Greenhouse gas exchange in West African savanna ecosystems - how important are emissions from termite mounds?

NASA Astrophysics Data System (ADS)

Brümmer, C.; Brüggemann, N.

2012-04-01

Savannas cover large areas of the Earth's surface and play an important role in global carbon and nitrogen cycling. In this study, we present the soil-atmosphere exchange of N2O, CH4, and CO2 during two field campaigns throughout the growing seasons 2005 and 2006 at a natural savanna site that was not subject to human disturbances except for annual burning, and four agricultural sites planted with sorghum (n=2), cotton and peanut in Burkina Faso. The annual N2O emission of the nature reserve site amounted to 0.52 kg N2O-N ha-1 yr-1 in 2005 and to 0.67 kg N2O-N ha-1 yr-1 in 2006, whereas the calculated average annual N2O release of the crop sites was only 0.19 and 0.20 kg N2O-N ha-1 yr-1 in 2005 and 2006, respectively. As a result of a temporal up-scaling approach, a lower bound of annual N2O release could be given for two fertilized sorghum plots, that is, 0.83 kg N2O-N ha-1 yr-1 for a highly fertilized plot and 0.44 kg N2O-N ha-1 yr-1 for a moderately fertilized plot. During the rainy season both CH4 uptake in the range of up to 20 μg CH4-C m-2 h-1 as well as CH4 emission up to 300 μg CH4-C m-2 h-1 were observed at the nature reserve site, which was on average a CH4 source of 87.4 and 30.8 μg CH4-C m-2 h-1 in 2005 and 2006, respectively. All crop sites were on average weak CH4 sinks without significant seasonal variation. Uptake rates ranged between 2.5 and 8.7 μg CH4-C m-2 h-1. Occasionally very low net CH4 emission was observed after heavy rainfall events. Mean annual CH4 rates could be estimated to 2.48 kg CH4-C ha-1 yr-1 and -0.68 kg CH4-C ha-1 yr-1 for the nature reserve site and the crop sites, respectively. Trace gas emissions from termite (Cubitermes fungifaber) mounds that were almost exclusively found at the nature reserve were one order of magnitude higher for N2O and CO2, and two orders of magnitude higher for CH4 than soil emissions of the respective trace gas. Termite N2O, CH4 and CO2 release at the nature reserve contributed only 3.2%, 8.1% and 0.4% to total soil N2O, CH4 and CO2 emissions, respectively.

Does Juncus effusus enhance methane emissions from grazed pastures on peat?

NASA Astrophysics Data System (ADS)

Henneberg, A.; Elsgaard, L.; Sorrell, B. K.; Brix, H.; Petersen, S. O.

2015-06-01

Methane (CH4) emissions from drained organic soils are generally low, but internal gas transport in aerenchymatous plants may result in local emission hotspots. In a paired-sample field study at three different sites we measured fluxes of CH4 with static chambers from adjacent sampling quadrats with and without Juncus effusus during four field campaigns. At all three sites, CH4 was observed in the soil at all sampling depths (5-100 cm), and in most cases both above and below the groundwater table. During spring, local maxima suggested methanogenesis took place above the water table at all three sites. We found significant CH4 emissions at all three sites, but emission controls were clearly different. Across the three sites, average emission rates (±1 SE) for sampling quadrats with and without J. effusus were 1.47 ± 0.28 and 1.37 ± 0.33 mg CH4 m-2 h-1 respectively, with no overall effect of J. effusus on CH4 emissions, but a significant effect at one of the three sites. At this site, local CH4 maxima were closer to the soil surface than at the other sites, and the upper soil layers were dryer. This could have affected both root CH4 accessibility and CH4 oxidation respectively, and together with limited gas diffusivity in the soil column, cause elevated CH4 emissions from J. effusus. We conclude that aerenchymatous plants has the potential to act as point sources of CH4 from drained peatlands, but more studies on the specific conditions under which there is an effect, are needed before the results can be used in modelling of CH4 emissions.

Does uncus effusus enhance methane emissions from grazed pastures on peat?

NASA Astrophysics Data System (ADS)

Henneberg, A.; Elsgaard, L.; Sorrell, B. K.; Brix, H.; Petersen, S. O.

2015-10-01

Methane (CH4) emissions from drained organic soils are generally low, but internal gas transport in aerenchymatous plants may result in local emission hotspots. In a paired-sample field study at three different sites we measured fluxes of CH4 with static chambers from adjacent sampling quadrats with and without Juncus effusus during four field campaigns. At all three sites, CH4 was observed in the soil at all sampling depths (5 to 100 cm), and in most cases both above and below the groundwater table. During spring, local maxima suggested methanogenesis also took place above the water table at all three sites. We found significant CH4 emissions at all three sites, but emission controls were clearly different. Across the three sites, average emission rates (±1 SE) for sampling quadrats with and without J. effusus were 1.47 ± 0.28 and 1.37 ± 0.33 mg CH4 m-2 h-1, respectively, with no overall effect of J. effusus on CH4 emissions. However, a significant effect of J. effusus was seen at one of the three sites. At this site, local CH4 maxima were closer to the soil surface than at the other sites, and the upper soil layers were dryer. This could have affected both root CH4 accessibility and CH4 oxidation respectively, and together with limited gas diffusivity in the soil column, cause elevated CH4 emissions from J. effusus. We conclude that J. effusus has the potential to act as point sources of CH4 from drained peatlands, but more studies on the specific conditions under which there is an effect, are needed before the results can be used in modelling of CH4 emissions.

Emerging role of wetland methane emissions in driving 21st century climate change.

PubMed

Zhang, Zhen; Zimmermann, Niklaus E; Stenke, Andrea; Li, Xin; Hodson, Elke L; Zhu, Gaofeng; Huang, Chunlin; Poulter, Benjamin

2017-09-05

Wetland methane (CH 4 ) emissions are the largest natural source in the global CH 4 budget, contributing to roughly one third of total natural and anthropogenic emissions. As the second most important anthropogenic greenhouse gas in the atmosphere after CO 2 , CH 4 is strongly associated with climate feedbacks. However, due to the paucity of data, wetland CH 4 feedbacks were not fully assessed in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The degree to which future expansion of wetlands and CH 4 emissions will evolve and consequently drive climate feedbacks is thus a question of major concern. Here we present an ensemble estimate of wetland CH 4 emissions driven by 38 general circulation models for the 21st century. We find that climate change-induced increases in boreal wetland extent and temperature-driven increases in tropical CH 4 emissions will dominate anthropogenic CH 4 emissions by 38 to 56% toward the end of the 21st century under the Representative Concentration Pathway (RCP2.6). Depending on scenarios, wetland CH 4 feedbacks translate to an increase in additional global mean radiative forcing of 0.04 W·m -2 to 0.19 W·m -2 by the end of the 21st century. Under the "worst-case" RCP8.5 scenario, with no climate mitigation, boreal CH 4 emissions are enhanced by 18.05 Tg to 41.69 Tg, due to thawing of inundated areas during the cold season (December to May) and rising temperature, while tropical CH 4 emissions accelerate with a total increment of 48.36 Tg to 87.37 Tg by 2099. Our results suggest that climate mitigation policies must consider mitigation of wetland CH 4 feedbacks to maintain average global warming below 2 °C.

Emerging role of wetland methane emissions in driving 21st century climate change

PubMed Central

Zimmermann, Niklaus E.; Stenke, Andrea; Li, Xin; Hodson, Elke L.; Zhu, Gaofeng; Huang, Chunlin; Poulter, Benjamin

2017-01-01

Wetland methane (CH4) emissions are the largest natural source in the global CH4 budget, contributing to roughly one third of total natural and anthropogenic emissions. As the second most important anthropogenic greenhouse gas in the atmosphere after CO2, CH4 is strongly associated with climate feedbacks. However, due to the paucity of data, wetland CH4 feedbacks were not fully assessed in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The degree to which future expansion of wetlands and CH4 emissions will evolve and consequently drive climate feedbacks is thus a question of major concern. Here we present an ensemble estimate of wetland CH4 emissions driven by 38 general circulation models for the 21st century. We find that climate change-induced increases in boreal wetland extent and temperature-driven increases in tropical CH4 emissions will dominate anthropogenic CH4 emissions by 38 to 56% toward the end of the 21st century under the Representative Concentration Pathway (RCP2.6). Depending on scenarios, wetland CH4 feedbacks translate to an increase in additional global mean radiative forcing of 0.04 W·m−2 to 0.19 W·m−2 by the end of the 21st century. Under the “worst-case” RCP8.5 scenario, with no climate mitigation, boreal CH4 emissions are enhanced by 18.05 Tg to 41.69 Tg, due to thawing of inundated areas during the cold season (December to May) and rising temperature, while tropical CH4 emissions accelerate with a total increment of 48.36 Tg to 87.37 Tg by 2099. Our results suggest that climate mitigation policies must consider mitigation of wetland CH4 feedbacks to maintain average global warming below 2 °C. PMID:28827347

Future methane emissions from animals

NASA Astrophysics Data System (ADS)

Anastasi, C.; Simpson, V. J.

1993-04-01

The future global emission of CH4 from enteric fermentation in animals has been estimated for cattle, sheep, and buffalo, which together contribute approximately 91% of the total CH4 emitted from domesticated animals at present. A simple model has been used to relate livestock levels to the national human populations for each country involved in breeding the three species included in this analysis. United Nations population predictions to 2025 were then included in the model to estimate future CH4 emissions. A variational analysis was carried out to investigate the effect of future changes in both the land available for grazing and the nutritional content of feedstocks. Results suggest that the total emission of CH4 from enteric fermentation in domestic animals will increase from 84 Tg CH4 per year (Tg = 1012 g) in 1990 to 119 (±12) Tg CH4 yr-1 by 2025. These values correspond to an average rate of increase over the next 35 years of 1.0 Tg CH4 yr-1.

Revised methane emissions from livestock in China

NASA Astrophysics Data System (ADS)

Yu, J.; Peng, S.; Chang, J.; Ciais, P.; Dumas, P.; Lin, X.; Piao, S.

2017-12-01

Livestock is the largest anthropogenic methane (CH4) source at the global scale. Previous inventories of this source for China were based on the accounting of livestock populations and constant emission factors (EFs) per head. Here, we re-evaluate how livestock CH4 emissions from China have changed over the last three decades, considering increasing population, body weight and milk production per head which cause EF to change with time, and decreasing average life span (ALS) of livestock. Our results show that annual CH4 emissions by livestock have increased from 4.5 to 11.8 Tg CH4 yr-1 over the period 1980-2013. The increasing trend in emissions (0.25 Tg CH4 yr-2) over this period is 12% larger than the estimate using constant EFs and ALS. The increasing livestock population, production per head and decreasing ALS contributed +91%, +28% and -19% to the increase in CH4 emissions from livestock, respectively. This implies that temporal changes in EF and ALS of livestock cannot be overlooked in inventories, especially in countries like China where livestock production systems are experiencing rapid transformations.

Measurements of an Anomalous Global Methane Increase During 1998

NASA Technical Reports Server (NTRS)

Dlugokencky, E. J.; Walter, B. P.; Masarie, K. A.; Lang, P. M.; Kasischke, E. S.; Hansen, James E. (Technical Monitor)

2001-01-01

Measurements of atmospheric methane from a globally distributed network of air sampling sites indicate that the globally averaged CH4 growth rate increased from an average of 3.9 ppb/yr during 1995-1997 to 12.7 +/- 0.6 ppb in 1998. The global growth rate then decreased to 2.6 +/- 0.6 ppb during 1999, indicating that the large increase in 1998 was an anomaly and not a return to the larger growth rates observed during the late 1970s and early 1980s. The increased growth rate represents an anomalous increase in the imbalance between CH4 sources and sinks equal to approximately 24 Tg CH4 during 1998. Wetlands and boreal biomass burning are sources that may have contributed to the anomaly. During 1998, the globally averaged temperature anomaly was +0.67 C, the largest temperature anomaly in the modern record. A regression model based on temperature and precipitation anomalies was used to calculate emission anomalies of 11.6 Tg CH4 from wetlands north of 30 N and 13 Tg CH4 for tropical wetlands during 1998 compared to average emissions calculated for 1982-1993. In 1999, calculated wetland emission anomalies were negative for high northern latitudes and the tropics, contributing to the low growth rate observed in 1999. Also 1998 was a severe fire year in boreal regions where approximately 1.3x10(exp 5) sq km of forest and peat land burned releasing an estimated 5.7 Tg CH4

First records of a field experiment on fertilizer effects on methane emission from rice fields in Hunan-Province (PR China)

NASA Astrophysics Data System (ADS)

Wassmann, R.; Wang, M. X.; Shangguan, X. J.; Xie, X. L.; Shen, R. X.; Wang, Y. S.; Papen, H.; Rennenberg, H.; Seiler, W.

Fertilizer effects on methane emission from Chinese rice fields were investigated by a praxis-oriented approach applying balanced amendments of N, P and K. The data set obtained covered the emission rates of app. one month in early rice and one month in late rice 1991. An intercomparison between the 4 treatments showed pronounced differences in the magnitudes of methane emission rates. The combined organic/mineral fertilizer application, commonly used as local farming practice, resulted in relatively high seasonal averages of methane emission rates (26.5 mg CH4 m-2 h-1 in early rice and 50.1 mg CH4 m-2 h-1 in late rice). The lowest emission rates were observed in the plot with pure mineral fertilization (6.5 mg CH4 m-2 h-1 in early rice and 14.3 mg CH4 m-2 h-1 in late rice). Pure organic fertilizers by unfermented substances yielded the highest methane emission rates of all field trials (38.6 mg CH4 m-2 h-1 in early rice and 56.2 CH4 m-2 h-1 in late rice). The fertilization with fermented material derived from biogas generators resulted in substantially lower emission rates than the other trials with organic amendments, the seasonal averages corresponded to 15.9 mg CH4 m-2 h-1 (early rice) and 22.5 mg CH4 m-2 h-1 (late rice). Interpretation of the results can be obtained from the different potentials of these fertilizers for methane production. Based on this concept the different methane emission rates observed with organic/mineral, pure mineral and pure unfermented-organic fertilizers could directly be attributed to the different quantities of organic matter incorporated into the soil. The low methane emission from the plot treated with fermented material could be explained by a depletion of potential methane precursors resulting from the preceding fermentation. The results of this investigation provide evidence that the extensive use of specific chemical fertilizers and the application of sludge from the operation of biogas generators could lead to a net reduction of the methane emission from rice fields.

Development of a low-maintenance measurement approach to continuously estimate methane emissions: A case study.

PubMed

Riddick, S N; Hancock, B R; Robinson, A D; Connors, S; Davies, S; Allen, G; Pitt, J; Harris, N R P

2018-03-01

The chemical breakdown of organic matter in landfills represents a significant source of methane gas (CH 4 ). Current estimates suggest that landfills are responsible for between 3% and 19% of global anthropogenic emissions. The net CH 4 emissions resulting from biogeochemical processes and their modulation by microbes in landfills are poorly constrained by imprecise knowledge of environmental constraints. The uncertainty in absolute CH 4 emissions from landfills is therefore considerable. This study investigates a new method to estimate the temporal variability of CH 4 emissions using meteorological and CH 4 concentration measurements downwind of a landfill site in Suffolk, UK from July to September 2014, taking advantage of the statistics that such a measurement approach offers versus shorter-term, but more complex and instantaneously accurate, flux snapshots. Methane emissions were calculated from CH 4 concentrations measured 700m from the perimeter of the landfill with observed concentrations ranging from background to 46.4ppm. Using an atmospheric dispersion model, we estimate a mean emission flux of 709μgm -2 s -1 over this period, with a maximum value of 6.21mgm -2 s -1 , reflecting the wide natural variability in biogeochemical and other environmental controls on net site emission. The emissions calculated suggest that meteorological conditions have an influence on the magnitude of CH 4 emissions. We also investigate the factors responsible for the large variability observed in the estimated CH 4 emissions, and suggest that the largest component arises from uncertainty in the spatial distribution of CH 4 emissions within the landfill area. The results determined using the low-maintenance approach discussed in this paper suggest that a network of cheaper, less precise CH 4 sensors could be used to measure a continuous CH 4 emission time series from a landfill site, something that is not practical using far-field approaches such as tracer release methods. Even though there are limitations to the approach described here, this easy, low-maintenance, low-cost method could be used by landfill operators to estimate time-averaged CH 4 emissions and their impact downwind by simultaneously monitoring plume advection and CH 4 concentrations. Copyright © 2016. Published by Elsevier Ltd.

Temperate forest methane sink diminished by tree emissions.

PubMed

Pitz, Scott; Megonigal, J Patrick

2017-06-01

Global budgets ascribe 4-10% of atmospheric methane (CH 4 ) sinks to upland soils and have assumed until recently that soils are the sole surface for CH 4 exchange in upland forests. Here we report that CH 4 is emitted from the stems of dominant tree species in a temperate upland forest, measured using both the traditional static-chamber method and a new high-frequency, automated system. Tree emissions averaged across 68 observations on 17 trees from May to September were 1.59 ± 0.88 μmol CH 4  m -2  stem h -1 (mean ± 95% confidence interval), while soils adjacent to the trees consumed atmospheric CH 4 at a rate of -4.52 ± 0.64 μmol CH 4  m -2  soil h -1 (P < 0.0001). High-frequency measurements revealed diurnal patterns in the rate of tree-stem CH 4 emissions. A simple scaling exercise suggested that tree emissions offset 1-6% of the growing season soil CH 4 sink and may have briefly changed the forest to a net CH 4 source. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Evidence for a nonmonotonic relationship between ecosystem-scale peatland methane emissions and water table depth

NASA Astrophysics Data System (ADS)

Brown, Mathew G.; Humphreys, Elyn R.; Moore, Tim R.; Roulet, Nigel T.; Lafleur, Peter M.

2014-05-01

Although temporal and spatial variations in peatland methane (CH4) emissions at broad scales are often related to water table (WT) using a linear relationship, a potentially complex relationship exists between these variables locally and over shorter time scales. To explore this issue, CH4 fluxes were measured using eddy covariance at the Mer Bleue bog over two summer seasons. Peak CH4 emissions (30 to 50 mg CH4-C m-2 d-1) occurred not when the WT was closest to the surface but instead, when it dropped to 40 to 55 cm below the surface. When the WT was below or above this zone, average fluxes were 14 mg CH4-C m-2 d-1. We speculate this critical zone coincides with the necessary redox potentials and sources of fresh organic material that lead to maximum production of CH4 and/or with conditions that lead to degassing of stored CH4. However, as expected, total summer CH4 emissions were 47% lower during the drier year. This occurred in part because the WT was within the critical zone for fewer days in the drier year but also because after an extended midsummer dry period there was little recovery of CH4 emissions, even a month after rewetting.

Large emissions from floodplain trees close the Amazon methane budget.

PubMed

Pangala, Sunitha R; Enrich-Prast, Alex; Basso, Luana S; Peixoto, Roberta Bittencourt; Bastviken, David; Hornibrook, Edward R C; Gatti, Luciana V; Marotta, Humberto; Calazans, Luana Silva Braucks; Sakuragui, Cassia Mônica; Bastos, Wanderley Rodrigues; Malm, Olaf; Gloor, Emanuel; Miller, John Bharat; Gauci, Vincent

2017-12-14

Wetlands are the largest global source of atmospheric methane (CH 4 ), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH 4 in the tropics, consistently underestimate the atmospheric burden of CH 4 determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH 4 emissions. Here we report CH 4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH 4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δ 13 C) of -66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH 4 a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a 'top-down' regional estimate of CH 4 emissions of 42.7 ± 5.6 teragrams of CH 4 a year for the Amazon basin, based on regular vertical lower-troposphere CH 4 profiles covering the period 2010-2013. We find close agreement between our 'top-down' and combined 'bottom-up' estimates, indicating that large CH 4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH 4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH 4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH 4 source when trees are combined with other emission sources.

Large emissions from floodplain trees close the Amazon methane budget

NASA Astrophysics Data System (ADS)

Pangala, Sunitha R.; Enrich-Prast, Alex; Basso, Luana S.; Peixoto, Roberta Bittencourt; Bastviken, David; Hornibrook, Edward R. C.; Gatti, Luciana V.; Marotta, Humberto; Calazans, Luana Silva Braucks; Sakuragui, Cassia Mônica; Bastos, Wanderley Rodrigues; Malm, Olaf; Gloor, Emanuel; Miller, John Bharat; Gauci, Vincent

2017-12-01

Wetlands are the largest global source of atmospheric methane (CH4), a potent greenhouse gas. However, methane emission inventories from the Amazon floodplain, the largest natural geographic source of CH4 in the tropics, consistently underestimate the atmospheric burden of CH4 determined via remote sensing and inversion modelling, pointing to a major gap in our understanding of the contribution of these ecosystems to CH4 emissions. Here we report CH4 fluxes from the stems of 2,357 individual Amazonian floodplain trees from 13 locations across the central Amazon basin. We find that escape of soil gas through wetland trees is the dominant source of regional CH4 emissions. Methane fluxes from Amazon tree stems were up to 200 times larger than emissions reported for temperate wet forests and tropical peat swamp forests, representing the largest non-ebullitive wetland fluxes observed. Emissions from trees had an average stable carbon isotope value (δ13C) of -66.2 ± 6.4 per mil, consistent with a soil biogenic origin. We estimate that floodplain trees emit 15.1 ± 1.8 to 21.2 ± 2.5 teragrams of CH4 a year, in addition to the 20.5 ± 5.3 teragrams a year emitted regionally from other sources. Furthermore, we provide a ‘top-down’ regional estimate of CH4 emissions of 42.7 ± 5.6 teragrams of CH4 a year for the Amazon basin, based on regular vertical lower-troposphere CH4 profiles covering the period 2010-2013. We find close agreement between our ‘top-down’ and combined ‘bottom-up’ estimates, indicating that large CH4 emissions from trees adapted to permanent or seasonal inundation can account for the emission source that is required to close the Amazon CH4 budget. Our findings demonstrate the importance of tree stem surfaces in mediating approximately half of all wetland CH4 emissions in the Amazon floodplain, a region that represents up to one-third of the global wetland CH4 source when trees are combined with other emission sources.

Methane emissions associated with the conversion of marshland to cropland and climate change on the Sanjiang Plain of Northeast China from 1950 to 2100

NASA Astrophysics Data System (ADS)

Li, T.; Huang, Y.; Zhang, W.; Yu, Y. Q.

2012-05-01

Wetland loss and climate change are known to alter regional and global methane (CH4) budgets. Over the last six decades, an extensive area of marshland has been converted to cropland on the Sanjiang Plain in Northeast China, and a significant increase in air temperature has also been observed there, while the impacts on regional CH4 budgets remain uncertain. Through model simulation, we estimated the changes in CH4 emissions associated with the conversion of marshland to cropland and climate change in this area. Model simulations indicated a significant reduction of 1.1 Tg yr-1 from the 1950s to the 2000s in regional CH4 emissions. The cumulative reduction of CH4 from 1960 to 2009 was estimated to be ~36 Tg relative to the 1950s, and marshland conversion and the climate contributed 86 % and 14 % of this change, respectively. Interannual variation in precipitation (linear trend with P > 0.2) contributed to yearly fluctuations in CH4 emissions, but the relatively lower amount of precipitation over the period 1960-2009 (47 mm yr-1 lower on average than in the 1950s) contributed ~91 % of the reduction in the area-weighted CH4 flux. Global warming at a rate of 0.3 °C per decade (P < 0.001) has increased CH4 emissions significantly since the 1990s. Relative to the mean of the 1950s, the warming-induced increase in the CH4 flux has averaged 19 kg ha-1 yr-1 over the last two decades. For the RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5 scenarios of the fifth IPCC assessment report (AR5), the CH4 flux is predicted to increase by 36 %, 52 %, 78 % and 95 %, respectively, by the 2080s compared to 1961-1990 in response to climate warming and wetting.

DEVELOPMENT OF AN EMPIRICAL MODEL OF METHANE EMISSIONS FROM LANDFILLS

EPA Science Inventory

The report gives results of a field study of 21 U.S. landfills with gas recovery systems, to gather information that can be used to develop an empirical model of methane (CH4) emissions. Site-specific information includes average CH4 recovery rate, landfill size, tons of refuse (...

Methane emissions from tundra environments in the Yukon-Kuskokwin Delta, Alaska

NASA Technical Reports Server (NTRS)

Bartlett, Karen B.; Crill, Patrick M.; Sass, Ronald L.; Harriss, Robert C.; Dise, Nancy B.

1992-01-01

This paper reports CH4 flux to the atmosphere from a variety of tundra environments near Bethel, Alaska during the summer months of 1988. Emissions from wet meadow tundra averaged 144 +/- 31 mg/sq m/d and ranged from 15.6 to 426 mg/sq m/d varying with soil moisture and temperature. Flux from the drier upland tundra was about two orders of magnitude lower and averaged 2.3 +/- 1.1 mg/sq m/d. Tundra lakes emit CH4 from the open water surface as well as from fringing aquatic vegetation; the presence of vegetation significantly enhanced flux over open water rates. Calculated diffusive fluxes from open water varied with lake size, the large lakes emitting 3.8 mg/sq m/d and small lakes emitting an average of 77 mg/sq m/d. An updated estimate of global emissions from tundra indicates an annual fluxes of approximately 11 +/- 3 Tg CH4.

Methane emissions from a Californian landfill, determined from airborne remote sensing and in situ measurements

NASA Astrophysics Data System (ADS)

Krautwurst, Sven; Gerilowski, Konstantin; Jonsson, Haflidi H.; Thompson, David R.; Kolyer, Richard W.; Iraci, Laura T.; Thorpe, Andrew K.; Horstjann, Markus; Eastwood, Michael; Leifer, Ira; Vigil, Samuel A.; Krings, Thomas; Borchardt, Jakob; Buchwitz, Michael; Fladeland, Matthew M.; Burrows, John P.; Bovensmann, Heinrich

2017-09-01

Fugitive emissions from waste disposal sites are important anthropogenic sources of the greenhouse gas methane (CH4). As a result of the growing world population and the recognition of the need to control greenhouse gas emissions, this anthropogenic source of CH4 has received much recent attention. However, the accurate assessment of the CH4 emissions from landfills by modeling and existing measurement techniques is challenging. This is because of inaccurate knowledge of the model parameters and the extent of and limited accessibility to landfill sites. This results in a large uncertainty in our knowledge of the emissions of CH4 from landfills and waste management. In this study, we present results derived from data collected during the research campaign COMEX (CO2 and MEthane eXperiment) in late summer 2014 in the Los Angeles (LA) Basin. One objective of COMEX, which comprised aircraft observations of methane by the remote sensing Methane Airborne MAPper (MAMAP) instrument and a Picarro greenhouse gas in situ analyzer, was the quantitative investigation of CH4 emissions. Enhanced CH4 concentrations or CH4 plumes were detected downwind of landfills by remote sensing aircraft surveys. Subsequent to each remote sensing survey, the detected plume was sampled within the atmospheric boundary layer by in situ measurements of atmospheric parameters such as wind information and dry gas mixing ratios of CH4 and carbon dioxide (CO2) from the same aircraft. This was undertaken to facilitate the independent estimation of the surface fluxes for the validation of the remote sensing estimates. During the COMEX campaign, four landfills in the LA Basin were surveyed. One landfill repeatedly showed a clear emission plume. This landfill, the Olinda Alpha Landfill, was investigated on 4 days during the last week of August and first days of September 2014. Emissions were estimated for all days using a mass balance approach. The derived emissions vary between 11.6 and 17.8 kt CH4 yr-1 with related uncertainties in the range of 14 to 45 %. The comparison of the remote sensing and in situ based CH4 emission rate estimates reveals good agreement within the error bars with an average of the absolute differences of around 2.4 kt CH4 yr-1 (±2. 8 kt CH4 yr-1). The US Environmental Protection Agency (EPA) reported inventory value is 11.5 kt CH4 yr-1 for 2014, on average 2.8 kt CH4 yr-1 (±1. 6 kt CH4 yr-1) lower than our estimates acquired in the afternoon in late summer 2014. This difference may in part be explained by a possible leak located on the southwestern slope of the landfill, which we identified in the observations of the Airborne Visible/Infrared Imaging Spectrometer - Next Generation (AVIRIS-NG) instrument, flown contemporaneously aboard a second aircraft on 1 day.

Analyzing source apportioned methane in northern California during Discover-AQ-CA using airborne measurements and model simulations

NASA Astrophysics Data System (ADS)

Johnson, Matthew S.; Yates, Emma L.; Iraci, Laura T.; Loewenstein, Max; Tadić, Jovan M.; Wecht, Kevin J.; Jeong, Seongeun; Fischer, Marc L.

2014-12-01

This study analyzes source apportioned methane (CH4) emissions and atmospheric mixing ratios in northern California during the Discover-AQ-CA field campaign using airborne measurement data and model simulations. Source apportioned CH4 emissions from the Emissions Database for Global Atmospheric Research (EDGAR) version 4.2 were applied in the 3-D chemical transport model GEOS-Chem and analyzed using airborne measurements taken as part of the Alpha Jet Atmospheric eXperiment over the San Francisco Bay Area (SFBA) and northern San Joaquin Valley (SJV). During the time period of the Discover-AQ-CA field campaign EDGAR inventory CH4 emissions were ∼5.30 Gg day-1 (Gg = 1.0 × 109 g) (equating to ∼1.90 × 103 Gg yr-1) for all of California. According to EDGAR, the SFBA and northern SJV region contributes ∼30% of total CH4 emissions from California. Source apportionment analysis during this study shows that CH4 mixing ratios over this area of northern California are largely influenced by global emissions from wetlands and local/global emissions from gas and oil production and distribution, waste treatment processes, and livestock management. Model simulations, using EDGAR emissions, suggest that the model under-estimates CH4 mixing ratios in northern California (average normalized mean bias (NMB) = -5.2% and linear regression slope = 0.20). The largest negative biases in the model were calculated on days when large amounts of CH4 were measured over local emission sources and atmospheric CH4 mixing ratios reached values >2.5 parts per million. Sensitivity emission studies conducted during this research suggest that local emissions of CH4 from livestock management processes are likely the primary source of the negative model bias. These results indicate that a variety, and larger quantity, of measurement data needs to be obtained and additional research is necessary to better quantify source apportioned CH4 emissions in California.

Analyzing source apportioned methane in northern California during Discover-AQ-CA using airborne measurements and model simulations

DOE PAGES

Johnson, Matthew S.; Yates, Emma L.; Iraci, Laura T.; ...

2014-12-01

This study analyzes source apportioned methane (CH 4) emissions and atmospheric mixing ratios in northern California during the Discover-AQ-CA field campaign using airborne measurement data and model simulations. Source apportioned CH 4 emissions from the Emissions Database for Global Atmospheric Research (EDGAR) version 4.2 were applied in the 3-D chemical transport model GEOS-Chem and analyzed using airborne measurements taken as part of the Alpha Jet Atmospheric eXperiment over the San Francisco Bay Area (SFBA) and northern San Joaquin Valley (SJV). During the time period of the Discover-AQ-CA field campaign EDGAR inventory CH 4 emissions were ~5.30 Gg day –1 (Ggmore » = 1.0 × 10 9 g) (equating to ~1.90 × 10 3 Gg yr –1) for all of California. According to EDGAR, the SFBA and northern SJV region contributes ~30% of total CH 4 emissions from California. Source apportionment analysis during this study shows that CH 4 mixing ratios over this area of northern California are largely influenced by global emissions from wetlands and local/global emissions from gas and oil production and distribution, waste treatment processes, and livestock management. Model simulations, using EDGAR emissions, suggest that the model under-estimates CH 4 mixing ratios in northern California (average normalized mean bias (NMB) = –5.2% and linear regression slope = 0.20). The largest negative biases in the model were calculated on days when large amounts of CH 4 were measured over local emission sources and atmospheric CH 4 mixing ratios reached values >2.5 parts per million. Sensitivity emission studies conducted during this research suggest that local emissions of CH 4 from livestock management processes are likely the primary source of the negative model bias. These results indicate that a variety, and larger quantity, of measurement data needs to be obtained and additional research is necessary to better quantify source apportioned CH 4 emissions in California.« less

Depth distribution of microbial production and oxidation of methane in northern boreal peatlands.

