomic-weight determinations and other cognate data in 2015, 2017, 2019 and 2021, the IUPAC (International Union of Pure and Applied Chemistry) Commission on Isotopic Abundances and Atomic Weights (CIAAW) reports changes of standard atomic weights. The symbol A r °(E) was selected for standard atomic weight of an element to distinguish it from the atomic weight of an element E in a specific substance P, designated A r (E, P). The CIAAW has changed the values of the standard atomic weights of five elements based on recent determinations of terrestrial isotopic abundances: Ar (argon): from 39.948 ± 0.001 to [39.792, 39.963] Hf (hafnium): from 178.49 ± 0.02 to 178.486 ± 0.006 Ir (iridium): from 192.217 ± 0.003 to 192.217 ± 0.002 Pb (lead): from 207.2 ± 0.1 to [206.14, 207.94] Yb (ytterbium): from 173.054 ± 0.005 to 173.045 ± 0.010 The standard atomic weight of argon and lead have changed to an interval to reflect that the natural variation in isotopic composition exceeds the measurement uncertainty of A r (Ar) and A r (Pb) in a specific substance. The standard atomic weights and/or the uncertainties of fourteen elements have been changed based on the Atomic Mass Evaluations 2016 and 2020 accomplished under the auspices of the International Union of Pure and Applied Physics (IUPAP). A r ° of Ho, Tb, Tm and Y were changed in 2017 and again updated in 2021: Al (aluminium), 2017: from 26.981 5385 ± 0.000 0007 to 26.981 5384 ± 0.000 0003 Au (gold), 2017: from 196.966 569 ± 0.000 005 to 196.966 570 ± 0.000 004 Co (cobalt), 2017: from 58.933 194 ± 0.000 004 to 58.933 194 ± 0.000 003 F (fluorine), 2021: from 18.998 403 163 ± 0.000 000 006 to 18.998 403 162 ± 0.000 000 005 (Ho (holmium), 2017: from 164.930 33 ± 0.000 02 to 164.930 328 ± 0.000 007) Ho (holmium), 2021: from 164.930 328 ± 0.000 007 to 164.930 329 ± 0.000 005 Mn (manganese), 2017: from 54.938 044 ± 0.000 003 to 54.938 043 ± 0.000 002 Nb (niobium), 2017: from 92.906 37 ± 0.000 02 to 92.906 37 ± 0.000 01 Pa (protactinium), 2017: from 231.035 88 ± 0.000 02 to 231.035 88 ± 0.000 01 Pr (praseodymium), 2017: from 140.907 66 ± 0.000 02 to 140.907 66 ± 0.000 01 Rh (rhodium), 2017: from 102.905 50 ± 0.000 02 to 102.905 49 ± 0.000 02 Sc (scandium), 2021: from 44.955 908 ± 0.000 005 to 44.955 907 ± 0.000 004 (Tb (terbium), 2017: from 158.925 35 ± 0.000 02 to 158.925 354 ± 0.000 008) Tb (terbium), 2021: from 158.925 354 ± 0.000 008 to 158.925 354 ± 0.000 007 (Tm (thulium), 2017: from 168.934 22 ± 0.000 02 to 168.934 218 ± 0.000 006) Tm (thulium), 2021: from 168.934 218 ± 0.000 006 to 168.934 219 ± 0.000 005 (Y (yttrium), 2017: from 88.905 84 ± 0.000 02 to 88.905 84 ± 0.000 01) Y (yttrium), 2021: from 88.905 84 ± 0.000 01 to 88.905 838 ± 0.000 002
    Type of Medium: Online Resource
    ISSN: 0033-4545 , 1365-3075
    URL: Article
    DOI: 10.1515/pac-2019-0603
    RVK:
    VA 6665
    Language: English
    Publisher: Walter de Gruyter GmbH
    Publication Date: 2022
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  • 9
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    Data_Sheet_1.docx
    Frontiers Media SA ; 2023
    In:  Frontiers in Nutrition Vol. 10 ( 2023-9-22)
    Details
    In: Frontiers in Nutrition, Frontiers Media SA, Vol. 10 ( 2023-9-22)
    Abstract: Accurate dietary assessment is crucial for nutrition and health research. Traditional methods, such as food records, food frequency questionnaires, and 24-hour dietary recalls (24HR), have limitations, such as the need for trained interviewers, time-consuming procedures, and inaccuracies in estimations. Novel technologies, such as image-based dietary assessment apps, have been developed to overcome these limitations. SNAQ is a novel image-based food-recognition app which, based on computer vision, assesses food type and volume, and provides nutritional information about dietary intake. This cross-sectional observational study aimed to investigate the validity of SNAQ as a dietary assessment tool for measuring energy and macronutrient intake in adult women with normal body weight ( n  = 30), compared to doubly labeled water (DLW), a reference method for total daily energy expenditure (TDEE). Energy intake was also estimated using a one-day 24HR for direct comparison. Bland–Altman plots, paired difference tests, and Pearson’s correlation coefficient were used to assess agreement and relationships between the methods. SNAQ showed a slightly higher agreement (bias = −329.6 kcal/day) with DLW for total daily energy intake (TDEI) compared to 24HR (bias = −543.0 kcal/day). While both SNAQ and 24HR tended to underestimate TDEI, only 24HR significantly differed from DLW in this regard ( p   & lt; 0.001). There was no significant relationship between estimated TDEI and TDEE using SNAQ ( R 2  = 27%, p  = 0.50) or 24HR ( R 2  = 34%, p  = 0.20) and there were no significant differences in energy and macronutrient intake estimates between SNAQ and 24HR (Δ = 213.4 kcal/day). In conclusion, these results indicate that SNAQ provides a closer representation of energy intake in adult women with normal body weight than 24HR when compared to DLW, but no relationship was found between the energy estimates of DLW and of the two dietary assessment tools. Further research is needed to determine the clinical relevance and support the implementation of SNAQ in research and clinical settings. Clinical trial registration : This study is registered on ClinicalTrials.gov with the unique identifier NCT04600596 ( https://clinicaltrials.gov/ct2/show/NCT04600596 ).
