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In this study, we present seasonal atmospheric measurements of δ13CCH4 from dairy farms in the San Joaquin Valley of California. We used δ13CCH4 to characterize emissions from enteric fermentation by measuring downwind of cattle housing (e.g., freestall barns, corrals) and from manure management areas (e.g., anaerobic manure lagoons) with a mobile platform equipped with cavity ring-down spectrometers. Across seasons, the δ13CCH4 from enteric fermentation source areas ranged from −69.7 ± 0.6 per mil (‰) to −51.6 ± 0.1‰ while the δ13CCH4 from manure lagoons ranged from −49.5 ± 0.1‰ to −40.5 ± 0.2‰. Measurements of δ13CCH4 of enteric CH4 suggest a greater than 10‰ difference between cattle production groups in accordance with diet. Isotopic signatures of CH4 were used to characterize enteric and manure CH4 from downwind plume sampling of dairies. Our findings show that δ13CCH4 measurements could improve the attribution of CH4 emissions from dairy sources at scales ranging from individual facilities to regions and help constrain the relative contributions from these different sources of emissions to the CH4 budget.

Marginal oil and gas wells, or wells that produce less than 15 barrels of oil equivalent per day, represent 80% of actively producing wells in the United States, although they produce less than 10% of energy supply. Marginal wells are a disproportionate source of methane (CH _4 ) relative to their production, and they emit harmful air pollutants, such as benzene and other hydrocarbons found in oil and natural gas. We made direct measurements of CH _4 and hydrogen sulfide (H _2 S) emissions from 46 wellheads in the Luling Field, Caldwell County, Texas, just east of the Austin/San Antonio Metroplex. We found that these wells are venting natural gas and are a large source of hydrogen sulfide (H _2 S), a poisonous air pollutant. Hydrogen sulfide emission rates ranged from 0 to 5 ± 0.5 g H _2 S hr ^−1 with an average emission rate of 1.6 ± 0.1 g H _2 S hr ^−1 . We also found ambient concentrations of H _2 S at dangerous levels (>100 ppm) near many of the wells. Methane emission rates were in line with previous studies of marginal wells, ranging from 0.0 to 2770 ± 390 g CH _4 hr ^−1 , with a skewed distribution and average emission rate of 710 ± 100 g CH _4 hr ^−1 . Oil production records from Texas were incomplete: some wells had oil production data from the year of sampling, but many had no production data for several years or decades, although they were actively pumping while we were on site. Interviews with local residents indicate that the closing of the county gas processing plant and subsequent loss of gathering lines may be the cause of gas venting and CH _4 and H _2 S emissions from production sites. This deserves further scrutiny, as marginal wells in this region are a major source of H _2 S, a health hazard to people living and working nearby.

Abstract The Satellite Coastal and Oceanic Atmospheric Pollution Experiment (SCOAPE) cruise in the Gulf of Mexico was conducted in May 2019 by NASA and the Bureau of Ocean Energy Management to determine the feasibility of using satellite data to measure air quality in a region of concentrated oil and natural gas (ONG) operations. SCOAPE addressed both technological and scientific issues related to measuring NO2 columns over the outer continental shelf. Featured were nitrogen dioxide (NO2) instruments (Pandora, Teledyne API analyzer) at Cocodrie, LA (29.26°, −90.66°), and on the Research Vessel Point Sur operating off the Louisiana coast with measurements of ozone, carbon monoxide, and volatile organic compounds (VOCs). The findings: (a) all NO2 observations revealed two atmospheric regimes over the Gulf, the first influenced by tropical air in 10–14 May, the second influenced by flow from urban areas on 15–17 May; (b) comparisons of OMI v4 and TROPOMI v1.3 TC (total column) NO2 data with shipboard Pandora NO2 column observations averaged 13% agreement with the largest difference during 15–17 May (∼20%). At Cocodrie, the satellite–Pandora agreement was ∼5%. (c) Three new‐model Pandora instruments displayed a TC NO2 precision of 0.01 Dobson Units (∼5%); (d) regions of smaller, older natural gas operations showed high methane readings from leakage; elevated VOCs were also detected. Neither satellite nor spectrometer captured the magnitude of ambient NO2 variability near ONG platforms. Given an absence of regular air quality monitoring over the Gulf of Mexico, SCOAPE data constitute a baseline against which future observations can be compared.