PubMed

Sundh, I; Nilsson, M; Granberg, G; Svensson, B H

1994-05-01

The depth distributions of anaerobic microbial methane production and potential aerobic microbial methane oxidation were assessed at several sites in both Sphagnum- and sedge-dominated boreal peatlands in Sweden, and compared with net methane emissions from the same sites. Production and oxidation of methane were measured in peat slurries, and emissions were measured with the closed-chamber technique. Over all eleven sites sampled, production was, on average, highest 12 cm below the depth of the average water table. On the other hand, highest potential oxidation of methane coincided with the depth of the average water table. The integrated production rate in the 0-60 cm interval ranged between 0.05 and 1.7 g CH4 m (-2) day(-) and was negatively correlated with the depth of the average water table (linear regression: r (2) = 0.50, P = 0.015). The depth-integrated potential CH4-oxidation rate ranged between 3.0 and 22.1 g CH4 m(-2) day(-1) and was unrelated to the depth of the average water table. A larger fraction of the methane was oxidized at sites with low average water tables; hence, our results show that low net emission rates in these environments are caused not only by lower methane production rates, but also by conditions more favorable for the development of CH4-oxidizing bacteria in these environments.

Methane emissions from Alaska in 2012 from CARVE airborne observations

PubMed Central

Chang, Rachel Y.-W.; Miller, Charles E.; Dinardo, Steven J.; Karion, Anna; Sweeney, Colm; Daube, Bruce C.; Henderson, John M.; Mountain, Marikate E.; Eluszkiewicz, Janusz; Miller, John B.; Bruhwiler, Lori M. P.; Wofsy, Steven C.

2014-01-01

We determined methane (CH4) emissions from Alaska using airborne measurements from the Carbon Arctic Reservoirs Vulnerability Experiment (CARVE). Atmospheric sampling was conducted between May and September 2012 and analyzed using a customized version of the polar weather research and forecast model linked to a Lagrangian particle dispersion model (stochastic time-inverted Lagrangian transport model). We estimated growing season CH4 fluxes of 8 ± 2 mg CH4⋅m−2⋅d−1 averaged over all of Alaska, corresponding to fluxes from wetlands of 56−13+22 mg CH4⋅m−2⋅d−1 if we assumed that wetlands are the only source from the land surface (all uncertainties are 95% confidence intervals from a bootstrapping analysis). Fluxes roughly doubled from May to July, then decreased gradually in August and September. Integrated emissions totaled 2.1 ± 0.5 Tg CH4 for Alaska from May to September 2012, close to the average (2.3; a range of 0.7 to 6 Tg CH4) predicted by various land surface models and inversion analyses for the growing season. Methane emissions from boreal Alaska were larger than from the North Slope; the monthly regional flux estimates showed no evidence of enhanced emissions during early spring or late fall, although these bursts may be more localized in time and space than can be detected by our analysis. These results provide an important baseline to which future studies can be compared. PMID:25385648

Methane emissions from Alaska in 2012 from CARVE airborne observations.

PubMed

Chang, Rachel Y-W; Miller, Charles E; Dinardo, Steven J; Karion, Anna; Sweeney, Colm; Daube, Bruce C; Henderson, John M; Mountain, Marikate E; Eluszkiewicz, Janusz; Miller, John B; Bruhwiler, Lori M P; Wofsy, Steven C

2014-11-25

We determined methane (CH4) emissions from Alaska using airborne measurements from the Carbon Arctic Reservoirs Vulnerability Experiment (CARVE). Atmospheric sampling was conducted between May and September 2012 and analyzed using a customized version of the polar weather research and forecast model linked to a Lagrangian particle dispersion model (stochastic time-inverted Lagrangian transport model). We estimated growing season CH4 fluxes of 8 ± 2 mg CH4⋅m(-2)⋅d(-1) averaged over all of Alaska, corresponding to fluxes from wetlands of 56(-13)(+22) mg CH4⋅m(-2)⋅d(-1) if we assumed that wetlands are the only source from the land surface (all uncertainties are 95% confidence intervals from a bootstrapping analysis). Fluxes roughly doubled from May to July, then decreased gradually in August and September. Integrated emissions totaled 2.1 ± 0.5 Tg CH4 for Alaska from May to September 2012, close to the average (2.3; a range of 0.7 to 6 Tg CH4) predicted by various land surface models and inversion analyses for the growing season. Methane emissions from boreal Alaska were larger than from the North Slope; the monthly regional flux estimates showed no evidence of enhanced emissions during early spring or late fall, although these bursts may be more localized in time and space than can be detected by our analysis. These results provide an important baseline to which future studies can be compared.

Isotopic constraints on methane's global sources and ENSO-dependence

NASA Astrophysics Data System (ADS)

Schaefer, Hinrich; Mikaloff Fletcher, Sara; Veidt, Cora; Lassey, Keith; Brailsford, Gordon; Bromley, Tony; Dlugokencky, Ed; Englund Michel, Sylvia; Miller, John; Levin, Ingeborg; Lowe, Dave; Martin, Ross; Vaughn, Bruce; White, James; Nichol, Sylvia

2017-04-01

Atmospheric levels of the potent greenhouse gas methane (CH4) have been rising since the industrial revolution, except for a plateau during the early 2000s. Stable carbon isotopes in methane (delta-13CH4) provide constraints on the budget changes associated with the plateau's onset and its end. We present a reconstruction of annual global delta-13CH4 averages based on a global network of stations, whose trends are indicative of global methane source and sink activity. A box model analysis shows that from the mid-1990s methane emissions with the characteristic thermogenic delta-13CH4 signature reduced, implying persistently lower emissions from fossil fuel productions as the cause of the plateau. However, variations in hydroxyl, the main CH4 sink, provide an equably plausible explanation for the plateau onset that may also account for strong variability in emission-vs-removal rates during the plateau period. In contrast, the renewed CH4 rise since 2006 can only be explained by increasing emissions with a biogenic isotope signature, i.e. agriculture or wetlands. We present correlation studies that test whether ENSO activity controls atmospheric delta-13CH4, and by extension methane levels, through tropical wetland emissions.

CO 2 is dominant greenhouse gas emitted from six hydropower reservoirs in southeastern United States during peak summer emissions

DOE PAGES

Bevelhimer, Mark S.; Stewart, Aurthur J.; Fortner, Allison M.; ...

2016-01-06

During August-September 2012, we sampled six hydropower reservoirs in southeastern United States. for CO 2 and CH 4 emissions via three pathways: diffusive emissions from water surface; ebullition in the water column; and losses from dam tailwaters during power generation. Average total emission rates of CO 2 for the six reservoirs ranged from 1,127 to 2,051 mg m -2 d -1, which is low to moderate compared to CO 2 emissions rates reported for tropical hydropower reservoirs and boreal ponds and lakes, and similar to rates reported for other temperate reservoirs. Similar average rates for CH 4 were also relativelymore » low, ranging from 5 to 83 mg m -2 d -1. On a whole-reservoir basis, total emissions of CO 2 ranged nearly 10-fold, from ~51,000 kg per day for Fontana to ~486,000 kg per day for Guntersville, and total emissions of CH 4 ranged nearly 20-fold, from ~5 kg per day for Fontana to ~83 kg per day for Allatoona. Emissions through the tailwater pathway varied among reservoirs, comprising from 20 to 50% of total CO 2 emissions and 0 to 90% of CH 4 emissions, depending on the reservoir. Furthermore, several explanatory factors related to reservoir morphology and water quality were considered for observed differences among reservoirs.« less

Inventory of methane emissions from livestock in China from 1980 to 2013

NASA Astrophysics Data System (ADS)

Yu, Jiashuo; Peng, Shushi; Chang, Jinfeng; Ciais, Philippe; Dumas, Patrice; Lin, Xin; Piao, Shilong

2018-07-01

Livestock is the largest anthropogenic methane (CH4) source at the global scale. Previous inventories of this source for China were based on the accounting of livestock populations and constant emission factors (EFs) per head. Here, we re-evaluate how livestock CH4 emissions have changed from China over the last three decades, considering increasing population, body weight and milk production per head which cause EF to change with time, and decreasing average life span (ALS) of livestock. Our results show that annual CH4 emissions by livestock have increased from 4.5 to 11.8 Tg CH4 yr-1 over the period 1980-2013. The increasing trend in emissions (0.25 Tg CH4 yr-2) over this period is ∼12% larger than that if using constant EFs and ALS. The increasing livestock population, production per head and decreasing ALS contributed +91%, +28% and -19% to the increase in CH4 emissions from livestock, respectively. This implies that the temporal changes in EF and ALS of livestock cannot be overlooked in inventories, especially in countries like China where livestock production systems are experiencing rapid transformations.

CH4 and N2O emissions from China's beef feedlots with ad libitum and restricted feeding in fall and spring seasons.

PubMed

Lin, Zhi; Liao, Wenhua; Yang, Yuanyuan; Gao, Zhiling; Ma, Wenqi; Wang, Dianwu; Cao, Yufeng; Li, Jianguo; Cai, Zhenjiang

2015-04-01

Accurately quantifying methane (CH4) and nitrous oxide (N2O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N2O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH4 from the beef feedlot with an ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N2O emissions between two feeding strategies was observed. The two-season average CH4 emission rates of the two intensive feedlots were 230 and 198gCH4animal(-1)d(-1) and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH4 conversion factor at the feedlot level. However, the average N2O emission rates (21.2g N2Oanimal(-1)d(-1)) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N2O emission rate and conversion factor of 9.2g N2Oanimal(-1)d(-1) and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N2O emissions from beef feedlots. In addition, comparison indicated that China's beef and dairy cattle in feedlots appeared to have similar CH4 conversion factors. Copyright © 2015 Elsevier Inc. All rights reserved.

Enhanced methane emissions from tropical wetlands during the 2011 La Niña

PubMed Central

Pandey, Sudhanshu; Houweling, Sander; Krol, Maarten; Aben, Ilse; Monteil, Guillaume; Nechita-Banda, Narcisa; Dlugokencky, Edward J.; Detmers, Rob; Hasekamp, Otto; Xu, Xiyan; Riley, William J.; Poulter, Benjamin; Zhang, Zhen; McDonald, Kyle C.; White, James W. C.; Bousquet, Philippe; Röckmann, Thomas

2017-01-01

Year-to-year variations in the atmospheric methane (CH4) growth rate show significant correlation with climatic drivers. The second half of 2010 and the first half of 2011 experienced the strongest La Niña since the early 1980s, when global surface networks started monitoring atmospheric CH4 mole fractions. We use these surface measurements, retrievals of column-averaged CH4 mole fractions from GOSAT, new wetland inundation estimates, and atmospheric δ13C-CH4 measurements to estimate the impact of this strong La Niña on the global atmospheric CH4 budget. By performing atmospheric inversions, we find evidence of an increase in tropical CH4 emissions of ∼6–9 TgCH4 yr−1 during this event. Stable isotope data suggest that biogenic sources are the cause of this emission increase. We find a simultaneous expansion of wetland area, driven by the excess precipitation over the Tropical continents during the La Niña. Two process-based wetland models predict increases in wetland area consistent with observationally-constrained values, but substantially smaller per-area CH4 emissions, highlighting the need for improvements in such models. Overall, tropical wetland emissions during the strong La Niña were at least by 5% larger than the long-term mean. PMID:28393869

Environmental factors controlling methane emissions from peatlands in northern Minnesota

NASA Technical Reports Server (NTRS)

Dise, Nancy B.; Gorham, Eville; Verry, Elon S.

1993-01-01

The environmental factors affecting the emission of methane from peatlands were investigated by correlating CH4 emission data for two years, obtained from five different peatland ecosystems in northern Minnesota, with peat temperature, water table position, and degree of peat humification. The relationship obtained between the CH4 flux and these factors was compared to results from a field manipulation experiment in which the water table was artificially raised in three experimental plots within the driest peatland. It was found that peat temperature, water table position, and degree of peat humification explained 91 percent of the variance in log CH4 flux, successfully predicted annual CH4 emission from individual wetlands, and predicted the change in flux due to the water table manipulation. Raising the water table in the bog corrals by an average of 6 cm in autumn 1989 and 10 cm in summer 1990 increased CH4 emission by 2.5 and 2.2 times, respectively.

Atmospheric CH4 in the first decade of the 21st century: Inverse modeling analysis using SCIAMACHY satellite retrievals and NOAA surface measurements

NASA Astrophysics Data System (ADS)

Bergamaschi, P.; Houweling, S.; Segers, A.; Krol, M.; Frankenberg, C.; Scheepmaker, R. A.; Dlugokencky, E.; Wofsy, S. C.; Kort, E. A.; Sweeney, C.; Schuck, T.; Brenninkmeijer, C.; Chen, H.; Beck, V.; Gerbig, C.

2013-07-01

causes of renewed growth in the atmospheric CH4 burden since 2007 are still poorly understood and subject of intensive scientific discussion. We present a reanalysis of global CH4 emissions during the 2000s, based on the TM5-4DVAR inverse modeling system. The model is optimized using high-accuracy surface observations from NOAA ESRL's global air sampling network for 2000-2010 combined with retrievals of column-averaged CH4 mole fractions from SCIAMACHY onboard ENVISAT (starting 2003).Using climatological OH fields, derived global total emissions for 2007-2010 are 16-20 Tg CH4/yr higher compared to 2003-2005. Most of the inferred emission increase was located in the tropics (9-14 Tg CH4/yr) and mid-latitudes of the northern hemisphere (6-8 Tg CH4/yr), while no significant trend was derived for Arctic latitudes. The atmospheric increase can be attributed mainly to increased anthropogenic emissions, but the derived trend is significantly smaller than estimated in the EDGARv4.2 emission inventory. Superimposed on the increasing trend in anthropogenic CH4 emissions are significant inter-annual variations (IAV) of emissions from wetlands (up to ±10 Tg CH4/yr), and biomass burning (up to ±7 Tg CH4/yr). Sensitivity experiments, which investigated the impact of the SCIAMACHY observations (versus inversions using only surface observations), of the OH fields used, and of a priori emission inventories, resulted in differences in the detailed latitudinal attribution of CH4 emissions, but the IAV and trends aggregated over larger latitude bands were reasonably robust. All sensitivity experiments show similar performance against independent shipboard and airborne observations used for validation, except over Amazonia where satellite retrievals improved agreement with observations in the free troposphere.

Diurnal variation of methane emissions from an alpine wetland on the eastern edge of Qinghai-Tibetan Plateau.

PubMed

Chen, Huai; Wu, Ning; Yao, Shouping; Gao, Yongheng; Wang, Yanfen; Tian, Jianqing; Yuan, Xingzhong

2010-05-01

Alpine wetland is a source for CH(4), but little is known about methane emission from such wetland, especially about its diurnal pattern. In this study we tried to probe the diurnal variation in methane emission from alpine wetland vegetation. The average methane emission rate was 9.6 +/- 3.4 mg CH(4) m(-2) h(-1). There was an apparent diurnal variation pattern in methane emission with one minor peak at 06:00 and a major one at 15:00. The sunrise peak was consistent with a two-way transport mechanism for plants (convective at daytime and diffusive at night-time). CH(4) emission was found significantly correlated with redox potentials. The afternoon peak could not be explained by diurnal variation in soil temperature, but could be attributable to changes in CH(4) oxidation and production driven by plant gas transport mechanism. The results have important implications for sampling and scaling strategies for estimating methane emission from alpine wetlands.

Controls of Methane Dynamics and Emissions in an Arctic Warming Experiment

NASA Astrophysics Data System (ADS)

Nielsen, C. S.; Elberling, B.; Michelsen, A.; Strobel, B. W.; Wulff, K.; Banyasz, I.

2015-12-01

Climatic changes have resulted in increasing air temperatures across the Arctic. This may increase anaerobic decomposition of soil organic matter to methane (CH4) in wetlands and increase plant growth and thereby production of substrate. Little is known about how seasonal variations in dissolved CH4 in soil water, substrate availability, and the effect of warming affect arctic wetland dynamics of CH4 production and emission. In 2013 we established two experiments in a fen at Disko Island, W Greenland; one with year round warming by open-top chambers and removal of shrubs, and one with removal of the aerenchymatous sedge Carex aquatilis ssp. stans. Throughout the growing season 2014 we measured how the treatments affected CH4 emissions, dissolved CH4 in the soil water, and substrate availability. Ecosystem CH4 emissions peaked at August 5th 2014 (7.5 μmol m-2 h-1) without coinciding with time of highest concentrations of dissolved CH4 or acetate indicating a decoupling between production and emission of CH4. The peak in dissolved CH4 concentration, at ten cm depth (1368 ppm, September 18th 2014), followed the peak in concentration of acetate in the same depth (0.30 ppm, August 30th 2014) highlighting the importance of this substance as a substrate for methanogenesis. C. aquatilis ssp. stans accounted for 60% and 77% of the ecosystem CH4 emissions in areas of the fen with water table above and below soil surface showing the importance of the presence of this species to serve as a pipe for CH4 emission which is bypassing the upper soil zone and potential methane oxidation. Throughout the season, warming increased the air temperature at soil surface by on average 0.89°C and occasionally warming and shrub removal increased soil temperature in 2 and 5 cm depth, but there was no effect of the treatments on the CH4 emissions indicating that this wetland is quite resilient towards future climate change.

Temporal variability of methane fluxes in West Siberian taiga bogs and its implications for estimating regional methane emission

NASA Astrophysics Data System (ADS)

Sabrekov, Alexander; Ilyasov, Danil; Terentieva, Irina; Glagolev, Mikhail; Maksyutov, Shamil

2017-04-01

The West Siberia Lowland (WSL) is the biggest peatland area in Eurasia and is situated in the high latitudes experiencing enhanced rate of climate change. During 2015-16 summer periods, seasonal measurements of methane emission were made at the field station «Mukhrino» in the WSL middle taiga zone. The study was made at 3 wetland ecosystem types covering 80% of the taiga wetland area: i) waterlogged hollows or depressed areas with water level above the moss surface, ii) oligotrophic hollows or depressed parts of bogs with water level beneath the moss surface, iii) forested bogs with dwarf shrubs-sphagnum vegetation. Seven series of measurements were made by a static chamber method in 2016 and four series - in 2015. In 2015, we observed non-typical weather conditions including early dry spring and short cold rainy summer. Oppositely, weather conditions in 2016 were closer to average long-term with warmer drier summer. Significant difference between these years allowed analyzing the temporal variability and its sources. Average methane flux rates from forested bogs were 0.57 mgCH4/m2/h in 2016 and 0.33 mgCH4/m2/h in 2015. Seasonal dynamic during both years had similar concave downward shape. The highest fluxes were observed in June and were corresponded to the highest WTL, the main limiting factor of emission from forested bogs. The lowest fluxes in July were related to the low WTL combining with the highest temperature of upper methanotrophy layer. Average methane flux rates from oligotrophic hollows were 7.18 mgCH4/m2/h in 2016 and 4.28 mgCH4/m2/h in 2015. Seasonal dynamic of methane emission was indistinct in 2015. On the contrary, in 2016 it had regular seasonal pattern with peak emissions in July, which were four times higher than in 2015. WTL was not the limiting factor for CH4 emission from oligotrophic hollows, because even in the driest ones it was only 10 cm below the surface. Thus, the difference between peak emissions in 2015 and 2016 was mainly related to the temperature, which was considerably higher in 2016. Average methane flux rates from waterlogged hollows were 2.19 mgCH4/m2/h in 2016 and 4.07 mgCH4/m2/h in 2015. Seasonal dynamic had prominent shape in both years, however, peak emissions were observed in different months. Overall, patterns of emission in these ecosystems had more complicate nature and needs future investigations. Regional methane emission was estimated using new wetland map by Terentieva et al. (2016). Seasonal dynamic data for 2015-16 years gave the regional flux of 161 and 1257 ktCH4/yr for forested bogs and oligotrophic hollows, respectively. Similar values were obtained using not seasonal dynamic but only flux medians for 2015-16 years. However, the usage of old dataset gave only 32 and 841 ktCH4/yr for forested bogs and oligotrophic hollows, respectively. Thus, seasonal dynamics data had lower impact on regional methane emission estimate comparing to interannual variability data. Terentieva, I.E., Glagolev, M.V., Lapshina, E.D., Sabrekov, A.F., Maksyutov, S. Mapping of West Siberian taiga wetland complexes using Landsat imagery: implications for methane emissions // Biogeosciences. 2016. V. 13. № 16. P. 4615-4626.

Seasonality and interannual variability of CH4 fluxes from the eastern Amazon Basin inferred from atmospheric mole fraction profiles.

PubMed

Basso, Luana S; Gatti, Luciana V; Gloor, Manuel; Miller, John B; Domingues, Lucas G; Correia, Caio S C; Borges, Viviane F

2016-01-16

The Amazon Basin is an important region for global CH 4 emissions. It hosts the largest area of humid tropical forests, and around 20% of this area is seasonally flooded. In a warming climate it is possible that CH 4 emissions from the Amazon will increase both as a result of increased temperatures and precipitation. To examine if there are indications of first signs of such changes we present here a 13 year (2000-2013) record of regularly measured vertical CH 4 mole fraction profiles above the eastern Brazilian Amazon, sensitive to fluxes from the region upwind of Santarém (SAN), between SAN and the Atlantic coast. Using a simple mass balance approach, we find substantial CH 4 emissions with an annual average flux of 52.8 ± 6.8 mg CH 4 m -2  d -1 over an area of approximately 1 × 10 6  km 2 . Fluxes are highest in two periods of the year: in the beginning of the wet season and during the dry season. Using a CO:CH 4 emission factor estimated from the profile data, we estimated a contribution of biomass burning of around 15% to the total flux in the dry season, indicating that biogenic emissions dominate the CH 4 flux. This 13 year record shows that CH 4 emissions upwind of SAN varied over the years, with highest emissions in 2008 (around 25% higher than in 2007), mainly during the wet season, representing 19% of the observed global increase in this year.

Evaluation of column-averaged methane in models and TCCON with a focus on the stratosphere

DOE PAGES

Ostler, Andreas; Sussmann, Ralf; Patra, Prabir K.; ...

2016-09-28

The distribution of methane (CH 4) in the stratosphere can be a major driver of spatial variability in the dry-air column-averaged CH 4 mixing ratio (XCH 4), which is being measured increasingly for the assessment of CH 4 surface emissions. Chemistry-transport models (CTMs) therefore need to simulate the tropospheric and stratospheric fractional columns of XCH 4 accurately for estimating surface emissions from XCH 4. Simulations from three CTMs are tested against XCH 4 observations from the Total Carbon Column Network (TCCON). We analyze how the model–TCCON agreement in XCH 4 depends on the model representation of stratospheric CH 4 distributions.more » Model equivalents of TCCON XCH 4 are computed with stratospheric CH 4 fields from both the model simulations and from satellite-based CH 4 distributions from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) and MIPAS CH 4 fields adjusted to ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) observations. Using MIPAS-based stratospheric CH 4 fields in place of model simulations improves the model–TCCON XCH 4 agreement for all models. For the Atmospheric Chemistry Transport Model (ACTM) the average XCH 4 bias is significantly reduced from 38.1 to 13.7 ppb, whereas small improvements are found for the models TM5 (Transport Model, version 5; from 8.7 to 4.3 ppb) and LMDz (Laboratoire de Météorologie Dynamique model with zooming capability; from 6.8 to 4.3 ppb). Replacing model simulations with MIPAS stratospheric CH 4 fields adjusted to ACE-FTS reduces the average XCH 4 bias for ACTM (3.3 ppb), but increases the average XCH 4 bias for TM5 (10.8 ppb) and LMDz (20.0 ppb). These findings imply that model errors in simulating stratospheric CH 4 contribute to model biases. Current satellite instruments cannot definitively measure stratospheric CH 4 to sufficient accuracy to eliminate these biases. Applying transport diagnostics to the models indicates that model-to-model differences in the simulation of stratospheric transport, notably the age of stratospheric air, can largely explain the inter-model spread in stratospheric CH 4 and, hence, its contribution to XCH 4. Furthermore, it would be worthwhile to analyze how individual model components (e.g., physical parameterization, meteorological data sets, model horizontal/vertical resolution) impact the simulation of stratospheric CH 4 and XCH 4.« less

Evaluation of column-averaged methane in models and TCCON with a focus on the stratosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ostler, Andreas; Sussmann, Ralf; Patra, Prabir K.

The distribution of methane (CH 4) in the stratosphere can be a major driver of spatial variability in the dry-air column-averaged CH 4 mixing ratio (XCH 4), which is being measured increasingly for the assessment of CH 4 surface emissions. Chemistry-transport models (CTMs) therefore need to simulate the tropospheric and stratospheric fractional columns of XCH 4 accurately for estimating surface emissions from XCH 4. Simulations from three CTMs are tested against XCH 4 observations from the Total Carbon Column Network (TCCON). We analyze how the model–TCCON agreement in XCH 4 depends on the model representation of stratospheric CH 4 distributions.more » Model equivalents of TCCON XCH 4 are computed with stratospheric CH 4 fields from both the model simulations and from satellite-based CH 4 distributions from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) and MIPAS CH 4 fields adjusted to ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) observations. Using MIPAS-based stratospheric CH 4 fields in place of model simulations improves the model–TCCON XCH 4 agreement for all models. For the Atmospheric Chemistry Transport Model (ACTM) the average XCH 4 bias is significantly reduced from 38.1 to 13.7 ppb, whereas small improvements are found for the models TM5 (Transport Model, version 5; from 8.7 to 4.3 ppb) and LMDz (Laboratoire de Météorologie Dynamique model with zooming capability; from 6.8 to 4.3 ppb). Replacing model simulations with MIPAS stratospheric CH 4 fields adjusted to ACE-FTS reduces the average XCH 4 bias for ACTM (3.3 ppb), but increases the average XCH 4 bias for TM5 (10.8 ppb) and LMDz (20.0 ppb). These findings imply that model errors in simulating stratospheric CH 4 contribute to model biases. Current satellite instruments cannot definitively measure stratospheric CH 4 to sufficient accuracy to eliminate these biases. Applying transport diagnostics to the models indicates that model-to-model differences in the simulation of stratospheric transport, notably the age of stratospheric air, can largely explain the inter-model spread in stratospheric CH 4 and, hence, its contribution to XCH 4. Furthermore, it would be worthwhile to analyze how individual model components (e.g., physical parameterization, meteorological data sets, model horizontal/vertical resolution) impact the simulation of stratospheric CH 4 and XCH 4.« less

Evaluation of column-averaged methane in models and TCCON with a focus on the stratosphere

NASA Astrophysics Data System (ADS)

Ostler, Andreas; Sussmann, Ralf; Patra, Prabir K.; Houweling, Sander; De Bruine, Marko; Stiller, Gabriele P.; Haenel, Florian J.; Plieninger, Johannes; Bousquet, Philippe; Yin, Yi; Saunois, Marielle; Walker, Kaley A.; Deutscher, Nicholas M.; Griffith, David W. T.; Blumenstock, Thomas; Hase, Frank; Warneke, Thorsten; Wang, Zhiting; Kivi, Rigel; Robinson, John

2016-09-01

The distribution of methane (CH4) in the stratosphere can be a major driver of spatial variability in the dry-air column-averaged CH4 mixing ratio (XCH4), which is being measured increasingly for the assessment of CH4 surface emissions. Chemistry-transport models (CTMs) therefore need to simulate the tropospheric and stratospheric fractional columns of XCH4 accurately for estimating surface emissions from XCH4. Simulations from three CTMs are tested against XCH4 observations from the Total Carbon Column Network (TCCON). We analyze how the model-TCCON agreement in XCH4 depends on the model representation of stratospheric CH4 distributions. Model equivalents of TCCON XCH4 are computed with stratospheric CH4 fields from both the model simulations and from satellite-based CH4 distributions from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) and MIPAS CH4 fields adjusted to ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer) observations. Using MIPAS-based stratospheric CH4 fields in place of model simulations improves the model-TCCON XCH4 agreement for all models. For the Atmospheric Chemistry Transport Model (ACTM) the average XCH4 bias is significantly reduced from 38.1 to 13.7 ppb, whereas small improvements are found for the models TM5 (Transport Model, version 5; from 8.7 to 4.3 ppb) and LMDz (Laboratoire de Météorologie Dynamique model with zooming capability; from 6.8 to 4.3 ppb). Replacing model simulations with MIPAS stratospheric CH4 fields adjusted to ACE-FTS reduces the average XCH4 bias for ACTM (3.3 ppb), but increases the average XCH4 bias for TM5 (10.8 ppb) and LMDz (20.0 ppb). These findings imply that model errors in simulating stratospheric CH4 contribute to model biases. Current satellite instruments cannot definitively measure stratospheric CH4 to sufficient accuracy to eliminate these biases. Applying transport diagnostics to the models indicates that model-to-model differences in the simulation of stratospheric transport, notably the age of stratospheric air, can largely explain the inter-model spread in stratospheric CH4 and, hence, its contribution to XCH4. Therefore, it would be worthwhile to analyze how individual model components (e.g., physical parameterization, meteorological data sets, model horizontal/vertical resolution) impact the simulation of stratospheric CH4 and XCH4.

Greenhouse gas emissions from oilfield-produced water in Shengli Oilfield, Eastern China.

PubMed

Yang, Shuang; Yang, Wei; Chen, Guojun; Fang, Xuan; Lv, Chengfu; Zhong, Jiaai; Xue, Lianhua

2016-08-01

Greenhouse gas (GHG) emissions from oil and gas systems are an important component of the GHG emission inventory. To assess the carbon emissions from oilfield-produced water under atmospheric conditions correctly, in situ detection and simulation experiments were developed to study the natural release of GHG into the atmosphere in the Shengli Oilfield, the second largest oilfield in China. The results showed that methane (CH4) and carbon dioxide (CO2) were the primary gases released naturally from the oilfield-produced water. The atmospheric temperature and release time played important roles in determining the CH4 and CO2 emissions under atmospheric conditions. Higher temperatures enhanced the carbon emissions. The emissions of both CH4 and CO2 from oilfield-produced water were highest at 27°C and lowest at 3°C. The bulk of CH4 and CO2 was released from the oilfield-produced water during the first release period, 0-2hr, for each temperature, with a maximum average emission rate of 0.415gCH4/(m(3)·hr) and 3.934gCO2/(m(3)·hr), respectively. Then the carbon emissions at other time periods gradually decreased with the extension of time. The higher solubility of CO2 in water than CH4 results in a higher emission rate of CH4 than CO2 over the same release duration. The simulation proved that oilfield-produced water is one of the potential emission sources that should be given great attention in oil and gas systems. Copyright © 2016. Published by Elsevier B.V.

Ammonia and greenhouse gas emissions from a modern U.S. swine breeding-gestation-farrowing system

NASA Astrophysics Data System (ADS)

Stinn, John P.; Xin, Hongwei; Shepherd, Timothy A.; Li, Hong; Burns, Robert T.

2014-12-01

Aerial emissions from livestock production continue to be an area of attention and concern for both the potential health and environmental impacts. However, information of gaseous, especially greenhouse gas (GHG), emissions for swine breeding/gestation and farrowing production systems is limited. The purpose of this study was to quantify ammonia (NH3), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) concentrations and emissions from a modern breeding-gestation-farrowing system located in central Iowa, USA. A 4300-sow farm was selected for the extensive field monitoring which employed a Mobile Air Emission Monitoring Unit equipped with state-of-the-art gas analyzers and a data acquisition system. The monitored portion of the farm facility consisted of a deep-pit breeding/early gestation (B/EG) barn (1800 head), a deep-pit late gestation (LG) barn (1800 head), and two shallow-pit (pull-plug) farrowing rooms (40 head per room). A dynamic flux chamber was used to monitor gaseous emissions from the external manure storage for the farrowing rooms. Data were collected for 29 consecutive months (January 2011 through June 2013). Daily indoor NH3, CO2, N2O, and CH4 concentrations (ppm, mean ± SD) were 12.0 (±7.6), 1594 (±797), 0.31 (±0.11), and 28.5 (±9.8), respectively, in the breeding/gestation barns; and 9.7 (±4.1), 1536 (±701), 0.30 (±0.10), and 78.3 (±37), respectively, in the farrowing rooms. Daily emissions per animal unit (AU, 500 kg live weight) were 35.1 g NH3, 7.46 kg CO2, 0.17 g N2O, and 263.4 g CH4 for sows in the B/EG barn; and 28.2 g NH3, 6.50 kg CO2, 0.12 g N2O, and 201.3 g CH4 for sows in the LG barn. The average daily emissions per AU (sow and piglets) of the farrowing rooms during the lactation period (birth to weaning) were: 59.7 g NH3, 16.4 kg CO2, 0.73 g N2O, and 107 g CH4. For the monitored period, the external manure storage had the following average daily emission per m2 surface area: 1.26 g NH3, 137 g CO2, and 94.8 g CH4, which was equivalent to daily emissions per AU in the farrowing rooms of 12.2 g NH3, 1.055 kg CO2, and 867 g CH4. Average daily emissions per AU for the total operation (including house-level and manure storage emissions) were 38.5 g NH3, 8.73 kg CO2 (including 7.3 kg from animal respiration), 0.25 g N2O, and 301 g CH4.

