A geochemial perspective of natural gas and atmospheric methane

Whiticar, Michael J.

doi:10.1016/0146-6380(90)90068-b

Cited by 178 publications

(134 citation statements)

References 40 publications

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“…Lamb et al (2016) found that natural gas used in Indianapolis is about 95% methane, and thus methane will be the dominant precursor for CO during natural gas combustion. Methane in natural gas has an average carbon isotopic signature of -44‰ (Whiticar, 1990;Kato et al, 1999). While the d 13 CO from methane combusted for heating purposes has not been previously measured, Kato et al (1999) (Figure 6).…”

Section: Assessment Of Co Emissions From Natural Gas Combustion For Hmentioning

confidence: 99%

Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source

Vimont

Turnbull

Petrenko

et al. 2017

Elementa: Science of the Anthropocene

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Vimont, IJ, et al. 2017 Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source. Elem Sci Anth, 5: 63. DOI: https://doi.org/10.1525/elementa.136 IntroductionUrban carbon monoxide (CO) is a regulated pollutant that impacts human health and influences atmospheric chemistry via its interaction with OH and its role in tropospheric ozone production. Urban emissions are also an important component of the global CO budget (Crutzen, 1973;Crutzen, 1979;Logan et al., 1981;Duncan et al., 2007). Within urban areas of the United States, CO emissions inventories may be inaccurate by as much as a factor of two (e.g. Turnbull et al., 2015;Parrish et al., 2006;Graven et al., 2009;LaFranchi et al., 2013; EPA NEI 2011). In addition to the atmospheric chemistry and health impacts, CO has been explored as a tracer for fossil fuel derived CO 2 (CO 2ff ) (Meijer et al., 1996;Levin and Karstens, 2007;Turnbull et al., 2006;Vogel et al., 2010;Turnbull et al., 2011; Turnbull et al., 2015). This method relies on an assumption that CO is produced entirely by combustion, which is not always true within urban regions (Turnbull et al., 2015). Turnbull et al. (2015) found that during winter at Indianapolis, using CO as a correlate tracer yielded CO 2ff enhancements that were in good agreement with those from 14 CO 2 measurements. This suggested that during the winter at Indianapolis, non-fossil fuel sources of CO do not contribute significantly. In contrast, during the summer, there is weaker correlation between CO and 14 C-derived CO 2ff , suggesting another summertime source of CO in Indianapolis (Turnbull et al., 2015) and in other locations (Turnbull et al., 2006;Miller et al., 2012). Stable isotopic measurements of urban CO can help quantify individual CO sources and sinks and provide an improved understanding of seasonal changes in the urban CO budget (e.g. Stevens et al., 1972;Brenninkmeijer, 1993;Conny, 1998).In order to quantify the sources and sinks of CO via isotopic analysis, the 13 CO and C 18 O isotopic signatures need to be known (Stevens et al., 1972;Brenninkmeijer, 1993;Rockmann and Brenninkmeijer, 1997; O) in air during the winters of 2013-14 and 2014-15 at tall tower sampling sites in and around Indianapolis, USA. A tower located upwind of the city was used to quantitatively remove the background CO signal, allowing for the first unambiguous isotopic characterization of the urban CO source and yielding 13CO of -27.7 ± 0.5‰ VPDB and C 18O of 17.7 ± 1.1‰ VSMOW for this source. We use the tower isotope measurements, results from a limited traffic study, as well as atmospheric reaction rates to examine contributions from different sources to the Indianapolis CO budget. Our results are consistent with earlier findings that traffic emissions are the dominant source, suggesting a contribution of 96% or more to the overall Indianapolis wintertime CO emissions. Our results are also consistent with the hypothesis ...

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Section: Assessment Of Co Emissions From Natural Gas Combustion For Hmentioning

confidence: 99%

Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source

Vimont

Turnbull

Petrenko

et al. 2017

Elementa: Science of the Anthropocene

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“…Irrespective of post-genetic alterations, C 1 /C 2 and C 2 /C 3 ratios, δ 13 C values of methane, ethane and carbon dioxide as well as gas dryness indices suggest that thermogenic constituents of the vent gas are sourced from immature to early mature kerogen of the sapropelic, marine type II (Rice and Claypool, 1981;Rooney et al, 1995;Whiticar, 1989;Whiticar, 1999) and/or from secondary production due to oil cracking (Milkov and Dzou, 2007;Prinzhofer and Huc, 1995;Seewald, 2003). δ 13 C-CO 2 values likewise suggest that carbon dioxide in the vent gas primarily originates from the degradation of kerogen and soluble organic matter (Dai et al, 1996;Irwin et al, 1977;Wycherley et al, 1999).…”

