ArticlePDF Available

Constraints on emissions of carbon monoxide, methane, and a suite of hydrocarbons in the Colorado Front Range using observations of (CO2)-C-14

DOI:10.5194/acpd-13-1609-2013
Authors:
Brian Lafranchi at Aclima, Inc
Brian Lafranchi
  • Aclima, Inc
Gabrielle Petron at University of Colorado
Gabrielle Petron
John B. Miller at National Oceanic and Atmospheric Administration
John B. Miller
S. J. Lehman
S. J. Lehman
S. J. Lehman
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Show all 16 authorsHide
Download full-text PDFDownload full-text PDF
Read full-text
Download citation

Abstract

Atmospheric radiocarbon (14CO) represents an important observational constraint on emissions of fossil-fuel derived carbon into the atmosphere due to the absence of 14CO in fossil fuel reservoirs. The high sensitivity and precision that accelerator mass spectrometry (AMS) affords in atmospheric 14CO analysis has greatly increased the potential for using such measurements to evaluate bottom-up emissions inventories of fossil fuel CO2 (CO2ff), as well as those for other co-emitted species. Here we use observations of 14CO2 and a series of hydrocarbons and combustion tracers from discrete air samples collected between June 2009 and September 2010 at the National Oceanic and Atmospheric Administration Boulder Atmospheric Observatory (BAO; Lat: 40.050° N, Lon: 105.004° W) to derive emission ratios of each species to CO2ff. From these emission ratios, we estimate emissions of these species by using the Vulcan CO2ff high resolution data product as a reference. The species considered in this analysis are carbon monoxide (CO), methane (CH4), acetylene (C2H2), benzene (C6H6), and C3-C5 alkanes. Comparisons of top-down emissions estimates are made to existing inventories of these species for Denver and adjacent counties, as well as to previous efforts to estimate emissions from atmospheric observations over the same area. We find that CO is overestimated in the 2008 National Emissions Inventory (NEI, 2008) by a factor of ~2. A close evaluation of the inventory suggests that the ratio of CO emitted per unit fuel burned from on-road gasoline vehicles is likely over-estimated by a factor of 2.5. The results also suggest that while the oil and gas sector is the largest contributor to the CH4 signal in air arriving from the north and east, it is very likely that other sources, including agricultural sources, contribute to this signal and must be accounted for when attributing these signals to oil and gas industry activity from a top-down perspective. Our results are consistent with ~60% of the total CH4 emissions from regions to the north and east of the BAO tower stemming from the oil and gas industry, equating to ~70 Gg yr-1 or ~1.7% of total natural gas production in the region.
5446a0160cf22b3c14dec3
16.pdf
Content uploaded by Kevin Robert Gurney
Author content
All content in this area was uploaded by Kevin Robert Gurney on Oct 21, 2014
Content may be subject to copyright.
Constraints on emissions of carbon monoxide, methane, and a suite of hydrocarbons in the Colorado Front Range using observations of (CO2)-C-
14.pdf
Available via license: CC BY 3.0
Content may be subject to copyright.
A preview of the PDF is not available
... attributes 64% of the total point source VOC emissions in Colorado to O&NG extraction activities, while in Weld County the O&NG contributions account for 90% of the total point source VOC emissions. Several studies conducted within the DJB since 2011 have found a clear O&NG signature in atmospheric VOCs, with enhancement in the alkanes and aromatics without corresponding increases in combustion tracers[Pétron et al., 2012;Gilman et al., 2013;LaFranchi et al., 2013;Swarthout et al., 2013;Thompson et al., 2014]. O&NG-related VOC sources include leaks from infrastructure and transport, fugitive emissions, and deliberate venting and flaring[Adgate et al., 2014;Vinciguerra et al., 2015]. ...
... O&NG-related VOC sources include leaks from infrastructure and transport, fugitive emissions, and deliberate venting and flaring[Adgate et al., 2014;Vinciguerra et al., 2015]. Increased concentrations of methane, light alkanes, and aromatics in the DJB have been connected to O&NG development[Pétron et al., 2012;Gilman et al., 2013;LaFranchi et al., 2013;Thompson et al., 2014;Eisele et al., 2016]. In addition to degrading air quality, high VOC concentrations are also a concern from a public health perspective. ...
... Instead, our observations suggest a stationary CO source and a separate, temporally variable benzene source, both located in the same general region to the SW of PAO. In Colorado CO emissions have been attributed to gasoline vehicles (66%) and nonroad gasolinepowered equipment (26%)[LaFranchi et al., 2013]. The remaining emissions are attributed to a variety of processes, including industrial activity and natural gas processing. ...