Field-scale simulation of methane emissions from coastal wetlands in China using an improved version of CH4MODwetland.

PubMed

Li, Tingting; Xie, Baohua; Wang, Guocheng; Zhang, Wen; Zhang, Qing; Vesala, Timo; Raivonen, Maarit

2016-07-15

Coastal wetlands are important CH4 sources to the atmosphere. Coastal wetlands account for ~10% of the total area of natural wetlands in China, but the size of this potential CH4 source remains highly uncertain. We introduced the influence of salinity on CH4 production and CH4 diffusion into a biogeophysical model named CH4MODwetland so that it can be used in coastal wetlands. The improved model can generally simulate seasonal CH4 variations from tidal marshes dominated by Phragmites and Scirpus. However, the model underestimated winter CH4 fluxes from tidal marshes in the Yellow River Delta and YanCheng Estuary. It also failed to capture the accurate timing of the CH4 peaks in YanCheng Estuary and ChongMing Island in 2012. The improved model could generally simulate the difference between the annual mean CH4 fluxes from mangrove sites in GuangZhou and HaiKou city under different salinity and water table depth conditions, although fluxes were systematically underestimated in the mangrove site of HaiKou city. Using the improved model, the seasonal CH4 emissions simulated across all of the coastal wetlands ranged from 0.1 to 44.90gm(-2), with an average value of 7.89gm(-2), which is in good agreement with the observed values. The improved model significantly decreased the RMSE and RMD from 424% to 14% and 314% to -2%, respectively, and improved the EF from -18.30 to 0.99. Model sensitivity analysis showed that CH4 emissions were most sensitive to Pox in the tidal marshes and salinity in the mangroves. The results show that previous studies may have overestimated CH4 emissions on a regional or global scale by neglecting the influence of salinity. In general, the CH4MODwetland model can simulate seasonal CH4 emissions from different types of coastal wetlands under various conditions. Further improvements of CH4MODwetland should include the specific characteristics of CH4 processes in mangroves to decrease the uncertainty in estimating regional or global CH4 emissions from natural wetlands. Copyright © 2016 Elsevier B.V. All rights reserved.

Gaseous fluxes from subsurface flow constructed wetlands for wastewater treatment.

PubMed

Mander, Ulo; Lõhmus, Krista; Teiter, Sille; Nurk, Kaspar; Mauring, Tõnu; Augustin, Jürgen

2005-01-01

We measured nitrous oxide (N2O), dinitrogen (N2), and methane (CH4) fluxes in two constructed wetlands (CW) in Estonia using the closed chamber method and the He-O method in the period from October 2000 to March 2003. Emission rates of N2O-N, N2-N and CH4-C from both CWs varied significantly on a both spatial and temporal scale, ranging from 1 to 2,600, 170 to 130,000, and -1.7 to 87,200 microg m(-2) h(-1) respectively. The average flux of N2O from the microsites in the Kodijärve horizontal subsurface flow (HSSF) CW and Kõo hybrid CW ranged from 27 to 370 and from 72 to 500 microg N2O-N m(-2) h(-1), respectively, whereas the average dinitrogen flux from the microsites in the HSSF CW in Kodijärve was 2-3 magnitudes higher than the N2O flux, ranging from 19,500 to 33,300 microg N2-N m(-2) h(-1). The average methane emissions from the microsites in the Kodijärve HSSF CW and the Kõo hybrid CW ranged from 31 to 12,100 and from 950 to 5,750 microg CH4-C m(-2) h(-1), respectively. The highest emission values for all three gases were observed in the warm period. There was a significant relationship between emission rates and water table depth: CH4 and N2 emission increased and N2O emission decreased when the water table did rise. Although the emission of N2O and CH4 from CWs was found to be relatively high, their global warming potential (GWP) in the time horizon of 100 years is not significant, ranging from 4.5 to 16.3 tonnes of CO2 equivalents per ha per year in Kodijärve and from 12.1 to 17.3 t CO2 equivalents ha(-1) yr(-1) in Kõo.

Reservoir water level drawdown as a novel, substantial, and manageable control on methane release to the atmosphere

NASA Astrophysics Data System (ADS)

Harrison, J.; Deemer, B. R.; Birchfield, M. K.

2014-12-01

Reservoirs constitute a globally important source of atmospheric methane (CH4). Although it is reasonably well-established that hydrostatic and barometric pressure can influence rates of CH4 release from lake and tidal sediments, the relationship between water-level manipulation and CH4 release from man-made impoundments has not been quantified or characterized. Furthermore, cross-system controls on CH4 production and release to the atmosphere have not been established. We collected CH4 emission (diffusion and ebullition) data for 8 reservoirs in the U.S. Pacific Northwest that are subject to a range of trophic conditions and water level management regimes. Our aim was to: (1) characterize CH4 emissions from these systems, and (2) quantify effects of water level management and eutrophication on CH4 fluxes. Results indicate very high fluxes, in some cases the highest reported reservoir emission rates, and a strong correspondence between lake level reduction and CH4 emissions, including quantitatively important bursts of CH4 bubbling. In one reservoir, drawdown-associated CH4 fluxes accounted for over 25% of annual CH4 emissions in a period of just 16 days (4% of the year). Average CH4 ebullition rates in a reservoir managed for hydropower peaking were nearly three-fold higher than in a paired upstream reservoir managed to maintain a constant water level (528 mg CH4 m-2 d-1 and 187 mg CH4 m-2 d-1 respectively). Highest gas fluxes were observed during the water level drawdown component of the hydropower peaking cycle (14.3 g CH4 m-2 d-1). In addition we observe a strong, positive relationship between eutrophication (as indicated by surface Chl a concentrations) and CH4 production (r2 = 0.88; P<0.001) and between eutrophication and the sensitivity of CH4 emissions to drawdown (r2 = 0.84; P<0.001). This work suggests that manipulation of water levels can significantly affect CH4 emissions from reservoirs to the atmosphere, and that sampling programs that miss drawdown periods may substantially underestimate CH4 fluxes. It also suggests that controlling nutrient loading may reduce greenhouse gas fluxes from surface waters to the atmosphere.

Methane emissions associated with the conversion of marshland to cropland and climate change on the Sanjiang Plain of northeast China from 1950 to 2100

NASA Astrophysics Data System (ADS)

Li, T.; Huang, Y.; Zhang, W.; Yu, Y.-Q.

2012-12-01

Wetland loss and climate change are known to alter regional and global methane (CH4) budgets. Over the last six decades, an extensive area of marshland has been converted to cropland on the Sanjiang Plain in northeast China, and a significant increase in air temperature has also been observed there, while the impacts on regional CH4 budgets remain uncertain. Through model simulation, we estimated the changes in CH4 emissions associated with the conversion of marshland to cropland and climate change in this area. Model simulations indicated a significant reduction of 1.1 Tg yr-1 (0.7-1.8 Tg yr-1) from the 1950s to the 2000s in regional CH4 emissions. The cumulative reduction of CH4 from 1960 to 2009 was estimated to be ~36 Tg (24-57 Tg) relative to the 1950s, and marshland conversion and the climate contributed 86% and 14% of this change, respectively. Interannual variation in precipitation (linear trend with P > 0.2) contributed to yearly fluctuations in CH4 emissions, but the relatively lower amount of precipitation over the period 1960-2009 (47 mm yr-1 lower on average than in the 1950s) contributed ~91% of the reduction in the area-weighted CH4 flux. Global warming at a rate of 0.3 ° per decade (P < 0.001) has increased CH4 emissions significantly since the 1990s. Relative to the mean of the 1950s, the warming-induced increase in the CH4 flux has averaged 19 kg ha-1 yr-1 over the last two decades. In the RCP (Representative Concentration Pathway) 2.6, RCP 4.5, RCP 6.0 and RCP 8.5 scenarios of the fifth IPCC assessment report (AR5), the CH4 fluxes are predicted to increase by 36%, 52%, 78% and 95%, respectively, by the 2080s compared to 1961-1990 in response to climate warming and wetting.

Mapping urban pipeline leaks: methane leaks across Boston.

PubMed

Phillips, Nathan G; Ackley, Robert; Crosson, Eric R; Down, Adrian; Hutyra, Lucy R; Brondfield, Max; Karr, Jonathan D; Zhao, Kaiguang; Jackson, Robert B

2013-02-01

Natural gas is the largest source of anthropogenic emissions of methane (CH(4)) in the United States. To assess pipeline emissions across a major city, we mapped CH(4) leaks across all 785 road miles in the city of Boston using a cavity-ring-down mobile CH(4) analyzer. We identified 3356 CH(4) leaks with concentrations exceeding up to 15 times the global background level. Separately, we measured δ(13)CH(4) isotopic signatures from a subset of these leaks. The δ(13)CH(4) signatures (mean = -42.8‰ ± 1.3‰ s.e.; n = 32) strongly indicate a fossil fuel source rather than a biogenic source for most of the leaks; natural gas sampled across the city had average δ(13)CH(4) values of -36.8‰ (± 0.7‰ s.e., n = 10), whereas CH(4) collected from landfill sites, wetlands, and sewer systems had δ(13)CH(4) signatures ~20‰ lighter (μ = -57.8‰, ± 1.6‰ s.e., n = 8). Repairing leaky natural gas distribution systems will reduce greenhouse gas emissions, increase consumer health and safety, and save money. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

PubMed

Tang, Haoye; Liu, Gang; Zhu, Jianguo; Kobayashi, Kazuhiko

2015-04-01

We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem. © 2014 John Wiley & Sons Ltd.

Quantification of methane sources in the Athabasca Oil Sands Region of Alberta by aircraft mass balance

NASA Astrophysics Data System (ADS)

Baray, Sabour; Darlington, Andrea; Gordon, Mark; Hayden, Katherine L.; Leithead, Amy; Li, Shao-Meng; Liu, Peter S. K.; Mittermeier, Richard L.; Moussa, Samar G.; O'Brien, Jason; Staebler, Ralph; Wolde, Mengistu; Worthy, Doug; McLaren, Robert

2018-05-01

Aircraft-based measurements of methane (CH4) and other air pollutants in the Athabasca Oil Sands Region (AOSR) were made during a summer intensive field campaign between 13 August and 7 September 2013 in support of the Joint Canada-Alberta Implementation Plan for Oil Sands Monitoring. Chemical signatures were used to identify CH4 sources from tailings ponds (BTEX VOCs), open pit surface mines (NOy and rBC) and elevated plumes from bitumen upgrading facilities (SO2 and NOy). Emission rates of CH4 were determined for the five primary surface mining facilities in the region using two mass-balance methods. Emission rates from source categories within each facility were estimated when plumes from the sources were spatially separable. Tailings ponds accounted for 45 % of total CH4 emissions measured from the major surface mining facilities in the region, while emissions from operations in the open pit mines accounted for ˜ 50 %. The average open pit surface mining emission rates ranged from 1.2 to 2.8 t of CH4 h-1 for different facilities in the AOSR. Amongst the 19 tailings ponds, Mildred Lake Settling Basin, the oldest pond in the region, was found to be responsible for the majority of tailings ponds emissions of CH4 ( > 70 %). The sum of measured emission rates of CH4 from the five major facilities, 19.2 ± 1.1 t CH4 h-1, was similar to a single mass-balance determination of CH4 from all major sources in the AOSR determined from a single flight downwind of the facilities, 23.7 ± 3.7 t CH4 h-1. The measured hourly CH4 emission rate from all facilities in the AOSR is 48 ± 8 % higher than that extracted for 2013 from the Canadian Greenhouse Gas Reporting Program, a legislated facility-reported emissions inventory, converted to hourly units. The measured emissions correspond to an emissions rate of 0.17 ± 0.01 Tg CH4 yr-1 if the emissions are assumed as temporally constant, which is an uncertain assumption. The emission rates reported here are relevant for the summer season. In the future, effort should be devoted to measurements in different seasons to further our understanding of the seasonal parameters impacting fugitive emissions of CH4 and to allow for better estimates of annual emissions and year-to-year variability.

Global methane emission estimates for 2000-2012 from CarbonTracker Europe-CH4 v1.0

NASA Astrophysics Data System (ADS)

Tsuruta, Aki; Aalto, Tuula; Backman, Leif; Hakkarainen, Janne; van der Laan-Luijkx, Ingrid T.; Krol, Maarten C.; Spahni, Renato; Houweling, Sander; Laine, Marko; Dlugokencky, Ed; Gomez-Pelaez, Angel J.; van der Schoot, Marcel; Langenfelds, Ray; Ellul, Raymond; Arduini, Jgor; Apadula, Francesco; Gerbig, Christoph; Feist, Dietrich G.; Kivi, Rigel; Yoshida, Yukio; Peters, Wouter

2017-03-01

We present a global distribution of surface methane (CH4) emission estimates for 2000-2012 derived using the CarbonTracker Europe-CH4 (CTE-CH4) data assimilation system. In CTE-CH4, anthropogenic and biospheric CH4 emissions are simultaneously estimated based on constraints of global atmospheric in situ CH4 observations. The system was configured to either estimate only anthropogenic or biospheric sources per region, or to estimate both categories simultaneously. The latter increased the number of optimizable parameters from 62 to 78. In addition, the differences between two numerical schemes available to perform turbulent vertical mixing in the atmospheric transport model TM5 were examined. Together, the system configurations encompass important axes of uncertainty in inversions and allow us to examine the robustness of the flux estimates. The posterior emission estimates are further evaluated by comparing simulated atmospheric CH4 to surface in situ observations, vertical profiles of CH4 made by aircraft, remotely sensed dry-air total column-averaged mole fraction (XCH4) from the Total Carbon Column Observing Network (TCCON), and XCH4 from the Greenhouse gases Observing Satellite (GOSAT). The evaluation with non-assimilated observations shows that posterior XCH4 is better matched with the retrievals when the vertical mixing scheme with faster interhemispheric exchange is used. Estimated posterior mean total global emissions during 2000-2012 are 516 ± 51 Tg CH4 yr-1, with an increase of 18 Tg CH4 yr-1 from 2000-2006 to 2007-2012. The increase is mainly driven by an increase in emissions from South American temperate, Asian temperate and Asian tropical TransCom regions. In addition, the increase is hardly sensitive to different model configurations ( < 2 Tg CH4 yr-1 difference), and much smaller than suggested by EDGAR v4.2 FT2010 inventory (33 Tg CH4 yr-1), which was used for prior anthropogenic emission estimates. The result is in good agreement with other published estimates from inverse modelling studies (16-20 Tg CH4 yr-1). However, this study could not conclusively separate a small trend in biospheric emissions (-5 to +6.9 Tg CH4 yr-1) from the much larger trend in anthropogenic emissions (15-27 Tg CH4 yr-1). Finally, we find that the global and North American CH4 balance could be closed over this time period without the previously suggested need to strongly increase anthropogenic CH4 emissions in the United States. With further developments, especially on the treatment of the atmospheric CH4 sink, we expect the data assimilation system presented here will be able to contribute to the ongoing interpretation of changes in this important greenhouse gas budget.

Airborne observations of methane emissions from rice cultivation in the Sacramento Valley of California

NASA Astrophysics Data System (ADS)

Peischl, J.; Ryerson, T. B.; Holloway, J. S.; Trainer, M.; Andrews, A. E.; Atlas, E. L.; Blake, D. R.; Daube, B. C.; Dlugokencky, E. J.; Fischer, M. L.; Goldstein, A. H.; Guha, A.; Karl, T.; Kofler, J.; Kosciuch, E.; Misztal, P. K.; Perring, A. E.; Pollack, I. B.; Santoni, G. W.; Schwarz, J. P.; Spackman, J. R.; Wofsy, S. C.; Parrish, D. D.

2012-12-01

Airborne measurements of methane (CH4) and carbon dioxide (CO2) were taken over the rice growing region of California's Sacramento Valley in the late spring of 2010 and 2011. From these and ancillary measurements, we show that CH4 mixing ratios were higher in the planetary boundary layer above the Sacramento Valley during the rice growing season than they were before it, which we attribute to emissions from rice paddies. We derive daytime emission fluxes of CH4 between 0.6 and 2.0% of the CO2 taken up by photosynthesis on a per carbon, or mole to mole, basis. We also use a mixing model to determine an average CH4/CO2 flux ratio of -0.6% for one day early in the growing season of 2010. We conclude the CH4/CO2 flux ratio estimates from a single rice field in a previous study are representative of rice fields in the Sacramento Valley. If generally true, the California Air Resources Board (CARB) greenhouse gas inventory emission rate of 2.7 × 1010 g CH4/yr is approximately three times lower than the range of probable CH4 emissions (7.8-9.3 × 1010 g CH4/yr) from rice cultivation derived in this study. We attribute this difference to decreased burning of the residual rice crop since 1991, which leads to an increase in CH4 emissions from rice paddies in succeeding years, but which is not accounted for in the CARB inventory.

Evaluation of seasonal changes in methane flux in a wetland ecosystem using the Closed Geosphere Experiment Facility

NASA Astrophysics Data System (ADS)

Suzuki, S.; Inubushi, K.; Yokozawa, M.; Hara, T.; Nishidate, K.; Tsuga, S.; Tako, Y.; Nakamura, Y.

2009-04-01

To estimate CH4 emission from a wetland ecosystem to the atmosphere, seasonal change in CH4 flux was measured continuously in the Closed Geosphere Experiment Facility (CGEF). Plant-mediated transport is one of the important pathways for CH4 emission from Phragmites australis-dominated vegetation because most CH4 emission occurs through P. australis plant. The CGEF is equipped with a Geosphere Module (GM) and a Geosphere Material Circulation (GMC) system. The size of the GM is 5.8 m Ã- 8.7 m in ground area with an average height of 11.9 m, including the soil depth of 3.1 m. A wetland ecosystem dominated by P. australis was introduced into the GM. The CGEF can control air temperature and CO2 concentration in the GM automatically. Hourly CH4 flux from the wetland ecosystem can be calculated easily by measuring continuously the changes in CH4 concentration in air, air temperature and pressure in the GM. The method showed that monthly CH4 flux varied from 0.39 to 1.11 g C m-2 month-1 from April to November and the CH4 emission for the plant growing season (eight months) was 5.64 g C m-2. The CGEF has an advantage in studying total CH4 emission from soil to the atmosphere through plant-mediated transport, diffusion and ebullition because of the large size of the GM.

Integral emission factors for methane determined using urban flux measurements and local-scale inverse models

NASA Astrophysics Data System (ADS)

Christen, Andreas; Johnson, Mark; Molodovskaya, Marina; Ketler, Rick; Nesic, Zoran; Crawford, Ben; Giometto, Marco; van der Laan, Mike

2013-04-01

The most important long-lived greenhouse gas (LLGHG) emitted during combustion of fuels is carbon dioxide (CO2), however also traces of the LLGHGs methane (CH4) and nitrous oxide (N2O) are released, the quantities of which depend largely on the conditions of the combustion process. Emission factors determine the mass of LLGHGs emitted per energy used (or kilometre driven for cars) and are key inputs for bottom-up emission modelling. Emission factors for CH4 are typically determined in the laboratory or on a test stand for a given combustion system using a small number of samples (vehicles, furnaces), yet associated with larger uncertainties when scaled to entire fleets. We propose an alternative, different approach - Can integrated emission factors be independently determined using direct micrometeorological flux measurements over an urban surface? If so, do emission factors determined from flux measurements (top-down) agree with up-scaled emission factors of relevant combustion systems (heating, vehicles) in the source area of the flux measurement? Direct flux measurements of CH4 were carried out between February and May, 2012 over a relatively densely populated, urban surface in Vancouver, Canada by means of eddy covariance (EC). The EC-system consisted of an ultrasonic anemometer (CSAT-3, Campbell Scientific Inc.) and two open-path infrared gas analyzers (Li7500 and Li7700, Licor Inc.) on a tower at 30m above the surface. The source area of the EC system is characterised by a relative homogeneous morphometry (5.3m average building height), but spatially and temporally varying emission sources, including two major intersecting arterial roads (70.000 cars drive through the 50% source area per day) and seasonal heating in predominantly single-family houses (natural gas). An inverse dispersion model (turbulent source area model), validated against large eddy simulations (LES) of the urban roughness sublayer, allows the determination of the spatial area that contributes to each measurement interval (30 min), which varies with wind direction and stability. A detailed geographic information system of the urban surface combined with traffic counts and building energy models makes it possible to statistically relate fluxes to vehicle density (km driven) and buildings (gas heated volume) - and ultimately quantify the contribution of space heating, transport sector and fugitive emissions to the total emitted CH4 from an urban environment. The measured fluxes of CH4 over the selected urban environment averaged to 22.8 mg CH4 m-2 day-1 during the study period. Compared with the simultaneously measured CO2 emissions, the contribution of CH4, however, accounts for only about 3% of the total LLGHG emissions from this particular urban surface. Traffic contributed 8.8 mg CH4 m-2 day-1, equivalent to 39% of the total CH4 flux. The determined emission factor for the typical fleet composition is 0.062 g CH4 per km driven which is higher than upscaled fleet emission factors (EPA) by a factor of two. This discrepancy can be partially explained through the slower city traffic with frequent idling (traffic congestion), fleet composition and cold starts. Emissions of CH4 by domestic space heating (55% of the total CH4 flux or 12.7 mg CH4 m-2 day-1) are also higher than estimated from upscaled emission factors. There is no evidence of substantial unknown sources such as soil processes, combustion of wood, and leakages from gas distribution pipes (residual: 6% or 1.3 mg CH4 m-2 day-1). The presented study is among the first direct measurements of CH4 emissions over an urban surface and demonstrates that flux measurements of greenhouse gases can be used to determine sources and emission factors in complex urban situations.

CH{sub 4} and N{sub 2}O emissions from China’s beef feedlots with ad libitum and restricted feeding in fall and spring seasons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Zhi; Liao, Wenhua; Yang, Yuanyuan

Accurately quantifying methane (CH{sub 4}) and nitrous oxide (N{sub 2}O) emissions from beef operations in China is necessary to evaluate the contribution of beef cattle to greenhouse gas budgets at the national and global level. Methane and N{sub 2}O emissions from two intensive beef feedlots in the North China Plain, one with a restricted feeding strategy and high manure collection frequency and the other with an ad libitum feeding strategy and low manure collection frequency, were quantified in the fall and spring seasons using an inverse dispersion technique. The diel pattern of CH{sub 4} from the beef feedlot with anmore » ad libitum feed strategy (single peak during a day) differed from that under a restricted feeding condition (multiple peaks during a day), but little difference in the diel pattern of N{sub 2}O emissions between two feeding strategies was observed. The two-season average CH{sub 4} emission rates of the two intensive feedlots were 230 and 198 g CH{sub 4} animal{sup −1} d{sup −1} and accounted for 6.7% and 6.8% of the gross energy intake, respectively, indicating little impact of the feeding strategy and manure collection frequency on the CH{sub 4} conversion factor at the feedlot level. However, the average N{sub 2}O emission rates (21.2 g N{sub 2}O animal{sup −1} d{sup −1}) and conversion factor (8.5%) of the feedlot with low manure collection frequency were approximately 131% and 174% greater, respectively, than the feedlot under high frequency conditions, which had a N{sub 2}O emission rate and conversion factor of 9.2 g N{sub 2}O animal{sup −1} d{sup −1} and 3.1%, respectively, indicating that increasing manure collection frequency played an important role in reducing N{sub 2}O emissions from beef feedlots. In addition, comparison indicated that China’s beef and dairy cattle in feedlots appeared to have similar CH{sub 4} conversion factors. - Highlights: • CH{sub 4} and N{sub 2}O emissions from China’s beef feedlots were provided in the first time. • Feeding strategies determined the diurnal pattern of feedlot CH{sub 4} emission. • Frequency of manure collection played an important role in N{sub 2}O from feedlots.« less

Methyl Chloride Emission from Tropical Plants

NASA Astrophysics Data System (ADS)

Yokouchi, Y.; Ikeda, M.; Ikeda, M.; Inuzuka, Y.; Yukawa, T.

2001-12-01

We studied CH3Cl emissions from tropical plants in Tropical Rainforest Glasshouse (25 m x 20 m x 10-24 m high) in Tsukuba Botanical Gardens, where more than 200 representative species from lowland tropical forests of Southeast Asia grow. CH3Cl concentrations were always higher in the glasshouse than outside and increased significantly when the windows were closed. The fluxes of CH3Cl from the tropical rainforest system in the glasshouse were calculated from the averages of their accumulation rates when the windows were closed (average; 142 pptv”h-1) with the dimension of the glasshouse. Emission rates per unit area for CH3Cl was 5.4 mg m-2 h-1. In order to determine which of the plants or whether the soil is responsible for the increase of CH3Cl, flux measurements were done by using an enclosure method. The soil was found to take up CH3Cl at a small rate. On the other hand, some plants from the Marattiaceae, Cyatheaceae (tree fern), Dicksoniaceae, and Dipterocarpaceae families were found to significantly emit CH3Cl. The first three families are ferns commonly growing in tropical forests, and Dipterocarpaceae species are dominant in the tropical rainforests of Southeast Asia. The average CH3Cl emission rate from the 9 plants in these families was around 0.5 mg (g dry leaf)-1”h-1. As for Cyatheaceae, we conducted a flux measurement from Cyathea lepifera E.Copel. in a subtropical forest in Okinawa and detected high emissions of CH3Cl amounting to 1.1 mg (g dry leaf)-1”h-1. Strong emissions of CH3Cl from tropical forests raises questions about the trends of chlorine compounds in the future and in the past.

Seasonality and interannual variability of CH4 fluxes from the eastern Amazon Basin inferred from atmospheric mole fraction profiles

PubMed Central

Gatti, Luciana V.; Gloor, Manuel; Miller, John B.; Domingues, Lucas G.; Correia, Caio S. C.; Borges, Viviane F.

2016-01-01

Abstract The Amazon Basin is an important region for global CH4 emissions. It hosts the largest area of humid tropical forests, and around 20% of this area is seasonally flooded. In a warming climate it is possible that CH4 emissions from the Amazon will increase both as a result of increased temperatures and precipitation. To examine if there are indications of first signs of such changes we present here a 13 year (2000–2013) record of regularly measured vertical CH4 mole fraction profiles above the eastern Brazilian Amazon, sensitive to fluxes from the region upwind of Santarém (SAN), between SAN and the Atlantic coast. Using a simple mass balance approach, we find substantial CH4 emissions with an annual average flux of 52.8 ± 6.8 mg CH4 m−2 d−1 over an area of approximately 1 × 106 km2. Fluxes are highest in two periods of the year: in the beginning of the wet season and during the dry season. Using a CO:CH4 emission factor estimated from the profile data, we estimated a contribution of biomass burning of around 15% to the total flux in the dry season, indicating that biogenic emissions dominate the CH4 flux. This 13 year record shows that CH4 emissions upwind of SAN varied over the years, with highest emissions in 2008 (around 25% higher than in 2007), mainly during the wet season, representing 19% of the observed global increase in this year. PMID:27642546

The impact of a pulsing groundwater table on greenhouse gas emissions in riparian grey alder stands.

PubMed

Mander, Ülo; Maddison, Martin; Soosaar, Kaido; Teemusk, Alar; Kanal, Arno; Uri, Veiko; Truu, Jaak

2015-02-01

Floods control greenhouse gas (GHG) emissions in floodplains; however, there is a lack of data on the impact of short-term events on emissions. We studied the short-term effect of changing groundwater (GW) depth on the emission of (GHG) carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) in two riparian grey alder (Alnus incana) stands of different age in Kambja, southern Estonia, using the opaque static chamber (five replicates in each site) and gas chromatography methods. The average carbon and total nitrogen content in the soil of the old alder (OA) stand was significantly higher than in the young alder (YA) stand. In both stands, one part was chosen for water table manipulation (Manip) and another remained unchanged with a stable and deeper GW table. Groundwater table manipulation (flooding) significantly increases CH4 emission (average: YA-Dry 468, YA-Manip 8,374, OA-Dry 468, OA-Manip 4,187 μg C m(-2) h(-1)) and decreases both CO2 (average: OA-Dry 138, OA-Manip 80 mg C m(-2) h(-1)) and N2O emissions (average: OA-Dry 23.1, OA-Manip 11.8 μg N m(-2) h(-1)) in OA sites. There was no significant difference in CO2 and CH4 emissions between the OA and YA sites, whereas in OA sites with higher N concentration in the soil, the N2O emission was significantly higher than at the YA sites. The relative CO2 and CH4 emissions (the soil C stock-related share of gaseous losses) were higher in manipulated plots showing the highest values in the YA-Manip plot (0.03 and 0.0030 % C day(-1), respectively). The soil N stock-related N2O emission was very low achieving 0.000019 % N day(-1) in the OA-Dry plot. Methane emission shows a negative correlation with GW, whereas the 20 cm depth is a significant limit below which most of the produced CH4 is oxidized. In terms of CO2 and N2O, the deeper GW table significantly increases emission. In riparian zones of headwater streams, the short-term floods (e.g. those driven by extreme climate events) may significantly enhance methane emission whereas the long-term lowering of the groundwater table is a more important initiator of N2O fluxes from riparian gley soils than flood pulses.

GOSAT Observations of Anthropogenic Emission of Carbon Dioxide and Methane

NASA Astrophysics Data System (ADS)

Janardanan Achari, R.; Maksyutov, S. S.; Oda, T.; Saito, M.; W Kaiser, J.; Ganshin, A.; Matsunaga, T.; Yoshida, Y.; Yokota, T.

2016-12-01

Carbon dioxide (CO2) and methane (CH4) are the most important greenhouse gases in terms of radiative forcing. Anthropogenic activities such as combustion of fossil fuel (for CO2) and gas leakage, animal agriculture, rice cultivation and landfill emissions (CH4), are considered to be major sources of those emissions. Still, emission data usually depend on national emission reports, which are seldom evaluated independently. Here we present a method for delineating anthropogenic contribution to global atmospheric CO2 (2009-2014) and CH4 (2009-2012) fields using GOSAT observations of column-average dry air mole fractions (XCO2 and XCH4) and atmospheric transport model simulations using high-resolution emission inventories. The CO2 and CH4 concentration enhancement due to anthropogenic activities, are estimated with the transport model at all GOSAT observation locations using high-resolution emission inventories (ODIAC for CO2 and EDGAR for CH4). Based on this estimate, using a threshold value, the observations are classified into two categories: data influenced by the anthropogenic sources and those not including them. To extract concentration enhancements due to the anthropogenic emissions, we define a clean background (the averaged values for the data free from contamination) in 10°×10° regions over the globe and are subtracted from the individual observational data including the anthropogenic contamination. Thus the anomalies contain contributions from anthropogenic sources. These anomalies are binned and analyzed for continental scale regions and countries. For CO2, we have found global and regional linear relationships between model and observed anomalies especially for Eurasia and North America. The analysis for East Asian region showed a systematic bias that is comparable in magnitude to the reported uncertainties in emission inventories in that region. In the case of CH4, we also found a good match between inventory-based estimates and GOSAT observations for continental regions and large countries. In ideal case, the regression slope between modeled and observed anomalies can be a correction factor for the emission inventory. If sufficient number of satellite observations is available, this method will be a useful tool for monitoring greenhouse gas emissions.

Eddy covariance measurements of greenhouse gases from a restored and rewetted raised bog ecosystem.

NASA Astrophysics Data System (ADS)

Lee, S. C.; Christen, A.; Black, T. A.; Johnson, M. S.; Ketler, R.; Nesic, Z.; Merkens, M.

2015-12-01

Wetland ecosystems play a significant role in the global carbon (C) cycle. Wetlands act as a major long-term storage of carbon by sequestrating carbon-dioxide (CO2) from the atmosphere. Meanwhile, they can emit significant amounts of methane (CH4) due to anaerobic microbial decomposition. The Burns Bog Ecological Conservancy Area (BBECA) is recognized as one of Canada's largest undeveloped natural areas retained within an urban area. Historically, it has been substantially reduced in size and degraded by peat mining and agriculture. Since 2005, the bog has been declared a conservancy area, and the restoration efforts in BBECA focus on rewetting the disturbed ecosystems to promote a transition back to a raised bog. A pilot study measured CH4, CO2 and N2O exchanges in 2014 and concluded to monitor CO2, CH4 fluxes continuously. From the perspective of greenhouse gas (GHG) emissions, CO2 sequestered in bog needs to be protected and additional CO2 and CH4 emissions due to land-cover change need to be reduced by wise management. In this study, we measured the growing-season (June-September) fluxes of CO2 and CH4 exchange using eddy covariance (EC). A floating platform with an EC system for both CO2 (closed-path) and CH4 (open-path) began operation in June 2015. During the growing-season, gross ecosystem photosynthesis (GEP) and ecosystem respiration (Re) averaged 5.87 g C m-2 day-1 and 2.02 g C m-2 day-1, respectively. The magnitude of GEP and Re were lower than in previous studies of pristine northern peatlands. The daily average CH4 emission was 0.99 (±1.14) g C m-2 day-1 and it was higher than in most previous studies. We also characterized how environmental factors affected the seasonal dynamics of these exchanges in this disturbed peatland. Our measurements showed that soil temperature and soil water content were major drivers of seasonal changes of GHG fluxes. The daily average GHG warming potential (GWP) of the emissions in the growing seasons (from CO2 and CH4) totals to 37.09 g CO2e m-2 day-1. CH4 was the significant constributor (99 % of GHG emissions) indicating that GHG exchange due to photosynthesis and respiration was of secondary order. Although oxygen limitation due to the high water table caused by the restoration strategy suppressed the Re it also promoted substantial CH4 formation under anoxic conditions.

