Evaluation of continuous δ13CH4 measurements in Heidelberg and at Schauinsland, Germany

2020 ◽  
Author(s):  
Antje Hoheisel ◽  
Frank Meinhardt ◽  
Martina Schmidt
Keyword(s):  
Isotopic Composition ◽  
Mole Fraction ◽  
Isotope Analysis ◽  
Ambient Air ◽  
Peak Height ◽  
West Germany ◽  
Livestock Farming ◽  
Biogenic Methane ◽  
The Mean ◽  
Instrumental Development

<p>Instrumental development in measurement technique now allows continuous in-situ isotope analysis of <sup>13</sup>CH<sub>4</sub> by Cavity Ring-Down Spectroscopy (CRDS). Analyses of the isotopic composition of methane in ambient air can potentially be used to partition between different CH<sub>4</sub> source categories.</p><p>Since 2014 a CRDS G2201-i analyser has been used to continuously measure CH<sub>4</sub> and its <sup>13</sup>C/<sup>12</sup>C ratio in ambient air at the Institute of Environmental Physics (IUP) in Heidelberg (116m a.s.l.), South-West Germany. Furthermore, the CRDS G2201-i analyser was installed twice for a month at the measurement station of the German Environment Agency at Schauinsland (1205m a.s.l.). In September 2018 and in February 2019 the analyser was moved to Schauinsland to examine the validity of evaluations of continuous δ<sup>13</sup>CH<sub>4 </sub>measurements at a semi-rural station.</p><p>As an urban station, the seasonal and daily variations of the measured CH<sub>4</sub> mole fraction and isotopic composition in Heidelberg vary much stronger than at the mountain station Schauinsland. The precision of the isotopic source signature calculation using a Keeling plot strongly depends on the CH<sub>4</sub> peak height and instrumental precision. Therefore, at Schauinsland station the lower variability in the CH<sub>4</sub> mole fraction makes the evaluation challenging. Different methods such as monthly/weekly interval evaluations and moving Keeling/Miller Tans methods has been used to calculate the isotopic source signature in ambient air.</p><p>The isotopic methane source signatures of the air in Heidelberg was found to be between -75 ‰ and -35 ‰, with an average of (-54 ± 2) ‰. An annual cycle can be noticed with more depleted values (-56 ‰) in summer and more enriched values (-51 ‰) in winter, due to larger biogenic emissions in summer and more thermogenic (e.g. natural gas) emissions in winter. The mean isotopic source signature calculated at Schauinsland shows variations, too, with more enriched values (−56 ‰) in winter and more depleted (−60 ‰) ones in autumn. The more depleted values in summer/autumn at Schauinsland corresponds to more biogenic methane and can be explained by dairy cows grazing near the station especially during this time.</p><p>The generally more enriched values at Schauinsland are caused by the more rural surrounding. Emission estimates of county provided by the LUBW Landesanstalt für Umwelt Baden-Württemberg shows that around Schauinsland 60 % of the CH<sub>4</sub> emissions are emitted by livestock farming and around Heidelberg only 28 %. The mean isotopic source signature calculated using these emissions is (-58 ± 2) ‰ for Schauinsland and (-53 ± 2) ‰ for Heidelberg. These results agreed well with the mean source signatures determined out of continuous isotopic measurements.</p>

scholarly journals Measurement report: Methane (CH<sub>4</sub>) sources in Krakow, Poland: insights from isotope analysis

2021 ◽  
Author(s):  
Malika Menoud ◽  
Carina van der Veen ◽  
Jaroslaw Necki ◽  
Jakub Bartyzel ◽  
Barbara Szénási ◽  
...  
Keyword(s):  
Time Series ◽  
Isotopic Composition ◽  
Transport Model ◽  
Isotope Analysis ◽  
Ambient Air ◽  
Coal Extraction ◽  
Night Time ◽  
Isotopic Signatures ◽  
Ch4 Emissions ◽  
Gas Leaks