Atmospheric benzene observations from oil and gas production in the Denver Julesburg basin in July and August 2014: Benzene observations from oil and gas
Article
  • Aug 2016
High time resolution measurements of volatile organic compounds (VOCs) were collected using a proton-transfer-reaction quadrupole mass spectrometry (PTR-QMS) instrument at the Platteville Atmospheric Observatory (PAO) in Colorado to investigate how oil and natural gas (O&NG) development impacts air quality within the Wattenburg Gas Field (WGF) in the Denver-Julesburg Basin. The measurements were carried out in July and August 2014 as part of NASA's DISCOVER-AQ field campaign. The PTR-QMS data were supported by pressurized whole air canister samples and airborne vertical and horizontal surveys of VOCs. Unexpectedly high benzene mixing ratios were observed at PAO at ground level (mean benzene = 0.53 ppbv, maximum benzene = 29.3 ppbv), primarily at night (mean nighttime benzene = 0.73 ppbv). These high benzene levels were associated with southwesterly winds. The airborne measurements indicate that benzene originated from within the WGF, and typical source signatures detected in the canister samples implicate emissions from O&NG activities rather than urban vehicular emissions as primary benzene source. This conclusion is backed by a regional toluene-to-benzene ratio analysis which associated southerly flow with vehicular emissions from the Denver area. Weak benzene-to-CO correlations confirmed that traffic emissions were not responsible for the observed high benzene levels. Previous measurements at the Boulder Atmospheric Observatory (BAO) and our data obtained at PAO allow us to locate the source of benzene enhancements between the two atmospheric observatories. Fugitive emissions of benzene from O&NG operations in the Platteville area are discussed as the most likely causes of enhanced benzene levels at PAO.
... Our flask-based R CO estimate is similar to but slightly lower than with other recent top-down observational studies in U.S. cities and regions (observations from 2004 to 2013), which have obtained R CO values ranging from 9 to 14 ppb/ppm [Turnbull et al., 2006; Graven et al., 2009; Wunch et al., 2009; Turnbull et al., 2011a; Miller et al., 2012; LaFranchi et al., 2013]. Our slightly lower values than observed previously are likely a consequence of two factors. ...
... 3.3.2. Winter R CO Comparison With Bottom-Up Inventory-Based Estimates Using R CO , and assuming that the emission flux of CO 2 ff is well constrained from the Hestia bottom-up data product, we can infer the CO emission flux [e.g., Turnbull et al., 2011a; Miller et al., 2012; LaFranchi et al., 2013]. This method relies on CO and CO 2 ff being coemitted and requires an estimate of the spatial extent of the tower footprint. ...
... The trend in USEPA NEI CO estimates through time suggests a possible decrease in CO emissions of a few percent from 2011 to 2012 (although 2012 data are not available), insufficient to explain the difference. A similar apparent overestimate of the CO emission flux from U.S. cities in the USEPA CO inventories has been observed in a number of studies in several other U.S. regions [Turnbull et al., 2006; Graven et al., 2009; Miller et al., 2012; Parrish, 2006; Hudman et al., 2008; Brioude et al., 2011; Kim et al., 2013] and is suspected to be due primarily to an overestimate of the on-road mobile emissions sector CO emissions [LaFranchi et al., 2013; Kota et al., 2014]. The USEPA NEI2011 also provides a breakdown of CO emissions by source sector, reporting that on-road vehicle (gasoline and diesel) emissions account for 69% of Marion County CO emissions or 114,000 tCO yr À1 (Table 3). ...
Toward quantification and source sector identification of fossil fuel CO 2 emissions from an urban area: Results from the INFLUX experiment: INFLUX urban fossil fuel CO2 emissions
Article
Full-text available
  • Dec 2014
The Indianapolis Flux Experiment (INFLUX) aims to develop and assess methods for quantifying urban greenhouse gas emissions. Here we use CO2, 14CO2 and CO measurements from tall towers around Indianapolis, USA to determine urban total CO2, the fossil fuel derived CO2 component (CO2ff) and CO enhancements relative to background measurements. When a local background directly upwind of the urban area is used, the wintertime total CO2 enhancement over Indianapolis can be entirely explained by urban CO2ff emissions. Conversely, when a continental background is used, CO2ff enhancements are larger and account for only half the total CO2 enhancement, effectively representing the combined CO2ff enhancement from Indianapolis and the wider region. In summer, we find that diurnal variability in both background CO2 mole fraction and co-varying vertical mixing make it difficult to use a simple upwind-downwind difference for a reliable determination of total CO2 urban enhancement. We use characteristic CO2ff source sector CO:CO2ff emission ratios to examine the contribution of the CO2ff source sectors to total CO2ff emissions. This method is strongly sensitive to the mobile sector, which produces most CO. We show that the inventory-based emission product (“bottom-up”) and atmospheric observations (“top-down”) can be directly compared throughout the diurnal cycle using this ratio method. For Indianapolis, the top-down observations are consistent with the bottom-up Hestia data product emission sector patterns for most of the diurnal cycle, but disagree during the nighttime hours. Further examination of both the top-down and bottom-up assumptions is needed to assess the exact cause of the discrepancy.