Analyzing Source Apportioned Methane in Northern California During DISCOVER-AQ-CA Using Airborne Measurements and Model Simulations

NASA Technical Reports Server (NTRS)

Johnson, Matthew S.

2014-01-01

This study analyzes source apportioned methane (CH4) emissions and atmospheric concentrations in northern California during the Discover-AQ-CA field campaign using airborne measurement data and model simulations. Source apportioned CH4 emissions from the Emissions Database for Global Atmospheric Research (EDGAR) version 4.2 were applied in the 3-D chemical transport model GEOS-Chem and analyzed using airborne measurements taken as part of the Alpha Jet Atmospheric eXperiment over the San Francisco Bay Area (SFBA) and northern San Joaquin Valley (SJV). During the time period of the Discover-AQ-CA field campaign EDGAR inventory CH4 emissions were 5.30 Gg/day (Gg 1.0 109 grams) (equating to 1.9 103 Gg/yr) for all of California. According to EDGAR, the SFBA and northern SJV region contributes 30 of total emissions from California. Source apportionment analysis during this study shows that CH4 concentrations over this area of northern California are largely influenced by global emissions from wetlands and local/global emissions from gas and oil production and distribution, waste treatment processes, and livestock management. Model simulations, using EDGAR emissions, suggest that the model under-estimates CH4 concentrations in northern California (average normalized mean bias (NMB) -5 and linear regression slope 0.25). The largest negative biases in the model were calculated on days when hot spots of local emission sources were measured and atmospheric CH4 concentrations reached values 3.0 parts per million (model NMB -10). Sensitivity emission studies conducted during this research suggest that local emissions of CH4 from livestock management processes are likely the primary source of the negative model bias. These results indicate that a variety, and larger quantity, of measurement data needs to be obtained and additional research is necessary to better quantify source apportioned CH4 emissions in California and further the understanding of the physical processes controlling them.

Minor methane emissions from an Alpine hydropower reservoir based on monitoring of diel and seasonal variability.

PubMed

Sollberger, Sébastien; Wehrli, Bernhard; Schubert, Carsten J; DelSontro, Tonya; Eugster, Werner

2017-10-18

We monitored CH 4 emissions during the ice-free period of an Alpine hydropower reservoir in the Swiss Alps, Lake Klöntal, to investigate mechanisms responsible for CH 4 variability and to estimate overall emissions to the atmosphere. A floating eddy-covariance platform yielded total CH 4 and CO 2 emission rates at high temporal resolution, while hydroacoustic surveys provided no indication of CH 4 ebullition. Higher CH 4 fluxes (2.9 ± 0.1 mg CH 4 per m 2 per day) occurred during the day when surface water temperatures were warmer and wind speeds higher than at night. Piston velocity estimates (k 600 ) showed an upper limit at high wind speeds that may be more generally valid also for other lakes and reservoirs with limited CH 4 dissolved in the water body: above 2.0 m s -1 a further increase in wind speed did not lead to higher CH 4 fluxes, because under such conditions it is not the turbulent mixing and transport that limits effluxes, but the resupply of CH 4 to the lake surface. Increasing CH 4 fluxes during the warm season showed a clear spatial gradient once the reservoir started to fill up and flood additional surface area. The warm period contributed 27% of the total CH 4 emissions (2.6 t CH 4 per year) estimated for the full year and CH 4 accounted for 63% of carbonic greenhouse gas emissions. Overall, the average CH 4 emissions (1.7 to 2.2 mg CH 4 per m 2 per day determined independently from surface water samplings and eddy covariance, respectively) were small compared to most tropical and some temperate reservoirs. The resulting greenhouse gas (GHG) emissions in CO 2 -equivalents revealed that electricity produced in the Lake Klöntal power plant was relatively climate-friendly with a low GHG-to-power output ratio of 1.24 kg CO 2,eq per MW h compared to 6.5 and 8.1 kg CO 2,eq per MW h associated with the operation of solar photovoltaics and wind energy, respectively, or about 980 kg CO 2,eq per MW h for coal-fired power plants.

WRF-Chem simulations in the Amazon region during wet and dry season transitions: evaluation of methane models and wetland inundation maps

NASA Astrophysics Data System (ADS)

Beck, V.; Gerbig, C.; Koch, T.; Bela, M. M.; Longo, K. M.; Freitas, S. R.; Kaplan, J. O.; Prigent, C.; Bergamaschi, P.; Heimann, M.

2012-09-01

The Amazon region as a large source of methane (CH4) contributes significantly to the global annual CH4 budget. For the first time in the Amazon region, a forward and inverse modelling framework on regional scale for the purpose of assessing the CH4 budget of the Amazon region is implemented. Here, we present forward simulations of CH4 based on a modified version of the Weather Research and Forecasting model with chemistry that allows for passive tracer transport of CH4, carbon monoxide, and carbon dioxide (WRF-GHG), in combination with two different process-based bottom-up models of CH4 emissions from anaerobic microbial production in wetlands and additional datasets prescribing CH4 emissions from other sources such as biomass burning, termites, or other anthropogenic emissions. We compare WRF-GHG simulations on 10 km horizontal resolution to flask and continuous CH4 observations obtained during two airborne measurement campaigns within the Balanço Atmosférico Regional de Carbono na Amazônia (BARCA) project in November 2008 and May 2009. In addition, three different wetland inundation maps, prescribing the fraction of inundated area per grid cell, are evaluated. Our results indicate that the wetland inundation map with inundated area changing in time represents the observations best except for the northern part of the Amazon basin and the Manaus area. WRF-GHG was able to represent the observed CH4 mixing ratios best at days with less convective activity. After adjusting wetland emissions to match the averaged observed mixing ratios of flights with little convective activity, the monthly CH4 budget of the Amazon lowland region obtained from four different simulations ranges from 1.5 to 4.8 Tg for November 2008 and from 1.3 to 5.5 Tg for May 2009. This corresponds to an average CH4 flux of 9-31 mg m-2 d-1 for November 2008 and 8-36 mg m-2 d-1 for May 2009.

WRF-Chem simulations in the Amazon region during wet and dry season transitions: evaluation of methane models and wetland inundation maps

NASA Astrophysics Data System (ADS)

Beck, V.; Gerbig, C.; Koch, T.; Bela, M. M.; Longo, K. M.; Freitas, S. R.; Kaplan, J. O.; Prigent, C.; Bergamaschi, P.; Heimann, M.

2013-08-01

The Amazon region, being a large source of methane (CH4), contributes significantly to the global annual CH4 budget. For the first time, a forward and inverse modelling framework on regional scale for the purpose of assessing the CH4 budget of the Amazon region is implemented. Here, we present forward simulations of CH4 as part of the forward and inverse modelling framework based on a modified version of the Weather Research and Forecasting model with chemistry that allows for passive tracer transport of CH4, carbon monoxide, and carbon dioxide (WRF-GHG), in combination with two different process-based bottom-up models of CH4 emissions from anaerobic microbial production in wetlands and additional datasets prescribing CH4 emissions from other sources such as biomass burning, termites, or other anthropogenic emissions. We compare WRF-GHG simulations on 10 km horizontal resolution to flask and continuous CH4 observations obtained during two airborne measurement campaigns within the Balanço Atmosférico Regional de Carbono na Amazônia (BARCA) project in November 2008 and May 2009. In addition, three different wetland inundation maps, prescribing the fraction of inundated area per grid cell, are evaluated. Our results indicate that the wetland inundation maps based on remote-sensing data represent the observations best except for the northern part of the Amazon basin and the Manaus area. WRF-GHG was able to represent the observed CH4 mixing ratios best at days with less convective activity. After adjusting wetland emissions to match the averaged observed mixing ratios of flights with little convective activity, the monthly CH4 budget for the Amazon basin obtained from four different simulations ranges from 1.5 to 4.8 Tg for November 2008 and from 1.3 to 5.5 Tg for May 2009. This corresponds to an average CH4 flux of 9-31 mg m-2 d-1 for November 2008 and 8-36 mg m-2 d-1 for May 2009.

Effects of coastal marsh conversion to shrimp aquaculture ponds on CH4 and N2O emissions

NASA Astrophysics Data System (ADS)

Yang, P.; Bastviken, D.; Lai, D. Y. F.; Jin, B. S.; Mou, X. J.; Tong, C.; Yao, Y. C.

2017-12-01

In this study, we compared the CH4 and N2O fluxes from a tidal brackish Cyperus malaccensis marsh ecosystem and nearby shrimp ponds, converted from C. malaccensis marsh in the last 3-4 years, in the Min River estuary of southeast China over the aquaculture period of the year. Significant differences in CH4 and N2O fluxes were observed in space (between brackish marsh and shrimp ponds) and in time (between sampling occasions that were distributed over the aquaculture period). CH4 fluxes from the shrimp ponds were on an average 10-fold higher than from the brackish marsh. N2O emissions, on the other hand, were lower from the shrimp pond (25% of the emissions from the brackish marsh). Accessory data indicates that these patterns were primarily linked to water level variability and temperature (all fluxes), sediment porewater sulfate concentrations (CH4 flux) and total nitrogen concentrations (N2O flux). Our research demonstrates that the coastal marsh ecosystem converted to aquaculture ponds considerably alter emissions of CH4 and N2O and provides input to the global discussion on how to account for emissions from various types of flooded land in greenhouse gas inventories.

Methane emissions from a landfill in north-east India: Performance of various landfill gas emission models.

PubMed

Gollapalli, Muralidhar; Kota, Sri Harsha

2018-03-01

Rapid urbanization and economic growth has led to significant increase in municipal solid waste generation in India during the last few decades and its management has become a major issue because of poor waste management practices. Solid waste generated is deposited into open dumping sites with hardly any segregation and processing. Carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) are the major greenhouse gases that are released from the landfill sites due to the biodegradation of organic matter. In this present study, CH 4 and CO 2 emissions from a landfill in north-east India are estimated using a flux chamber during September, 2015 to August, 2016. The average emission rates of CH 4 and CO 2 are 68 and 92 mg/min/m 2 , respectively. The emissions are highest in the summer whilst being lowest in winter. The diurnal variation of emissions indicated that the emissions follow a trend similar to temperature in all the seasons. Correlation coefficients of CH 4 and temperature in summer, monsoon and winter are 0.99, 0.87 and 0.97, respectively. The measured CH 4 in this study is in the range of other studies around the world. Modified Triangular Method (MTM), IPCC model and the USEPA Landfill gas emissions model (LandGEM) were used to predict the CH 4 emissions during the study year. The consequent simulation results indicate that the MTM, LandGEM-Clean Air Act, LandGEM-Inventory and IPCC models predict 1.9, 3.3, 1.6 and 1.4 times of the measured CH 4 emission flux in this study. Assuming that this higher prediction of CH 4 levels observed in this study holds well for other landfills in this region, a new CH 4 emission inventory (Units: Tonnes/year), with a resolution of 0.1 0  × 0.1 0 has been developed. This study stresses the importance of biodegradable composition of waste and meteorology, and also points out the drawbacks of the widely used landfill emission models. Copyright © 2017 Elsevier Ltd. All rights reserved.

Isotopic signatures of anthropogenic CH4 sources in Alberta, Canada

NASA Astrophysics Data System (ADS)

Lopez, M.; Sherwood, O. A.; Dlugokencky, E. J.; Kessler, R.; Giroux, L.; Worthy, D. E. J.

2017-09-01

A mobile system was used for continuous ambient measurements of stable CH4 isotopes (12CH4 and 13CH4) and ethane (C2H6). This system was used during a winter mobile campaign to investigate the CH4 isotopic signatures and the C2H6/CH4 ratios of the main anthropogenic sources of CH4 in the Canadian province of Alberta. Individual signatures were derived from δ13CH4 and C2H6 measurements in plumes arriving from identifiable single sources. Methane emissions from beef cattle feedlots (n = 2) and landfill (n = 1) had δ13CH4 signatures of -66.7 ± 2.4‰ and -55.3 ± 0.2‰, respectively. The CH4 emissions associated with the oil or gas industry had distinct δ13CH4 signatures, depending on the formation process. Emissions from oil storage tanks (n = 5) had δ13CH4 signatures ranging from -54.9 ± 2.9‰ to -60.6 ± 0.6‰ and non-detectable C2H6, characteristic of secondary microbial methanogenesis in oil-bearing reservoirs. In contrast, CH4 emissions associated with natural gas facilities (n = 8) had δ13CH4 signatures ranging from -41.7 ± 0.7‰ to -49.7 ± 0.7‰ and C2H6/CH4 molar ratios of 0.10 for raw natural gas to 0.04 for processed/refined natural gas, consistent with thermogenic origins. These isotopic signatures and C2H6/CH4 ratios have been used for source discrimination in the weekly atmospheric measurements of stable CH4 isotopes over a two-month winter period at the Lac La Biche (LLB) measurement station, located in Alberta, approximately 200 km northeast of Edmonton. The average signature of -59.5 ± 1.4‰ observed at LLB is likely associated with transport of air after passing over oil industry sources located south of the station.

Quantifying methane and nitrous oxide emissions from the UK using a dense monitoring network

NASA Astrophysics Data System (ADS)

Ganesan, A. L.; Manning, A. J.; Grant, A.; Young, D.; Oram, D. E.; Sturges, W. T.; Moncrieff, J. B.; O'Doherty, S.

2015-01-01

The UK is one of several countries around the world that has enacted legislation to reduce its greenhouse gas emissions. Monitoring of emissions has been done through a detailed sectoral level bottom-up inventory (UK National Atmospheric Emissions Inventory, NAEI) from which national totals are submitted yearly to the United Framework Convention on Climate Change. In parallel, the UK government has funded four atmospheric monitoring stations to infer emissions through top-down methods that assimilate atmospheric observations. In this study, we present top-down emissions of methane (CH4) and nitrous oxide (N2O) for the UK and Ireland over the period August 2012 to August 2014. We used a hierarchical Bayesian inverse framework to infer fluxes as well as a set of covariance parameters that describe uncertainties in the system. We inferred average UK emissions of 2.08 (1.72-2.47) Tg yr-1 CH4 and 0.105 (0.087-0.127) Tg yr-1 N2O and found our derived estimates to be generally lower than the inventory. We used sectoral distributions from the NAEI to determine whether these discrepancies can be attributed to specific source sectors. Because of the distinct distributions of the two dominant CH4 emissions sectors in the UK, agriculture and waste, we found that the inventory may be overestimated in agricultural CH4 emissions. We also found that N2O fertilizer emissions from the NAEI may be overestimated and we derived a significant seasonal cycle in emissions. This seasonality is likely due to seasonality in fertilizer application and in environmental drivers such as temperature and rainfall, which are not reflected in the annual resolution inventory. Through the hierarchical Bayesian inverse framework, we quantified uncertainty covariance parameters and emphasized their importance for high-resolution emissions estimation. We inferred average model errors of approximately 20 and 0.4 ppb and correlation timescales of 1.0 (0.72-1.43) and 2.6 (1.9-3.9) days for CH4 and N2O, respectively. These errors are a combination of transport model errors as well as errors due to unresolved emissions processes in the inventory. We found the largest CH4 errors at the Tacolneston station in eastern England, which is possibly to do with sporadic emissions from landfills and offshore gas in the North Sea.

Short communication: Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted.

PubMed

Dorich, C D; Varner, R K; Pereira, A B D; Martineau, R; Soder, K J; Brito, A F

2015-04-01

The objective of this study was to measure enteric CH4 emissions using a new portable automated open-circuit gas quantification system (GQS) and the sulfur hexafluoride tracer technique (SF6) in midlactation Holstein cows housed in a tiestall barn. Sixteen cows averaging 176 ± 34 d in milk, 40.7 ± 6.1 kg of milk yield, and 685 ± 49 kg of body weight were randomly assigned to 1 out of 2 treatments according to a crossover design. Treatments were (1) ad libitum (adjusted daily to yield 10% orts) and (2) restricted feed intake [set to restrict feed by 10% of baseline dry matter intake (DMI)]. Each experimental period lasted 22d, with 14 d for treatment adaptation and 8d for data and sample collection. A common diet was fed to the cows as a total mixed ration and contained 40.4% corn silage, 11.2% grass-legume haylage, and 48.4% concentrate on a dry matter basis. Spot 5-min measurements using the GQS were taken twice daily with a 12-h interval between sampling and sampling times advanced 2h daily to account for diurnal variation in CH4 emissions. Canisters for the SF6 method were sampled twice daily before milking with 4 local background gas canisters inside the barn analyzed for background gas concentrations. Enteric CH4 emissions were not affected by treatments and averaged 472 and 458 g/d (standard error of the mean = 18 g/d) for ad libitum and restricted intake treatments, respectively (data not shown). The GQS appears to be a reliable method because of the relatively low coefficients of variation (ranging from 14.1 to 22.4%) for CH4 emissions and a moderate relationship (coefficient of determination = 0.42) between CH4 emissions and DMI. The SF6 resulted in large coefficients of variation (ranging from 16.0 to 111%) for CH4 emissions and a poor relationship (coefficient of determination = 0.17) between CH4 emissions and DMI, likely because of limited barn ventilation and high background gas concentration. Research with improved barn ventilation systems or outdoors is warranted to further assess the GQS and SF6 methodologies. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Inverse modelling of European CH4 emissions during 2006-2012 using different inverse models and reassessed atmospheric observations

NASA Astrophysics Data System (ADS)

Bergamaschi, Peter; Karstens, Ute; Manning, Alistair J.; Saunois, Marielle; Tsuruta, Aki; Berchet, Antoine; Vermeulen, Alexander T.; Arnold, Tim; Janssens-Maenhout, Greet; Hammer, Samuel; Levin, Ingeborg; Schmidt, Martina; Ramonet, Michel; Lopez, Morgan; Lavric, Jost; Aalto, Tuula; Chen, Huilin; Feist, Dietrich G.; Gerbig, Christoph; Haszpra, László; Hermansen, Ove; Manca, Giovanni; Moncrieff, John; Meinhardt, Frank; Necki, Jaroslaw; Galkowski, Michal; O'Doherty, Simon; Paramonova, Nina; Scheeren, Hubertus A.; Steinbacher, Martin; Dlugokencky, Ed

2018-01-01

We present inverse modelling (top down) estimates of European methane (CH4) emissions for 2006-2012 based on a new quality-controlled and harmonised in situ data set from 18 European atmospheric monitoring stations. We applied an ensemble of seven inverse models and performed four inversion experiments, investigating the impact of different sets of stations and the use of a priori information on emissions. The inverse models infer total CH4 emissions of 26.8 (20.2-29.7) Tg CH4 yr-1 (mean, 10th and 90th percentiles from all inversions) for the EU-28 for 2006-2012 from the four inversion experiments. For comparison, total anthropogenic CH4 emissions reported to UNFCCC (bottom up, based on statistical data and emissions factors) amount to only 21.3 Tg CH4 yr-1 (2006) to 18.8 Tg CH4 yr-1 (2012). A potential explanation for the higher range of top-down estimates compared to bottom-up inventories could be the contribution from natural sources, such as peatlands, wetlands, and wet soils. Based on seven different wetland inventories from the Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP), total wetland emissions of 4.3 (2.3-8.2) Tg CH4 yr-1 from the EU-28 are estimated. The hypothesis of significant natural emissions is supported by the finding that several inverse models yield significant seasonal cycles of derived CH4 emissions with maxima in summer, while anthropogenic CH4 emissions are assumed to have much lower seasonal variability. Taking into account the wetland emissions from the WETCHIMP ensemble, the top-down estimates are broadly consistent with the sum of anthropogenic and natural bottom-up inventories. However, the contribution of natural sources and their regional distribution remain rather uncertain. Furthermore, we investigate potential biases in the inverse models by comparison with regular aircraft profiles at four European sites and with vertical profiles obtained during the Infrastructure for Measurement of the European Carbon Cycle (IMECC) aircraft campaign. We present a novel approach to estimate the biases in the derived emissions, based on the comparison of simulated and measured enhancements of CH4 compared to the background, integrated over the entire boundary layer and over the lower troposphere. The estimated average regional biases range between -40 and 20 % at the aircraft profile sites in France, Hungary and Poland.

Methane and CO2 emissions from China's hydroelectric reservoirs: a new quantitative synthesis.

PubMed

Li, Siyue; Zhang, Quanfa; Bush, Richard T; Sullivan, Leigh A

2015-04-01

Controversy surrounds the green credentials of hydroelectricity because of the potentially large emission of greenhouse gases (GHG) from associated reservoirs. However, limited and patchy data particularly for China is constraining the current global assessment of GHG releases from hydroelectric reservoirs. This study provides the first evaluation of the CO2 and CH4 emissions from China's hydroelectric reservoirs by considering the reservoir water surface and drawdown areas, and downstream sources (including spillways and turbines, as well as river downstream). The total emission of 29.6 Tg CO2/year and 0.47 Tg CH4/year from hydroelectric reservoirs in China, expressed as CO2 equivalents (eq), corresponds to 45.6 Tg CO2eq/year, which is 2-fold higher than the current GHG emission (ca. 23 Tg CO2eq/year) from global temperate hydropower reservoirs. China's average emission of 70 g CO2eq/kWh from hydropower amounts to 7% of the emissions from coal-fired plant alternatives. China's hydroelectric reservoirs thus currently mitigate GHG emission when compared to the main alternative source of electricity with potentially far great reductions in GHG emissions and benefits possible through relatively minor changes to reservoir management and design. On average, the sum of drawdown and downstream emission including river reaches below dams and turbines, which is overlooked by most studies, represents the equivalent of 42% of the CO2 and 92% of CH4 that emit from hydroelectric reservoirs in China. Main drivers on GHG emission rates are summarized and highlight that water depth and stratification control CH4 flux, and CO2 flux shows significant negative relationships with pH, DO, and Chl-a. Based on our finding, a substantial revision of the global carbon emissions from hydroelectric reservoirs is warranted.

Annual methane budgets of sheep grazing systems were regulated by grazing intensities in the temperate continental steppe: A two-year case study

NASA Astrophysics Data System (ADS)

Ma, Lei; Zhong, Mengying; Zhu, Yuhao; Yang, Helong; Johnson, Douglas A.; Rong, Yuping

2018-02-01

Methane (CH4) emission from animal husbandry accounts for a large percentage of anthropogenic contributions to CH4 emissions. Fully understanding of grazing management effects on the CH4 budget is essential for mitigating CH4 emissions in the temperate grazing steppe systems. Annual CH4 budgets for the sheep grazed steppes at various grazing intensities, un-grazing (UG, 0 sheep ha-1year-1), defer grazing (DG, 1.0 sheep ha-1 year-1), moderate grazing (MG, 1.43 sheep ha-1year-1), and heavy grazing (HG, 2.43 sheep ha-1year-1) were assessed across 2012-2014 in the agro-pastoral region of northern China. Annual soil CH4 uptake averaged across 2012-2014 were 1.1 ± 0.1, 2.4 ± 0.2, 2.2 ± 0.2, and 1.3 ± 0.1 kg CH4-C ha-1 for UG, DG (only 2013-2014), MG and HG sites. Non-growing season CH4 uptake comprised 50.0 ± 4.3% of annual CH4 uptake in 2012-2013 and 37.7 ± 2.0% in 2013-2014. DG and MG significantly promoted annual soil CH4 uptake (P < 0.05), while there was no difference between HG and UG (P > 0.05). Bell-shaped relationship was presented between stocking rates and soil CH4 uptake (r2 = 0.59, P < 0.05). Annual soil CH4 uptake significant linearly and positively correlated with root biomass (r2 = 0.30, P < 0.05). Annual CH4 budgets for the grazed grasslands were -1.1 ± 0.1, 5.7 ± 0.6, 11.5 ± 1.5 and 15.5 ± 1.3 kg CH4-C ha-1 year-1 in UG, DG (only 2013-2014), MG and HG across 2012-2014. Soil CH4 uptake could offset 29.7 ± 5.6, 15.9 ± 4.3 and 6.8 ± 1.0% of total annual CH4 emissions from sheep, sheepfold and faeces in DG, MG, and HG. All grazed steppes are sources for atmospheric CH4 and the magnitude is regulated by grazing intensities. Sheep CH4 emissions for 1-g liveweight gain were 0.21, 0.32 and 0.37 g CH4-C in DG, MG and HG, respectively. DG is the recommended grazing management in this region to achieve greater herbage mass, higher sheep performance and lower CH4 emissions simultaneously.

Potential effects of ultraviolet radiation reduction on tundra nitrous oxide and methane fluxes in maritime Antarctica.

PubMed

Bao, Tao; Zhu, Renbin; Wang, Pei; Ye, Wenjuan; Ma, Dawei; Xu, Hua

2018-02-27

Stratospheric ozone has begun to recover in Antarctica since the implementation of the Montreal Protocol. However, the effects of ultraviolet (UV) radiation on tundra greenhouse gas fluxes are rarely reported for Polar Regions. In the present study, tundra N 2 O and CH 4 fluxes were measured under the simulated reduction of UV radiation in maritime Antarctica over the last three-year summers. Significantly enhanced N 2 O and CH 4 emissions occurred at tundra sites under the simulated reduction of UV radiation. Compared with the ambient normal UV level, a 20% reduction in UV radiation increased tundra emissions by an average of 8 μg N 2 O m -2 h -1 and 93 μg CH 4 m -2 h -1 , whereas a 50% reduction in UV radiation increased their emissions by an average of 17 μg N 2 O m -2 h -1 and 128 μg CH 4 m -2 h -1 . No statistically significant correlation (P > 0.05) was found between N 2 O and CH 4 fluxes and soil temperature, soil moisture, total carbon, total nitrogen, NO 3 - -N and NH 4 + -N contents. Our results confirmed that UV radiation intensity is an important factor affecting tundra N 2 O and CH 4 fluxes in maritime Antarctica. Exclusion of the effects of reduced UV radiation might underestimate their budgets in Polar Regions with the recovery of stratospheric ozone.

Methane emissions in East Asia for 2000-2011 estimated using an atmospheric Bayesian inversion

NASA Astrophysics Data System (ADS)

Thompson, R. L.; Stohl, A.; Zhou, L. X.; Dlugokencky, E.; Fukuyama, Y.; Tohjima, Y.; Kim, S.-Y.; Lee, H.; Nisbet, E. G.; Fisher, R. E.; Lowry, D.; Weiss, R. F.; Prinn, R. G.; O'Doherty, S.; Young, D.; White, J. W. C.

2015-05-01

We present methane (CH4) emissions for East Asia from a Bayesian inversion of CH4 mole fraction and stable isotope (δ13C-CH4) measurements. Emissions were estimated at monthly resolution from 2000 to 2011. A posteriori, the total emission for East Asia increased from 43 ± 4 to 59 ± 4 Tg yr-1 between 2000 and 2011, owing largely to the increase in emissions from China, from 39 ± 4 to 54 ± 4 Tg yr-1, while emissions in other East Asian countries remained relatively stable. For China, South Korea, and Japan, the total emissions were smaller than the prior estimates (i.e., Emission Database for Global Atmospheric Research 4.2 FT2010 for anthropogenic emissions) by an average of 29%, 20%, and 23%, respectively. For Mongolia, Taiwan, and North Korea, the total emission was less than 2 Tg yr-1 and was not significantly different from the prior. The largest reductions in emissions, compared to the prior, occurred in summer in regions important for rice agriculture suggesting that this source is overestimated in the prior. Furthermore, an analysis of the isotope data suggests that the prior underestimates emissions from landfills and ruminant animals for winter 2010 to spring 2011 (no data available for other times). The inversion also found a lower average emission trend for China, 1.2 Tg yr-1 compared to 2.8 Tg yr-1 in the prior. This trend was not constant, however, and increased significantly after 2005, up to 2.0 Tg yr-1. Overall, the changes in emissions from China explain up to 40% of the increase in global emissions in the 2000s.

Methane emissions from floodplains in the Amazon Basin: challenges in developing a process-based model for global applications

NASA Astrophysics Data System (ADS)

Ringeval, B.; Houweling, S.; van Bodegom, P. M.; Spahni, R.; van Beek, R.; Joos, F.; Röckmann, T.

2014-03-01

Tropical wetlands are estimated to represent about 50% of the natural wetland methane (CH4) emissions and explain a large fraction of the observed CH4 variability on timescales ranging from glacial-interglacial cycles to the currently observed year-to-year variability. Despite their importance, however, tropical wetlands are poorly represented in global models aiming to predict global CH4 emissions. This publication documents a first step in the development of a process-based model of CH4 emissions from tropical floodplains for global applications. For this purpose, the LPX-Bern Dynamic Global Vegetation Model (LPX hereafter) was slightly modified to represent floodplain hydrology, vegetation and associated CH4 emissions. The extent of tropical floodplains was prescribed using output from the spatially explicit hydrology model PCR-GLOBWB. We introduced new plant functional types (PFTs) that explicitly represent floodplain vegetation. The PFT parameterizations were evaluated against available remote-sensing data sets (GLC2000 land cover and MODIS Net Primary Productivity). Simulated CH4 flux densities were evaluated against field observations and regional flux inventories. Simulated CH4 emissions at Amazon Basin scale were compared to model simulations performed in the WETCHIMP intercomparison project. We found that LPX reproduces the average magnitude of observed net CH4 flux densities for the Amazon Basin. However, the model does not reproduce the variability between sites or between years within a site. Unfortunately, site information is too limited to attest or disprove some model features. At the Amazon Basin scale, our results underline the large uncertainty in the magnitude of wetland CH4 emissions. Sensitivity analyses gave insights into the main drivers of floodplain CH4 emission and their associated uncertainties. In particular, uncertainties in floodplain extent (i.e., difference between GLC2000 and PCR-GLOBWB output) modulate the simulated emissions by a factor of about 2. Our best estimates, using PCR-GLOBWB in combination with GLC2000, lead to simulated Amazon-integrated emissions of 44.4 ± 4.8 Tg yr-1. Additionally, the LPX emissions are highly sensitive to vegetation distribution. Two simulations with the same mean PFT cover, but different spatial distributions of grasslands within the basin, modulated emissions by about 20%. Correcting the LPX-simulated NPP using MODIS reduces the Amazon emissions by 11.3%. Finally, due to an intrinsic limitation of LPX to account for seasonality in floodplain extent, the model failed to reproduce the full dynamics in CH4 emissions but we proposed solutions to this issue. The interannual variability (IAV) of the emissions increases by 90% if the IAV in floodplain extent is accounted for, but still remains lower than in most of the WETCHIMP models. While our model includes more mechanisms specific to tropical floodplains, we were unable to reduce the uncertainty in the magnitude of wetland CH4 emissions of the Amazon Basin. Our results helped identify and prioritize directions towards more accurate estimates of tropical CH4 emissions, and they stress the need for more research to constrain floodplain CH4 emissions and their temporal variability, even before including other fundamental mechanisms such as floating macrophytes or lateral water fluxes.

Methane emissions estimate from airborne measurements over a western United States natural gas field

NASA Astrophysics Data System (ADS)

Karion, Anna; Sweeney, Colm; PéTron, Gabrielle; Frost, Gregory; Michael Hardesty, R.; Kofler, Jonathan; Miller, Ben R.; Newberger, Tim; Wolter, Sonja; Banta, Robert; Brewer, Alan; Dlugokencky, Ed; Lang, Patricia; Montzka, Stephen A.; Schnell, Russell; Tans, Pieter; Trainer, Michael; Zamora, Robert; Conley, Stephen

2013-08-01

(CH4) emissions from natural gas production are not well quantified and have the potential to offset the climate benefits of natural gas over other fossil fuels. We use atmospheric measurements in a mass balance approach to estimate CH4 emissions of 55 ± 15 × 103 kg h-1 from a natural gas and oil production field in Uintah County, Utah, on 1 day: 3 February 2012. This emission rate corresponds to 6.2%-11.7% (1σ) of average hourly natural gas production in Uintah County in the month of February. This study demonstrates the mass balance technique as a valuable tool for estimating emissions from oil and gas production regions and illustrates the need for further atmospheric measurements to determine the representativeness of our single-day estimate and to better assess inventories of CH4 emissions.

