Using stable isotopes of hydrogen to quantify biogenic and thermogenic atmospheric methane sources: A case study from the Colorado Front Range

Townsend‐Small, Amy; Botner, E. Claire; Jimenez, Kristine L.; Schroeder, J.; Blake, N. J.; Meinardi, Simone; Blake, D. R.; Sive, B. C.; Bon, D.; Crawford, J. H.; Pfister, Gabriele; Flocke, Frank

doi:10.1002/2016gl071438

Cited by 41 publications

(34 citation statements)

References 50 publications

(98 reference statements)

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“…A few other studies that have apportioned (Peischl et al, 2018;Petron et al, 2014;Townsend-Small et al, 2016) or quantified (Eilerman et al, 2016;Fried et al, 2015;Gilman, 2017;Tzompa-Sosa et al, 2017;Yuan et al, 2017) CH 4 in the DJB study area exist, but none have attempted to source apportion CH 4 based on excess columns. These results can be used to assess how the concept of excess columns compares with results based on in situ observations.…”

Section: Comparison With the Literaturementioning

confidence: 99%

“…These results can be used to assess how the concept of excess columns compares with results based on in situ observations. The data by Townsend-Small et al (2016) remain somewhat ambiguous whether the majority of CH 4 is from NG or agriculture. The attribution to NG agrees well with values reported in studies by Petron et al (2014) for Weld County in May 2012 and Peischl et al (2018) as shown in Table 1, where the dominating source of CH 4 is determined to be the NG sector.…”

Section: Comparison With the Literaturementioning

confidence: 99%

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Separation of Methane Emissions From Agricultural and Natural Gas Sources in the Colorado Front Range

Kille

Chiu

Frey

et al. 2019

Geophysical Research Letters

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This proof‐of‐concept study demonstrates that methane (CH4) emissions from natural gas (NG) and agriculture can be disentangled using the concept of excess column observations. A network of cost‐effective sensors measured excess column‐averaged dry‐air mole fractions for CH4 (ΔXCH4), ethane (ΔXC2H6 as NG tracer), and ammonia (ΔXNH3 from agriculture) in the Denver‐Julesburg Basin during March 2015. ΔXCH4 varied up to 17 ppb and was >3 times higher with winds from directions where NG is produced. The ΔXCH4 variance is explained by variations in the C2H6‐NH3 tracer pair, attributing 63 ± 17% to NG, 25 ± 10% to agriculture, and 12 ± 12% to other sources. The ratios ΔXC2H6/ΔXCH4 (16 ± 2%; indicates wet NG) and ΔXNH3/ΔXCH4 (43 ± 12%) were compatible with in situ measured ratios. Excess columns are independent of boundary layer height, characterize gases in the open atmosphere, are inherently calibrated, average over extended spatial scales, and provide a complementary perspective to quantify and attribute CH4 emissions on regional scales.

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Section: Comparison With the Literaturementioning

confidence: 99%

Section: Comparison With the Literaturementioning

confidence: 99%

Separation of Methane Emissions From Agricultural and Natural Gas Sources in the Colorado Front Range

Kille

Chiu

Frey

et al. 2019

Geophysical Research Letters

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“…Average enhancements of CH 4 were similar for both periods (July: 52 ppbv; August: 50 ppbv; or ∼ 2.5 % increase). Methane has a relatively high background at BAO due to large emissions of CH 4 in nearby Weld County from livestock production and oil and gas development (Pétron et al, 2014;Townsend-Small et al, 2016). Taken together, the larger background of CH 4 and the large local sources of CH 4 in the Front Range served to mute the impact of the August smoke on overall CH 4 abundances.…”

Section: Smoke Eventsmentioning

confidence: 99%

Changes in ozone and precursors during two aged wildfire smoke events in the Colorado Front Range in summer 2015