Climate-sensitive Arctic lakes have been identified as conduits for ancient permafrost-carbon (C) emissions and as such accelerate warming. However, the environmental factors that control emission pathways and their sources are unclear; this complicates upscaling, forecasting and climate-impact-assessment efforts. Here we show that current whole-lake CH4 and CO2 emissions from widespread lakes in Arctic Alaska primarily originate from organic matter fixed within the past 3-4 millennia (modern to 3,300 ± 70 years before the present), and not from Pleistocene permafrost C. Furthermore, almost 100% of the annual diffusive C flux is emitted as CO2. Although the lakes mostly processed younger C (89 ± 3% of total C emissions), minor contributions from ancient C sources were two times greater in fine-textured versus coarse-textured Pleistocene sediments, which emphasizes the importance of the underlying geological substrate in current and future emissions. This spatially extensive survey considered the environmental and temporal variability necessary to monitor and forecast the fate of ancient permafrost C as Arctic warming progresses.

Global atmospheric concentrations of methane (CH4), a powerful greenhouse gas, are increasing, but because there are many natural and anthropogenic sources of CH4, it is difficult to assess which sources may be increasing in magnitude. Here we present a data set of δ2H-CH4 measurements of individual sources and air in the Colorado Front Range, USA. We show that δ2H-CH4, but not δ13C, signatures are consistent in air sampled downwind of landfills, cattle feedlots, and oil and gas wells in the region. Applying these source signatures to air in ground and aircraft samples indicates that at least 50% of CH4 emitted in the region is biogenic, perhaps because regulatory restrictions on leaking oil and natural gas wells are helping to reduce this source of CH4. Source apportionment tracers such as δ2H may help close the gap between CH4 observations and inventories, which may underestimate biogenic as well as thermogenic sources.

Oil and natural gas operations have continued to expand and move closer to densely populated areas, contributing to growing public concerns regarding exposure to hazardous air pollutants. During the Barnett Shale Coordinated Campaign in October, 2013, ground-based whole air samples collected downwind of oil and gas sites revealed enhancements in several potentially toxic volatile organic compounds (VOCs) when compared to background values. Molar emissions ratios relative to methane were determined for hexane, benzene, toluene, ethylbenzene, and xylene (BTEX compounds). Using methane leak rates measured from the Picarro mobile flux plane (MFP) system and a Barnett Shale regional methane emissions inventory, the rates of emission of these toxic gases were calculated. Benzene emissions ranged between 51 ± 4 and 60 ± 4 kg h-1. Hexane, the most abundantly emitted pollutant, ranged from 642 ± 45 to 1070 ± 340 kg h-1. While observed hydrocarbon enhancements fall below federal workplace standards, results may indicate a link between emissions from oil and natural gas operations and concerns about exposure to hazardous air pollutants. The larger public health risks associated with the production and distribution of natural gas are of particular importance and warrant further investigation, particularly as the use of natural gas increases in the United States and internationally.

Atmospheric methane (CH4) continues to increase, but there are multiple anthropogenic source categories that can be targeted for cost-effective emissions reduction. Cities emit CH4 to the atmosphere from a mixture of anthropogenic CH4 sources, which include, but are not limited to, fugitive emissions from natural gas distribution systems, wastewater treatment facilities, waste-and rainwater networks, and landfills. Therefore, to target mitigation measures, it is important to locate and quantify local urban emissions to prioritize mitigation opportunities in large cities. Using mobile measurement techniques, we located street-level CH4 leak indications, measured flux rates, and determined potential source origins (using carbon and hydrogen stable isotopic composition along with ethane: CH4 ratios) of CH4 in Bucharest, Romania. We found 969 confirmed CH4 leak indication locations, where the maximum mole fraction elevation (above background) was 38.3 ppm (mean = 0.9 ppm ± 0.1 ppm s.e.; n = 2482). Individual leak indicator fluxes, derived using a previously established empirical relation, ranged up to around 15 metric tons CH4 yr-1 (mean = 0.8 metric tons yr-1 ± 0.05, s.e.; n = 969). The total estimated city emission rate is 1832 tons CH4 yr-1 (min = 1577 t yr-1 and max = 2113 t yr-1). More than half (58%–63%) of the CH4 elevations were attributed to biogenic wastewater, mostly from venting storm grates and manholes connecting to sewer pipelines. Hydrogen isotopic composition of CH4 and ethane:methane ratios were the most useful tracers of CH4 sources, due to similarities in carbon isotope ratios between wastewater gas and natural gas. The annual city-wide CH4 emission estimate of Bucharest exceeded emissions of Hamburg, Germany by 76% and Paris, France by 90%.