Methane emission to the atmosphere from landfills in the Canary Islands

NASA Astrophysics Data System (ADS)

Hernández, Pedro A.; Asensio-Ramos, María; Rodríguez, Fátima; Alonso, Mar; García-Merino, Marta; Amonte, Cecilia; Melián, Gladys V.; Barrancos, José; Rodríguez-Delgado, Miguel A.; Hernández-Abad, Marta; Pérez, Erica; Alonso, Monica; Tassi, Franco; Raco, Brunella; Pérez, Nemesio M.

2017-04-01

Methane (CH4) is one of the most powerful greenhouse gases, and is increasing in the atmosphere by 0.6% each year (Intergovernmental Panel on Climate Change, IPCC, 2013). This gas is produced in landfills in large quantities following the anaerobic degradation of organic matter. The IPCC has estimated that more than 10% of the total anthropogenic emissions of CH4 are originated in landfills. Even after years of being no operative (closed), a significant amount of landfill gas could be released to the atmosphere through its surface as diffuse or fugitive degassing. Many landfills currently report their CH4 emissions to the atmosphere using model-based methods, which are based on the rate of production of CH4, the oxidation rate of CH4 and the amount of CH4 recovered (Bingemer and Crutzen, 1987). This approach often involves large uncertainties due to inaccuracies of input data and many assumptions in the estimation. In fact, the estimated CH4 emissions from landfills in the Canary Islands published by the Spanish National Emission and Pollutant Sources Registration (PRTR-Spain) seem to be overestimated due to the use of protocols and analytical methodologies based on mathematical models. For this reason, direct measurements to estimate CH4 emissions in landfills are essential to reduce this uncertainty. In order to estimate the CH4 emissions to the atmosphere from landfills in the Canary Islands 23 surveys have been performed since 1999. Each survey implies hundreds of CO2and CH4 efflux measurements covering the landfill surface area. Surface landfill CO2 efflux measurements were carried out at each sampling site by means of a portable non-dispersive infrared spectrophotometer (NDIR) model LICOR Li800 following the accumulation chamber method. Samples of landfill gases were taken in the gas accumulated in the chamber and CO2 and CH4 were analyzed using a double channel VARIAN 4900 micro-GC. The CH4 efflux measurent was computed combining CO2 efflux and CH4/CO2 ratio. To quantify the the diffuse or fugitive CO2 and CH4 emission, gas efflux contour maps were constructed using sequential Gaussian simulation (sGs) as interpolation method. Considering that (a) there are 5 controlled landfills in the Canary Islands, (b) the average area of the 23 studied cells is 0.17 km2 and (c) the mean value of the CH4 emission estimated for the studied cells range between 6.9 and 8.1 kt km-2 y-1, the estimated CH4 emission to the atmosphere from landfills in the Canary Islands showed a range of 7.0 - 7.8 kt y-1. On the contrary and for the same period of time, the PRTR-Spain estimates CH4 emission in the order of 10.3 - 14.9 kt y-1, nearly two times our estimated value. This result demonstrates the need to perform direct measurements to estimate the surface fugitive emission of CH4 from landfills. Bingemer, H. G., and P. J. Crutzen (1987). The production of methane from solid wastes, J. Geophys. Res. 92, 2182-2187

Global average concentration and trend for hydroxyl radicals deduced from ALE/GAGE trichloroethane (methyl chloroform) data for 1978-1990

NASA Technical Reports Server (NTRS)

Prinn, R.; Cunnold, D.; Simmonds, P.; Alyea, F.; Boldi, R.; Crawford, A.; Fraser, P.; Gutzler, D.; Hartley, D.; Rosen, R.

1992-01-01

An optimal estimation inversion scheme is utilized with atmospheric data and emission estimates to determined the globally averaged CH3CCl3 tropospheric lifetime and OH concentration. The data are taken from atmospheric measurements from surface stations of 1,1,1-trichloroethane and show an annual increase of 4.4 +/- 0.2 percent. Industrial emission estimates and a small oceanic loss rate are included, and the OH concentration for the same period (1978-1990) are incorporated at 1.0 +/- 0.8 percent/yr. The positive OH trend is consistent with theories regarding OH and ozone trends with respect to land use and global warming. Attention is given to the effects of the ENSO on the CH3CCl3 data and the assumption of continuing current industrial anthropogenic emissions. A novel tropical atmospheric tracer-transport mechanism is noted with respect to the CH3CCl3 data.

Aircraft emissions of methane and nitrous oxide during the alternative aviation fuel experiment.

PubMed

Santoni, Gregory W; Lee, Ben H; Wood, Ezra C; Herndon, Scott C; Miake-Lye, Richard C; Wofsy, Steven C; McManus, J Barry; Nelson, David D; Zahniser, Mark S

2011-08-15

Given the predicted growth of aviation and the recent developments of alternative aviation fuels, quantifying methane (CH(4)) and nitrous oxide (N(2)O) emission ratios for various aircraft engines and fuels can help constrain projected impacts of aviation on the Earth's radiative balance. Fuel-based emission indices for CH(4) and N(2)O were quantified from CFM56-2C1 engines aboard the NASA DC-8 aircraft during the first Alternative Aviation Fuel Experiment (AAFEX-I) in 2009. The measurements of JP-8 fuel combustion products indicate that at low thrust engine states (idle and taxi, or 4% and 7% maximum rated thrusts, respectively) the engines emit both CH(4) and N(2)O at a mean ± 1σ rate of 170 ± 160 mg CH(4) (kg Fuel)(-1) and 110 ± 50 mg N(2)O (kg Fuel)(-1), respectively. At higher thrust levels corresponding to greater fuel flow and higher engine temperatures, CH(4) concentrations in engine exhaust were lower than ambient concentrations. Average emission indices for JP-8 fuel combusted at engine thrusts between 30% and 100% of maximum rating were -54 ± 33 mg CH(4) (kg Fuel)(-1) and 32 ± 18 mg N(2)O (kg Fuel)(-1), where the negative sign indicates consumption of atmospheric CH(4) in the engine. Emission factors for the synthetic Fischer-Tropsch fuels were statistically indistinguishable from those for JP-8.

Estimating methane emissions from dairies in the Los Angeles Basin

NASA Astrophysics Data System (ADS)

Viatte, C.; Lauvaux, T.; Hedelius, J.; Parker, H. A.; Chen, J.; Jones, T.; Franklin, J.; Deng, A.; Gaudet, B.; Duren, R. M.; Verhulst, K. R.; Wunch, D.; Roehl, C. M.; Dubey, M. K.; Wofsy, S.; Wennberg, P. O.

2015-12-01

Inventory estimates of methane (CH4) emissions among the individual sources (mainly agriculture, energy production, and waste management) remain highly uncertain at regional and urban scales. Accurate atmospheric measurements can provide independent estimates to evaluate bottom-up inventories, especially in urban region, where many different CH4 sources are often confined in relatively small areas. Among these sources, livestock emissions, which are mainly originating from dairy cows, account for ~55% of the total CH4 emissions in California in 2013. This study aims to rigorously estimate the amount of CH4 emitted by the largest dairies in the Southern California region by combining measurements from four mobile ground-based spectrometers (EM27/SUN), in situ isotopic methane measurements from a CRDS analyzer (Picarro), and a high-resolution atmospheric transport model (the Weather Research and Forecasting model) in Large-Eddy Simulation mode. The remote sensing spectrometers measure the total column-averaged dry-air mole fractions of CH4 and CO2 (XCH4 and XCO2) in the near infrared region, providing information about total emissions of the dairies. Gradients measured by the four EM27 ranged from 0.2 to 22 ppb and from 0.7 to 3 ppm for XCH4 and XCO2, respectively. To assess the fluxes of the dairies, measurements of these gradients are used in conjunction with the local atmospheric dynamics simulated at 111 m resolution. Inverse modelling from WRF-LES is employed to resolve the spatial distribution of CH4 emissions in the domain. A Bayesian inversion and a Monte-Carlo approach were used to provide the CH4 emissions over the dairy with their associated uncertainties. The isotopic δ13C sampled at different locations in the area ranges from -40 ‰ to -55 ‰, indicating a mixture of anthropogenic and biogenic sources.

Greenhouse gas emissions from green waste composting windrow.

PubMed

Zhu-Barker, Xia; Bailey, Shannon K; Paw U, Kyaw Tha; Burger, Martin; Horwath, William R

2017-01-01

The process of composting is a source of greenhouse gases (GHG) that contribute to climate change. We monitored three field-scale green waste compost windrows over a one-year period to measure the seasonal variance of the GHG fluxes. The compost pile that experienced the wettest and coolest weather had the highest average CH 4 emission of 254±76gCday -1 dry weight (DW) Mg -1 and lowest average N 2 O emission of 152±21mgNday -1 DW Mg -1 compared to the other seasonal piles. The highest N 2 O emissions (342±41mgNday -1 DW Mg -1 ) came from the pile that underwent the driest and hottest weather. The compost windrow oxygen (O 2 ) concentration and moisture content were the most consistent factors predicting N 2 O and CH 4 emissions from all seasonal compost piles. Compared to N 2 O, CH 4 was a higher contributor to the overall global warming potential (GWP) expressed as CO 2 equivalents (CO 2 eq.). Therefore, CH 4 mitigation practices, such as increasing O 2 concentration in the compost windrows through moisture control, feedstock changes to increase porosity, and windrow turning, may reduce the overall GWP of composting. Based on the results of the present study, statewide total GHG emissions of green waste composting were estimated at 789,000Mg of CO 2 eq., representing 2.1% of total annual GHG emissions of the California agricultural sector and 0.18% of the total state emissions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Environmental and physical controls on northern terrestrial methane emissions across permafrost zones

USGS Publications Warehouse

Olefeldt, David; Turetsky, Merritt R.; Crill, Patrick M.; McGuire, A. David

2013-01-01

Methane (CH4) emissions from the northern high-latitude region represent potentially significant biogeochemical feedbacks to the climate system. We compiled a database of growing-season CH4 emissions from terrestrial ecosystems located across permafrost zones, including 303 sites described in 65 studies. Data on environmental and physical variables, including permafrost conditions, were used to assess controls on CH4 emissions. Water table position, soil temperature, and vegetation composition strongly influenced emissions and had interacting effects. Sites with a dense sedge cover had higher emissions than other sites at comparable water table positions, and this was an effect that was more pronounced at low soil temperatures. Sensitivity analysis suggested that CH4 emissions from ecosystems where the water table on average is at or above the soil surface (wet tundra, fen underlain by permafrost, and littoral ecosystems) are more sensitive to variability in soil temperature than drier ecosystems (palsa dry tundra, bog, and fen), whereas the latter ecosystems conversely are relatively more sensitive to changes of the water table position. Sites with near-surface permafrost had lower CH4 fluxes than sites without permafrost at comparable water table positions, a difference that was explained by lower soil temperatures. Neither the active layer depth nor the organic soil layer depth was related to CH4 emissions. Permafrost thaw in lowland regions is often associated with increased soil moisture, higher soil temperatures, and increased sedge cover. In our database, lowland thermokarst sites generally had higher emissions than adjacent sites with intact permafrost, but emissions from thermokarst sites were not statistically higher than emissions from permafrost-free sites with comparable environmental conditions. Overall, these results suggest that future changes to terrestrial high-latitude CH4 emissions will be more proximately related to changes in moisture, soil temperature, and vegetation composition than to increased availability of organic matter following permafrost thaw.

Methane and carbon dioxide emission from two pig finishing barns.

PubMed

Ni, Ji-Qin; Heber, Albert J; Lim, Teng Teeh; Tao, Pei Chun; Schmidt, Amy M

2008-01-01

Agricultural activities are an important source of greenhouse gases. However, comprehensive, long-term, and high-quality measurement data of these gases are lacking. This article presents a field study of CH(4) and CO(2) emission from two 1100-head mechanically ventilated pig (Sus scrofa) finishing barns (B1 and B2) with shallow manure flushing systems and propane space heaters from August 2002 to July 2003 in northern Missouri. Barn 2 was treated with soybean oil sprinkling, misting essential oils, and misting essential oils with water to reduce air pollutant emissions. Only days with CDFB (complete-data-full-barn), defined as >80% of valid data during a day with >80% pigs in the barns, were used. The CH(4) average daily mean (ADM) emission rates were 36.2 +/- 2.0 g/d AU (ADM +/- 95% confidence interval; animal unit = 500 kg live mass) from B1 (CDFB days = 134) and 28.8 +/- 1.8 g/d AU from B2 (CDFB days = 131). The CO(2) ADM emission rates were 17.5 +/- 0.8 kg/d AU from B1 (CDFB days = 146) and 14.2 +/- 0.6 kg/d AU from B2 (CDFB days = 137). The treated barn reduced CH(4) emission by 20% (P < 0.01) and CO(2) emission by 19% (P < 0.01). The CH(4) and CO(2) released from the flushing lagoon effluent were equivalent to 9.8 and 4.1% of the CDFB CH(4) and CO(2) emissions, respectively. The emission data were compared with the literature, and the characteristics of CH(4) and CO(2) concentrations and emissions were discussed.

Near-zero methane emission from an abandoned boreal peatland pasture based on eddy covariance measurements

PubMed Central

Wang, Mei; Luan, Junwei; Lafleur, Peter; Chen, Huai; Zhu, Xinbiao

2017-01-01

Although estimates of the annual methane (CH4) flux from agriculturally managed peatlands exist, knowledge of controls over the variation of CH4 at different time-scales is limited due to the lack of high temporal-resolution data. Here we present CH4 fluxes measured from May 2014 to April 2016 using the eddy covariance technique at an abandoned peatland pasture in western Newfoundland, Canada. The goals of the study were to identify the controls on the seasonal variations in CH4 flux and to quantify the annual CH4 flux. The seasonal variation in daily CH4 flux was not strong in the two study years, however a few periods of pronounced emissions occurred in the late growing season. The daily average CH4 flux was small relative to other studies, ranging from -4.1 to 9.9 nmol m-2 s-1 in 2014–15 and from -7.1 to 12.1 nmol m-2 s-1 in 2015–16. Stepwise multiple regression was used to investigate controls on CH4 flux and this analysis found shifting controls on CH4 flux at different periods of the growing season. During the early growing season CH4 flux was closely related to carbon dioxide fixation rates, suggesting substrate availability was the main control. The peak growing season CH4 flux was principally controlled by the CH4 oxidation in 2014, where the CH4 flux decreased and increased with soil temperature at 50 cm and soil water content at 10 cm, but a contrasting temperature-CH4 relation was found in 2015. The late growing season CH4 flux was found to be regulated by the variation in water table level and air temperature in 2014. The annual CH4 emission was near zero in both study years (0.36 ± 0.30 g CH4 m-2 yr-1 in 2014–15 and 0.13 ± 0.38 g CH4 m-2 yr-1 in 2015–16), but fell within the range of CH4 emissions reported for agriculturally managed peatlands elsewhere. PMID:29252998

Near-zero methane emission from an abandoned boreal peatland pasture based on eddy covariance measurements.

PubMed

Wang, Mei; Wu, Jianghua; Luan, Junwei; Lafleur, Peter; Chen, Huai; Zhu, Xinbiao

2017-01-01

Although estimates of the annual methane (CH4) flux from agriculturally managed peatlands exist, knowledge of controls over the variation of CH4 at different time-scales is limited due to the lack of high temporal-resolution data. Here we present CH4 fluxes measured from May 2014 to April 2016 using the eddy covariance technique at an abandoned peatland pasture in western Newfoundland, Canada. The goals of the study were to identify the controls on the seasonal variations in CH4 flux and to quantify the annual CH4 flux. The seasonal variation in daily CH4 flux was not strong in the two study years, however a few periods of pronounced emissions occurred in the late growing season. The daily average CH4 flux was small relative to other studies, ranging from -4.1 to 9.9 nmol m-2 s-1 in 2014-15 and from -7.1 to 12.1 nmol m-2 s-1 in 2015-16. Stepwise multiple regression was used to investigate controls on CH4 flux and this analysis found shifting controls on CH4 flux at different periods of the growing season. During the early growing season CH4 flux was closely related to carbon dioxide fixation rates, suggesting substrate availability was the main control. The peak growing season CH4 flux was principally controlled by the CH4 oxidation in 2014, where the CH4 flux decreased and increased with soil temperature at 50 cm and soil water content at 10 cm, but a contrasting temperature-CH4 relation was found in 2015. The late growing season CH4 flux was found to be regulated by the variation in water table level and air temperature in 2014. The annual CH4 emission was near zero in both study years (0.36 ± 0.30 g CH4 m-2 yr-1 in 2014-15 and 0.13 ± 0.38 g CH4 m-2 yr-1 in 2015-16), but fell within the range of CH4 emissions reported for agriculturally managed peatlands elsewhere.

Determination of GHG and ammonia emissions from stored dairy cattle slurry by using a floating dynamic chamber.

PubMed

Minato, Keiko; Kouda, Yasuyuki; Yamakawa, Masaaki; Hara, Satoshi; Tamura, Tadashi; Osada, Takashi

2013-02-01

We developed a system for measuring emissions from stored slurry by using a floating dynamic chamber. CH(4) , CO(2) , N(2) O and NH(3) emitted from the storage tank of a dairy cattle farm in eastern Hokkaido were measured during summer 2008 (7/16-8/6), fall 2008 (10/2-10/26), spring 2009 (6/2-6/21) and winter 2009 (3/11). Average daily gas emission rates in summer, fall and spring were, respectively, 54.8, 54.2 and 34.3 g/m(2) for CH(4) ; 602, 274 and 254 g/m(2) for CO(2) ; 55.4, 68.2 and trace mg/m(2) for N(2) O; and 0.55, 0.73 and 0.46 g/m(2) for NH(3) . CH(4) , CO(2) and NH(3) emission rates during the brief measurement period in winter were reduced to 1/4, 1/23 and 1/2, respectively, of summer emission rate levels. All gas emissions showed diurnal fluctuation and were greatest during the daytime, when the ambient temperature rose. CH(4) , NH(3) and CO(2) emissions increased significantly during the daytime, and the daily emission (in grams) of each gas was positively correlated with maximum daily temperature. According to the combined spring, summer and fall measurements, the CH(4) , N(2) O and NH(3) annual emission factors were 1.42% (g CH(4) /g volatile solids), 0.02% (g N(2) O-N/g total N) and 0.43% (g NH(3) -N/g total N), respectively. © 2012 The Authors. Animal Science Journal © 2012 Japanese Society of Animal Science.

Assessment of a landfill methane emission screening method using an unmanned aerial vehicle mounted thermal infrared camera - A field study.

PubMed

Fjelsted, L; Christensen, A G; Larsen, J E; Kjeldsen, P; Scheutz, C

2018-05-28

An unmanned aerial vehicle (UAV)-mounted thermal infrared (TIR) camera's ability to delineate landfill gas (LFG) emission hotspots was evaluated in a field test at two Danish landfills (Hedeland landfill and Audebo landfill). At both sites, a test area of 100 m 2 was established and divided into about 100 measuring points. The relationship between LFG emissions and soil surface temperatures were investigated through four to five measuring campaigns, in order to cover different atmospheric conditions along with increasing, decreasing and stable barometric pressure. For each measuring campaign, a TIR image of the test area was obtained followed by the measurement of methane (CH 4 ) and carbon dioxide (CO 2 ) emissions at each measuring point, using a static flux chamber. At the same time, soil temperatures measured on the surface, at 5 cm and 10 cm depths, were registered. At the Hedeland landfill, no relationship was found between LFG emissions and surface temperatures. In addition, CH 4 emissions were very limited, on average 0.92-4.52 g CH 4  m -2  d -1 , and only measureable on the two days with decreasing barometric pressure. TIR images from Hedeland did not show any significant temperature differences in the test area. At the Audebo landfill, an area with slightly higher surface temperatures was found in the TIR images, and the same pattern with slightly higher temperatures was found at a depth of 10 cm. The main LFG emissions were found in the area with the higher surface temperatures. LFG emissions at Audebo were influenced significantly by changes in barometric pressure, and the average CH 4 emissions varied between 111 g m -2  d -1 and 314 g m -2  d -1 , depending on whether the barometric pressure gradient had increased or decreased, respectively. The temperature differences observed in the TIR images from both landfills were limited to between 0.7 °C and 1.2 °C. The minimum observable CH 4 emission for the TIR camera to identify an emission hotspot was 150 g CH 4  m -2  d -1 from an area of more than 1 m 2 . Copyright © 2018 Elsevier Ltd. All rights reserved.

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase.

PubMed

Rice, Andrew L; Butenhoff, Christopher L; Teama, Doaa G; Röger, Florian H; Khalil, M Aslam K; Rasmussen, Reinhold A

2016-09-27

Observations of atmospheric methane (CH4) since the late 1970s and measurements of CH4 trapped in ice and snow reveal a meteoric rise in concentration during much of the twentieth century. Since 1750, levels of atmospheric CH4 have more than doubled to current globally averaged concentration near 1,800 ppb. During the late 1980s and 1990s, the CH4 growth rate slowed substantially and was near or at zero between 1999 and 2006. There is no scientific consensus on the drivers of this slowdown. Here, we report measurements of the stable isotopic composition of atmospheric CH4 ((13)C/(12)C and D/H) from a rare air archive dating from 1977 to 1998. Together with more modern records of isotopic atmospheric CH4, we performed a time-dependent retrieval of methane fluxes spanning 25 y (1984-2009) using a 3D chemical transport model. This inversion results in a 24 [18, 27] Tg y(-1) CH4 increase in fugitive fossil fuel emissions since 1984 with most of this growth occurring after year 2000. This result is consistent with some bottom-up emissions inventories but not with recent estimates based on atmospheric ethane. In fact, when forced with decreasing emissions from fossil fuel sources our inversion estimates unreasonably high emissions in other sources. Further, the inversion estimates a decrease in biomass-burning emissions that could explain falling ethane abundance. A range of sensitivity tests suggests that these results are robust.

Atmospheric methane isotopic record favors fossil sources flat in 1980s and 1990s with recent increase

NASA Astrophysics Data System (ADS)

Rice, Andrew L.; Butenhoff, Christopher L.; Teama, Doaa G.; Röger, Florian H.; Khalil, M. Aslam K.; Rasmussen, Reinhold A.

2016-09-01

Observations of atmospheric methane (CH4) since the late 1970s and measurements of CH4 trapped in ice and snow reveal a meteoric rise in concentration during much of the twentieth century. Since 1750, levels of atmospheric CH4 have more than doubled to current globally averaged concentration near 1,800 ppb. During the late 1980s and 1990s, the CH4 growth rate slowed substantially and was near or at zero between 1999 and 2006. There is no scientific consensus on the drivers of this slowdown. Here, we report measurements of the stable isotopic composition of atmospheric CH4 (13C/12C and D/H) from a rare air archive dating from 1977 to 1998. Together with more modern records of isotopic atmospheric CH4, we performed a time-dependent retrieval of methane fluxes spanning 25 y (1984-2009) using a 3D chemical transport model. This inversion results in a 24 [18, 27] Tg y-1 CH4 increase in fugitive fossil fuel emissions since 1984 with most of this growth occurring after year 2000. This result is consistent with some bottom-up emissions inventories but not with recent estimates based on atmospheric ethane. In fact, when forced with decreasing emissions from fossil fuel sources our inversion estimates unreasonably high emissions in other sources. Further, the inversion estimates a decrease in biomass-burning emissions that could explain falling ethane abundance. A range of sensitivity tests suggests that these results are robust.

Novel stable isotope laser spectrometry elucidates changing mechanisms of CH4 production and consumption across a climate change sequence in an arctic wetland

NASA Astrophysics Data System (ADS)

McCalley, C. K.; Wehr, R.; Crill, P. M.; Chanton, J.; Hodgkins, S. B.; Nelson, D. D.; McManus, J. B.; Zahniser, M. S.; Rich, V.; Tyson, G.; Mondav, R.; Frolking, S.; Li, C.; Saleska, S. R.

2011-12-01

Methane flux from high latitude wetlands is both a critical component of the global CH4 budget, and highly sensitive to global climate change, with expected increases in emissions as permafrost thaws. Gaps in our understanding of the mechanisms driving changing CH4 production and consumption dynamics under permafrost thaw, however, limit our ability to predict the magnitude of this response under future climate conditions. To address these gaps, we quantified the isotopic composition of carbon gas fluxes (δ13C of CH4 and CO2) from a high latitude (68° N) wetland in Sweden (Stordalen Mire) to partition net CH4 emissions into its component parts, methanogenesis (including both acetoclastic, and CO2-reductive pathways) and methanotrophy (which consumes CH4 primarily via aerobic metabolism). We used newly developed quantum cascade laser technology, linked to automated chambers, to quantify isotopes at high frequency. Our measurements across a permafrost thaw gradient, going from permafrost-dominated, well-drained palsas to intermediate permafrost sites dominated by Sphagnum spp. to wet sites with no underlying permafrost, dominated by Eriophorum angustifolium, show both large increases in productivity and CH4 emissions as well as shifts in the CH4 production pathway. Across this permafrost thaw gradient the isotopic composition of CH4 becomes 13C enriched, due to increased acetoclastic CH4 production. While the palsa sites have no detectable CH4 emissions, fluxes in the Sphagnum site have an average isotopic composition of -79%, a value indicative of CH4 production dominated by CO2 reduction, in contrast the isotopic composition of CH4 produced in the Eriophorum sites ranged from -71 to -57%, showing increased CH4 production via the acetate pathway. We also observed an increase in acetoclastic methanogenesis as the growing season progressed. Together, these initial results suggest that thaw induced changes in hydrology and plant community composition increase peat lability, stimulating acetate fermentation and yielding increased methane emissions. We conclude that the biological controls on metabolic pathways of methanogenesis, though poorly represented in most ecosystem models, may nonetheless be important, in interaction with permafrost thaw dynamics, in determining future CH4 emissions under changing climate.

A cautionary tale: A study of a methane enhancement over the North Sea

NASA Astrophysics Data System (ADS)

Cain, M.; Warwick, N. J.; Fisher, R. E.; Lowry, D.; Lanoisellé, M.; Nisbet, E. G.; France, J.; Pitt, J.; O'Shea, S.; Bower, K. N.; Allen, G.; Illingworth, S.; Manning, A. J.; Bauguitte, S.; Pisso, I.; Pyle, J. A.

2017-07-01

Airborne measurements of a methane (CH4) plume over the North Sea from August 2013 are analyzed. The plume was only observed downwind of circumnavigated gas fields, and three methods are used to determine its source. First, a mass balance calculation assuming a gas field source gives a CH4 emission rate between 2.5 ± 0.8×104 and 4.6 ± 1.5×104 kg h-1. This would be greater than the industry's reported 0.5% leak rate if it were emitting for more than half the time. Second, annual average UK CH4 emissions are combined with an atmospheric dispersion model to create pseudo-observations. Clean air from the North Atlantic passed over mainland UK, picking up anthropogenic emissions. To best explain the observed plume using pseudo-observations, an additional North Sea source from the gas rigs area is added. Third, the δ13C-CH4 from the plume is shown to be -53‰, which is lighter than fossil gas but heavier than the UK average emission. We conclude that either an additional small-area mainland source is needed, combined with temporal variability in emission or transport in small-scale meteorological features. Alternatively, a combination of additional sources that are at least 75% from the mainland (-58‰) and up to 25% from the North Sea gas rigs area (-32‰) would explain the measurements. Had the isotopic analysis not been performed, the likely conclusion would have been of a gas field source of CH4. This demonstrates the limitation of analyzing mole fractions alone, as the simplest explanation is rejected based on analysis of isotopic data.

Temperature, productivity and sediment characteristics as drivers of seasonal and spatial variations of dissolved methane in the near-shore coastal areas (Belgian coastal zone, North Sea)

NASA Astrophysics Data System (ADS)

Borges, Alberto V.; Speeckaert, Gaëlle; Champenois, Willy; Scranton, Mary I.; Gypens, Nathalie

2017-04-01

The open ocean is a modest source of CH4 to the atmosphere compared to other natural and anthropogenic CH4 emissions. Coastal regions are more intense sources of CH4 to the atmosphere than open oceanic waters, in particular estuarine zones. The CH4 emission to the atmosphere from coastal areas is sustained by riverine inputs and methanogenesis in the sediments due to high organic matter (OM) deposition. Additionally, natural gas seeps are sources of CH4 to bottom waters leading to high dissolved CH4 concentrations in bottom waters (from tenths of nmol L-1 up to several µmol L-1). We report a data set of dissolved CH4 concentrations obtained at nine fixed stations in the Belgian coastal zone (Southern North Sea), during one yearly cycle, with a bi-monthly frequency in spring, and a monthly frequency during the rest of the year. This is a coastal area with multiple possible sources of CH4 such as from rivers and gassy sediments, and where intense phytoplankton blooms are dominated by the high dimethylsulfoniopropionate (DMSP) producing micro-algae Phaeocystis globosa, leading to DMSP and dimethylsulfide (DMS) concentrations. Furthermore, the BCZ is a site of important OM sedimentation and accumulation unlike the rest of the North Sea. Spatial variations of dissolved CH4 concentrations were very marked with a minimum yearly average of 9 nmol L-1 in one of the most off-shore stations and maximum yearly average of 139 nmol L-1 at one of the most near-shore stations. The spatial variations of dissolved CH4 concentrations were related to the organic matter (OM) content of sediments, although the highest concentrations seemed to also be related to inputs of CH4 from gassy sediments associated to submerged peat. In the near-shore stations with fine sand or muddy sediments with a high OM content, the seasonal cycle of dissolved CH4 concentration closely followed the seasonal cycle of water temperature, suggesting the control of methanogenesis by temperature in these OM replete sediments. In the off-shore stations with permeable sediments with a low OM content, the seasonal cycle of dissolved CH4 concentration showed a yearly peak following the chlorophyll-a spring peak. This suggests that in these OM poor sediments, methanogenesis depended on the delivery to the sediments of freshly produced OM. In both types of sediments, the seasonal cycle of dissolved CH4 concentrations was unrelated the seasonal cycles of DMS, and DMSP, despite the fact that these quantities were very high during the spring Phaeocystis globosa bloom. This suggests that in this shallow coastal environment CH4 production is overwhelmingly related to benthic processes and unrelated to DMS(P) transformations in the water column as recently suggested in several open ocean regions. The annual average CH4 emission was 41 mmol m-2 yr-1 in the most near-shore stations ( 4 km from the coast) and 10 mmol m-2 yr-1 in the most off-shore stations ( 23 km from the coast), 410-100 times higher than the average value in the open ocean (0.1 mmol m-2 yr-1). The strong control of CH4 concentrations by sediment OM content and by temperature suggests that marine coastal CH4 emissions, in particular shallow coastal areas, should respond in future to eutrophication and warming of climate. This is confirmed by the comparison of CH4 concentrations at five stations obtained in March in years 1990 and 2016, showing a decreasing trend consistent with alleviation of eutrophication in the area.

Inverse modelling of CH4 emissions for 2010-2011 using different satellite retrieval products from GOSAT and SCIAMACHY

NASA Astrophysics Data System (ADS)

Alexe, M.; Bergamaschi, P.; Segers, A.; Detmers, R.; Butz, A.; Hasekamp, O.; Guerlet, S.; Parker, R.; Boesch, H.; Frankenberg, C.; Scheepmaker, R. A.; Dlugokencky, E.; Sweeney, C.; Wofsy, S. C.; Kort, E. A.

