Evaluating Cropland N2O Emissions and Fertilizer Plant Greenhouse Gas Emissions With Airborne Observations

Agricultural activity is a significant source of greenhouse gas emissions. The fertilizer production process emits N2O, CO2, and CH4, and fertilized croplands emit N2O. We present continuous airborne observations of these trace gases in the Lower Mississippi River Basin to quantify emissions from both fertilizer plants and croplands during the early growing season. Observed hourly emission rates from two fertilizer plants are compared with reported inventory values, showing agreement for N2O and CO2 emissions but large underestimation in reported CH4 emissions by up to a factor of 100. These CH4 emissions are consistent with loss rates of 0.6–1.2%. We quantify regional emission fluxes (100 km) of N2O using the airborne mass balance technique, a first application for N2O, and explore linkages to controlling processes. Finally, we demonstrate the ability to use airborne measurements to distinguish N2O emission differences between neighboring fields, determining we can distinguish different emission behaviors of regions on the order of 2.5 km2 with emissions differences of approximately 0.026 μmol m−2 s−1. This suggests airborne approaches such as outlined here could be used to evaluate the impact of different agricultural practices at critical field‐size spatial scales.Key PointsReported N2O and CO2 emissions from fertilizer plants agree with observations, but CH4 is underestimated by orders of magnitudeWe demonstrate mass balance quantification of N2O emissions from agriculture at 10–100 km scalesAirborne measurements can observe and quantify N2O emission differences between agricultural fields of ∼2.5 km2Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156438/3/jgrd56401.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156438/2/jgrd5640-sup-0001-Figure_SI-S01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156438/1/jgrd56401_am.pd

Large Fugitive Methane Emissions From Urban Centers Along the U.S. East Coast

Urban emissions remain an underexamined part of the methane budget. Here we present and interpret aircraft observations of six old and leak‐prone major cities along the East Coast of the United States. We use direct observations of methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), ethane (C2H6), and their correlations to quantify CH4 emissions and attribute to natural gas. We find the five largest cities emit 0.85 (0.63, 1.12) Tg CH4/year, of which 0.75 (0.49, 1.10) Tg CH4/year is attributed to natural gas. Our estimates, which include all thermogenic methane sources including end use, are more than twice that reported in the most recent gridded EPA inventory, which does not include end‐use emissions. These results highlight that current urban inventory estimates of natural gas emissions are substantially low, either due to underestimates of leakage, lack of inclusion of end‐use emissions, or some combination thereof.Plain Language SummaryRecent efforts to quantify fugitive methane associated with the oil and gas sector, with a particular focus on production, have resulted in significant revisions upward of emission estimates. In comparison, however, there has been limited focus on urban methane emissions. Given the volume of gas distributed and used in cities, urban losses can impact national‐level emissions. In this study we use aircraft observations of methane, carbon dioxide, carbon monoxide, and ethane to determine characteristic correlation slopes, enabling quantification of urban methane emissions and attribution to natural gas. We sample nearly 12% of the U.S. population and 4 of the 10 most populous cities, focusing on older, leak‐prone urban centers. Emission estimates are more than twice the total in the U.S. EPA inventory for these regions and are predominantly attributed to fugitive natural gas losses. Current estimates for methane emissions from the natural gas supply chain appear to require revision upward, in part possibly by including end‐use emissions, to account for these urban losses.Key PointsAircraft observations downwind of six major cities along the U.S. East Coast are used to estimate urban methane emissionsObserved urban methane estimates are about twice that reported in the Gridded EPA inventoryMethane emissions from natural gas (including end use) in five cities combined exceeds nationwide emissions estimate from local distributionPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151283/1/grl59329.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151283/2/grl59329_am.pd

Circadian deep sequencing reveals stress-response genes that adopt robust rhythmic expression during aging

Disruption of the circadian clock, which directs rhythmic expression of numerous output genes, accelerates aging. To enquire how the circadian system protects aging organisms, here we compare circadian transcriptomes in heads of young and old Drosophila melanogaster. The core clock and most output genes remained robustly rhythmic in old flies, while others lost rhythmicity with age, resulting in constitutive over- or under-expression. Unexpectedly, we identify a subset of genes that adopted increased or de novo rhythmicity during aging, enriched for stress-response functions. These genes, termed late-life cyclers, were also rhythmically induced in young flies by constant exposure to exogenous oxidative stress, and this upregulation is CLOCK-dependent. We also identify age-onset rhythmicity in several putative primary piRNA transcripts overlapping antisense transposons. Our results suggest that, as organisms age, the circadian system shifts greater regulatory priority to the mitigation of accumulating cellular stress

Fugitive emissions from the Bakken shale illustrate role of shale production in global ethane shift

