scholarly journals Characterisation of interferences to in-situ observations of δ<sup>13</sup>CH<sub>4</sub> and C<sub>2</sub>H<sub>6</sub> when using a Cavity Ring Down Spectrometer at industrial sites

2016 ◽  
Author(s):  
Sabina Assan ◽  
Alexia Baudic ◽  
Ali Guemri ◽  
Philippe Ciais ◽  
Valerie Gros ◽  
...  
Keyword(s):  
Natural Gas ◽  
Radiative Forcing ◽  
Industrial Revolution ◽  
Near Infrared ◽  
Isotope Analysis ◽  
Isotopic Signature ◽  
Atmospheric Methane ◽  
Ambient Conditions ◽  
Identification Methods ◽  
Mixing Ratios

Abstract. The increase of atmospheric methane (CH4) is the second largest contributor to the increased radiative forcing since the industrial revolution. Natural gas extraction and distribution is associated with CH4 leaks of uncertain magnitude that has spurred interest for developing new methods to measure them. Using a CRDS instrument we evaluate two methane identification methods commonly used to better constrain emission estimates from natural gas leaks, namely stable isotope analysis and the ethane: methane ratio (C2H6 : CH4). Recently it has come to light that CRDS measurements of δ13CH4 and C2H6 in the near infrared spectral domain are subject to cross sensitivities due to absorption from multiple gases. These sensitivities translate into biases in the retrieval of δ13CH4 and C2H6 concentrations in air samples, and should thus be accounted for during data processing. Here we present extensive laboratory tests using two CRDS instruments to characterize their cross sensitivities and propose corrections to calculate unbiased δ13CH4 and C2H6. Methane isotopic measurements were found to be subject to interference from elevated C2H6 concentrations (a secondary component in many natural gas types) resulting in heavier δ13CH4 by +23.5 ‰ per ppm C2H6 / ppm CH4. Measured C2H6 is subject to absorption interference from a number of other trace gases, the predominant being H2O (with an average linear sensitivity of 0.9 ppm C2H6 per % H2O in ambient conditions, meaning that the presence of H2O causes the inference of too high C2H6 mixing ratios if no correction is applied). Yet, this sensitivity was found to be discontinuous with a strong hysteresis effect. Throughout the range of C2H6 concentrations measured in this study (0–5 ppm C2H6), both CRDS instruments consistently measure concentrations double that reported by a GC, thus we have calculated a calibration factor of 0.5. To demonstrate the significance of the corrections we test the source identification methods on air measured at a natural gas compressor station. The presence of C2H6 in gas emissions at an average level of 0.3 ppm was found to shift the isotopic signature by 2.5 ‰. We find that after correction and calibration the average C2H6 : CH4 ratio shifts by +0.06. These results indicate that when using such a CRDS instrument in conditions of elevated C2H6 for CH4 source determination it is imperative to account for the biases discussed within this study.

scholarly journals Characterization of interferences to in situ observations of <i>δ</i><sup>13</sup>CH<sub>4</sub> and C<sub>2</sub>H<sub>6</sub> when using a cavity ring-down spectrometer at industrial sites

2017 ◽  
Vol 10 (6) ◽  
pp. 2077-2091 ◽  
Author(s):  
Sabina Assan ◽  
Alexia Baudic ◽  
Ali Guemri ◽  
Philippe Ciais ◽  
Valerie Gros ◽  
...  
Keyword(s):  
Near Infrared ◽  
Field Tests ◽  
Isotopic Signature ◽  
Ambient Conditions ◽  
Industrial Sites ◽  
Source Determination ◽  
Infrared Spectral ◽  
The Subject

Abstract. Due to increased demand for an understanding of CH4 emissions from industrial sites, the subject of cross sensitivities caused by absorption from multiple gases on δ13CH4 and C2H6 measured in the near-infrared spectral domain using CRDS has become increasingly important. Extensive laboratory tests are presented here, which characterize these cross sensitivities and propose corrections for the biases they induce. We found methane isotopic measurements to be subject to interference from elevated C2H6 concentrations resulting in heavier δ13CH4 by +23.5 ‰ per ppm C2H6 ∕ ppm CH4. Measured C2H6 is subject to absorption interference from a number of other trace gases, predominantly H2O (with an average linear sensitivity of 0.9 ppm C2H6 per  % H2O in ambient conditions). Yet, this sensitivity was found to be discontinuous with a strong hysteresis effect and we suggest removing H2O from gas samples prior to analysis. The C2H6 calibration factor was calculated using a GC and measured as 0.5 (confirmed up to 5 ppm C2H6). Field tests at a natural gas compressor station demonstrated that the presence of C2H6 in gas emissions at an average level of 0.3 ppm shifted the isotopic signature by 2.5 ‰, whilst after calibration we find that the average C2H6 : CH4 ratio shifts by +0.06. These results indicate that, when using such a CRDS instrument in conditions of elevated C2H6 for CH4 source determination, it is imperative to account for the biases discussed within this study.