2015-01-01

At the beginning of 2009 new space-borne observations of dry-air column-averaged mole fractions of atmospheric methane (XCH4) became available from the Thermal And Near infrared Sensor for carbon Observations-Fourier Transform Spectrometer (TANSO-FTS) instrument on board the Greenhouse Gases Observing SATellite (GOSAT). Until April 2012 concurrent {methane (CH4) retrievals} were provided by the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) instrument on board the ENVironmental SATellite (ENVISAT). The GOSAT and SCIAMACHY XCH4 retrievals can be compared during the period of overlap. We estimate monthly average CH4 emissions between January 2010 and December 2011, using the TM5-4DVAR inverse modelling system. In addition to satellite data, high-accuracy measurements from the Cooperative Air Sampling Network of the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA ESRL) are used, providing strong constraints on the remote surface atmosphere. We discuss five inversion scenarios that make use of different GOSAT and SCIAMACHY XCH4 retrieval products, including two sets of GOSAT proxy retrievals processed independently by the Netherlands Institute for Space Research (SRON)/Karlsruhe Institute of Technology (KIT), and the University of Leicester (UL), and the RemoTeC "Full-Physics" (FP) XCH4 retrievals available from SRON/KIT. The GOSAT-based inversions show significant reductions in the root mean square (rms) difference between retrieved and modelled XCH4, and require much smaller bias corrections compared to the inversion using SCIAMACHY retrievals, reflecting the higher precision and relative accuracy of the GOSAT XCH4. Despite the large differences between the GOSAT and SCIAMACHY retrievals, 2-year average emission maps show overall good agreement among all satellite-based inversions, with consistent flux adjustment patterns, particularly across equatorial Africa and North America. Over North America, the satellite inversions result in a significant redistribution of CH4 emissions from North-East to South-Central United States. This result is consistent with recent independent studies suggesting a systematic underestimation of CH4 emissions from North American fossil fuel sources in bottom-up inventories, likely related to natural gas production facilities. Furthermore, all four satellite inversions yield lower CH4 fluxes across the Congo basin compared to the NOAA-only scenario, but higher emissions across tropical East Africa. The GOSAT and SCIAMACHY inversions show similar performance when validated against independent shipboard and aircraft observations, and XCH4 retrievals available from the Total Carbon Column Observing Network (TCCON).

Estimating Amazonian methane emissions through 4D-Var inverse modelling with satellite observations from GOSAT and IASI

NASA Astrophysics Data System (ADS)

Wilson, C. J.; Chipperfield, M.; Gloor, M.; McNorton, J.; Miller, J. B.; Gatti, L. V.; Siddans, R.; Bloom, A. A.; Basso, L. S.; Boesch, H.; Parker, R.; Monks, S. A.

2015-12-01

Methane (CH4) is emitted from a range of anthropogenic and natural sources, and since the industrial revolution its mean atmospheric concentration has climbed dramatically. CH4 produces a relatively high radiative forcing effect upon the Earth's climate, and its atmospheric lifetime of approximately 10 years makes it an appealing target for the mitigation of climate change. However, the spatial and temporal variation of CH4 emissions are not well understood, though in recent years a number of top-down and bottom-up studies have attempted to construct improved emission budgets. However, some top-down studies suffer from poor observational coverage near the Amazon basin, particularly in the planetary boundary layer. Since emissions from this region, coming mainly from wetland and burning sources, are thought to be relatively high, additional observations in this region would greatly help to constrain the geographical distribution of the global CH4 emission budget. To this end, regular flask measurements of CH4 and other trace gases have been taken during flights over four Amazonian sites since 2010, as part of the AMAZONICA project. The GOSAT has been used to retrieve global column-average CH4 concentrations since mid-2009, whilst IASI, on-board Metop-A, has also been measuring atmospheric CH4 concentrations since its launch in 2006. We present an assessment of Amazonian methane emissions for 2010 and 2011 using the TOMCAT Chemical Transport Model and the new variational inverse model, INVICAT. These models are used to attribute methane variations at each Amazon site to a source type and region, to assess the ability of our current CH4 flux estimates to reproduce these observations and to produce improved posterior emission estimates through assimilation of atmospheric observations. This study represents the first use of the INVICAT scheme to constrain emissions of any atmospheric trace gas. Whilst there is generally good agreement between the model and the observations prior to data assimilation, some high-methane events indicated by the observations are not captured by the model. We assimilate observations from the NOAA surface measurement network, from the AMAZONICA aircraft and from the GOSAT and IASI satellites, and find that tropical South American CH4 emissions approach 50 Tg(CH4)/yr.

Symposium review: Uncertainties in enteric methane inventories, measurement techniques, and prediction models.

PubMed

Hristov, A N; Kebreab, E; Niu, M; Oh, J; Bannink, A; Bayat, A R; Boland, T B; Brito, A F; Casper, D P; Crompton, L A; Dijkstra, J; Eugène, M; Garnsworthy, P C; Haque, N; Hellwing, A L F; Huhtanen, P; Kreuzer, M; Kuhla, B; Lund, P; Madsen, J; Martin, C; Moate, P J; Muetzel, S; Muñoz, C; Peiren, N; Powell, J M; Reynolds, C K; Schwarm, A; Shingfield, K J; Storlien, T M; Weisbjerg, M R; Yáñez-Ruiz, D R; Yu, Z

2018-04-18

Ruminant production systems are important contributors to anthropogenic methane (CH 4 ) emissions, but there are large uncertainties in national and global livestock CH 4 inventories. Sources of uncertainty in enteric CH 4 emissions include animal inventories, feed dry matter intake (DMI), ingredient and chemical composition of the diets, and CH 4 emission factors. There is also significant uncertainty associated with enteric CH 4 measurements. The most widely used techniques are respiration chambers, the sulfur hexafluoride (SF 6 ) tracer technique, and the automated head-chamber system (GreenFeed; C-Lock Inc., Rapid City, SD). All 3 methods have been successfully used in a large number of experiments with dairy or beef cattle in various environmental conditions, although studies that compare techniques have reported inconsistent results. Although different types of models have been developed to predict enteric CH 4 emissions, relatively simple empirical (statistical) models have been commonly used for inventory purposes because of their broad applicability and ease of use compared with more detailed empirical and process-based mechanistic models. However, extant empirical models used to predict enteric CH 4 emissions suffer from narrow spatial focus, limited observations, and limitations of the statistical technique used. Therefore, prediction models must be developed from robust data sets that can only be generated through collaboration of scientists across the world. To achieve high prediction accuracy, these data sets should encompass a wide range of diets and production systems within regions and globally. Overall, enteric CH 4 prediction models are based on various animal or feed characteristic inputs but are dominated by DMI in one form or another. As a result, accurate prediction of DMI is essential for accurate prediction of livestock CH 4 emissions. Analysis of a large data set of individual dairy cattle data showed that simplified enteric CH 4 prediction models based on DMI alone or DMI and limited feed- or animal-related inputs can predict average CH 4 emission with a similar accuracy to more complex empirical models. These simplified models can be reliably used for emission inventory purposes. The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Comparison of atmospheric CH4 concentration observed by GOSAT and in-situ measurements in Thailand and India

NASA Astrophysics Data System (ADS)

Hayashida, S.; Ono, A.; Ishikawa, S.; Terao, Y.; Takeuchi, W.

2012-12-01

The concentration of atmospheric methane (CH4) has more than doubled since pre-industrial levels and the observed long-term changes in the CH4 concentration have been attributed to anthropogenic activity. However, despite the importance of atmospheric CH4 in global warming, the strength of individual sources of CH4 remains highly uncertain [e.g.,Dlugokencky et al., 2011]. To characterize and quantify the emissions of CH4 especially in Monsoon Asia and Siberia, which are the most important regions as CH4 source, we started a new project, "Characterization and Quantification of global methane emissions by utilizing GOSAT and in-situ measurements " by support of the Environment Research and Technology Development Fund (ERTDF) from June 2012 under the umbrella of Ministry of Environment Japan. The projects includes (1) satellite data applications, (2) in-situ measurements in Siberia, over Western Pacific and in Monsoon Asia, (3) development of the inverse model to derive CH4 emissions by top-down approach, and (4) flux measurements in Siberia and Asia to improve the bottom-up inventories. As an initiatory approach in the project, we started air sampling in Thailand and India where there are only a few CH4 data of direct sampling with high precision. We took eight air samples at Kohn Kaen and Pimai in Thailand on June 9 and 10, 2012. The high CH4 concentration near rice paddy field contrasted to the lower CH4 concentration near Cassava field. We are planning to take more samples in India in mid-August. The satellite CH4 data including GOSAT and SCIAMACHY are also compared with the Land Surface Water Coverage (LSWC) and the Normalized Difference Vegetation Index (NDVI). The analysis revealed the seasonal variation in of xCH4 is closely related to the variation of the LSWC, coupled with NDVI. However, the satellite measurements are all column-averaged mixing ratio (xCH4), and therefore do not necessarily reflect high CH4 concentration near the surface over the emission regions. To optimize "inverse approach", we need to investigate the relation between xCH4 and the surface concentration, and need to combine it to the bottom-up approach. We will also discuss representativeness of GOSAT measurement from the viewpoint of spatial and time scale when it observes such heterogeneous emission regions.

Seasonal CH4 and N2O emissions and plant growth characteristics of several cultivars in direct seeded rice systems

NASA Astrophysics Data System (ADS)

Simmonds, M.; Anders, M. M.; Adviento-Borbe, M. A.; Van Kessel, C.; McClung, A.; Linquist, B.

2014-12-01

Understanding cultivar effects on field greenhouse gas (GHG) emissions in rice (Oryza sativa L.) systems is needed to improve the accuracy of predictive models used for estimating GHG emissions, and to determine to what extent choice of cultivar may have on GHG mitigation. We compared CH4 and N2O emissions, global warming potential (GWP = N2O + CH4), yield-scaled GWP (GWPY = GWP Mg-1 grain), and plant growth characteristics of 8 cultivars within 4 study sites in California and Arkansas. Seasonal CH4 emissions differed between cultivars by a factor of 2.1 and 1.3 at one California and one Arkansas site, respectively. Nitrous oxide emissions were negligible, comprised <10% of GWP, and were not different among cultivars. When sites and cultivars were pooled, and data were normalized to site averages, there was a positive correlation (r = 0.33) between root biomass at heading and seasonal CH4 emissions, but no correlation with shoot biomass at heading, or grain or straw biomass at maturity. Although differences in GWP and GWPY were observed, the consistency of some of the trends was variable across sites, indicating the importance of the genotype x environment interaction. While no high-yielding and low CH4-emitting cultivars were identified at the California sites, among the Southern varieties tested at the Arkansas site, the lowest emitting cultivar had the highest yield. This highlights the potential for breeding high-yielding varieties with low GWP, the ideal scenario to achieve low GWPY due to simultaneously mitigating GHG emissions and improving global food security.

Aircraft-Based Measurements of Point Source Methane Emissions in the Barnett Shale Basin.

PubMed

Lavoie, Tegan N; Shepson, Paul B; Cambaliza, Maria O L; Stirm, Brian H; Karion, Anna; Sweeney, Colm; Yacovitch, Tara I; Herndon, Scott C; Lan, Xin; Lyon, David

2015-07-07

We report measurements of methane (CH4) emission rates observed at eight different high-emitting point sources in the Barnett Shale, Texas, using aircraft-based methods performed as part of the Barnett Coordinated Campaign. We quantified CH4 emission rates from four gas processing plants, one compressor station, and three landfills during five flights conducted in October 2013. Results are compared to other aircraft- and surface-based measurements of the same facilities, and to estimates based on a national study of gathering and processing facilities emissions and 2013 annual average emissions reported to the U.S. EPA Greenhouse Gas Reporting Program (GHGRP). For the eight sources, CH4 emission measurements from the aircraft-based mass balance approach were a factor of 3.2-5.8 greater than the GHGRP-based estimates. Summed emissions totaled 7022 ± 2000 kg hr(-1), roughly 9% of the entire basin-wide CH4 emissions estimated from regional mass balance flights during the campaign. Emission measurements from five natural gas management facilities were 1.2-4.6 times larger than emissions based on the national study. Results from this study were used to represent "super-emitters" in a newly formulated Barnett Shale Inventory, demonstrating the importance of targeted sampling of "super-emitters" that may be missed by random sampling of a subset of the total.

Greenhouse gas emissions in a faba bean crop: incluence of management practices and cultivars

NASA Astrophysics Data System (ADS)

Sánchez-Navarro, Virginia; Zornoza, Raúl; Faz, Ángel; Fernández, Juan

2016-04-01

In this study we evaluated the effect of two cultivars of faba bean (Muchamiel and Palenca) with two different management practices (conventional and organic) on the direct emissions of N2O and CH4 during the crop cycle and their interaction with soil properties. The study was randomly designed in blocks with four replications, in plots of 10 m2. Faba bean crop spanned from 24 November 2014 to 2 March 2015. Gas samples were taken in different times (0, 30 and 60 minutes) once a week using the static gas chamber technique for crop cycle. The results showed that accumulated N2O was higher for both cultivars under conventional management practice with comparison to organic management, with an average increase of 18.27 mg m-2 in Muchamiel cultivar and 8.95 mg m-2 in Palenca cultivar. Accumulated CH4 was higher in Palenca cultivar under conventional management practice, with an average increase of 455.28 mg m-2 over this cultivar under organic management practice. We observed significant negative correlations between N2O emission and β-glucosaminidase activity, and between CH4 and sodium content in soil. In addition, CH4 emission showed a positive correlation with the enzyme activities arylesterase and cellulase. Acknowledgements: This research was financed by the FP7 European Project Eurolegume (FP7-KBBE- 613781).

[Emission inventory of greenhouse gases from agricultural residues combustion: a case study of Jiangsu Province].

PubMed

Liu, Li-hua; Jiang, Jing-yan; Zong, Liang-gang

2011-05-01

Burning of agricultural crop residues was a major source greenhouse gases. In this study, the proportion of crop straws (rice, wheat, maize, oil rape, cotton and soja) in Jiangsu used as household fuel and direct open burning in different periods (1990-1995, 1996-2000, 2001-2005 and 2006-2008) was estimated through questionnaire. The emission factors of CO2, CO, CH4 and NO20 from the above six types of crop straws were calculated by the simulated burning experiment. Thus the emission inventory of greenhouse gases from crop straws burning was established according to above the burning percentages and emission factors, ratios of dry residues to production and crop productions of different periods in Jiangsu province. Results indicated that emission factors of CO2, CO, CH4 and N2O depended on crop straw type. The emission factors of CO2 and CH4 were higher for oil rape straw than the other straws, while the maize and the rice straw had the higher N2O and CO emission factor. Emission inventory of greenhouse gases from agricultural residues burning in Jiangsu province showed, the annual average global warming potential (GWP) of six tested crop straws were estimated to be 9.18 (rice straw), 4.35 (wheat straw), 2.55 (maize straw), 1.63 (oil rape straw), 0.55 (cotton straw) and 0. 39 (soja straw) Tg CO2 equivalent, respectively. Among the four study periods, the annual average GWP had no obvious difference between the 1990-1995 and 2006-2008 periods, while the maximal annual average GWP (23.83 Tg CO2 equivalent) happened in the 1996-2000 period, and the minimum (20.30 Tg CO2 equivalent) in 1996-2000 period.

Dynamics and controls of CO2 and CH4 emissions in the wetland of a montane permafrost region, northeast China

NASA Astrophysics Data System (ADS)

Liu, Xia; Guo, Yuedong; Hu, Haiqing; Sun, Chengkun; Zhao, Xikuan; Wei, Changlei

2015-12-01

To quantify the fluxes and examine the controls on greenhouse gas emissions from the permafrost marshes where the fate of the large quantity of soil organic carbon remains poorly understood, we measured carbon dioxide (CO2) and methane (CH4) emissions in the northern region of the Great Xing'an Mountains, northeast China, in the thawing seasons of 2011 and 2012. The mean CO2 and CH4 fluxes from the marshes were estimated at 403.47 and 0.14 mg m-2 h-1 on average during the two years. Soil temperature was determined as the primary control on the seasonal greenhouse gas emissions during the growing period. The Q10 values, calculated from the exponential regression between soil temperature and CO2 emissions, suggest that the sensitivity of CO2 flux to climate warming has a high spatially variability in the study area. Absorption of atmospheric CH4 was seasonally detected at the sites with lower water table, which confirms the potential of the natural marshes as CH4 sink when water table goes down due to climate change. When viewed from the ecosystem scale, the mean annual water table level and aboveground primary production were deemed as the dominant influencing factors for the mean annual fluxes, which suggests that there were different controls on the gas emissions at different spatial scales. Therefore, the primary controls of the CO2 and CH4 emissions at different spatial scales need to be surveyed in more detail when focusing on the future alteration of greenhouse gas emissions from permafrost marshes due to climate warming.

Fall season atypically warm weather event leads to substantial CH4 loss in Arctic ecosystems?

NASA Astrophysics Data System (ADS)

Zona, Donatella; Moreaux, Virginie; Liljedahl, Anna; Losacco, Salvatore; Murphy, Patrick; Oechel, Walter

2014-05-01

In the last century (during 1875-2008) high-latitudes are warming at a rate of 1.360C century-1, almost 2 times faster than the Northern Hemisphere trend (Bekryaev et al., 2010). This warming has been more intense outside of the summer season, with anomalies of 1.09, 1.59, 1.730C in the fall, winter, and spring season respectively (Bekryaev et al., 2010). This substantial temperature anomalies have the potential to increase the emission of greenhouse gas (CO2 and CH4) fluxes from arctic tundra ecosystems. In particular, CH4 emissions, which are primarily controlled by temperature (in addition to water table), can steeply increase with warming. Despite the potential relevance of CH4 emissions, very few measurements have been performed outside of the growing season across the entire Arctic, due to logistic constrains. Importantly, no flux measurements achieved a temporal and spatial data coverage sufficient to estimate with confidence an annual CH4 emissions from tundra ecosystem in Alaska, and its sensitivity to warming. Fall 2013 was unusually warm in central and northern Alaska. Following a relatively warm summer with dramatically above-average rainfall, the October mean monthly temperatures was the 4th and top warmest in Barrow (1949-2013) and Ivotuk (1998-2013), respectively. As we just upgraded several eddy covariance towers to measure CO2 and CH4 fluxes year-round, the atypical weather conditions of fall 2013 represented a unique chance for testing the sensitivity of CH4 loss to these atypically warm temperatures. All our sites across a latitudinal gradient (from the northern site, Barrow, to the southern site, Ivotuk), presented substantial CH4 loss in the fall. Importantly, in two of these sites (Barrow, Ivotuk) where the fall weather was substantially warmer than the long term trend, fall CH4 emission represented between 44-63% of the June-November cumulative emission. Surprisingly, in the southernmost site (Ivotuk), when the temperature anomaly was the highest, cumulative fall CH4 emission outpaced even the summer emission. This shows the sensitivity of CH4 loss to abnormal conditions, and the importance of fall periods for the annual CH4 budget in these Arctic ecosystems. Bekryaev, R. V., I. V. Polyakov, and V. A. Alexeev. 2010. Role of polar amplification in long-term surface air temperature variations and modern Arctic warming. Journal of Climate 23(14):3888-3906.

Development of methane and nitrous oxide emission factors for the biomass fired circulating fluidized bed combustion power plant.

PubMed

Cho, Chang-Sang; Sa, Jae-Hwan; Lim, Ki-Kyo; Youk, Tae-Mi; Kim, Seung-Jin; Lee, Seul-Ki; Jeon, Eui-Chan

2012-01-01

This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB) boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH(4)), Nitrous oxide (N(2)O). The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF), RDF and Refused Plastic Fuel (RPF) of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH(4) and N(2)O were measured to be 2.78 ppm and 7.68 ppm, respectively. The analyzed values and data collected from the field survey were used to calculate the emission factor of CH(4) and N(2)O exhausted from the CFB boiler. As a result, the emission factors of CH(4) and N(2)O are 1.4 kg/TJ (0.9-1.9 kg/TJ) and 4.0 kg/TJ (2.9-5.3 kg/TJ) within a 95% confidence interval. Biomass combined with the combustion technology for the CFB boiler proved to be more effective in reducing the N(2)O emission, compared to the emission factor of the CFB boiler using fossil fuel.

Effect of an acidifying diet combined with zeolite and slight protein reduction on air emissions from laying hens of different ages.

PubMed

Wu-Haan, W; Powers, W J; Angel, C R; Hale, C E; Applegate, T J

2007-01-01

The objectives of the study were to evaluate the effectiveness of a reduced-emission (RE) diet containing 6.9% of a CaSO(4)-zeolite mixture and slightly reduced CP to 21-, 38-, and 59-wk-old Hy-Line W-36 hens (trials 1, 2, and 3, respectively) on egg production and emissions of NH(3), H(2)S, NO, NO(2), CO(2), CH(4), and non-CH(4) total hydrocarbons as compared with feeding a commercial (CM) diet. At each age, 640 hens were allocated, randomly to 8 environmental chambers for a 3-wk period. On an analyzed basis, the CM diet contained 18.0, 17.0, and 16.2% CP and 0.25, 0.18, and 0.20% S in trials 1, 2, and 3, and the RE diet contained 17.0, 15.5, and 15.6% CP and 0.99, 1.20, and 1.10% S in trials 1, 2, and 3. Diets were formulated to contain similar Ca and P contents. Average daily egg weight (56.3 g), average daily egg production (81%), average daily feed intake (92.4 g), and BW change (23.5 g), across ages, were unaffected by diet (P > 0.05) over the study period. Age effects were observed for all performance variables and NH(3) emissions (P < 0.05). In trials 1, 2, and 3, daily NH(3) emissions from hens fed the RE diets (185.5, 312.2, and 333.5 mg/bird) were less than emissions from hens fed the CM diet (255.1, 560.6, and 616.3 mg/bird; P < 0.01). Daily emissions of H(2)S across trials from hens fed the RE diet were 4.08 mg/bird compared with 1.32 mg/bird from hens fed the CM diet (P < 0.01). Diet (P < 0.05) and age (P < 0.05) affected emissions of CO(2) and CH(4). A diet effect (P < 0.01) on NO emissions was observed. No diet or age effects (P > 0.05) were observed for NO(2) or non-CH(4) total hydrocarbons. Results demonstrated that diet and layer age influence air emissions from poultry operations.

Carbon dioxide and methane emissions from the Yukon River system

USGS Publications Warehouse

Striegl, Robert G.; Dornblaser, Mark M.; McDonald, Cory P.; Rover, Jennifer R.; Stets, Edward G.

2012-01-01

Carbon dioxide (CO2) and methane (CH4) emissions are important, but poorly quantified, components of riverine carbon (C) budgets. This is largely because the data needed for gas flux calculations are sparse and are spatially and temporally variable. Additionally, the importance of C gas emissions relative to lateral C exports is not well known because gaseous and aqueous fluxes are not commonly measured on the same rivers. We couple measurements of aqueous CO2 and CH4 partial pressures (pCO2, pCH4) and flux across the water-air interface with gas transfer models to calculate subbasin distributions of gas flux density. We then combine those flux densities with remote and direct observations of stream and river water surface area and ice duration, to calculate C gas emissions from flowing waters throughout the Yukon River basin. CO2emissions were 7.68 Tg C yr−1 (95% CI: 5.84 −10.46), averaging 750 g C m−2 yr−1 normalized to water surface area, and 9.0 g C m−2 yr−1 normalized to river basin area. River CH4 emissions totaled 55 Gg C yr−1 or 0.7% of the total mass of C emitted as CO2 plus CH4 and ∼6.4% of their combined radiative forcing. When combined with lateral inorganic plus organic C exports to below head of tide, C gas emissions comprised 50% of total C exported by the Yukon River and its tributaries. River CO2 and CH4 derive from multiple sources, including groundwater, surface water runoff, carbonate equilibrium reactions, and benthic and water column microbial processing of organic C. The exact role of each of these processes is not yet quantified in the overall river C budget.

Assessment of the Contribution of Poultry and Pig Production to Greenhouse Gas Emissions in South Korea Over the Last 10 Years (2005 through 2014).

PubMed

Boontiam, Waewaree; Shin, Yongjin; Choi, Hong Lim; Kumari, Priyanka

2016-12-01

The goal of this study was to estimate the emissions of greenhouse gases (GHG), namely methane (CH 4 ), nitrous oxide (N 2 O), and carbon dioxide (CO 2 ) from poultry and pig production in South Korea over the last 10 years (2005 through 2014). The calculations of GHG emissions were based on Intergovernmental Panel on Climate Change (IPCC) guidelines. Over the study period, the CH 4 emission from manure management decreased in layer chickens, nursery to finishing pigs and gestating to lactating sows, but there was a gradual increase in CH 4 emission from broiler chickens and male breeding pigs. Both sows and nursery to finishing pigs were associated with greater emissions from enteric fermentation than the boars, especially in 2009. Layer chickens produced lower direct and indirect N 2 O emissions from 2009 to 2014, whereas the average direct and indirect N 2 O emissions from manure management for broiler chickens were 12.48 and 4.93 Gg CO 2 -eq/yr, respectively. Annual direct and indirect N 2 O emissions for broiler chickens tended to decrease in 2014. Average CO 2 emission from direct on-farm energy uses for broiler and layer chickens were 46.62 and 136.56 Gg CO 2 -eq/yr, respectively. For pig sectors, the N 2 O emission from direct and indirect sources gradually increased, but they decreased for breeding pigs. Carbon dioxide emission from direct on-farm energy uses reached a maximum of 53.93 Gg CO 2 -eq/yr in 2009, but this total gradually declined in 2010 and 2011. For boars, the greatest CO 2 emission occurred in 2012 and was 9.44 Gg CO 2 -eq/yr. Indirect N 2 O emission was the largest component of GHG emissions in broilers. In layer chickens, the largest contributing factor to GHG emissions was CO 2 from direct on-farm energy uses. For pig production, the largest component of GHG emissions was CH 4 from manure management, followed by CO 2 emission from direct on-farm energy use and CH 4 enteric fermentation emission, which accounted for 8.47, 2.85, and 2.82 Gg-CO 2 /yr, respectively. The greatest GHG emission intensity occurred in female breeding sows relative to boars. Overall, it is an important issue for the poultry and pig industry of South Korea to reduce GHG emissions with the effective approaches for the sustainability of agricultural practices.

Assessment of the Contribution of Poultry and Pig Production to Greenhouse Gas Emissions in South Korea Over the Last 10 Years (2005 through 2014)

PubMed Central

Boontiam, Waewaree; Shin, Yongjin; Choi, Hong Lim; Kumari, Priyanka

2016-01-01

The goal of this study was to estimate the emissions of greenhouse gases (GHG), namely methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) from poultry and pig production in South Korea over the last 10 years (2005 through 2014). The calculations of GHG emissions were based on Intergovernmental Panel on Climate Change (IPCC) guidelines. Over the study period, the CH4 emission from manure management decreased in layer chickens, nursery to finishing pigs and gestating to lactating sows, but there was a gradual increase in CH4 emission from broiler chickens and male breeding pigs. Both sows and nursery to finishing pigs were associated with greater emissions from enteric fermentation than the boars, especially in 2009. Layer chickens produced lower direct and indirect N2O emissions from 2009 to 2014, whereas the average direct and indirect N2O emissions from manure management for broiler chickens were 12.48 and 4.93 Gg CO2-eq/yr, respectively. Annual direct and indirect N2O emissions for broiler chickens tended to decrease in 2014. Average CO2 emission from direct on-farm energy uses for broiler and layer chickens were 46.62 and 136.56 Gg CO2-eq/yr, respectively. For pig sectors, the N2O emission from direct and indirect sources gradually increased, but they decreased for breeding pigs. Carbon dioxide emission from direct on-farm energy uses reached a maximum of 53.93 Gg CO2-eq/yr in 2009, but this total gradually declined in 2010 and 2011. For boars, the greatest CO2 emission occurred in 2012 and was 9.44 Gg CO2-eq/yr. Indirect N2O emission was the largest component of GHG emissions in broilers. In layer chickens, the largest contributing factor to GHG emissions was CO2 from direct on-farm energy uses. For pig production, the largest component of GHG emissions was CH4 from manure management, followed by CO2 emission from direct on-farm energy use and CH4 enteric fermentation emission, which accounted for 8.47, 2.85, and 2.82 Gg-CO2/yr, respectively. The greatest GHG emission intensity occurred in female breeding sows relative to boars. Overall, it is an important issue for the poultry and pig industry of South Korea to reduce GHG emissions with the effective approaches for the sustainability of agricultural practices. PMID:26954125

Airborne Ethane Observations in the Barnett Shale: Quantification of Ethane Flux and Attribution of Methane Emissions.

PubMed

Smith, Mackenzie L; Kort, Eric A; Karion, Anna; Sweeney, Colm; Herndon, Scott C; Yacovitch, Tara I

2015-07-07

We present high time resolution airborne ethane (C2H6) and methane (CH4) measurements made in March and October 2013 as part of the Barnett Coordinated Campaign over the Barnett Shale formation in Texas. Ethane fluxes are quantified using a downwind flight strategy, a first demonstration of this approach for C2H6. Additionally, ethane-to-methane emissions ratios (C2H6:CH4) of point sources were observationally determined from simultaneous airborne C2H6 and CH4 measurements during a survey flight over the source region. Distinct C2H6:CH4 × 100% molar ratios of 0.0%, 1.8%, and 9.6%, indicative of microbial, low-C2H6 fossil, and high-C2H6 fossil sources, respectively, emerged in observations over the emissions source region of the Barnett Shale. Ethane-to-methane correlations were used in conjunction with C2H6 and CH4 fluxes to quantify the fraction of CH4 emissions derived from fossil and microbial sources. On the basis of two analyses, we find 71-85% of the observed methane emissions quantified in the Barnett Shale are derived from fossil sources. The average ethane flux observed from the studied region of the Barnett Shale was 6.6 ± 0.2 × 10(3) kg hr(-1) and consistent across six days in spring and fall of 2013.

The predominance of young carbon in Arctic whole-lake CH4 and CO2 emissions and implications for Boreal yedoma lakes.

NASA Astrophysics Data System (ADS)

Elder, C.; Xu, X.; Walker, J. C.; Walter Anthony, K. M.; Pohlman, J.; Arp, C. D.; Townsend-Small, A.; Hinkel, K. M.; Czimczik, C. I.

2017-12-01

Lakes in Arctic and Boreal regions are hotspots for atmospheric exchange of the greenhouse gases CO2 and CH4. Thermokarst lakes are a subset of these Northern lakes that may further accelerate climate warming by mobilizing ancient permafrost C (> 11,500 years old) that has been disconnected from the active C cycle for millennia. Northern lakes are thus potentially powerful agents of the permafrost C-climate feedback. While they are critical for projecting the magnitude and timing these feedbacks from the rapidly warming circumpolar region, we lack datasets capturing the diversity of northern lakes, especially regarding their CH4contributions to whole-lake C emissions and their ability to access and mobilize ancient C. We measured the radiocarbon (14C) ages of CH4 and CO2 emitted from 60 understudied lakes and ponds in Arctic and Boreal Alaska during winter and summer to estimate the ages of the C sources yielding these gases. Integrated mean ages for whole-lake emissions were inferred from the 14C-age of dissolved gases sampled beneath seasonal ice. Additionally, we measured concentrations and 14C values of gases emitted by ebullition and diffusion in summer to apportion C emission pathways. Using a multi-sourced mass balance approach, we found that whole-lake CH4 and CO2 emissions were predominantly sourced from relatively young C in most lakes. In Arctic lakes, CH4 originated from 850 14C-year old C on average, whereas dissolved CO2 was sourced from 400 14C-year old C, and represented 99% of total dissolved C flux. Although ancient C had a minimal influence (11% of total emissions), we discovered that lakes in finer-textured aeolian deposits (Yedoma) emitted twice as much ancient C as lakes in sandy regions. In Boreal, yedoma-type lakes, CH4 and CO2 were fueled by significantly older sources, and mass balance results estimated CH4-ebullition to comprise 50-60% of whole-lake CH4 emissions. The mean 14C-age of Boreal emissions was 6,000 14C-years for CH4-C, and 2,400 14C-years for CO2-C. Seasonal differences in dissolved CH4 revealed a clear influence of trapped ebullition dissolving into the water below lake ice in Boreal, but not Arctic lakes. Together, our data demonstrate that regional surficial geology exerts a larger control than climate on C ages and gas emission pathways from lakes.

Interannual, seasonal, and retrospective analysis of the methane and carbon dioxide budgets of a temperate peatland

NASA Astrophysics Data System (ADS)

Olson, D. M.; Griffis, T. J.; Noormets, A.; Kolka, R.; Chen, J.

2013-03-01

Three years (2009-2011) of near-continuous methane (CH4) and carbon dioxide (CO2) fluxes were measured with the eddy covariance (EC) technique at a temperate peatland located within the Marcell Experimental Forest, in northern Minnesota, USA. The peatland was a net source of CH4 and a net sink of CO2 in each year with annual carbon budgets of -26.8 (±18.7), -15.5 (±14.8), and -14.6 (±21.5) g C m-2 yr-1 for 2009-2011, respectively. Differences in the seasonal hydrometeorological conditions among the three study years were most pronounced during 2011, which was considerably warmer (+1.3°C) and wetter (+40 mm) than the 30 year average. The annual CH4 budget was +11.8 (±3.1), +12.2 (±3.0), and +24.9 (±5.6) g C m-2 yr-1 for the respective years and accounted for 23%-39% of the annual carbon budget. The larger CH4 emission in 2011 is attributed to significant warming of the peat column coupled with a high water table position throughout the entire growing season. Historical (1991-2011) CH4 emissions were estimated based on long-term hydrometeorological records and functional relationships derived from our 3 year field study. The predicted historical annual CH4 budget ranged from +7.8 to +15.2 (±2.7) g CH4-C m-2 yr-1. Recent (2007-2011) increases in temperature, precipitation, and rising water table at this site suggest that CH4 emissions have been increasing, but were generally greater from 1991 to 1999 when average soil temperature and precipitation were higher than in recent years. The global warming potential (considering CO2 and CH4) for this peatland was calculated based on a 100 year time horizon. In all three study years, the peatland had a net positive radiative forcing on climate and was greatest (+187 g C m-2) in 2011. The interannual variability in CH4 exchange at this site suggests high sensitivity to variations in hydrometeorological conditions.