A growing dependence on natural gas for energy may exacerbate emissions of the greenhouse gas methane (CH4). Identifying fingerprints of these emissions is critical to our understanding of potential impacts. Here, we compare stable isotopic and alkane ratio tracers of natural gas, agricultural, and urban CH4 sources in the Barnett Shale hydraulic fracturing region near Fort Worth, Texas. Thermogenic and biogenic sources were compositionally distinct, and emissions from oil wells were enriched in alkanes and isotopically depleted relative to natural gas wells. Emissions from natural gas production varied in δ(13)C and alkane ratio composition, with δD-CH4 representing the most consistent tracer of natural gas sources. We integrated our data into a bottom-up inventory of CH4 for the region, resulting in an inventory of ethane (C2H6) sources for comparison to top-down estimates of CH4 and C2H6 emissions. Methane emissions in the Barnett are a complex mixture of urban, agricultural, and fossil fuel sources, which makes source apportionment challenging. For example, spatial heterogeneity in gas composition and high C2H6/CH4 ratios in emissions from conventional oil production add uncertainty to top-down models of source apportionment. Future top-down studies may benefit from the addition of δD-CH4 to distinguish thermogenic and biogenic sources.

Nitrous oxide (N2O) is a powerful greenhouse gas increasing in atmospheric mixing ratio and linked to increasing amounts of reactive N in the environment, particularly fertilizer use in agriculture. The consequences of urbanization of agricultural land for global and regional N2O emissions are unclear, due to high spatial and temporal variability of fluxes from different ecosystems and relatively few studies of urban ecosystems. We measured fluxes and the stable isotope composition (δ 15N and δ 18O) of N2O over 1 year in urban (ornamental lawns and athletic fields) and agricultural (corn and vegetable fields) ecosystems near Los Angeles, California, United States. We found that urban landscapes (lawns and athletic fields) have annual N2O fluxes equal to or greater than agricultural fields. Fertilization rates of urban landscapes were equal to or greater than agricultural fields, with comparable N2O emissions factors. δ 15N and δ 18O of N2O varied widely in all ecosystems, and were not consistent with ecosystem type, season, soil moisture, or temperature. There was, however, a consistent response of δ 15N-N2O to pulses of N2O emission following fertilization, with an initial depletion in δ 15N relative to prefertilization values, then gradual enrichment to background values within about 1 week. Preliminary scaling calculations indicated that N2O emissions from urban landscapes are approximately equal to or greater than agricultural emissions in urbanized areas of southern California, which further implies that current estimates of regional N2O emissions (based on agricultural land area) may be too low.

Oil and gas production wells are a major anthropogenic source of the greenhouse gas methane (CH _4 ) in the United States. Oil and gas production rates from these wells fluctuate due to changes in demand, and is expected to decline over the coming decades to centuries due to the transition to renewable energy. The CH _4 emissions profile from wells that are ‘shut-in’ to accommodate changes in demand has not been previously measured, and thus it is unclear whether reduced demand will actually result in reduced CH _4 emissions from oil and gas production. Here we present the results of a measurement campaign of CH _4 emissions from shut-in and other non-producing oil wells in the Permian Basin, Texas, the largest oil production basin on Earth. All the wells we measured were conventionally drilled oil wells, and we did not measure CH _4 emissions from any shut-in unconventional wells. We found that, of 37 wells measured, two-thirds had an emission rate of less than 1 g CH _4 hr ^−1 , with the remaining seven wells ranging from 1.3 to 132.0 g CH _4 hr ^−1 . The average CH _4 emission rate from all wells was 6.2 g CH _4 hr ^−1 , lower than previous measurements of CH _4 emissions from active conventional wells in the Permian Basin (∼400 g CH _4 hr ^−1 ) (Robertson et al (2020 Environ. Sci. Technol. 54 13926–34)). Some shut-in wells could be a substantial source of CH _4 emissions if this category is not subject to leak detection and repair regulations. We also found five orphaned wells that were a source of produced water to the surface, sometimes in very large quantities (1000s of liters per minute), with evidence for emissions of CH _4 , hydrogen sulfide, brine, and possibly other hazardous chemicals such as oil residue. Future work should further characterize the impacts of shut-in and orphaned wells on greenhouse gas emissions, water quality and human health.