... Another study reports on radiocarbon measurements in California (Riley et al., 2008). Graven et al. (2011) andLaFranchi et al. (2013) use radiocarbon observations from an aircraft and a tall tower, respectively, to estimate the contribution of anthropogenic and biogenic CO 2 emissions in Colorado. Beyond these studies, radiocarbon measurements are not widely used in regional-or continental-scale inversions. ...
Constraining sector-specific CO<sub>2</sub> and CH<sub>4</sub> emissions in the US
Article
Full-text available
This review paper explores recent efforts to estimate state- and national-scale carbon dioxide (CO2) and methane (CH4) emissions from individual anthropogenic source sectors in the US. Nearly all state and national climate change regulations in the US target specific source sectors, and detailed monitoring of individual sectors presents a greater challenge than monitoring total emissions. We particularly focus on opportunities to synthesize disparate types of information on emissions, including emission inventory data and atmospheric greenhouse gas data. We find that inventory estimates of sector-specific CO2 emissions are sufficiently accurate for policy evaluation at the national scale but that uncertainties increase at state and local levels. CH4 emission inventories are highly uncertain for all source sectors at all spatial scales, in part because of the complex, spatially variable relationships between economic activity and CH4 emissions. In contrast to inventory estimates, top-down estimates use measurements of atmospheric mixing ratios to infer emissions at the surface; thus far, these efforts have had some success identifying urban CO2 emissions and have successfully identified sector-specific CH4 emissions in several opportunistic cases. We also describe a number of forward-looking opportunities that would aid efforts to estimate sector-specific emissions: fully combine existing top-down datasets, expand intensive aircraft measurement campaigns and measurements of secondary tracers, and improve the economic and demographic data (e.g., activity data) that drive emission inventories. These steps would better synthesize inventory and top-down data to support sector-specific emission reduction policies.
... (Brandt et al., 2014). While there are an increasing number of field studies addressing methane leakage (Allen et al., 2013; Karion et al., 2013; Miller et al., 2013; Phillips et al., 2013; Caulton et al., 2014b; Karion et al., 2015; Lan et al., 2015; Lavoie et al., 2015; Peischl et al., 2015; Yacovitch et al., 2015; Zimmerle et al., 2015), other field studies have addressed simultaneously emitted higher hydrocarbon emissions as a result of UOG exploration (Petron et al., 2012; Gilman et al., 2013; LaFranchi et al., 2013; Peischl et al., 2013; Swarthout et al., 2013; Edwards et al., 2014; Helmig et al., 2014; Macey et al., 2014; Petron et al., 2014; Thompson et al., 2014; Zavala-Araiza et al., 2014; Smith et al., 2015; Townsend-Small et al., 2015; Yuan et al., 2015). Ethane has been used as an indicator of the UOG exploration methane source (Simpson et al., 2012; Smith et al., 2015; Townsend-Small et al., 2015; Vinciguerra et al., 2015), and the large variety of volatile, non-methane hydrocarbons (NMHCs) associated with oil and gas and their potential impacts on atmospheric ozone formation have been investigated in detail (Kemball-Cook et al., 2010; Carter and Seinfeld, 2012; Edwards et al., 2014; Helmig et al., 2014; Ahmadov et al., 2015; Field et al., 2015; Koss et al., 2015). ...