et al. 2017

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Abstract. The relative importance of wildfire smoke for air quality over the western US is expected to increase as the climate warms and anthropogenic emissions decline. We report on in situ measurements of ozone (O 3 ), a suite of volatile organic compounds (VOCs), and reactive oxidized nitrogen species collected during summer 2015 at the Boulder Atmospheric Observatory (BAO) in Erie, CO. Aged wildfire smoke impacted BAO during two distinct time periods during summer 2015: 6-10 July and 16-30 August. The smoke was transported from the Pacific Northwest and Canada across much of the continental US. Carbon monoxide and particulate matter increased during the smoke-impacted periods, along with peroxyacyl nitrates and several VOCs that have atmospheric lifetimes longer than the transport timescale of the smoke. During the August smokeimpacted period, nitrogen dioxide was also elevated during the morning and evening compared to the smoke-free periods. There were nine empirically defined high-O 3 days during our study period at BAO, and two of these days were smoke impacted. We examined the relationship between O 3 and temperature at BAO and found that for a given temperature, O 3 mixing ratios were greater (∼ 10 ppbv) during the smoke-impacted periods. Enhancements in O 3 during the August smoke-impacted period were also observed at two long-term monitoring sites in Colorado: Rocky Mountain National Park and the Arapahoe National Wildlife Refuge near Walden, CO. Our data provide a new case study of how aged wildfire smoke can influence atmospheric composition at an urban site, and how smoke can contribute to increased O 3 abundances across an urban-rural gradient.

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“…(iii) Source signatures could also exhibit temporal variation due to changing emission processes. Examples of 10.1029/2018GB006065 Global Biogeochemical Cycles temporal variation include changing oil and gas extraction depths within a producing basin over time (Townsend-Small et al, 2016), or wetland methanogenesis at a given location changing due to changing environmental conditions (McCalley et al, 2014). For all sources, measurements assessing temporal source signature variability are more limited than those assessing spatial variability.…”

Section: Isotopic Ratio Measurementsmentioning

confidence: 99%

Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement

Ganesan

Schwietzke²,

Poulter

et al. 2019

Global Biogeochemical Cycles

100

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The 2015 Paris Agreement of the United Nations Framework Convention on Climate Change aims to keep global average temperature increases well below 2 °C of preindustrial levels in the Year 2100. Vital to its success is achieving a decrease in the abundance of atmospheric methane (CH4), the second most important anthropogenic greenhouse gas. If this reduction is to be achieved, individual nations must make and meet reduction goals in their nationally determined contributions, with regular and independently verifiable global stock taking. Targets for the Paris Agreement have been set, and now the capability must follow to determine whether CH4 reductions are actually occurring. At present, however, there are significant limitations in the ability of scientists to quantify CH4 emissions accurately at global and national scales and to diagnose what mechanisms have altered trends in atmospheric mole fractions in the past decades. For example, in 2007, mole fractions suddenly started rising globally after a decade of almost no growth. More than a decade later, scientists are still debating the mechanisms behind this increase. This study reviews the main approaches and limitations in our current capability to diagnose the drivers of changes in atmospheric CH4 and, crucially, proposes ways to improve this capability in the coming decade. Recommendations include the following: (i) improvements to process‐based models of the main sectors of CH4 emissions—proposed developments call for the expansion of tropical wetland flux measurements, bridging remote sensing products for improved measurement of wetland area and dynamics, expanding measurements of fossil fuel emissions at the facility and regional levels, expanding country‐specific data on the composition of waste sent to landfill and the types of wastewater treatment systems implemented, characterizing and representing temporal profiles of crop growing seasons, implementing parameters related to ruminant emissions such as animal feed, and improving the detection of small fires associated with agriculture and deforestation; (ii) improvements to measurements of CH4 mole fraction and its isotopic variations—developments include greater vertical profiling at background sites, expanding networks of dense urban measurements with a greater focus on relatively poor countries, improving the precision of isotopic ratio measurements of 13CH4, CH3D, 14CH4, and clumped isotopes, creating isotopic reference materials for international‐scale development, and expanding spatial and temporal characterization of isotopic source signatures; and (iii) improvements to inverse modeling systems to derive emissions from atmospheric measurements—advances are proposed in the areas of hydroxyl radical quantification, in systematic uncertainty quantification through validation of chemical transport models, in the use of source tracers for estimating sector‐level emissions, and in the development of time and space resolved national inventories. These and other recommendations are proposed for...

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Using stable isotopes of hydrogen to quantify biogenic and thermogenic atmospheric methane sources: A case study from the Colorado Front Range

Cited by 41 publications

References 50 publications

Separation of Methane Emissions From Agricultural and Natural Gas Sources in the Colorado Front Range

Separation of Methane Emissions From Agricultural and Natural Gas Sources in the Colorado Front Range

Changes in ozone and precursors during two aged wildfire smoke events in the Colorado Front Range in summer 2015

Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement

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