The Satellite Coastal and Oceanic Atmospheric Pollution Experiment (SCOAPE) cruise in the Gulf of Mexico was conducted in May 2019 by NASA and the Bureau of Ocean Energy Management to determine the feasibility of using satellite data to measure air quality in a region of concentrated oil and natural gas (ONG) operations. SCOAPE addressed both technological and scientific issues related to measuring NO2 columns over the outer continental shelf. Featured were nitrogen dioxide (NO2) instruments (Pandora, Teledyne API analyzer) at Cocodrie, LA (29.26°, −90.66°), and on the Research Vessel Point Sur operating off the Louisiana coast with measurements of ozone, carbon monoxide, and volatile organic compounds (VOCs). The findings: (a) all NO2 observations revealed two atmospheric regimes over the Gulf, the first influenced by tropical air in 10–14 May, the second influenced by flow from urban areas on 15–17 May; (b) comparisons of OMI v4 and TROPOMI v1.3 TC (total column) NO2 data with shipboard Pandora NO2 column observations averaged 13% agreement with the largest difference during 15–17 May (∼20%). At Cocodrie, the satellite–Pandora agreement was ∼5%. (c) Three new‐model Pandora instruments displayed a TC NO2 precision of 0.01 Dobson Units (∼5%); (d) regions of smaller, older natural gas operations showed high methane readings from leakage; elevated VOCs were also detected. Neither satellite nor spectrometer captured the magnitude of ambient NO2 variability near ONG platforms. Given an absence of regular air quality monitoring over the Gulf of Mexico, SCOAPE data constitute a baseline against which future observations can be compared. Plain Language Summary: The Satellite Coastal and Oceanic Atmospheric Pollution Experiment (SCOAPE) cruise in the Gulf of Mexico (GOM) conducted on the Research Vessel Point Sur in May 2019 investigated the feasibility of using satellite data to measure air quality in a region of concentrated oil and natural gas (ONG) operations. SCOAPE addressed both technological and scientific issues related to measuring NO2 columns in a prototypical coastal environment. The results are as follows. First, measurements from SCOAPE demonstrated that satellite NO2 data can be used to monitor ONG activity over the GOM. Second, during SCOAPE both OMI and TROPOMI TC (total column) NO2 amounts were higher over land and sometimes the near‐shore ONG‐rich Gulf, than over deepwater regions farther offshore. This was confirmed by Pandora spectrometer "ground truth" TC NO2 data measured throughout SCOAPE on shore and on ship. Third, SCOAPE established the reliability and precision of a new generation of Pandora spectrometers. Fourth, comparisons of satellite and Pandora TC NO2 data in SCOAPE confirm previous land–water interface studies that point to limitations in satellite NO2 in coastal regions. Finally, neither satellite nor spectrometer captures the magnitude of ambient ("nose‐level") NO2 variability in a region dotted with hundreds of ONG platforms. Key Points: Shipboard Pandora NO2 columns and surface O3, NO2, CO, and volatile organic compounds (VOCs) over the Gulf of Mexico (GOM), May 2019, displayed two air quality (AQ) regimesGOM AQ was dominated by continental NO2 sources and near‐shore VOC; deepwater oil platforms were in a clean marine regimePandora and satellite total column NO2 over GOM agreed overall within 5% in clean, clear‐sky conditions along the coast and 13% over water [ABSTRACT FROM AUTHOR]

Ninety per cent of marine organic matter burial occurs in continental margin sediments, where a substantial fraction of organic carbon escapes oxidation and enters long-term geologic storage within sedimentary rocks. In such environments, microbial metabolism is limited by the diffusive supply of electron acceptors. One strategy to optimize energy yields in a resource-limited habitat is symbiotic metabolite exchange among microbial associations (1,2).Thermodynamic and geochemical considerations indicate that microbial cometabolisms are likely to play a critical part in sedimentary organic carbon cycling (3-5). Yet only one association, between methanotrophic archaea and sulphate-reducing bacteria, has been demonstrated in marine sediments in situ (6,7), and little is known of the role of microbial symbiotic interactions in other sedimentary biogeochemical cycles (8). Here we report in situ molecular and incubation-based evidence for a novel symbiotic consortium between two chemolithotrophic bacteria--anaerobic ammonium-oxidizing (anammox) bacteria and the nitrate-sequestering sulphur-oxidizing Thioploca species--in anoxic sediments of the Soledad basin at the Mexican Pacific margin. A mass balance of benthic solute fluxes and the corresponding nitrogen isotope composition of nitrate and ammonium fluxes indicate that anammox bacteria rely on Thioploca species for the supply of metabolic substrates and account for about 57 ± 21 per cent of the total benthic [N.sub.2] production. We show that Thioploca-anammox symbiosis intensifies benthic fixed nitrogen losses in anoxic sediments, bypassing diffusion-imposed limitations by efficiently coupling the carbon, nitrogen and sulphur cycles., Interspecies metabolite exchange is an effective strategy for harvesting potential energy in resource-limited environments. In organic-rich marine sediments, which are characterized by a strong deficit of electron acceptors, symbiotic microbial [...]