scholarly journals Atmospheric methane and carbon dioxide from SCIAMACHY satellite data: initial comparison with chemistry and transport models

2004 ◽  
Vol 4 (6) ◽  
pp. 7217-7279 ◽  
Author(s):  
M. Buchwitz ◽  
R. de Beek ◽  
J. P. Burrows ◽  
H. Bovensmann ◽  
T. Warneke ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Reasonable Agreement ◽  
Near Infrared ◽  
Weighting Function ◽  
Lower Surface ◽  
Retrieval Algorithm ◽  
Atmospheric Methane ◽  
Mixing Ratios ◽  
Data Products ◽  
Carbon Dioxide Co2

Abstract. The remote sensing of the atmospheric greenhouse gases methane (CH4) and carbon dioxide (CO2) in the troposphere from instrumentation aboard satellites is a new area of research. In this manuscript, results obtained from observations of the up-welling radiation in the near-infrared by SCIAMACHY (Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY), which flies on board ENVISAT, are presented. Vertical columns of CH4, CO2 and oxygen (O2) have been retrieved and the (air or) O2-normalized CH4 and CO2 column amounts, the dry air column averaged mixing ratios XCH4 and XCO2 derived. In this manuscript the first results, obtained by using the version 0.4 of the Weighting Function Modified (WFM) DOAS retrieval algorithm applied to SCIAMACHY data, are described and compared with global models. This is an important step in assessing the quality and information content of the data products derived from SCIAMACHY observations. This study investigates the behaviour of CO2 and CH4 in the period from January to October 2003. The SCIAMACHY greenhouse gas column amounts and their mixing ratios for cloud free scenes over land are shown to be in reasonable agreement with models. Over the ocean, as a result of the lower surface spectral reflectance and resultant low signal to noise with the exception of sun glint conditions, the accuracy of the individual data products is poorer. The measured methane column amounts agree with the model columns within a few percent. The inter-hemispheric difference of the methane mixing ratios, determined from single day cloud free measurements over land, is in the range 30–110 ppbv and in reasonable agreement with the corresponding model data (48–71 ppbv). For the set of individual measurements the standard deviations of the difference with respect to the models are in the range ~100–200 ppbv (5–10%) and ±14.4 ppmv (3.9%) for XCH

Significant fluxes of methane over tropical wetlands and their associated δ13C isotopic source signatures

2020 ◽  
Author(s):  
James L. France ◽  
Anna Jones ◽  
Tom Lachlan-Cope ◽  
Alex Weiss ◽  
Marcos Andrade ◽  
...  
Keyword(s):  
Amazon Basin ◽  
Mixed Boundary ◽  
Ground Level ◽  
Isotopic Analysis ◽  
Isotopic Signature ◽  
Direct Access ◽  
Atmospheric Methane ◽  
Tropical Wetlands ◽  
Mixing Ratios ◽  
Methane Fluxes

&lt;p&gt;Tropical wetlands have been proposed as a potential driver for the recent rise in global atmospheric methane. However, direct access and quantification of emissions is difficult. In March 2019, a pilot study was given permission to overfly the Bolivian Llanos de Moxos wetlands to measure atmospheric mixing ratios of methane and collect spot samples for isotopic analysis. Combined with this was a short ground campaign to collect isotopic samples directly above the wetland edge to compare with the integrated atmospheric signature.&lt;/p&gt;&lt;p&gt;Atmospheric mixing ratios of methane reached a maximum of 2400 ppb (500 ppb above baseline concentrations) in the well mixed boundary layer flying at 400m above the wetland. Upwind and downwind transects were a maximum of 300 km, and methane mixing ratios increased roughly linearly with distance downwind. The isotopic data from the airborne surveys and ground surveys give a bulk isotopic signature for &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;CH4&lt;/sub&gt; of ~-59 &amp;#8240; &amp;#177; 4, which is less negative than Amazon floodplain work focusing on emission of methane through trees, but match well with bulk isotopic values from the Amazon Basin. Ground based wetland samples taken concurrently near Trinidad, Bolivia, gave a source signature of -56 &amp;#8240; &amp;#177; 4 re-enforcing the likelihood that the atmospheric enhancements measured are related to the wetland emissions. For comparison, tropical wetlands measured at ground level during a recent Ugandan and Zambian campaign gave heavier &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;CH4&lt;/sub&gt; isotopic source signatures of -50 to -54 &amp;#8240;. Based on this snap shot study, flux estimations suggest that the Bolivian wetlands could be emitting ~10mg CH&lt;sub&gt;4&lt;/sub&gt; m&lt;sup&gt;-2 &lt;/sup&gt;h&lt;sup&gt;-1&lt;/sup&gt;. The observed mole fractions will be compared to model simulations to determine how well the Bolivian wetland methane fluxes are represented.&lt;/p&gt;

scholarly journals Detection of Methane Emission from a Local Source Using GOSAT Target Observations