Section: Station Nomentioning

confidence: 99%

Molecular and isotopic partitioning of low-molecular-weight hydrocarbons during migration and gas hydrate precipitation in deposits of a high-flux seepage site

et al. 2010

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Detailed knowledge of the extent of post-genetic modifications affecting shallow submarine hydrocarbons fueled from the deep subsurface is fundamental for evaluating source and reservoir properties. We investigated gases from a submarine high-flux seepage site in the anoxic Eastern Black Sea in order to elucidate molecular and isotopic alterations of low-molecular-weight hydrocarbons (LMWHC) associated with upward migration through the sediment and precipitation of shallow gas hydrates. For this, nearsurface sediment pressure cores and free gas venting from the seafloor were collected using autoclave technology at the Batumi seep area at 845 m water depth within the gas hydrate stability zone. Vent gas, gas from pressure core degassing, and from hydrate dissociation were strongly dominated by methane (> 99.85 mol.% of ∑[C 1 -C 4 , CO 2 ]). Molecular ratios of LMWHC (C 1 /[C 2 + C 3 ] > 1000) and stable isotopic compositions of methane (δ 13 C = − 53.5‰ V-PDB; D/H around − 175‰ SMOW) indicated predominant microbial methane formation. C 1 /C 2+ ratios and stable isotopic compositions of LMWHC distinguished three gas types prevailing in the seepage area. Vent gas discharged into bottom waters was depleted in methane by > 0.03 mol.% (∑[C 1 -C 4 , CO 2 ]) relative to the other gas types and the virtual lack of 14 C-CH 4 indicated a negligible input of methane from degradation of fresh organic matter. Of all gas types analyzed, vent gas was least affected by molecular fractionation, thus, its origin from the deep subsurface rather than from decomposing hydrates in near-surface sediments is likely. As a result of the anaerobic oxidation of methane, LMWHC in pressure cores in top sediments included smaller methane fractions [0.03 mol.% ∑(C 1 -C 4 , CO 2 )] than gas released from pressure cores of more deeply buried sediments, where the fraction of methane was maximal due to its preferential incorporation in hydrate lattices. No indications for stable carbon isotopic fractionations of methane during hydrate crystallization from vent gas were found. Enrichments of 14 C-CH 4 (1.4 pMC) in short cores relative to lower abundances (max. 0.6 pMC) in gas from long cores and gas hydrates substantiates recent methanogenesis utilizing modern organic matter deposited in top sediments of this high-flux hydrocarbon seep area.

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“…The NMHC/ methane ratio is rather low in "dry" bacterial and late mature gases but may be as high as 20% in "wet" oil associated gases [cf. Whiticar, 1990]. Ehhalt and Rudolph [ 1984] used a methane/NMHC ratio of 5 which is the average for the United States and assumed that about one fifth (by weight) of these NMHC consists of ethane.…”

Section: Data Setmentioning

confidence: 99%

The tropospheric distribution and budget of ethane

Rudolph¹

1995

J. Geophys. Res.

163

170

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Abstract. From about 1500 measurements of ethane in the remote troposphere the longitudinally and vertically averaged latitudinal and seasonal variability of ethane was derived. To improve the data coverage, several data sets from literature were included. There are only very few data sets available for the southern hemisphere. Nevertheless, the uncertainty of the average seasonal/latitudinal ethane profile is estimated to less than 30%. The global annually averaged ethane mixing ratio is 860 ppt. There is a strong interhemispheric gradient with an average north/south ratio of 3.5. Within the northern hemisphere there is an average gradient from the highest annual mean value of 2500 ppt around 65øN to about 600 ppt at the equator. In the southern hemisphere there is only a small gradient at low latitudes and at middle and high southern latitudes no significant gradient can be seen. In both hemispheres a significant seasonal cycle with highest mixing ratios in late winter is observed. The ethane source strength needed to balance the atmospheric budget of ethane is estimated to 15.5 Tg/yr, with most of the emissions in the northern hemisphere. An independent estimate of the sources indicate that most of the emissions are due to natural gas losses (6 Tg/yr) and biomass burning (6.4 Tg/yr). This is also compatible with the latitudinal and seasonal variation of the atmospheric ethane removal rates. However, these estimates have substantial uncertainties and it should be noted that the role of the biosphere for the atmospheric budget of ethane is presently not understood.

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A geochemial perspective of natural gas and atmospheric methane

Cited by 178 publications

References 40 publications

Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source

Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source

Molecular and isotopic partitioning of low-molecular-weight hydrocarbons during migration and gas hydrate precipitation in deposits of a high-flux seepage site

The tropospheric distribution and budget of ethane

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