Analysis of non-methane hydrocarbon data from a monitoring station affected by oil and gas development in the Eagle Ford shale, Texas
Article
Full-text available
  • Mar 2016
Abstract Within the last decade, unconventional oil and gas exploration in the US has become a new source of atmospheric hydrocarbons. Although a geographically dispersed source, field measurements in and downwind of a number of shale basins demonstrate the impact exploration activities have on ambient levels of hydrocarbons. Due to concerns related to ozone production, regulatory agencies are adding monitoring stations to better understand the potential influence of emissions from areas with increased oil and gas related activities. The Eagle Ford shale in south Texas is a rapidly developing shale play producing both oil and natural gas, providing 10% and 5% of US domestic oil and gas production, respectively, in 2013. We analyzed the first year of measurements from a newly established monitoring site at its central north edge. The data reveal median ethane mixing ratios—used as a marker for oil and gas exploration related emissions—at five times its typical clean air background. Ethane mixing ratios above ten times the background occurred regularly. Saturated hydrocarbons with likely origin in oil and gas exploration explain half of the data set’s variability. They dominate OH radical reactivity at levels both similar to other shale areas and similar to Houston’s ship channel area a decade ago. Air advecting slowly across the shale area from east-southeast and southwest directions shows the most elevated hydrocarbon concentrations, and evidence is presented linking elevated alkene abundances to flaring in the shale area. A case study is presented linking high emissions from an upwind facility to hydrocarbon plumes observed at the monitor.
... This is false and represents a misunderstanding of a decadeslong effort within the biogeochemistry and climate-change research communities to validate anthropogenic emissions inventories. As described in a series of peer-reviewed articles (e.g., see Cambaliza et al. 2015;Gurney 2014;Duren and Miller 2011;LaFranchi et al. 2013;Hutyra et al. 2014;Turnbull et al. 2011Turnbull et al. , 2015Brioude et al. 2012;McKain et al. 2012;Weiss and Prinn 2011), the approach taken by the Hestia Project is specifically constructed to best leverage atmospheric concentration measurements as validation in a "top-down/ bottom-up" procedure. Atmospheric concentration measurements have been used for decades in this way, with a recent review and recommendation of continued research by the U.S. National Research Council (NRC), among others (NRC 2010). ...
... Carbon monoxide can be used to separate anthropogenic CO2 from biotic sources (Vogel et al., 2010;Turnbull et al., 2011;LaFranchi et al., 2013), provided the emission ratios of the two gases is known. ...
Seasonal Variability in Local Carbon Dioxide Biomass Burning Sources over the Central and Eastern US using Airborne In Situ Enhancement Ratios
Article
Full-text available
  • Dec 2021
We present observations of local enhancements in carbon dioxide (CO2) from local emissions sources over three eastern US regions during four deployments of the Atmospheric Carbon Transport‐America (ACT‐America) campaign between summer 2016 and spring 2018. Local CO2 emissions were characterized by carbon monoxide (CO) to CO2 enhancement ratios (i.e., ΔCO/ΔCO2) in air mass mixing observed during aircraft transects within the planetary boundary layer. By analyzing regional‐scale variability of CO2 enhancements as a function of ΔCO/ΔCO2 enhancement ratios, observed relative contributions to CO2 emissions were separated into fossil fuel and biomass burning (BB) regimes across regions and seasons. CO2 emission contributions attributed to biomass burning (ΔCO/ΔCO2 > 4%) were negligible during summer and fall in all regions but climbed to ∼9%–11% of observed combustion contributions in the South during winter and spring. Relative CO2 fire emission trends matched observed winter and spring BB contributions, but conflictingly predicted similar levels of BB during the fall. Satellite fire data from MODIS and VIIRS suggested the use of higher spatial resolution fire data that might improve modeled BB emissions but were not able to explain the bulk of the discrepancy.
Exploring the Potential of Using Carbonyl Sulfide to Track the Urban Biosphere Signal
Article
Full-text available
  • Jul 2021
Cities are implementing additional urban green as a means to capture CO2 and become more carbon neutral. However, cities are complex systems where anthropogenic and natural components of the CO2 budget interact with each other, and the ability to measure the efficacy of such measures is still not properly addressed. There is still a high degree of uncertainty in determining the contribution of the vegetation signal, which furthermore confounds the use of CO2 mole fraction measurements for inferring anthropogenic emissions of CO2. Carbonyl sulfide (OCS) is a tracer of photosynthesis which can aid in constraining the biosphere signal. This study explores the potential of using OCS to track the urban biosphere signal. We used the Sulfur Transport and dEposition Model (STEM) to simulate the OCS concentrations and the Carnegie Ames Stanford Approach ecosystem model to simulate global CO2 fluxes over the Bay Area of San Francisco during March 2015. Two observation towers provided measurements of OCS and CO2: The Sutro tower in San Francisco (upwind from the area of study providing background observations), and a tower located at Sandia National Laboratories in Livermore (downwind of the highly urbanized San Francisco region). Our results show that the STEM model works better under stable marine influence, and that the boundary layer height and entrainment are driving the diurnal changes in OCS and CO2 at the downwind Sandia site. However, the STEM model needs to better represent the transport and boundary layer variability, and improved estimates of gross primary productivity for characterizing the urban biosphere signal are needed.