Large-scale patterns in summer diffusive CH4 fluxes across boreal lakes, and contribution to diffusive C emissions.

PubMed

Rasilo, Terhi; Prairie, Yves T; Del Giorgio, Paul A

2015-03-01

Lakes are a major component of boreal landscapes, and whereas lake CO2 emissions are recognized as a major component of regional C budgets, there is still much uncertainty associated to lake CH4 fluxes. Here, we present a large-scale study of the magnitude and regulation of boreal lake summer diffusive CH4 fluxes, and their contribution to total lake carbon (C) emissions, based on in situ measurements of concentration and fluxes of CH4 and CO2 in 224 lakes across a wide range of lake type and environmental gradients in Québec. The diffusive CH4 flux was highly variable (mean 11.6 ± 26.4 SD mg m(-2)  d(-1) ), and it was positively correlated with temperature and lake nutrient status, and negatively correlated with lake area and colored dissolved organic matter (CDOM). The relationship between CH4 and CO2 concentrations fluxes was weak, suggesting major differences in their respective sources and/or regulation. For example, increasing water temperature leads to higher CH4 flux but does not significantly affect CO2 flux, whereas increasing CDOM concentration leads to higher CO2 flux but lower CH4 flux. CH4 contributed to 8 ± 23% to the total lake C emissions (CH4  + CO2 ), but 18 ± 25% to the total flux in terms of atmospheric warming potential, expressed as CO2 -equivalents. The incorporation of ebullition and plant-mediated CH4 fluxes would further increase the importance of lake CH4 . The average Q10 of CH4 flux was 3.7, once other covarying factors were accounted for, but this apparent Q10 varied with lake morphometry and was higher for shallow lakes. We conclude that global climate change and the resulting shifts in temperature will strongly influence lake CH4 fluxes across the boreal biome, but these climate effects may be altered by regional patterns in lake morphometry, nutrient status, and browning. © 2014 John Wiley & Sons Ltd.

A comparison of CH4, N2O and CO2 emissions from three different cover types in a municipal solid waste landfill.

PubMed

Wang, Xiaojun; Jia, Mingsheng; Lin, Xiangyu; Xu, Ying; Ye, Xin; Kao, Chih Ming; Chen, Shaohua

2017-04-01

High-density polyethylene (HDPE) membranes are commonly used as a cover component in sanitary landfills, although only limited evaluations of its effect on greenhouse gas (GHG) emissions have been completed. In this study, field GHG emission were investigated at the Dongbu landfill, using three different cover systems: HDPE covering; no covering, on the working face; and a novel material-Oreezyme Waste Cover (OWC) material as a trial material. Results showed that the HDPE membrane achieved a high CH 4 retention, 99.8% (CH 4 mean flux of 12 mg C m -2 h -1 ) compared with the air-permeable OWC surface (CH4 mean flux of 5933 mg C m -2 h -1 ) of the same landfill age. Fresh waste at the working face emitted a large fraction of N 2 O, with average fluxes of 10 mg N m -2 h -2 , while N 2 O emissions were small at both the HDPE and the OWC sections. At the OWC section, CH 4 emissions were elevated under high air temperatures but decreased as landfill age increased. N 2 O emissions from the working face had a significant negative correlation with air temperature, with peak values in winter. A massive presence of CO 2 was observed at both the working face and the OWC sections. Most importantly, the annual GHG emissions were 4.9 Gg yr -1 in CO 2 equivalents for the landfill site, of which the OWC-covered section contributed the most CH 4 (41.9%), while the working face contributed the most N 2 O (97.2%). HDPE membrane is therefore, a recommended cover material for GHG control. Monitoring of GHG emissions at three different cover types in a municipal solid waste landfill during a 1-year period showed that the working face was a hotspot of N 2 O, which should draw attention. High CH 4 fluxes occurred on the permeable surface covering a 1- to 2-year-old landfill. In contrast, the high-density polyethylene (HDPE) membrane achieved high CH 4 retention, and therefore is a recommended cover material for GHG control.

Response of the global climate to changes in atmospheric chemical composition due to fossil fuel burning

NASA Technical Reports Server (NTRS)

Cess, R. D.; Hameed, S.; Hogan, J. S.

1980-01-01

Tropospheric ozone and methane might increase in the future as the result of increasing anthropogenic emissions of CO, NOx and CH4 due to fossil fuel burning. Since O3 and CH4 are both greenhouse gases, increases in their concentrations could augment global warming due to larger future amounts of atmospheric CO2. To test this possible climatic impact, a zonal energy-balance climate model has been combined with a vertically-averaged tropospheric chemical model. The latter model includes all relevant chemical reactions which affect species derived from H2O, O2, CH4 and NOx. The climate model correspondingly incorporates changes in the infrared heating of the surface-troposphere system resulting from chemically induced changes in tropospheric ozone and methane. This coupled climate-chemical model indicates that global climate is sensitive to changes in emissions of CO, NOx and CH4, and that future increases in these emissions could enhance global warming due to increasing atmospheric CO2.

Methane emissions partially offset “blue carbon” burial in mangroves

PubMed Central

Maher, Damien T.

2018-01-01

Organic matter burial in mangrove forests results in the removal and long-term storage of atmospheric CO2, so-called “blue carbon.” However, some of this organic matter is metabolized and returned to the atmosphere as CH4. Because CH4 has a higher global warming potential than the CO2 fixed in the organic matter, it can offset the CO2 removed via carbon burial. We provide the first estimate of the global magnitude of this offset. Our results show that high CH4 evasion rates have the potential to partially offset blue carbon burial rates in mangrove sediments on average by 20% (sensitivity analysis offset range, 18 to 22%) using the 20-year global warming potential. Hence, mangrove sediment and water CH4 emissions should be accounted for in future blue carbon assessments.

GOSAT observations of anthropogenic emission of carbon dioxide and methane

NASA Astrophysics Data System (ADS)

Janardanan, Rajesh; Maksyutov, Shamil; Oda, Tomohiro; Saito, Makoto; Ito, Akihiko; Kaiser, Johannes W.; Ganshin, Alexander; Yoshida, Yukio; Yokota, Tatsuya; Matsunaga, Tsuneo

2017-04-01

Carbon dioxide (CO2) and methane (CH4) are the most important greenhouse gases in terms of radiative forcing. Human activities such as combustion of fossil fuel (for CO2), and gas leakage, animal agriculture, rice cultivation and landfill emissions (for CH4), are considered to be major sources of their emissions. Global emissions datasets usually depend on emission estimates reported by countries, which are seldom evaluated in an objective way. Here we present a method for delineating anthropogenic contributions to global atmospheric CO2 and CH4 (2009-2014) concentration fields using GOSAT observations of column-average dry air mole fractions (XCO2 and XCH4) and atmospheric transport model simulations using high-resolution emissions datasets (ODIAC for CO2 and EDGAR for CH4). The XCO2 and XCH4 concentration enhancements due to anthropogenic emissions are estimated at all GOSAT observation locations using the transport model simulation. We calculated threshold values to classify GOSAT observations into two categories: (1) data influenced by the anthropogenic sources and (2) those not influenced. We defined a clean background (averaged concentrations of GOSAT data that are free from contamination) in 10˚ ×10˚ regions over the globe and subtracted the background values from individual GOSAT observations. The anomalies (GOSAT observed values minus background values) were binned and compared to model-based anomalies over continental regions and selected countries. For CO2, we have found global and regional linear relationships between model and observed anomalies especially for Eurasia and North America. The analysis for East Asian region showed a systematic bias that is somewhat comparable in magnitude to the uncertainties in emission inventories in that region, which were reported by recent studies. In the case of CH4, we found a good match between inventory-based estimates and GOSAT observations for continental regions and large countries. The inventory-based estimate over North American region is biased which is in agreement with recent studies. Currently, our method is limited by the numbers of GOSAT observations available. If sufficient numbers of satellite observations are available from a instrument like GOSAT, our method could be a useful tool for monitoring greenhouse gas emissions using the regression slope between modeled and observed anomalies as a correction factor for nationally reported emissions.

Spatially Resolved Measurements of CO2 and CH4 Concentration and Gas-Exchange Velocity Highly Influence Carbon-Emission Estimates of Reservoirs

PubMed Central

2017-01-01

The magnitude of diffusive carbon dioxide (CO2) and methane (CH4) emission from man-made reservoirs is uncertain because the spatial variability generally is not well-represented. Here, we examine the spatial variability and its drivers for partial pressure, gas-exchange velocity (k), and diffusive flux of CO2 and CH4 in three tropical reservoirs using spatially resolved measurements of both gas concentrations and k. We observed high spatial variability in CO2 and CH4 concentrations and flux within all three reservoirs, with river inflow areas generally displaying elevated CH4 concentrations. Conversely, areas close to the dam are generally characterized by low concentrations and are therefore not likely to be representative for the whole system. A large share (44–83%) of the within-reservoir variability of gas concentration was explained by dissolved oxygen, pH, chlorophyll, water depth, and within-reservoir location. High spatial variability in k was observed, and kCH4 was persistently higher (on average, 2.5 times more) than kCO2. Not accounting for the within-reservoir variability in concentrations and k may lead to up to 80% underestimation of whole-system diffusive emission of CO2 and CH4. Our findings provide valuable information on how to develop field-sampling strategies to reliably capture the spatial heterogeneity of diffusive carbon fluxes from reservoirs. PMID:29257874

Atmospheric variability of methane over Pakistan, Afghanistan and adjoining areas using retrievals from SCIAMACHY/ENVISAT

NASA Astrophysics Data System (ADS)

ul-Haq, Zia; Tariq, Salman; Ali, Muhammad

2015-12-01

In the present work we have studied spatial and temporal variability of methane total column (MTC) over Pakistan and neighboring regions of Afghanistan, India and Iran by using observations of SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) aboard EOS ENVISAT. Satellite measurements show large spatio-temporal variations in MTC over the study domain at different time scales. We find an average MTC of 1787±22 ppb (annual average±standard deviation) with 3.7% (slope 7.14±1.28, y-intercept 1751±7.19, r=0.91) increase during the period of January 2003 to April 2012. An enhanced MTC is observed mostly over the Indo-Gangetic Plain and areas with high anthropogenic activities. MTC exhibits a seasonal peak of 1804±28 ppb in summer followed by autumn (1800±25 ppb) and winter (1777±24 ppb). We have also discussed anthropogenic emission estimates in the study area obtained from EDGAR database. Substantial increments of 77% and 61% are observed in anthropogenic CH4 emissions for Pakistan and Afghanistan, respectively, during 1990-2008. Anthropogenic CH4 emissions from enteric fermentation and livestock sectors are found to be the highest. EDGAR data have also identified megacity Lahore, Sukkur, megacity Karachi, Dera Ghazi Khan, megacity Delhi and Ahmedabad as large point sources of CH4 emissions in the region. The emissions from Karachi show the highest increase of 107%, while Lahore is found with the highest annual average emissions of 8.8×10-10 kg m-2 s-1.

Toward a better understanding and quantification of methane emissions from shale gas development

PubMed Central

Caulton, Dana R.; Shepson, Paul B.; Santoro, Renee L.; Sparks, Jed P.; Howarth, Robert W.; Ingraffea, Anthony R.; Cambaliza, Maria O. L.; Sweeney, Colm; Karion, Anna; Davis, Kenneth J.; Stirm, Brian H.; Montzka, Stephen A.; Miller, Ben R.

2014-01-01

The identification and quantification of methane emissions from natural gas production has become increasingly important owing to the increase in the natural gas component of the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern PA in June 2012. A large regional flux, 2.0–14 g CH4 s−1 km−2, was quantified for a ∼2,800-km2 area, which did not differ statistically from a bottom-up inventory, 2.3–4.6 g CH4 s−1 km−2. Large emissions averaging 34 g CH4/s per well were observed from seven well pads determined to be in the drilling phase, 2 to 3 orders of magnitude greater than US Environmental Protection Agency estimates for this operational phase. The emissions from these well pads, representing ∼1% of the total number of wells, account for 4–30% of the observed regional flux. More work is needed to determine all of the sources of methane emissions from natural gas production, to ascertain why these emissions occur and to evaluate their climate and atmospheric chemistry impacts. PMID:24733927

Toward a better understanding and quantification of methane emissions from shale gas development.

PubMed

Caulton, Dana R; Shepson, Paul B; Santoro, Renee L; Sparks, Jed P; Howarth, Robert W; Ingraffea, Anthony R; Cambaliza, Maria O L; Sweeney, Colm; Karion, Anna; Davis, Kenneth J; Stirm, Brian H; Montzka, Stephen A; Miller, Ben R

2014-04-29

The identification and quantification of methane emissions from natural gas production has become increasingly important owing to the increase in the natural gas component of the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern PA in June 2012. A large regional flux, 2.0-14 g CH4 s(-1) km(-2), was quantified for a ∼ 2,800-km(2) area, which did not differ statistically from a bottom-up inventory, 2.3-4.6 g CH4 s(-1) km(-2). Large emissions averaging 34 g CH4/s per well were observed from seven well pads determined to be in the drilling phase, 2 to 3 orders of magnitude greater than US Environmental Protection Agency estimates for this operational phase. The emissions from these well pads, representing ∼ 1% of the total number of wells, account for 4-30% of the observed regional flux. More work is needed to determine all of the sources of methane emissions from natural gas production, to ascertain why these emissions occur and to evaluate their climate and atmospheric chemistry impacts.

Carbon emission from global hydroelectric reservoirs revisited.

PubMed

Li, Siyue; Zhang, Quanfa

2014-12-01

Substantial greenhouse gas (GHG) emissions from hydropower reservoirs have been of great concerns recently, yet the significant carbon emitters of drawdown area and reservoir downstream (including spillways and turbines as well as river reaches below dams) have not been included in global carbon budget. Here, we revisit GHG emission from hydropower reservoirs by considering reservoir surface area, drawdown zone and reservoir downstream. Our estimates demonstrate around 301.3 Tg carbon dioxide (CO2)/year and 18.7 Tg methane (CH4)/year from global hydroelectric reservoirs, which are much higher than recent observations. The sum of drawdown and downstream emission, which is generally overlooked, represents 42 % CO2 and 67 % CH4 of the total emissions from hydropower reservoirs. Accordingly, the global average emissions from hydropower are estimated to be 92 g CO2/kWh and 5.7 g CH4/kWh. Nonetheless, global hydroelectricity could currently reduce approximate 2,351 Tg CO2eq/year with respect to fuel fossil plant alternative. The new findings show a substantial revision of carbon emission from the global hydropower reservoirs.

Characterizing Methane Emission Response to the Past 60 Years of Permafrost Thaw in Thermokarst Lakes

NASA Astrophysics Data System (ADS)

Meyer, F. J.; Walter Anthony, K. M.; Regmi, P.; Engram, M. J.; Wirth, L.; Grosse, G.

2016-12-01

In this NASA ABoVE-funded project, we combine geospatial data products derived from airborne and spaceborne remote sensing (RS) data with targeted field observations and modeling in order to quantify ecosystem responses to Arctic and boreal environmental change. Specifically, we quantify methane (CH4) ebullition (bubbling) emissions associated with 60 years of permafrost thaw in thousands of Alaskan and NW Canadian lakes by direct observation with RS systems. To achieve our goals, we have developed statistically-significant models that are using SAR, optical and infrared RS data in order to detect and quantify CH4 ebullition emissions at intra-, whole- and regional-lake scales. We also established a relationship between observed CH4 ebullition and average annual soil organic carbon (SOC) inputs to a handful of Alaskan lakes via thermokarst-margin expansion during recent decades using field data, radiocarbon dating and modeling. Our paper we will provide an overview of the goals, datasets, and methods used for the various components of this project. We will present on (1) the collection of new and synthesis of existing field data on CH4 ebullition, thaw-bulbs and SOC; (2) the analysis of existing data from aerial surveys, SAR and optical RS of CH4 in lake ice; (3) the orthorectification of historic aerial photos for comparison to high-resolution satellite imagery to produce fine-scale regional maps of lake area change, (4) the modelling of permafrost SOC quantities eroded into lakes; (5) the radiocarbon dating of CH4 and SOC, (6) GIS modeling to produce multi-temporal regional maps of historic lake area change, associated CH4 emissions, and permafrost SOC stocks; and (7) outreach to stakeholders at Alaska village and rural community field sites. To demonstrate the scientific relevance of our work we will also showcase a set of research results that we have been able to achieve so far. These will include (1) first regional-scale RS-based estimates of lake-borne CH4 ebullition emissions; (2) regional scale estimates of lake area change from an analysis of 50 years of remote sensing data; and (3) regression models linking lake area change to CH4 emissions.

Spatial surveys of CH4 emissions with a mobile multi-gas sensing platform during DISCOVER-AQ and CAREBEIJING-NCP field campaigns

NASA Astrophysics Data System (ADS)

Tao, L.; Sun, K.; Miller, D. J.; Zhu, T.; Zondlo, M. A.

2013-12-01

Methane (CH4) is the second most important greenhouse gas, which has a greenhouse warming potential 25 times that of carbon dioxide (CO2) on a per molecule basis and century timescale. Since pre-industrial times, the atmospheric concentration of CH4 has increased by 150% and contributes significantly to global warming. CH4 emits from a wide range of both anthropogenic and natural sources, which make the CH4 emission measurements difficult. As a result, there is still a large uncertainty in the partitioning of estimated CH4 emissions. Mobile platforms have been used and demonstrated as an effective tool to map the CH4 emissions and provide a large spatial coverage over cities and localized rural sources. However, the information we can get is very limited based on the measured atmospheric CH4 concentrations solely, due to the complexity of the various CH4 sources and limited time resolution. We have developed a mobile multi-gas open-path laser-based sensing platform that performs high resolution (5 Hz), in-situ and simultaneous measurements of NH3, CH4, CO2, N2O, CO and H2O. The combination of six important trace gases helps to understand the characteristics of different CH4 sources and identify them. With this mobile platform, we have participated and perform spatial surveys in two field campaigns: DISCOVER-AQ in California and CAREBEIJING-NCP in China. During the DISCOVER-AQ campaigns, our mobile platform has covered around 4300 km (81 hours) in winter 2013 including agricultural regions in San Joaquin Valley and multiple cities urban areas along the coast. In the CAREBEIJING-NCP campaign, a survey along 3300 km (61 hours) of roadway in Beijing and its surrounding North China Plain has been conducted in June, 2013. A wide variety of CH4 emission sources have been identified and measured, such as livestock farming, oil/gas drilling, wastewater treatment, landfill, biomass burning and motor vehicles (include liquefied nature gas (LNG) vehicles). For example, the averaged value of measured CH4 in Tulare County, CA is ~2.44 ppmv with a maximum and minimum value of 1.91 ppmv and 67.80 ppmv, respectively. The dominant sources in Tulare County are dairy farms. Whereas in Beijing , the mean value of measured CH4 concentration for a full day sampling on the fourth ring road is ~2.40 ppmv with a minimum and maximum value of 2.18 ppmv and 12.8 ppmv CH4. The major sources in Beijing are motor vehicles, wastewater treatment facilities and gas stations. We analyze the signatures of different CH4 emission sources and provide their partitioning in our sample dataset.

[Estimation of carbonaceous gases emission from forest fires in Xiao Xing'an Mountains of Northeast China in 1953-2011].

PubMed

Hu, Hai-Qing; Luo, Bi-Zhen; Wei, Shu-Jing; Sun, Long; Wei, Shu-Wei; Wen, Zheng-Min

2013-11-01

Based on the forest resources investigation data and the forest fire inventory in 1953-2011, in combining with our field research in burned areas and our laboratory experiments, this paper estimated the carbonaceous gases carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), and nonmethane hydrocarbons (NMHC) emission from the forest fires in Xiao Xing' an Mountains of Heilongjiang Province, Northeast China in 1953-2011. The total carbon emission from the forest fires in the Xiao Xing'an Mountains in 1953-2011 was 1.12 x 10(7) t, and the annual emission was averagely 1.90 x10(5) t, accounting for 1.7% of the annual average total carbon emission from the forest fires in China. The emission of CO2, CO, CH4, and NMHC was 3.39 x 10(7), 1.94 x 10(5), 1.09 x 10(5), and 7.46 x 10(4) t, respectively, and the corresponding annual average emission was 5.74 x 10(5), 3.29 x 10(4), 1.85 x 10(3), and 1.27 x 10(3) t, accounting for 1.4%, 1.2%, 1.7%, and 1.1% of the annual carbonaceous gases emitted from the forest fires in China, respectively. The combustion efficiency and the carbon emission per unit burned area of different forest types decreased in order of coniferous forest > broad-leaved forest > coniferous broadleaved mixed forest. Some rational forest fire management measures were put forward.

Methane Flux of Amazonian Peatland Ecosystems: Large Ecosystem Fluxes with Substantial Contribution from Palm (maritia Flexuosa) STEM Emissions

NASA Astrophysics Data System (ADS)

Van Haren, J. L. M.; Cadillo-Quiroz, H.

2015-12-01

Methane (CH4) emissions through plants have long been known in wetlands. However, most measurements have focused on stem tops and leaves. Recently, measurements at the lower parts of stems have shown that stem emissions can exceed soil CH4 emissions in Asian peatlands (Pangala et al. 2013). The addition of stem fluxes to soil fluxes for total ecosystem fluxes has the potential to bridge the discrepancy between modeled to measured and bottom-up to top-down flux estimates. Our measurements in peatlands of Peru show that especially Mauritia flexuosa, a palm species, can emit very large quantities of CH4, although most trees emitted at least some CH4. We used flexible stem chambers to adapt to stems of any size above 5cm in diameter. The chambers were sampled in closed loop with a Gasmet DX4015 for flux measurements, which lasted ~5 minutes after flushing with ambient air. We found that M. flexuosa stem fluxes decrease with height along the stem and were positively correlated with soil fluxes. Most likely CH4 is transported up the stem with the xylem water. Measured M. flexuosa stem fluxes below 1.5m averaged 11.2±1.5 mg-C m-2 h-1 (±95% CI) with a maximum of 123±3.5 mg-C m-2 h-1 (±SE), whereas soil fluxes averaged 6.7±1.7 mg-C m-2 h-1 (±95% CI) with a maximum of 31.6±0.4 mg-C m-2 h-1 (±SE). Significant CH4 fluxes were measured up to 5 m height along the stems. Combined with the high density of ~150 M. flexuosa individuals per hectare in these peatlands and the consistent diameter of ~30cm, the high flux rates add ~20% to the soil flux. With anywhere between 1 and 5 billion M. flexuosa stems across Amazon basin wetlands, stem fluxes from this palm species could represent a major addition to the overall Amazon basin CH4 flux.

Development of Methane and Nitrous Oxide Emission Factors for the Biomass Fired Circulating Fluidized Bed Combustion Power Plant

PubMed Central

Cho, Chang-Sang; Sa, Jae-Hwan; Lim, Ki-Kyo; Youk, Tae-Mi; Kim, Seung-Jin; Lee, Seul-Ki; Jeon, Eui-Chan

2012-01-01

This study makes use of this distinction to analyze the exhaust gas concentration and fuel of the circulating fluidized bed (CFB) boiler that mainly uses wood biomass, and to develop the emission factors of Methane (CH4), Nitrous oxide (N2O). The fuels used as energy sources in the subject working sites are Wood Chip Fuel (WCF), RDF and Refused Plastic Fuel (RPF) of which heating values are 11.9 TJ/Gg, 17.1 TJ/Gg, and 31.2 TJ/Gg, respectively. The average concentrations of CH4 and N2O were measured to be 2.78 ppm and 7.68 ppm, respectively. The analyzed values and data collected from the field survey were used to calculate the emission factor of CH4 and N2O exhausted from the CFB boiler. As a result, the emission factors of CH4 and N2O are 1.4 kg/TJ (0.9–1.9 kg/TJ) and 4.0 kg/TJ (2.9–5.3 kg/TJ) within a 95% confidence interval. Biomass combined with the combustion technology for the CFB boiler proved to be more effective in reducing the N2O emission, compared to the emission factor of the CFB boiler using fossil fuel. PMID:23365540

Greenhouse gas emissions from home composting of organic household waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andersen, J.K., E-mail: jka@env.dtu.d; Boldrin, A.; Christensen, T.H.

2010-12-15

The emission of greenhouse gases (GHGs) is a potential environmental disadvantage of home composting. Because of a lack of reliable GHG emission data, a comprehensive experimental home composting system was set up. The system consisted of six composting units, and a static flux chamber method was used to measure and quantify the GHG emissions for one year composting of organic household waste (OHW). The average OHW input in the six composting units was 2.6-3.5 kg week{sup -1} and the temperature inside the composting units was in all cases only a few degrees (2-10 {sup o}C) higher than the ambient temperature.more » The emissions of methane (CH{sub 4}) and nitrous oxide (N{sub 2}O) were quantified as 0.4-4.2 kg CH{sub 4} Mg{sup -1} input wet waste (ww) and 0.30-0.55 kg N{sub 2}O Mg{sup -1} ww, depending on the mixing frequency. This corresponds to emission factors (EFs) (including only CH{sub 4} and N{sub 2}O emissions) of 100-239 kg CO{sub 2}-eq. Mg{sup -1} ww. Composting units exposed to weekly mixing had the highest EFs, whereas the units with no mixing during the entire year had the lowest emissions. In addition to the higher emission from the frequently mixed units, there was also an instant release of CH{sub 4} during mixing which was estimated to 8-12% of the total CH{sub 4} emissions. Experiments with higher loads of OHW (up to 20 kg every fortnight) entailed a higher emission and significantly increased overall EFs (in kg substance per Mg{sup -1} ww). However, the temperature development did not change significantly. The GHG emissions (in kg CO{sub 2}-eq. Mg{sup -1} ww) from home composting of OHW were found to be in the same order of magnitude as for centralised composting plants.« less

Greenhouse gas emissions from home composting of organic household waste.

PubMed

Andersen, J K; Boldrin, A; Christensen, T H; Scheutz, C

2010-12-01

The emission of greenhouse gases (GHGs) is a potential environmental disadvantage of home composting. Because of a lack of reliable GHG emission data, a comprehensive experimental home composting system was set up. The system consisted of six composting units, and a static flux chamber method was used to measure and quantify the GHG emissions for one year composting of organic household waste (OHW). The average OHW input in the six composting units was 2.6-3.5 kg week(-1) and the temperature inside the composting units was in all cases only a few degrees (2-10 °C) higher than the ambient temperature. The emissions of methane (CH(4)) and nitrous oxide (N(2)O) were quantified as 0.4-4.2 kg CH(4)Mg(-1) input wet waste (ww) and 0.30-0.55 kg N(2)OMg(-1)ww, depending on the mixing frequency. This corresponds to emission factors (EFs) (including only CH(4) and N(2)O emissions) of 100-239 kg CO(2)-eq.Mg(-1)ww. Composting units exposed to weekly mixing had the highest EFs, whereas the units with no mixing during the entire year had the lowest emissions. In addition to the higher emission from the frequently mixed units, there was also an instant release of CH(4) during mixing which was estimated to 8-12% of the total CH(4) emissions. Experiments with higher loads of OHW (up to 20 kg every fortnight) entailed a higher emission and significantly increased overall EFs (in kg substance per Mg(-1)ww). However, the temperature development did not change significantly. The GHG emissions (in kg CO(2)-eq.Mg(-1)ww) from home composting of OHW were found to be in the same order of magnitude as for centralised composting plants. Copyright © 2010 Elsevier Ltd. All rights reserved.

Effects of animal activity and air temperature on methane and ammonia emissions from a naturally ventilated building for dairy cows

NASA Astrophysics Data System (ADS)

Ngwabie, N. M.; Jeppsson, K.-H.; Gustafsson, G.; Nimmermark, S.

2011-12-01

Knowledge of how different factors affect gas emissions from animal buildings can be useful for emission prediction purposes and for the improvement of emission abatement techniques. In this study, the effects of dairy cow activity and indoor air temperature on gas emissions were examined. The concentrations of CH 4, NH 3, CO 2 and N 2O inside and outside a dairy cow building were measured continuously between February and May together with animal activity and air temperature. The building was naturally ventilated and had a solid concrete floor which sloped towards a central urine gutter. Manure was scraped from the floor once every hour in the daytime and once every second hour at night into a partly covered indoor pit which was emptied daily at 6 a.m. and at 5 p.m. Gas emissions were calculated from the measured gas concentrations and ventilation rates estimated by the CO 2 balance method. The animal activity and emission rates of CH 4 and NH 3 showed significant diurnal variations with two peaks which were probably related to the feeding routine. On an average day, CH 4 emissions ranged from 7 to 15 g LU -1 h -1 and NH 3 emissions ranged from 0.4 to 1.5 g LU -1 h -1 (1 LU = 500 kg animal weight). Mean emissions of CH 4 and NH 3 were 10.8 g LU -1 h -1 and 0.81 g LU -1 h -1, respectively. The NH 3 emissions were comparable to emissions from tied stall buildings and represented a 4% loss in manure nitrogen. At moderate levels, temperature seems to affect the behaviour of dairy cows and in this study where the daily indoor air temperature ranged from about 5 up to about 20 °C, the daily activity of the cows decreased with increasing indoor air temperature ( r = -0.78). Results suggest that enteric fermentation is the main source of CH 4 emissions from systems of the type in this study, while NH 3 is mainly emitted from the manure. Daily CH 4 emissions increased significantly with the activity of the cows ( r = 0.61) while daily NH 3 emissions increased significantly with the indoor air temperatures ( r = 0.66). Daily CH 4 emissions were negatively correlated to the indoor air temperature ( r = -0.84). This suggests that increased daily indoor air temperatures due to seasonal changes may bring about decreased animal activity which may decrease the release of CH 4 from dairy cows. Finally, changes in daily NH 3 emissions were influenced more by the indoor air temperature than by the activity of the cows.

Effects of three years of simulated nitrogen deposition on soil nitrogen dynamics and greenhouse gas emissions in a Korean pine plantation of northeast China.

PubMed

Song, Lei; Tian, Peng; Zhang, Jinbo; Jin, Guangze

2017-12-31

Continuously enhanced nitrogen (N) deposition alters the pattern of N and carbon (C) transformations, and thus influences greenhouse gas emissions. It is necessary to clarify the effect of N deposition on greenhouse gas emissions and soil N dynamics for an accurate assessment of C and N budgets under increasing N deposition. In this study, four simulated N deposition treatments (control [CK: no N addition], low-N [L: 20kgNha -1 yr -1 ], medium-N [M: 40kgNha -1 yr -1 ], and high-N [H: 80kgNha -1 yr -1 ]) were operated from 2014. Carbon dioxide, methane and nitrous oxide fluxes were monitored semimonthly, as were soil variables such as temperature, moisture and the concentrations of total dissolved N (TDN), NO 3 - , NO 2 - , NH 4 + , and dissolved organic N (DON) in soil solutions. The simulated N deposition resulted in a significant increase in TDN, NO 3 - and DON concentrations in soil solutions. The average CO 2 emission rate ranged from 222.6mgCO 2 m -2 h -1 in CK to 233.7mgCO 2 m -2 h -1 in the high-N treatment. Three years of simulated N deposition had no effect on soil CO 2 emission, which was mainly controlled by soil temperature. The mean N 2 O emission rate during the whole 3years was 0.02mgN 2 Om -2 h -1 for CK, which increased significantly to 0.05mgN 2 Om -2 h -1 in the high-N treatment. The N 2 O emission rate positively correlated with NH 4 + concentrations, and negatively correlated with soil moisture. The average CH 4 flux during the whole 3years was -0.74μgCH 4 m -2 h -1 in CK, which increased to 1.41μgCH 4 m -2 h -1 in the low-N treatment. CH 4 flux positively correlated with NO 3 - concentrations. These results indicate that short-term N deposition did not affect soil CO 2 emissions, while CH 4 and N 2 O emissions were sensitive to N deposition. Copyright © 2017 Elsevier B.V. All rights reserved.