Ethane is the second most abundant atmospheric hydrocarbon, exerts a strong influence on tropospheric ozone, and reduces the atmosphere’s oxidative capacity. Global observations showed declining ethane abundances from 1984 to 2010, while a regional measurement indicated increasing levels since 2009, with the reason for this subject to speculation. The Bakken shale is an oil and gas‐producing formation centered in North Dakota that experienced a rapid increase in production beginning in 2010. We use airborne data collected over the North Dakota portion of the Bakken shale in 2014 to calculate ethane emissions of 0.23 ± 0.07 (2σ) Tg/yr, equivalent to 1–3% of total global sources. Emissions of this magnitude impact air quality via concurrent increases in tropospheric ozone. This recently developed large ethane source from one location illustrates the key role of shale oil and gas production in rising global ethane levels.Key PointsThe Bakken shale in North Dakota accounted for 1–3% total global ethane emissions in 2014These findings highlight the importance of shale production in global atmospheric ethane shiftThese emissions impact air quality and influence interpretations of recent global methane changesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142509/1/grl54333.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142509/2/grl54333-sup-0001-2016GL068703-SI.pd

Quantifying atmospheric methane emissions from oil and natural gas production in the Bakken shale region of North Dakota

We present in situ airborne measurements of methane (CH4) and ethane (C2H6) taken aboard a NOAA DHC‐6 Twin Otter research aircraft in May 2014 over the Williston Basin in northwestern North Dakota, a region of rapidly growing oil and natural gas production. The Williston Basin is best known for the Bakken shale formation, from which a significant increase in oil and gas extraction has occurred since 2009. We derive a CH4 emission rate from this region using airborne data by calculating the CH4 enhancement flux through the planetary boundary layer downwind of the region. We calculate CH4 emissions of (36 ± 13), (27 ± 13), (27 ± 12), (27 ± 12), and (25 ± 10) × 103 kg/h from five transects on 3 days in May 2014 downwind of the Bakken shale region of North Dakota. The average emission, (28 ± 5) × 103 kg/h, extrapolates to 0.25 ± 0.05 Tg/yr, which is significantly lower than a previous estimate of CH4 emissions from northwestern North Dakota and southeastern Saskatchewan using satellite remote sensing data. We attribute the majority of CH4 emissions in the region to oil and gas operations in the Bakken based on the similarity between atmospheric C2H6 to CH4 enhancement ratios and the composition of raw natural gas withdrawn from the region.Key PointsCH4 emissions from the Bakken region of North Dakota quantifiedFirst emission estimate using in situ CH4 measurementsCH4 sources dominated by oil‐ and gas‐related activitiesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/122415/1/jgrd52986.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/122415/2/jgrd52986_am.pd

Testing and evaluation of a new airborne system for continuous N₂O, CO₂, CO, and H₂O measurements: the Frequent Calibration High-performance Airborne Observation System (FCHAOS)

We present the development and assessment of a new flight system that uses a commercially available continuous-wave, tunable infrared laser direct absorption spectrometer to measure N2O, CO2, CO, and H2O. When the commercial system is operated in an off-the-shelf manner, we find a clear cabin pressure–altitude dependency for N2O, CO2, and CO. The characteristics of this artifact make it difficult to reconcile with conventional calibration methods. We present a novel procedure that extends upon traditional calibration approaches in a high-flow system with high-frequency, short-duration sampling of a known calibration gas of near-ambient concentration. This approach corrects for cabin pressure dependency as well as other sources of drift in the analyzer while maintaining a  ∼ 90&thinsp;% duty cycle for 1&thinsp;Hz sampling. Assessment and validation of the flight system with both extensive in-flight calibrations and comparisons with other flight-proven sensors demonstrate the validity of this method. In-flight 1σ precision is estimated at 0.05&thinsp;ppb, 0.10&thinsp;ppm, 1.00&thinsp;ppb, and 10&thinsp;ppm for N2O, CO2, CO, and H2O respectively, and traceability to World Meteorological Organization (WMO) standards (1σ) is 0.28&thinsp;ppb, 0.33&thinsp;ppm, and 1.92&thinsp;ppb for N2O, CO2, and CO. We show the system is capable of precise, accurate 1&thinsp;Hz airborne observations of N2O, CO2, CO, and H2O and highlight flight data, illustrating the value of this analyzer for studying N2O emissions on  ∼ 100&thinsp;km spatial scales.</p

Airborne measurements from the GEM study

Please see README file for a detailed description of the data.This archive contains airborne measurements from the GEM campaign. Data are archived in association with the following manuscript: Yu, X., D.B. Millet, K.C. Wells, T.J. Griffis, X. Chen, J.M. Baker, S.A. Conley, M.L. Smith, A. Gvakharia, E.A. Kort, G. Plant, and J.D. Wood (2020), Top-down constraints on methane point source emissions from animal agriculture and waste based on new airborne measurements in the US Upper Midwest, J. Geophys. Res., 125, e2019JG005429, doi:10.1029/2019JG005429.NASA (#NNX17AK18G, #80NSSC18K1393