Abstract. Methane (CH4) emissions from human activities are a threat to the resilience of our current climate system, and to the adherence of the Paris Agreement goals. The stable isotopic composition of methane (δ13C and δ2H) allows to distinguish between the different CH4 origins. A significant part of the European CH4 emissions, 3.6 % in 2018, comes from coal extraction in Poland; the Upper Silesian Coal Basin (USCB) being the main hotspot. Measurements of CH4 mole fraction (χ(CH4)), δ13C and δ2H in CH4 in ambient air were performed continuously during 6 months in 2018 and 2019 at Krakow, Poland, 50 km east of the USCB. In addition, air samples were collected during parallel mobile campaigns, from multiple CH4 sources in the footprint area of the continuous measurements. The resulting isotopic signatures from sampled plumes allowed us to distinguish between natural gas leaks, coal mine fugitive emissions, landfill and sewage, and ruminants. The use of δ2H in CH4 is crucial to distinguish the fossil fuel emissions in the case of Krakow, because their relatively depleted δ13C values overlap with the ones of microbial sources. The observed χ(CH4) time series showed regular daily night-time accumulations, sometimes combined with irregular pollution events during the day. The isotopic signatures of each peak were obtained using the Keeling plot method, and generally fall in the range of thermogenic CH4 formation – with δ13C between −55.3 and −39.4 ‰ V-PDB, and δ2H between −285 and −124 ‰ V-SMOW. They compare well with the signatures measured for gas leaks in Krakow and USCB mines. The CHIMERE transport model was used to compute the CH4 and isotopic composition time series in Krakow, based on two emission inventories. The χ(CH4) are generally under-estimated in the model. The simulated isotopic source signatures, obtained with Keeling plots on each simulated peak using the EDGAR v5.0 inventory, indicate that a higher contribution from fuel combustion sources in EDGAR would lead to a better agreement. The isotopic mismatches between model and observations are mainly caused by uncertainties in the assigned isotopic signatures for each source category, and the way they are classified in the inventory. These uncertainties are larger for emissions close to the study site, which are more heterogenous than the ones advected from the USCB coal mines. Our isotope approach proves to be very sensitive in this region, thus helping to evaluate emission estimates.

scholarly journals Real-time analysis of <i>δ</i><sup>13</sup>C- and <i>δ</i>D-CH<sub>4</sub> in ambient air with laser spectroscopy: method development and first intercomparison results

2016 ◽  
Vol 9 (1) ◽  
pp. 263-280 ◽  
Author(s):  
S. Eyer ◽  
B. Tuzson ◽  
M. E. Popa ◽  
C. van der Veen ◽  
T. Röckmann ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Real Time ◽  
Method Development ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Ambient Air ◽  
Repeated Measurements ◽  
Laser Absorption ◽  
Real Time Analysis

Abstract. In situ and simultaneous measurement of the three most abundant isotopologues of methane using mid-infrared laser absorption spectroscopy is demonstrated. A field-deployable, autonomous platform is realized by coupling a compact quantum cascade laser absorption spectrometer (QCLAS) to a preconcentration unit, called trace gas extractor (TREX). This unit enhances CH4 mole fractions by a factor of up to 500 above ambient levels and quantitatively separates interfering trace gases such as N2O and CO2. The analytical precision of the QCLAS isotope measurement on the preconcentrated (750 ppm, parts-per-million, µmole mole−1) methane is 0.1 and 0.5 ‰ for δ13C- and δD-CH4 at 10 min averaging time. Based on repeated measurements of compressed air during a 2-week intercomparison campaign, the repeatability of the TREX–QCLAS was determined to be 0.19 and 1.9 ‰ for δ13C and δD-CH4, respectively. In this intercomparison campaign the new in situ technique is compared to isotope-ratio mass spectrometry (IRMS) based on glass flask and bag sampling and real time CH4 isotope analysis by two commercially available laser spectrometers. Both laser-based analyzers were limited to methane mole fraction and δ13C-CH4 analysis, and only one of them, a cavity ring down spectrometer, was capable to deliver meaningful data for the isotopic composition. After correcting for scale offsets, the average difference between TREX–QCLAS data and bag/flask sampling–IRMS values are within the extended WMO compatibility goals of 0.2 and 5 ‰ for δ13C- and δD-CH4, respectively. This also displays the potential to improve the interlaboratory compatibility based on the analysis of a reference air sample with accurately determined isotopic composition.

scholarly journals Real-time analysis of δ<sup>13</sup>C- and δD-CH<sub>4</sub> in ambient air with laser spectroscopy: method development and first intercomparison results