Multispecies Assessment of Factors Influencing Regional CO 2 and CH 4 Enhancements During the Winter 2017 ACT‐America Campaign
Article
Full-text available
  • Jan 2020
Diagnosing carbon dioxide (CO2) and methane (CH4) fluxes at subcontinental scales is complicated by sparse observations, limited knowledge of prior fluxes and their uncertainties, and background and transport errors. Multispecies measurements in flasks sampled during the wintertime ACT‐America campaign were used for background characterization and source apportionment of regional anthropogenic CO2 and CH4 fluxes when ecosystem CO2 exchange is likely to be least active. Continental background trace gas mole fractions for regional enhancements are defined using samples from the upper troposphere and assessed using model products. Trace gas enhancements taken from flask samples in the lower troposphere with background levels subtracted out are then interpreted to inform CO2 and CH4 enhancement variability in the eastern United States. Strong correlations between CO2 and CH4 enhancements in the Midwestern and Mid‐Atlantic United States indicated colocated anthropogenic sources. Oil and natural gas influence was also broadly observed throughout the entire observational domain. In the Midwestern United States, agricultural influence on CO2 and CH4 enhancement variability was evident during above‐average wintertime temperatures. Weaker correlations between CO2 and anthropogenic tracer enhancements in the Southeastern United States indicated potentially nonnegligible wintertime ecosystem CO2 exchange, with biogenic tracers indicating more active surface processing than other regions. These whole‐air flask samples illuminated significant regional CO2 and CH4 sources or sinks during Atmospheric Carbon and Transport‐America (ACT‐America) and can provide additional information for informing regional inverse modeling efforts.
Identification of Preferential Paths of Fossil Carbon within Water Resource Recovery Facilities via Radiocarbon Analysis
Article
The Intergovernmental Panel on Climate Change (IPCC) reported that all carbon dioxide (CO2) emissions generated by water resource recovery facilities (WRRFs) during treatment are modern, based on available literature. Therefore, such emissions were omitted from IPCC's greenhouse gas (GHG) accounting procedures. However, a fraction of wastewater's carbon is fossil in origin. We hypothesized that since the fossil carbon entering municipal WRRFs is mostly from soaps and detergents as dissolved organic matter, its fate can be selectively determined during the universally applied separation treatment processes. Analyzing radiocarbon at different treatment points within municipal WRRFs, we verified that the fossil content could amount to 28% in primary influent and showed varying distribution leaving different unit operations. We recorded the highest proportion of fossil carbon leaving the secondary treatment as off-gas and as solid sludge (averaged 2.08 kg fossil-CO2-emission-potential m(-3) wastewater treated). By including fossil CO2, total GHG emission in municipal WRRFs increased 13%, and 23% if an on-site energy recovery system exists although much of the postdigestion fossil carbon remained in biosolids rather than in biogas, offering yet another carbon sequestration opportunity during biosolids handling. In comparison, fossil carbon contribution to GHG emission can span from negligible to substantial in different types of industrial WRRFs. With such a considerable impact, CO2 should be analyzed for each WRRF and not omitted from GHG accounting.
Continental-scale enrichment of atmospheric <sup>14</sup>CO<sub>2</sub> from the nuclear power industry: potential impact on the estimation of fossil fuel-derived CO<sub>2</sub>
Article
Full-text available
The 14C-free fossil carbon added to atmospheric CO2 by combustion dilutes the atmospheric 14C/C ratio (Δ14C), potentially providing a means to verify fossil CO2 emissions calculated using economic inventories. However, sources of 14C from nuclear power generation and spent fuel reprocessing can counteract this dilution and may bias 14C/C-based estimates of fossil fuel-derived CO2 if these nuclear influences are not correctly accounted for. Previous studies have examined nuclear influences on local scales, but the potential for continental-scale influences on Δ14C has not yet been explored. We estimate annual 14C emissions from each nuclear site in the world and conduct an Eulerian transport modeling study to investigate the continental-scale, steady-state gradients of Δ14C caused by nuclear activities and fossil fuel combustion. Over large regions of Europe, North America and East Asia, nuclear enrichment may offset at least 20% of the fossil fuel dilution in Δ14C, corresponding to potential biases of more than −0.25 ppm in the CO2 attributed to fossil fuel emissions, larger than the bias from plant and soil respiration in some areas. Model grid cells including high 14C-release reactors or fuel reprocessing sites showed much larger nuclear enrichment, despite the coarse model resolution of 1.8°×1.8°. The recent growth of nuclear 14C emissions increased the potential nuclear bias over 1985–2005, suggesting that changing nuclear activities may complicate the use of Δ14C observations to identify trends in fossil fuel emissions. The magnitude of the potential nuclear bias is largely independent of the choice of reference station in the context of continental-scale Eulerian transport and inversion studies, but could potentially be reduced by an appropriate choice of reference station in the context of local-scale assessments.