    Type of Medium: Online Resource
    ISSN: 2296-861X
    URL: Article
    URL: Article
    DOI: 10.3389/fnut.2023.1255499
    DOI: 10.3389/fnut.2023.1255499.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
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  • 10
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    Evaluation of a field-deployable Nafion™-based air-drying system for collecting whole air samples and its application to stable isotope measurements of CO〈sub〉2〈/sub〉
    Copernicus GmbH ; 2020
    In:  Atmospheric Measurement Techniques Vol. 13, No. 7 ( 2020-07-28), p. 4051-4064
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    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 13, No. 7 ( 2020-07-28), p. 4051-4064
    Abstract: Abstract. Atmospheric flask samples are either collected at atmospheric pressure by opening a valve of a pre-evacuated flask or pressurized with the help of a pump to a few bar above ambient pressure. Under humid conditions, there is a risk that water vapor in the sample leads to condensation on the walls of the flask, notably at higher than ambient sampling pressures. Liquid water in sample flasks is known to affect the CO2 mixing ratios and also alters the isotopic composition of oxygen (17O and 18O) in CO2 via isotopic equilibration. Hence, for accurate determination of CO2 mole fractions and its stable isotopic composition, it is vital to dry the air samples to a sufficiently low dew point before they are pressurized in flasks to avoid condensation. Moreover, the drying system itself should not influence the mixing ratio and the isotopic composition of CO2 or that of the other constituents under study. For the Airborne Stable Isotopes of Carbon from the Amazon (ASICA) project focusing on accurate measurements of CO2 and its singly substituted stable isotopologues over the Amazon, an air-drying system capable of removing water vapor from air sampled at a dew point lower than −2 ∘C, flow rates up to 12 L min−1 and without the need for electrical power was needed. Since to date no commercial air-drying device that meets these requirements has been available, we designed and built our own consumable-free, power-free and portable drying system based on multitube Nafion™ gas sample driers (Perma Pure, Lakewood, USA). The required dry purge air is provided by feeding the exhaust flow of the flask sampling system through a dry molecular sieve (type 3A) cartridge. In this study we describe the systematic evaluation of our Nafion™-based air sample dryer with emphasis on its performance concerning the measurements of atmospheric CO2 mole fractions and the three singly substituted isotopologues of CO2 (16O13C16O, 16O12C17O and 16O12C18O), as well as the trace gas species CH4, CO, N2O and SF6. Experimental results simulating extreme tropical conditions (saturated air at 33 ∘C) indicated that the response of the air dryer is almost instantaneous and that approximately 85 L of air, containing up to 4 % water vapor, can be processed staying below a −2 ∘C dew point temperature (at 275 kPa). We estimated that at least eight flasks can be sampled (at an overpressure of 275 kPa) with a water vapor content below −2 ∘C dew point temperature during a typical flight sampling up to 5 km altitude over the Amazon, whereas the remaining samples would stay well below 5 ∘C dew point temperature (at 275 kPa). The performance of the air dryer on measurements of CO2, CH4, CO, N2O, and SF6 and the CO2 isotopologues 16O13C16O and 16O12C18O was tested in the laboratory simulating real sampling conditions by compressing humidified air from a calibrated cylinder, after being dried by the air dryer, into sample flasks. We found that the mole fraction and the isotopic composition difference between the different test conditions (including the dryer) and the base condition (dry air, without dryer) remained well within or very close to, in the case of N2O, the World Meteorological Organization recommended compatibility goals for independent measurement programs, proving that the test condition induced no significant bias on the sample measurements.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-13-4051-2020
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2020
    detail.hit.zdb_id: 2505596-3
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