2015 ◽  
Vol 8 (8) ◽  
pp. 8925-8970 ◽  
Author(s):  
S. Eyer ◽  
B. Tuzson ◽  
M. E. Popa ◽  
C. van der Veen ◽  
T. Röckmann ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Real Time ◽  
Method Development ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Ambient Air ◽  
Laser Absorption ◽  
Real Time Analysis ◽  
Averaging Time

Abstract. In situ and simultaneous measurement of the three most abundant isotopologues of methane using mid-infrared laser absorption spectroscopy is demonstrated. A field-deployable, autonomous platform is realized by coupling a compact quantum cascade laser absorption spectrometer (QCLAS) to a preconcentration unit, called TRace gas EXtractor (TREX). This unit enhances CH4 mole fractions by a factor of up to 500 above ambient levels and quantitatively separates interfering trace gases such as N2O and CO2. The analytical precision of the QCLAS isotope measurement on the preconcentrated (750 ppm, parts-per-million, μmole/mole) methane is 0.1 and 0.5 ‰ for δ13C- and δD-CH4 at 10 min averaging time. Based on replicate measurements of compressed air during a two-week intercomparison campaign, the repeatability of the TREX-QCLAS was determined to be 0.19 and 1.9 ‰ for δ13C and δD-CH4, respectively. In this intercomparison campaign the new in situ technique is compared to isotope-ratio mass-spectrometry (IRMS) based on glass flask and bag sampling and real time CH4 isotope analysis by two commercially available laser spectrometers. Both laser-based analyzers were limited to methane mole fraction and δ13C-CH4 analysis, and only one of them, a cavity ring down spectrometer, was capable to deliver meaningful data for the isotopic composition. After correcting for scale offsets, the average difference between TREX–QCLAS data and bag/flask sampling–IRMS values are within the extended WMO compatibility goals of 0.2 and 5 ‰ for δ13C- and δD-CH4, respectively. Thus, the intercomparison also reveals the need for reference air samples with accurately determined isotopic composition of CH4 to further improve the interlaboratory compatibility.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

scholarly journals Different long-term trends of the oxygen red 630.0 nm line nightglow intensity as the result of lowering the ionosphere F2 layer

2008 ◽  
Vol 26 (8) ◽  
pp. 2069-2080 ◽  
Author(s):  
N. B. Gudadze ◽  
G. G. Didebulidze ◽  
L. N. Lomidze ◽  
G. Sh. Javakhishvili ◽  
M. A. Marsagishvili ◽  
...  
Keyword(s):  
Electron Density ◽  
Line Intensity ◽  
Peak Height ◽  
Height Distribution ◽  
Theoretical Simulation ◽  
Type Layer ◽  
Long Term Trends ◽  
The Mean ◽  
Long Term Trend

Abstract. Long-term observations of total nightglow intensity of the atomic oxygen red 630.0 nm line at Abastumani (41.75° N, 42.82° E) in 1957–1993 and measurements of the ionosphere F2 layer parameters from the Tbilisi ionosphere station (41.65° N, 44.75° E) in 1963–1986 have been analyzed. It is shown that a decrease in the long-term trend of the mean annual red 630.0 nm line intensity from the pre-midnight value (+0.770±1.045 R/year) to its minimum negative value (−1.080±0.670 R/year) at the midnight/after midnight is a possible result of the observed lowering of the peak height of the ionosphere F2 layer electron density hmF2 (−0.455±0.343 km/year). A theoretical simulation is carried out using a simple Chapman-type layer (damping in time) for the height distribution of the F2 layer electron density. The estimated values of the lowering in the hmF2, the increase in the red line intensity at pre-midnight and its decrease at midnight/after midnight are close to their observational ones, when a negative trend in the total neutral density of the upper atmosphere and an increase in the mean northward wind (or its possible consequence – a decrease in the southward one) are assumed.

