27 research outputs found
Relative Flux Measurements of Biogenic Methane and Natural Gas for Seven U.S. Cities
No full textThis dataset contains the aircraft data relevant to the manuscript titled: Relative Flux Measurements of Biogenic Methane and Natural Gas for Seven U.S. Cities.
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Airborne Methane Flux Quantification and Source Identification Using High Resolution Measurements of Ethane and Methane
No full textThe work presented herein demonstrates the use of high resolution trace gas measurements of methane CH4and ethane C2H6 to quantify CH4 fluxes and attribute them to specific sources. In The North Slope of Alaska we were able to make measurements of the total CH4 flux from The Prudhoe Bay Oil Field (PBOF) by separating its emissions from the trace gas signature of surrounding methanogenic metabolism within the Arctic permafrost. We found that the total emissions of CH4 were 1500 [1151, 1888] kg CH4 hr-1 and that the available bottom-up estimates were low by a factor of 2-5. Our estimates of CH4 flux from PBOF are the first such estimates made using a top-down measurement approach. After then developing an C2H6 spectrometer capable of making, what we believe to be, one of the world’s most precise airborne C2H6 measurements from a compact laser absorption spectrometer, we deployed our instrument package to a host of urban areas and characterized their CH4 emission profiles. We were able to partition sources of natural gas from the total CH4 enhancement observed downwind of a city using the ratio of CH4 to C2H6 in urban natural gas. We developed methodologies to subtract the signal of upwind CH4 sources from the downwind enhancements and quantify the contribution from only the domains of interest. Our work in the urban sector shows that the total CH4 flux from an individual city can be dominated by sources of both biogenic (landfills, waste water, ect..) and thermogenic (natural gas) origin and that the emission profile has a strong seasonal dependence with thermogenic sources emitting a larger fraction of the total CH4 flux in the winter months. A comparison of our results to currently available inventory products also show that sources within the urban domain are poorly understood and require significant further study.Earth and Planetary Science
Large Fugitive Methane Emissions From Urban Centers Along the U.S. East Coast
No full textUrban 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
Modulation of volatile organic compound formation in the Mycodiesel-producing endophyte Hypoxylon sp. CI-4
No full textAir Pollutant Mapping with a Mobile Laboratory During the BEE-TEX Field Study
No full textThe Aerodyne Mobile Laboratory was deployed to the Houston Ship Channel and surrounding areas during the Benzene and Other Toxics Exposure field study in February 2015. We evaluated atmospheric concentrations of volatile organic hydrocarbons and other hazardous air pollutants of importance to human health, including benzene, 1,3-butadiene, toluene, xylenes, ethylbenzenes, styrene, and NO 2 . Ambient concentration measurements were focused on the neighborhoods of Manchester, Harrisburg, and Galena Park. The most likely measured concentration of 1,3-butadiene in the Manchester neighborhood (0.17 ppb) exceeds the Environmental Protection Agency's E-5 lifetime cancer risk level of 0.14 ppb. In all the three neighborhoods, the measured benzene concentration falls below or within the E-5 lifetime cancer risk levels of 0.4–1.4 ppb for benzene. Pollution maps as a function of wind direction show the impact of nearby sources
Variability of Ammonia and Methane Emissions from Animal Feeding Operations in Northeastern Colorado
No full textHypoxylon sp., an Endophyte of Persea indica, Producing 1,8-Cineole and Other Bioactive Volatiles with Fuel Potential
No full textMethane Emissions from Natural Gas Infrastructure and Use in the Urban Region of Boston, Massachusetts
No full textArchival datasets associated with with the paper McKain K, et al. (2015), including: continuous atmospheric methane and ethane concentration observations, and inventories of methane emissions by source type and natural gas consumption
Observations of Methane Emissions from Natural Gas-Fired Power Plants
No full textCurrent research efforts on the atmospheric
impacts of natural
gas (NG) have focused heavily on the production, storage/transmission,
and processing sectors, with less attention paid to the distribution
and end use sectors. This work discusses 23 flights at 14 natural
gas-fired power plants (NGPPs) using an aircraft-based mass balance
technique and methane/carbon dioxide enhancement ratios (ΔCH4/ΔCO2) measured from stack plumes to quantify
the unburned fuel. By comparing the ΔCH4/ΔCO2 ratio measured in stack plumes to that measured downwind,
we determined that, within uncertainty of the measurement, all observed
CH4 emissions were stack-based, that is, uncombusted NG
from the stack rather than fugitive sources. Measured CH4 emission rates (ER) ranged from 8 (±5) to 135 (±27) kg
CH4/h (±1σ), with the fractional CH4 throughput lost (loss rate) ranging from −0.039% (±0.076%)
to 0.204% (±0.054%). We attribute negative values to partial
combustion of ambient CH4 in the power plant. The average
calculated emission factor (EF) of 5.4 (+10/–5.4) g CH4/million British thermal units (MMBTU) is within uncertainty
of the Environmental Protection Agency (EPA) EFs. However, one facility
measured during startup exhibited substantially larger stack emissions
with an EF of 440 (+660/–440) g CH4/MMBTU and a
loss rate of 2.5% (+3.8/–2.5%)
Analysis of local-scale background concentrations of methane and other gas-phase species in the Marcellus Shale
No full textThe Marcellus Shale is a rapidly developing unconventional natural gas resource found in part of the Appalachian region. Air quality and climate concerns have been raised regarding development of unconventional natural gas resources. Two ground-based mobile measurement campaigns were conducted to assess the impact of Marcellus Shale natural gas development on local scale atmospheric background concentrations of air pollution and climate relevant pollutants in Pennsylvania. The first campaign took place in Northeastern and Southwestern PA in the summer of 2012. Compounds monitored included methane (CH4), ethane, carbon monoxide (CO), nitrogen dioxide, and Proton Transfer Reaction Mass Spectrometer (PTR-MS) measured volatile organic compounds (VOC) including oxygenated and aromatic VOC. The second campaign took place in Northeastern PA in the summer of 2015. The mobile monitoring data were analyzed using interval percentile smoothing to remove bias from local unmixed emissions to isolate local-scale background concentrations. Comparisons were made to other ambient monitoring in the Marcellus region including a NOAA SENEX flight in 2013. Local background CH4 mole fractions were 140 ppbv greater in Southwestern PA compared to Northeastern PA in 2012 and background CH4 increased 100 ppbv from 2012 to 2015. CH4 local background mole fractions were not found to have a detectable relationship between well density or production rates in either region. In Northeastern PA, CO was observed to decrease 75 ppbv over the three year period. Toluene to benzene ratios in both study regions were found to be most similar to aged rural air masses indicating that the emission of aromatic VOC from Marcellus Shale activity may not be significantly impacting local background concentrations. In addition to understanding local background concentrations the ground-based mobile measurements were useful for investigating the composition of natural gas emissions in the region