2020 ◽  
Vol 12 (2) ◽  
pp. 267
Author(s):  
Akihiko Kuze ◽  
Nobuhiro Kikuchi ◽  
Fumie Kataoka ◽  
Hiroshi Suto ◽  
Kei Shiomi ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Near Infrared ◽  
Time Series Data ◽  
Single Point ◽  
Wrf Model ◽  
Lower Troposphere ◽  
Series Data ◽  
Local Source ◽  
Atmospheric Methane ◽  
Carbon Dioxide Co2

Emissions of atmospheric methane (CH4), which greatly contributes to radiative forcing, have larger uncertainties than those for carbon dioxide (CO2). The Thermal And Near-infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT) launched in 2009 has demonstrated global grid observations of the total column density of CO2 and CH4 from space, and thus reduced uncertainty in the global flux estimation. In this paper, we present a case study on local CH4 emission detection from a single-point source using an available series of GOSAT data. By modifying the grid observation pattern, the pointing mechanism of TANSO-FTS targets a natural gas leak point at Aliso Canyon in Southern California, where the clear-sky frequency is high. To enhance local emission estimates, we retrieved CO2 and CH4 partial column-averaged dry-air mole fractions of the lower troposphere (XCO2 (LT) and XCH4 (LT)) by simultaneous use of both sunlight reflected from Earth’s surface and thermal emissions from the atmosphere. The time-series data of Aliso Canyon showed a large enhancement that decreased with time after its initial blowout, compared with reference point data and filtered with wind direction simulated by the Weather Research and Forecasting (WRF) model.

scholarly journals Effects of Strongly Enhanced Atmospheric Methane Concentrations in a Fully Coupled Chemistry-Climate Model

2020 ◽  
Author(s):  
Laura Stecher ◽  
Franziska Winterstein ◽  
Martin Dameris ◽  
Patrick Jöckel ◽  
Michael Ponater ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Water Vapour ◽  
Climate Sensitivity ◽  
Radiative Forcing ◽  
Climate Model ◽  
Atmospheric Methane ◽  
Climate Feedbacks ◽  
Mixing Ratios ◽  
Radiative Impact ◽  
Stratospheric Water Vapour

Abstract. In a previous study the quasi-instantaneous chemical impacts (rapid adjustments) of strongly enhanced methane (CH4) mixing ratios have been analyzed. However, to quantify the influence of the respective slow climate feedbacks on the chemical composition it is necessary to include the radiation driven temperature feedback. Therefore, we perform sensitivity simulations with doubled and fivefold present-day (year 2010) CH4 mixing ratios with the chemistry-climate model EMAC and include in a novel set-up a mixed layer ocean model to account for tropospheric warming. We find that the slow climate feedbacks counteract the reduction of the hydroxyl radical in the troposphere, which is caused by the strongly enhanced CH4 mixing ratios. Thereby also the resulting prolongation of the tropospheric CH4 lifetime is weakened compared to the quasi-instantaneous response considered previously. Changes in the stratospheric circulation evolve clearly with the warming of the troposphere. The Brewer-Dobson circulation strengthens, affecting the response of trace gases, such as ozone, water vapour and CH4 in the stratosphere, and also causing stratospheric temperature changes. In the middle and upper stratosphere, the increase of stratospheric water vapour is reduced with respect to the quasi-instantaneous response. Weaker increases of the hydroxyl radical cause the chemical depletion of CH4 to be less strongly enhanced and thus the in situ source of stratospheric water vapour as well. However, in the lower stratosphere water vapour increases more strongly when tropospheric warming is accounted for enlarging its overall radiative impact. The response of the stratospheric adjusted temperatures driven by slow climate feedbacks is dominated by these increases of stratospheric water vapour, as well as strongly decreased ozone mixing ratios above the tropical tropopause, which result from enhanced tropical upwelling. While rapid radiative adjustments from ozone and stratospheric water vapour make an essential contribution to the effective CH4 radiative forcing, the radiative impact of the respective slow feedbacks is rather moderate. In line with this, the climate sensitivity from CH4 changes in this chemistry-climate model setup is not significantly different from the climate sensitivity in carbon dioxide-driven simulations, provided that the CH4 effective radiative forcing includes the rapid adjustments from ozone and stratospheric water vapour changes.