The influence of pH on the synthesis of mixed Fe-Mn oxide minerals

Clay Minerals ◽  
1990 ◽  
Vol 25 (4) ◽  
pp. 507-518 ◽  
Author(s):  
M. H. Ebinger ◽  
D. G. Schulze
Keyword(s):  
Iron Oxides ◽  
Mole Fraction ◽  
Unit Cell ◽  
Mn Oxide ◽  
Cell Dimensions ◽  
The Mean ◽  
Mn Substitution ◽  
Oxide Minerals ◽  
Unit Cell Dimensions ◽  
Influence Of Ph

AbstractMn-substituted iron oxides were synthesized at pH 4, 6, 8, and 10 from Fe-Mn systems with Mn mole fractions (Mn/(Mn + Fe)) of 0, 0·2, 0·4, 0·6, 0·8, and 1·0, and kept at 50°C for 40 days. The Mn mole fraction in goethite was <0·07 at pH 4 but increased to ∼0.47 at pH 6. Goethite and/or hematite formed in Fe and Fe + Mn syntheses at pH 4 and pH 6 at Mn mole fractions ≤0·8, and at Mn mole fractions ≤0·2 at pH 8 and pH 10. Hausmannite and jacobsite formed at pH 8 and pH 10 at Mn mole fractions ≥0·4. In the pure Mn syntheses, manganite (γ-MnOOH) formed at pH 4 and pH 6, whereas hausmannite (Mn3O4) formed at pH 8 and pH 10. As the Mn substitution increased, the unit-cell dimensions of goethite shifted toward those of groutite, and the mean crystallite dimensions of goethite decreased.

A global meta-analysis reveals a significant offset in δ2H between plant water and its sources

2021 ◽  
Author(s):  
Javier de la Casa ◽  
Adrià Barbeta ◽  
Asun Rodriguez-Uña ◽  
Lisa Wingate ◽  
Jérôme Ogeé ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Soil Water ◽  
Meta Analysis ◽  
Water Evaporation ◽  
Source Water ◽  
Plant Water ◽  
Water Line ◽  
Plant Source ◽  
Sampling Campaign ◽  
The Mean

&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Long-standing ecological theory establishes that the isotopic composition of the plant water reflects that of the root-accessed sources, at least in non-saline or non-xeric environments. However, a growing number of studies challenge this assumption by reporting plant-source offsets in water isotopic composition, for a wide range of ecosystems. We conducted a global meta-analysis to systematically quantify the magnitude of this plant-source offset in water isotopic composition and its potential explanatory factors. We compiled 108 studies reporting dual water isotopic composition (&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O) of plant and source water. From these studies, we extracted the &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H and &amp;#948;&lt;sup&gt;18&lt;/sup&gt;O of both plant and source waters for 223 plant species from artic to tropical biomes. For each species and sampling campaign, within each study, we calculated the mean line conditioned excess (LC-excess), with the slope and intercept of the local meteoric water line, and the mean soil water line conditioned excess (SWL-excess), from the slope and intercept of the soil water evaporation line. For each study site and sampling campaign, we obtained land surface temperature and volumetric soil water from the ERA5 database. For each study species, we recorded the functional type, leaf habit and for those available wood density. We found, on average, a significantly negative SWL-excess: plant water was systematically more depleted in &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H than soil water. In &gt; 90% of the cases with significantly negative SWL-excess, we also found negative LC-excess values, meaning that access to sources alternative to soil water was unlikely to explain negative SWL-excess values.&amp;#160;&lt;/p&gt;&lt;p&gt;Calculated SWL-excess was affected by temperature and humidity: there were larger mismatches between plant and source water in isotopic composition in colder and wetter sites. Angiosperms, broadleaved and deciduous species exhibited more negative SWL-excess values than gymnosperms, narrow-leaved and evergreen species. Our results suggest that when using the dual isotopic approach, potential biases in the adscription of plant water sources are more likely in broadleaved forests in humid, and cold regions. Potential underlying mechanism for these isotopic mismatches will be discussed.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals In-situ observations of the isotopic composition of methane at the Cabauw tall tower site

2016 ◽  
Author(s):  
Thomas Röckmann ◽  
Simon Eyer ◽  
Carina van der Veen ◽  
Maria E. Popa ◽  
Béla Tuzson ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
High Precision ◽  
Temporal Resolution ◽  
Isotope Ratio ◽  
Mesoscale Model ◽  
Ambient Air ◽  
Model Calculations ◽  
Dual Isotope ◽  
Methane Budget