Discussion-Reporting of 14
Article
Full-text available
Count rates, representing the rate of 14 C decay, are the basic data obtained in a 14 C laboratory. The conversion of this information into an age or geochemical parameters appears a simple matter at first. However, the path between counting and suitable 14 C data reporting (table 1) causes headaches to many. Minor deflections in pathway, depending on personal interpretations, are possible and give end results that are not always useful for inter-laboratory comparisons. This discussion is an attempt to identify some of these problems and to recommend certain procedures by which reporting ambiguities can be avoided.
The Tropospheric 14CO2 Level in Mid-Latitudes of the Northern Hemisphere (1959–2003)
Article
A comprehensive tropospheric 14 CO 2 data set of quasi-continuous observations covering the time span from 1959 to 2003 is presented. Samples were collected at 3 European mountain sites at height levels of 1205 m (Schauinsland), 1800 m (Vermunt), and 3450 m asl (Jungfraujoch), and analyzed in the Heidelberg Radiocarbon Laboratory. The data set from Jungfraujoch (1986–2003) is considered to represent the free tropospheric background level at mid-latitudes of the Northern Hemisphere, as it compares well with recent (yet unpublished) measurements made at the marine baseline station Mace Head (west coast of Ireland). The Vermunt and Schauinsland records are significantly influenced by regional European fossil fuel CO 2 emissions. The respective Δ 14 CO 2 depletions, on an annual mean basis, are, however, only 5 less than at Jungfraujoch. Vermunt and Schauinsland both represent the mean continental European troposphere.
The tropospheric (CO2)-C-14 level in mid-latitudes of the Northern Hemisphere (1959-2003)
Article
A comprehensive tropospheric (CO2)-C-14 data set of quasi-continuous observations covering the time span from 1959 to 2003 is presented. Samples were collected at 3 European mountain sites at height levels of 1205 m (Schauinsiand), 1800 m (Vermunt), and 3450 m. as] (Jungfraujoch), and analyzed in the Heidelberg Radiocarbon Laboratory. The data set from Jungfraujoch (1986-2003) is considered to represent the free tropospheric background level at mid-latitudes of the Northern Hemisphere, as it compares well with recent (yet unpublished) measurements made at the marine baseline station Mace Head (west coast of Ireland). The Vermunt and Schauinsland records are significantly influenced by regional European fossil fuel CO2 emissions. The respective Delta(CO2)-C-14 depletions, on an annual mean basis, are, however, only 5 parts per thousand less than at Jungfraujoch. Vermunt and Schauinsland both represent the mean continental European troposphere.
Stable isotope measurements of atmospheric CO2 and CH4
Chapter
  • Dec 2004
Isotopic analyses of CO2 and CH4 provide key tools for better understanding global budgets of these trace gases. This chapter discusses two different methods for measuring carbon and oxygen isotopes in atmospheric CO2 and a method for measuring carbon isotopes in atmospheric CH4. The first method for CO2 uses traditional dual inlet Isotope Ratio Mass Spectrometry (IRMS) with cryogenic extraction on fairly large air samples. The second method for CO2 uses Gas Chromatography- Isotope Ratio Mass Spectrometry (GC-IRMS), which utilizes an order of magnitude smaller air samples. The GC-IRMS method is less precise than the dual inlet, but the elimination of liquid nitrogen use for CO2 extraction, and no requirement for the N20 correction. Carbon and oxygen stable isotope ratios of atmospheric carbon dioxide, δ13CO2 and δC18OO, provides independent information about carbon sources and sinks. Therefore, it is a method for high-precision, low volume, automated and relatively fast measurements which allowed to analyze air samples for δ13C of methane on a weekly basis from six sites around the globe. It is possible only by employing the GC-IRMS method and the NOAA global flask sampling network.