scholarly journals Proxy Measures and Novel Strategies for Estimating Nitrogen Utilisation Efficiency in Dairy Cattle

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 343
Author(s):  
Anna Lavery ◽  
Conrad Ferris
Keyword(s):  
Near Infrared ◽  
Isotope Analysis ◽  
Strong Relationship ◽  
Nitrogen Isotope ◽  
Invasive Technique ◽  
Infrared Analysis ◽  
Resonance Spectroscopy ◽  
Dietary Nitrogen ◽  
Nitrogen Utilisation ◽  
Utilisation Efficiency

The efficiency with which dairy cows convert dietary nitrogen (N) to milk N is generally low (typically 25%). As a result, much of the N consumed is excreted in manure, from which N can be lost to the environment. Therefore there is increasing pressure to reduce N excretion and improve N use efficiency (NUE) on dairy farms. However, assessing N excretion and NUE on farms is difficult, thus the need to develop proximate measures that can provide accurate estimates of nitrogen utilisation. This review examines a number of these proximate measures. While a strong relationship exists between blood urea N and urinary N excretion, blood sampling is an invasive technique unsuitable for regular herd monitoring. Milk urea N (MUN) can be measured non-invasively, and while strong relationships exist between dietary crude protein and MUN, and MUN and urinary N excretion, the technique has limitations. Direct prediction of NUE using mid-infrared analysis of milk has real potential, while techniques such as near-infrared spectroscopy analysis of faeces and manure have received little attention. Similarly, techniques such as nitrogen isotope analysis, nuclear magnetic resonance spectroscopy of urine, and breath ammonia analysis may all offer potential in the future, but much research is still required.

Near-Infrared Off-Axis Integrated Cavity Output Spectroscopic Gas Sensor for Real-Time, In Situ Atmospheric Methane Monitoring

2020 ◽  
pp. 1-1
Author(s):  
Kaiyuan Zheng ◽  
Chuantao Zheng ◽  
Haipeng Zhang ◽  
Junhao Li ◽  
Zidi Liu ◽  
...  
Keyword(s):  
Real Time ◽  
Gas Sensor ◽  
Near Infrared ◽  
Atmospheric Methane ◽  
Cavity Output

scholarly journals Historical greenhouse gas concentrations

2016 ◽  
Author(s):  
Malte Meinshausen ◽  
Elisabeth Vogel ◽  
Alexander Nauels ◽  
Katja Lorbacher ◽  
Nicolai Meinshausen ◽  
...  
Keyword(s):  
Climate Change ◽  
Greenhouse Gas ◽  
Radiative Forcing ◽  
Sulfur Hexafluoride ◽  
Climate Model ◽  
Future Climate Change ◽  
Large Set ◽  
Mixing Ratios ◽  
Surface Mixing ◽  
Cooling Effects

Abstract. Atmospheric greenhouse gas concentrations are at unprecedented, record-high levels compared to pre-industrial reconstructions over the last 800,000 years. Those elevated greenhouse gas concentrations warm the planet and together with net cooling effects by aerosols, they are the reason of observed climate change over the past 150 years. An accurate representation of those concentrations is hence important to understand and model recent and future climate change. So far, community efforts to create composite datasets with seasonal and latitudinal information have focused on marine boundary layer conditions and recent trends since 1980s. Here, we provide consolidated data sets of historical atmospheric (volume) mixing ratios of 43 greenhouse gases specifically for the purpose of climate model runs. The presented datasets are based on AGAGE and NOAA networks and a large set of literature studies. In contrast to previous intercomparisons, the new datasets are latitudinally resolved, and include seasonality over the period between year 0 to 2014. We assimilate data for CO2, methane (CH4) and nitrous oxide (N2O), 5 chlorofluorocarbons (CFCs), 3 hydrochlorofluorocarbons (HCFCs), 16 hydrofluorocarbons (HFCs), 3 halons, methyl bromide (CH3Br), 3 perfluorocarbons (PFCs), sulfur hexafluoride (SF6), nitrogen triflouride (NF3) and sulfuryl fluoride (SO2F2). We estimate 1850 annual and global mean surface mixing ratios of CO2 at 284.3 ppmv, CH4 at 808.2 ppbv and N2O at 273.0 ppbv and quantify the seasonal and hemispheric gradients of surface mixing ratios. Compared to earlier intercomparisons, the stronger implied radiative forcing in the northern hemisphere winter (due to the latitudinal gradient and seasonality) may help to improve the skill of climate models to reproduce past climate and thereby reduce uncertainty in future projections.

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