Abstract. High precision analyses of the isotopic composition of methane in ambient air can potentially be used to discriminate between different source categories. Due to the complexity of isotope ratio measurements, such analyses have generally been performed in the laboratory on air samples collected in the field. This poses a limitation on the temporal resolution at which the isotopic composition can be monitored with reasonable logistical effort. Here we present the performance of a dual isotope ratio mass spectrometric system (IRMS) and a quantum cascade laser absorption spectroscopy (QCLAS) based technique for in-situ analysis of the isotopic composition of methane under field conditions. Both systems were deployed at the Cabauw experimental site for atmospheric research (CESAR) in the Netherlands and performed in-situ, high-frequency (approx. hourly) measurements for a period of more than 5 months. The IRMS and QCLAS instruments were in excellent agreement with a slight systematic offset of +(0.05 ± 0.03) ‰ for δ13C and –(3.6 ± 0.4) ‰ for δD. This was corrected for, yielding a combined dataset with more than 2500 measurements of both δ13C and δD. The high precision and temporal resolution dataset does not only reveal the overwhelming contribution of isotopically depleted agricultural CH4 emissions from ruminants at the Cabauw site, but also allows the identification of specific events with elevated contributions from more enriched sources such as natural gas and landfills. The final dataset was compared to model calculations using the global model TM5 and the mesoscale model FLEXPART-COSMO. The results of both models agree better with the measurements when the TNO-MACC emission inventory is used in the models than when the EDGAR inventory is used. This suggests that high-resolution isotope measurements have the potential to further constrain the methane budget, when they are performed at multiple sites that are representative for the entire European domain.

scholarly journals On the isotopic composition of precipitation in tropical stations (*).

1985 ◽  
Vol 15 (1-2) ◽  
pp. 121-140 ◽  
Author(s):  
Roberto Gonfiantini
Keyword(s):  
Isotopic Composition ◽  
Water Vapour ◽  
Seasonal Variations ◽  
Pacific Islands ◽  
Continental Effect ◽  
The Mean

Some of the trends and characteristics of the isotopic composition oh precipitation in tropical stations are discussed. Stations in small Pacific islands show a variation with latitude, with lower 8-values between 15°N and 1S°S and higher values at higher. Inland stations are depleted in heavy isotopes with respect to coastal stations but sometimes this continental effect is rather complex, as f,or instance in África. Mean monthly 8-values show a remarkable correlation with the amount of precipitation, but the slope variations do not show a clear dependence on the mean long term 8-value,as should be expected theoretically. In Southern American stations the seasonal variations of the meanmonthly 5-values are correlated and they are greater in inland stations due to con-tinentaly. The possible effects of recycling of water vapour by evapotranspiration are also discussed.

scholarly journals Direct Calculation of Thermodynamic Wet-Bulb Temperature as a Function of Pressure and Elevation

2013 ◽  
Vol 30 (8) ◽  
pp. 1757-1765 ◽  
Author(s):  
Sayed-Hossein Sadeghi ◽  
Troy R. Peters ◽  
Douglas R. Cobos ◽  
Henry W. Loescher ◽  
Colin S. Campbell
Keyword(s):  
Air Temperature ◽  
Mean Absolute Error ◽  
Direct Calculation ◽  
Ambient Air ◽  
Absolute Error ◽  
Mean Square ◽  
Air Temperatures ◽  
Order Polynomial ◽  
The Mean ◽  
Very High

Abstract A simple analytical method was developed for directly calculating the thermodynamic wet-bulb temperature from air temperature and the vapor pressure (or relative humidity) at elevations up to 4500 m above MSL was developed. This methodology was based on the fact that the wet-bulb temperature can be closely approximated by a second-order polynomial in both the positive and negative ranges in ambient air temperature. The method in this study builds upon this understanding and provides results for the negative range of air temperatures (−17° to 0°C), so that the maximum observed error in this area is equal to or smaller than −0.17°C. For temperatures ≥0°C, wet-bulb temperature accuracy was ±0.65°C, and larger errors corresponded to very high temperatures (Ta ≥ 39°C) and/or very high or low relative humidities (5% &lt; RH &lt; 10% or RH &gt; 98%). The mean absolute error and the root-mean-square error were 0.15° and 0.2°C, respectively.

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