First In Vivo Measurements of Methane Emissions from Ruminant Livestock Enteric Fermentation in Mexico Using Respiration Chambers

NASA Astrophysics Data System (ADS)

Castelan-Ortega, O. A.; Ku-Vera, J. C.; Molina, L. T.; Pedraza-Beltrán, P. E.; Canul-Solis, J. R.; Piñeiro-Vázquez, A.; Hernández-Pineda, G.; Benaouda, M.

2015-12-01

Until recently there were no facilities in Mexico to measure in vivo methane (CH4) emission by livestock. Inventories were calculated using emission factors from the IPCC, so the uncertainty in calculation is high. In 2014 the first laboratory equipped to measure CH4 started operations at the Universidad Autónoma de Yucatán. The second laboratory was built at the Universidad Autónoma del Estado de México and it began operations in June 2015. The first laboratory consists of two open-circuit respiration chambers, which are currently used to measure CH4 emissions by cattle in Mexico's tropical regions. Chamber dimensions are: 3.0 x 2.14 x 1.44 m (DxHxW). Air exiting the chambers is drawn by a mass flowmeter (Flowkit 500) at a rate of 500 L/min. The air sample is passed through a multiplexer and then through a chemical desiccant before entering the methane infrared analyzer (MA-10). All the instruments were fabricated by Sable Systems International, Las Vegas, USA. The average CH4 emission factor for Nelore bulls of 350 kg live weight fed with a tropical grass was 117.3 L/day and it increased to 198.6 L/day when 3 kg of concentrate feed were supplemented. For adult crossbred cows also fed with a tropical grass CH4 emission ranged from 92.7 to 137.3 L/day. The second laboratory consist of a respiration chamber of the head box type. It consists of a head box of 1.05 x 0.8 x 1.80 m (WxDxH) made of 3.5 x 3.5 cm stainless steel angle, and on the bottom, top, sides, back and front of the head box, 0.6 cm clear acrylic sheeting was used to provide comfortable vision to the animal, and a metabolic cage of 1.08 x 2.92 x 1.8 m (WxDxH) made of iron tubes with steel sheeting floor adapted for feces and urine collection. The methane analyzer and the mass flowmeter were of the same model as in the first laboratory. Once calibrated, in vivo measurements were performed using high yielding adult Holstein cows with an average live weight of 573 ±71 kg and milk yield of 30kg/day. The cows were fed maize silage, alfalfa hay and 4 kg concentrate feed. The average CH4 production was 484 ± 132 L/day. Emission factors obtained from both laboratories differed substantially from those used previously for inventories calculation in Mexico. IPCC factors are higher than those observed in our work particularly for cattle in the tropical regions of the country.

Methane and Nitrous Oxide Emissions Reduced Following Conversion of Rice Paddies to Inland Crab-Fish Aquaculture in Southeast China.

PubMed

Liu, Shuwei; Hu, Zhiqiang; Wu, Shuang; Li, Shuqing; Li, Zhaofu; Zou, Jianwen

2016-01-19

Aquaculture is an important source of atmospheric methane (CH4) and nitrous oxide (N2O), while few direct flux measurements are available for their regional and global source strength estimates. A parallel field experiment was performed to measure annual CH4 and N2O fluxes from rice paddies and rice paddy-converted inland crab-fish aquaculture wetlands in southeast China. Besides N2O fluxes dependent on water/sediment mineral N and CH4 fluxes related to water chemical oxygen demand, both CH4 and N2O fluxes from aquaculture were related to water/sediment temperature, sediment dissolved organic carbon, and water dissolved oxygen concentration. Annual CH4 and N2O fluxes from inland aquaculture averaged 0.37 mg m(-2) h(-1) and 48.1 μg m(-2) h(-1), yielding 32.57 kg ha(-1) and 2.69 kg N2O-N ha(-1), respectively. The conversion of rice paddies to aquaculture significantly reduced CH4 and N2O emissions by 48% and 56%, respectively. The emission factor for N2O was estimated to be 0.66% of total N input in the feed or 1.64 g N2O-N kg(-1) aquaculture production in aquaculture. The conversion of rice paddies to inland aquaculture would benefit for reconciling greenhouse gas mitigation and agricultural income increase as far as global warming potentials and net ecosystem economic profits are of concomitant concern. Some agricultural practices such as better aeration and feeding, and fallow season dredging would help to lower CH4 and N2O emissions from inland aquaculture. More field measurements from inland aquaculture are highly needed to gain an insight into national and global accounting of CH4 and N2O emissions.

Use and uncertainty evaluation of a process-based model for assessing the methane budgets of global terrestrial ecosystems

NASA Astrophysics Data System (ADS)

Ito, A.; Inatomi, M.

2011-07-01

We assessed the global terrestrial budget of methane (CH4) using a process-based biogeochemical model (VISIT) and inventory data. Emissions from wetlands, paddy fields, biomass burning, and plants, and oxidative consumption by upland soils, were simulated by the model. Emissions from livestock ruminants and termites were evaluated by an inventory approach. These CH4 flows were estimated for each of the model's 0.5° × 0.5° grid cells from 1901 to 2009, while accounting for atmospheric composition, meteorological factors, and land-use changes. Estimation uncertainties were examined through ensemble simulations using different parameterization schemes and input data (e.g. different wetland maps and emission factors). From 1996 to 2005, the average global terrestrial CH4 budget was estimated on the basis of 576 simulations, and terrestrial ecosystems were found to be a net source of 320.4 ± 18.9 Tg CH4 yr-1. Wetland and ruminant emissions were the primary sources. The results of our simulations indicate that sources and sinks are distributed highly heterogeneously over the Earth's land surface. Seasonal and interannual variability in the terrestrial budget was assessed. The trend of increasing net terrestrial sources and its relationship with temperature variability imply that terrestrial CH4 feedbacks will play an increasingly important role as a result of future climatic change.

Estimation of wetland methane emissions in a biogeochemical model integrated in CESM: sensitivity analysis and comparison against surface and atmospheric measurements

NASA Astrophysics Data System (ADS)

Meng, L.; Mahowald, N. M.; Hess, P. G.; Yavitt, J. B.; Riley, W. J.; Subin, Z. M.; Lawrence, D. M.; Swenson, S. C.; Jauhiainen, J.; Fuka, D. R.

2012-12-01

Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources is still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al. 2011) into the Community Land Model 4.0 (CLM4CN) in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model because there are large differences between simulated fractional inundation and satellite observations and thus we do not use CLM4 simulated inundated area. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993-2004 were 256 Tg CH4 y-1 (including the soil sink). Tropical wetlands contributed 201 Tg CH4 y-1, or 78% of the global wetland flux. Northern latitude (>50N) systems contributed 12 Tg CH4 y-1. Our sensitivity studies show a large range (150-346 Tg CH4 y-1) in predicted global methane emissions. In order to evaluate our methane emissions on the regional and global scales against atmospheric measurements, we conducted simulations with the Community Atmospheric Model with chemistry (CAM-chem) forced with our baseline simulation of wetland and rice paddy emissions along with other methane sources (e.g. anthropogenic, fire, and termite emissions) and compared model simulations against measured atmospheric concentrations obtained from the World Data Centre for Greenhouse Gases (WDCGG) at http://ds.data.jma.go.jp/gmd/wdcgg/. Overall, using our estimated wetland and rice paddy emissions, CAM-chem model can produce seasonal and interannual variations of observed atmospheric concentration performs well. Thus, within the current level of uncertainty, our emissions appear to be reasonable.

[Effect of Biochar on Soil Greenhouse Gas Emissions in Semi-arid Region].

PubMed

Guo, Yan-liang; Wang, Dan-dan; Zheng, Ji-yong; Zhao, Shi-wei; Zhang, Xing-chang

2015-09-01

This study aimed to investigate the effects of biochar addition on the emission of greenhouse gases from farmland soil in semi-arid region. Through an in-situ experiments, the influence of sawdust biochar(J) and locust tree skin biochar (H) at three doses (1%, 3%, and 5% of quality percentage) on C2, CH4 and N2O emissions were studied within the six months in the south of Ningxiaprovince. The results indicated that soil CO2 emission flux was slightly increased with the addition doses for both biochars, and the averaged CO2 emission flux for sawdust and locust tree skin biochar was enhanced by 1. 89% and 3. 34% compared to the control, but the difference between treatments was not statistically significant. The soil CH4 emission was decreased with the increasing of biochar doses, by 1. 17%, 2. 55%, 4. 32% for J1, J3, J5 and 2. 35%, 5. 83%, 7. 32% for H1, H3, H5, respectively. However, the difference was statistically significant only for J5, H3 and H5 treatments (P <0. 05). Across addition doses, there was no apparent effect on soil N2O emission. Our study indicated that the biochar has no significant influence on soil CO2 and N2O emissions within six months in semi-arid region and can significantly influence soil CH4 emissions (P < 0. 05). As for biochar type, the locust tree skin biochar is significantly better than the sawdust biochar in terms of restraining CH4 emission(P = 0. 048).

Characterization of interferences to in situ observations of δ13CH4 and C2H6 when using a cavity ring-down spectrometer at industrial sites

NASA Astrophysics Data System (ADS)

Assan, Sabina; Baudic, Alexia; Guemri, Ali; Ciais, Philippe; Gros, Valerie; Vogel, Felix R.

2017-06-01

Due to increased demand for an understanding of CH4 emissions from industrial sites, the subject of cross sensitivities caused by absorption from multiple gases on δ13CH4 and C2H6 measured in the near-infrared spectral domain using CRDS has become increasingly important. Extensive laboratory tests are presented here, which characterize these cross sensitivities and propose corrections for the biases they induce. We found methane isotopic measurements to be subject to interference from elevated C2H6 concentrations resulting in heavier δ13CH4 by +23.5 ‰ per ppm C2H6 / ppm CH4. Measured C2H6 is subject to absorption interference from a number of other trace gases, predominantly H2O (with an average linear sensitivity of 0.9 ppm C2H6 per % H2O in ambient conditions). Yet, this sensitivity was found to be discontinuous with a strong hysteresis effect and we suggest removing H2O from gas samples prior to analysis. The C2H6 calibration factor was calculated using a GC and measured as 0.5 (confirmed up to 5 ppm C2H6). Field tests at a natural gas compressor station demonstrated that the presence of C2H6 in gas emissions at an average level of 0.3 ppm shifted the isotopic signature by 2.5 ‰, whilst after calibration we find that the average C2H6 : CH4 ratio shifts by +0.06. These results indicate that, when using such a CRDS instrument in conditions of elevated C2H6 for CH4 source determination, it is imperative to account for the biases discussed within this study.

Temporal variability in methane fluxes from tropical peatlands within the Peruvian Amazon

NASA Astrophysics Data System (ADS)

Murphy, Wayne; Berrio, Juan Carlos; Boom, Arnoud; Page, Sue; Arn Teh, Yit

2016-04-01

Tropical peatlands are one of the largest soil carbon (C) reservoirs globally and play a significant role in modulating fluxes of C between the tropical biosphere and atmosphere. These C fluxes are of global importance because tropical wetlands are the single largest natural source of atmospheric methane (CH4); while land-use change and biomass burning also contribute to the growing global atmospheric carbon dioxide (CO2) burden. Amazonian peatlands play a potentially important role in regional and global atmospheric budgets of C because of their large extent. These ecosystems cover an estimated 150,000km2, which is roughly three-quarters the size of Indonesian peatlands; the world's most extensive and well-studied tropical peatlands. Here we report CH4 fluxes from a lowland tropical peatland in the Pastaza-Maranon foreland basin in Peru, one of the largest peatland complexes in the lowland Amazon Basin. Strong prolonged seasonal rainfall events and the annual Amazon River flood-pulse may lead to pronounced temporal variability in biogeochemical cycling and trace gas fluxes, and this study explored how CH4 fluxes varied among wet and dry season periods in a number of key vegetation types in this region. Sampling was concentrated in 3 of the most numerically-dominant vegetation types: Forested Swamp, Mixed Palm Swamp and Mauritia flexuosa-dominated Palm Swamp, with data collection occurring in both wet and dry seasons over a 2 year period from 2012-2014 (4 field campaigns in total). Overall mean CH4 fluxes from the Forested Swamp, Mixed Palm Swamp and Mauritia flexuosa-dominated Palm Swamp for the entire sampling period were 31.06 ± 3.42 mg CH4 - C m-2 d-1, 52.03 ± 16.05 mg CH4 - C m-2 d-1 and 36.68 ± 4.32 mg CH4 - C m-2 d-1. CH4 emissions, when averaged across the entire dataset, did not differ significantly among habitats. However, when CH4 emissions were aggregated by season, the Mixed Palm Swamp showed a significantly different emissions from all other habitats (Fischers LSD, P<0.0001). All of the vegetation types showed pronounced seasonality in CH4 fluxes. Mean dry and wet season fluxes for the Forested Swamp were 18.82 ± 2.61 mg CH4 - C m-2 d-1 and 60.42 ± 9.11 mg CH4 - C m-2 d-1; 85.51 ± 26.36 mg CH4 - C m-2 d-1 and 5.15 ± 2.73 mg CH4 - C m-2 d-1 for the Mixed Palm Swamp; and 25.54 ± 2.9 mg CH4 - C m-2 d-1 and 53.36 ± 9.78 mg CH4 - C m-2 d-1 for the Mauritia flexuosa-dominated Palm Swamp. Dry season fluxes did not differ from each other between years. In contrast, wet season fluxes showed significant differences between years, with CH4 emissions in the 2012 wet season more than double the emissions from the 2014 year. These observed differences in CH4 emissions during different seasons suggest that seasonal variability in water availability and flooding is a key control on CH4 emissions from Amazonian peatlands.

Greenhouse gas (CO2 and CH4) emissions from a high altitude hydroelectric reservoir in the tropics (Riogrande II, Colombia)

NASA Astrophysics Data System (ADS)

Guérin, Frédéric; Leon, Juan

2015-04-01

Tropical hydroelectric reservoirs are considered as very significant source of methane (CH4) and carbon dioxide (CO2), especially when flooding dense forest. We report emissions from the Rio Grande II Reservoir located at 2000 m.a.s.l. in the Colombian Andes. The dam was built at the confluence of the Rio Grande and Rio Chico in 1990. The reservoir has a surface of 12 km2, a maximum depth of 40m and a residence time of 2.5 month. Water quality (temperature, oxygen, pH, conductivity), nitrate, ammonium, dissolved and particulate organic carbon (DOC and POC), CO2 and CH4 were monitored bi-monthly during 1.5 year at 9 stations in the reservoir. Diffusive fluxes of CO2 and CH4 and CH4 ebullition were measured at 5 stations. The Rio grande II Reservoir is weakly stratified thermally with surface temperature ranging from 20 to 24°C and a constant bottom temperature of 18°C. The reservoir water column is well oxygenated at the surface and usually anoxic below 10m depth. At the stations close to the tributaries water inputs, the water column is well mixed and oxygenated from the surface to the bottom. As reported for other reservoirs located in "clear water" watersheds, the concentrations of nutrients are low (NO3-<0.1ppm, NH4+<0.2ppm), the concentrations of DOC are high (2-8 mg L-1) and POC concentrations are low (< 3 mg L-1). Surface CH4 concentrations at the central stations of the reservoirs are 0.5 μmol L-1 (0.07-2.14 μmol L-1) and 3 times higher at the stations close to the tributaries inputs (up to 7 μmol L-1). In the hypolimnion, CH4 concentration is <100 μmol L-1 in the wet season and can reach up to 400 μmol L-1 in the dry season. The spatial and temporal variability are lower for CO2. Surface CO2 concentration was on average 72 μmol L-1 (up to 300) and hypolimnic concentration ranged between 250 and 1000 μmol L-1. The CO2 diffusive flux is 517±331 mmol m-2 d-1 with little seasonal and spatial variations. At the center of the reservoir, the median diffusive flux of CH4 is 1.75 mmol m-2 d-1 and sporadic high fluxes (>10 mmol m-2 d-1) were observed during the dry season. Close to the tributaries water inputs where the water column is well mixed, the average diffusive flux is 8 mmol m-2 d-1. CH4 ebullition was 3.5 mmol m-2 d-1 and no ebullition was observed for a water depth higher than 5m. The zone under the influence of the water inputs from tributaries represents 25% of the surface of the reservoir but contributed half of total CH4 emissions from the reservoir (29MgC month-1). Ebullition contributed only to 12% of total CH4 emissions over a year but it contributed up to 60% during the dry season. CH4 emissions from the Rio Grande Reservoir contributed 30% of the total GHG emissions (38GgCO2eq y-1). Overall, this study show that the majority of CH4 emissions from this reservoir occur through hotspot and hot moments and that mountainous reservoir located in the tropics could have emission factors as high as Amazonian reservoirs.

Development of the Vista Methane Emissions Inventory for Southern California: A GIS-Based Approach for Mapping Methane Emissions

NASA Astrophysics Data System (ADS)

Carranza, V.; Frausto-Vicencio, I.; Rafiq, T.; Verhulst, K. R.; Hopkins, F. M.; Rao, P.; Duren, R. M.; Miller, C. E.

2016-12-01

Atmospheric methane (CH4) is the second most prevalent anthropogenic greenhouse gas. Improved estimates of CH4 emissions from cities is essential for carbon cycle science and climate mitigation efforts. Development of spatially-resolved carbon emissions data sets may offer significant advances in understanding and managing carbon emissions from cities. Urban CH4 emissions in particular require spatially resolved emission maps to help resolve uncertainties in the CH4 budget. This study presents a Geographic Information System (GIS)-based approach to mapping CH4 emissions using locations of infrastructure known to handle and emit methane. We constrain the spatial distribution of sources to the facility level for the major CH4 emitting sources in the South Coast Air Basin. GIS spatial modeling was combined with publicly available datasets to determine the distribution of potential CH4 sources. The datasets were processed and validated to ensure accuracy in the location of individual sources. This information was then used to develop the Vista emissions prior, which is a one-year long, spatially-resolved CH4 emissions estimate. Methane emissions were calculated and spatially allocated to produce 1 km x 1 km gridded CH4 emission map spanning the Los Angeles Basin. In future work, the Vista CH4 emissions prior will be compared with existing, coarser-resolution emissions estimates and will be evaluated in inverse modeling studies using atmospheric observations. The Vista CH4 emissions inventory presents the first detailed spatial maps of CH4 sources and emissions estimates in the Los Angeles Basin and is a critical step towards sectoral attribution of CH4 emissions at local to regional scales.

Transport and transformation of soil-derived CO2, CH4 and DOC sustain CO2 supersaturation in small boreal streams.

PubMed

Rasilo, Terhi; Hutchins, Ryan H S; Ruiz-González, Clara; Del Giorgio, Paul A

2017-02-01

Streams are typically supersaturated in carbon dioxide (CO 2 ) and methane (CH 4 ), and are recognized as important components of regional carbon (C) emissions in northern landscapes. Whereas there is consensus that in most of the systems the CO 2 emitted by streams represents C fixed in the terrestrial ecosystem, the pathways delivering this C to streams are still not well understood. We assessed the contribution of direct soil CO 2 injection versus the oxidation of soil-derived dissolved organic C (DOC) and CH 4 in supporting CO 2 supersaturation in boreal streams in Québec. We measured the concentrations of CO 2 , CH 4 and DOC in 43 streams and adjacent soil waters during summer base-flow period. A mass balance approach revealed that all three pathways are significant, and that the mineralization of soil-derived DOC and CH 4 accounted for most of the estimated stream CO 2 emissions (average 75% and 10%, respectively), and that these estimated contributions did not change significantly between the studied low order (≤3) streams. Whereas some of these transformations take place in the channel proper, our results suggest that they mainly occur in the hyporheic zones of the streams. Our results further show that stream CH 4 emissions can be fully explained by soil CH 4 inputs. This study confirms that these boreal streams, and in particular their hyporheic zones, are extremely active processors of soil derived DOC and CH 4 , not just vents for soil produced CO 2 . Copyright © 2016 Elsevier B.V. All rights reserved.

Use of a process-based model for assessing the methane budgets of global terrestrial ecosystems and evaluation of uncertainty

NASA Astrophysics Data System (ADS)

Ito, A.; Inatomi, M.

2012-02-01

We assessed the global terrestrial budget of methane (CH4) by using a process-based biogeochemical model (VISIT) and inventory data for components of the budget that were not included in the model. Emissions from wetlands, paddy fields, biomass burning, and plants, as well as oxidative consumption by upland soils, were simulated by the model. Emissions from ruminant livestock and termites were evaluated by using an inventory approach. These CH4 flows were estimated for each of the model's 0.5° × 0.5° grid cells from 1901 to 2009, while accounting for atmospheric composition, meteorological factors, and land-use changes. Estimation uncertainties were examined through ensemble simulations using different parameterization schemes and input data (e.g., different wetland maps and emission factors). From 1996 to 2005, the average global terrestrial CH4 budget was estimated on the basis of 1152 simulations, and terrestrial ecosystems were found to be a net source of 308.3 ± 20.7 Tg CH4 yr-1. Wetland and livestock ruminant emissions were the primary sources. The results of our simulations indicate that sources and sinks are distributed highly heterogeneously over the Earth's land surface. Seasonal and interannual variability in the terrestrial budget was also assessed. The trend of increasing net emission from terrestrial sources and its relationship with temperature variability imply that terrestrial CH4 feedbacks will play an increasingly important role as a result of future climatic change.

Effects of the fungicides mancozeb and chlorothalonil on fluxes of CO2, N2O, and CH4 in a fertilized Colorado grassland soil

USGS Publications Warehouse

Kinney, C.A.; Mosier, A.R.; Ferrer, I.; Furlong, E.T.; Mandernack, K.W.

2004-01-01

Management of agricultural soil plays an important role in present and future atmospheric concentrations of the greenhouse gases carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). Pesticides are used as management tools in crop production, but little is known about their effects on soil-atmosphere exchange of CO2, N2O, and CH4. Field studies described in this paper determined the effect of two commonly used fungicides, mancozeb and chlorothalonil, on trace gas exchange. Separate experimental plots, 1 m2, were established in nitrogen fertilized no-tilled native grassland and tilled soils with and without fungicide application. Two studies were conducted. The first study was initiated in June 1999 and lasted for 1 year with monthly flux measurements from tilled and no-till soils. The second study commenced in August 2001 with twelve weekly measurements from tilled soils only. From both studies mancozeb suppressed emissions of CO2 and N2O in the tilled soil by an average of 28% and 47%, respectively. This suppression corresponded with efficacy periods of 14-29 and 56-77 days, respectively. From the no-till soils mancozeb decreased CO2 and N2O emissions by 33% and 80% for periods of 29 and 94 days, respectively. Mancozeb inhibited CH4 consumption in the first study by 46% and 71% in the tilled and no-till soil for periods of 8 and 29 days, respectively, but had no effect in the second study. From both studies chlorothalonil initially suppressed CO2 and N2O emissions and enhanced CH4 uptake in the tilled soil by an average of 37%, 40%, and 115%, respectively. These effects corresponded with efficacy periods of 14-29, 21-56, and 1-14 days, respectively. In the no-till soil chlorothalonil inhibited CO2 and N2O emissions and enhanced CH4 uptake by 29%, 48%, and 86% for periods of 29, 56, and 56 days, respectively. Following the initial period of suppression, chlorothalonil subsequently enhanced N2O emissions in the tilled soil by an average of 51% and in the no-till soil by 81% before returning to near background levels. The beginning of increased N2O emissions from the chlorothalonil-amended plots corresponded with a maximum soil concentration of the chlorothalonil degradate, 4-hydroxy-2, 5, 6-trichloroisophthalonitrile. The site specific global warming potential (GWP) resulting from the fluxes of CO2, N2O, and CH4 from all soils was determined to decrease by an average 26% and 21% as a result of a single application of mancozeb or chlorothalonil, respectively. The decrease in CO2 emissions in the fungicide-amended plots potentially could result in the conservation of as much as 1200 and 2400 kg C ha-1 yr-1 organic carbon in the tilled and no-till plots, respectively. Therefore it is feasible that application of certain fungicides to agricultural soil might lead to enhanced soil carbon sequestration and thus have additional positive effects on atmospheric CO2 concentrations. Copyright 2004 by the American Geophysical Union.

Interstellar PAH emission in the 11-14 micron region: new insights from laboratory data and a tracer of ionized PAHs

NASA Technical Reports Server (NTRS)

Hudgins, D. M.; Allamandola, L. J.

1999-01-01

The Ames infrared spectral database of isolated, neutral and ionized polycyclic aromatic hydrocarbons (PAHS) shows that aromatic CH out-of-plane bending frequencies are significantly shifted upon ionization. For solo- and duet-CH groups, the shift is pronounced and consistently toward higher frequencies. The solo-CH modes are blueshifted by an average of 27 cm-1 and the duet-CH modes by an average of 17 cm-1. For trio- and quartet-CH groups, the ionization shifts of the out-of-plane modes are more erratic and typically more modest. As a result of these ionization shifts, the solo-CH out-of-plane modes move out of the region classically associated with these vibrations in neutral PAHS, falling instead at frequencies well above those normally attributed to out-of-plane bending, vibrations of any type. In addition, for the compact PAHs studied, the duet-CH out-of-plane modes are shifted into the frequency range traditionally associated with the solo-CH modes. These results refine our understanding of the origin of the dominant interstellar infrared emission feature near 11.2 microns, whose envelope has traditionally been attributed only to the out-of-plane bending of solo-CH groups on PAHS, and provide a natural explanation for the puzzling emission feature near 11.0 microns within the framework of the PAH model. Specifically, the prevalent but variable long-wavelength wing or shoulder that is often observed near 11.4 microns likely reflects the contributions of duet-CH units in PAH cations. Also, these results indicate that the emission between 926 and 904 cm-1 (10.8 and 11.1 microns) observed in many sources can be unambiguously attributed to the out-of-plane wagging, of solo-CH units in moderately sized (fewer than 50 carbon atom) PAH cations, making this emission an unequivocal tracer of ionized interstellar PAHS.

Greenhouse gas and ammonia emissions from an open-freestall dairy in southern idaho.

PubMed

Leytem, April B; Dungan, Robert S; Bjorneberg, David L; Koehn, Anita C

2013-01-01

Concentrated dairy operations emit trace gases such as ammonia (NH), methane (CH), and nitrous oxide (NO) to the atmosphere. The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. Our objective was to determine the emission rates of NH, CH, and NO from the open-freestall and wastewater pond source areas on a commercial dairy in southern Idaho using a flush system with anaerobic digestion. Gas concentrations and wind statistics were measured and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open-freestall source area were 0.08 kg NH, 0.41 kg CH, and 0.02 kg NO. Average emissions from the wastewater ponds (g m d) were 6.8 NH, 22 CH, and 0.2 NO. The combined emissions on a per cow per day basis from the open-freestall and wastewater pond areas averaged 0.20 kg NH and 0.75 kg CH. Combined NO emissions were not calculated due to limited available data. The wastewater ponds were the greatest source of total farm NH emissions (67%) in spring and summer. The emissions of CH were approximately equal from the two source areas in spring and summer. During the late fall and winter months, the open-freestall area constituted the greatest source area of NH and CH emissions. Data from this study can be used to develop trace gas emissions factors from open-freestall dairies in southern Idaho and other open-freestall production systems in similar climatic regions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

A multi-scale comparison of modeled and observed seasonal methane emissions in northern wetlands

DOE PAGES

Xu, Xiyan; Riley, William J.; Koven, Charles D.; ...

2016-09-13

Wetlands are the largest global natural methane (CH 4) source, and emissions between 50 and 70° N latitude contribute 10-30 % to this source. Predictive capability of land models for northern wetland CH 4 emissions is still low due to limited site measurements, strong spatial and temporal variability in emissions, and complex hydrological and biogeochemical dynamics. To explore this issue, we compare wetland CH 4 emission predictions from the Community Land Model 4.5 (CLM4.5-BGC) with site- to regional-scale observations. A comparison of the CH 4 fluxes with eddy flux data highlighted needed changes to the model's estimate of aerenchyma area,more » which we implemented and tested. The model modification substantially reduced biases in CH 4 emissions when compared with CarbonTracker CH 4 predictions. CLM4.5 CH 4 emission predictions agree well with growing season (May–September) CarbonTracker Alaskan regional-level CH 4 predictions and site-level observations. However, CLM4.5 underestimated CH 4 emissions in the cold season (October–April). The monthly atmospheric CH 4 mole fraction enhancements due to wetland emissions are also assessed using the Weather Research and Forecasting-Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) model coupled with daily emissions from CLM4.5 and compared with aircraft CH 4 mole fraction measurements from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) campaign. Both the tower and aircraft analyses confirm the underestimate of cold-season CH 4 emissions by CLM4.5. The greatest uncertainties in predicting the seasonal CH 4 cycle are from the wetland extent, cold-season CH 4 production and CH 4 transport processes. We recommend more cold-season experimental studies in high-latitude systems, which could improve the understanding and parameterization of ecosystem structure and function during this period. Predicted CH 4 emissions remain uncertain, but we show here that benchmarking against observations across spatial scales can inform model structural and parameter improvements.« less

A multi-scale comparison of modeled and observed seasonal methane emissions in northern wetlands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Xiyan; Riley, William J.; Koven, Charles D.

Wetlands are the largest global natural methane (CH 4) source, and emissions between 50 and 70° N latitude contribute 10-30 % to this source. Predictive capability of land models for northern wetland CH 4 emissions is still low due to limited site measurements, strong spatial and temporal variability in emissions, and complex hydrological and biogeochemical dynamics. To explore this issue, we compare wetland CH 4 emission predictions from the Community Land Model 4.5 (CLM4.5-BGC) with site- to regional-scale observations. A comparison of the CH 4 fluxes with eddy flux data highlighted needed changes to the model's estimate of aerenchyma area,more » which we implemented and tested. The model modification substantially reduced biases in CH 4 emissions when compared with CarbonTracker CH 4 predictions. CLM4.5 CH 4 emission predictions agree well with growing season (May–September) CarbonTracker Alaskan regional-level CH 4 predictions and site-level observations. However, CLM4.5 underestimated CH 4 emissions in the cold season (October–April). The monthly atmospheric CH 4 mole fraction enhancements due to wetland emissions are also assessed using the Weather Research and Forecasting-Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) model coupled with daily emissions from CLM4.5 and compared with aircraft CH 4 mole fraction measurements from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) campaign. Both the tower and aircraft analyses confirm the underestimate of cold-season CH 4 emissions by CLM4.5. The greatest uncertainties in predicting the seasonal CH 4 cycle are from the wetland extent, cold-season CH 4 production and CH 4 transport processes. We recommend more cold-season experimental studies in high-latitude systems, which could improve the understanding and parameterization of ecosystem structure and function during this period. Predicted CH 4 emissions remain uncertain, but we show here that benchmarking against observations across spatial scales can inform model structural and parameter improvements.« less

Development of methane emission factors for enteric fermentation in cattle from Benin using IPCC Tier 2 methodology.

PubMed

Kouazounde, J B; Gbenou, J D; Babatounde, S; Srivastava, N; Eggleston, S H; Antwi, C; Baah, J; McAllister, T A

2015-03-01

The objective of this study was to develop emission factors (EF) for methane (CH4) emissions from enteric fermentation in cattle native to Benin. Information on livestock characteristics and diet practices specific to the Benin cattle population were gathered from a variety of sources and used to estimate EF according to Tier 2 methodology of the 2006 Intergovernmental Panel on Climate Change (IPCC) Guidelines for National Greenhouse Gas Inventories. Most cattle from Benin are Bos taurus represented by Borgou, Somba and Lagune breeds. They are mainly multi-purpose, being used for production of meat, milk, hides and draft power and grazed in open pastures and crop lands comprising tropical forages and crops. Estimated enteric CH4 EFs varied among cattle breeds and subcategory owing to differences in proportions of gross energy intake expended to meet maintenance, production and activity. EFs ranged from 15.0 to 43.6, 16.9 to 46.3 and 24.7 to 64.9 kg CH4/head per year for subcategories of Lagune, Somba and Borgou cattle, respectively. Average EFs for cattle breeds were 24.8, 29.5 and 40.2 kg CH4/head per year for Lagune, Somba and Borgou cattle, respectively. The national EF for cattle from Benin was 39.5 kg CH4/head per year. This estimated EF was 27.4% higher than the default EF suggested by IPCC for African cattle with the exception of dairy cattle. The outcome of the study underscores the importance of obtaining country-specific EF to estimate global enteric CH4 emissions.

Evaluating greenhouse gas emissions from hydropower complexes on large rivers in Eastern Washington

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arntzen, Evan V.; Miller, Benjamin L.; O'Toole, Amanda C.

2013-03-15

Water bodies, such as freshwater lakes, are known to be net emitters of carbon dioxide (CO2), and methane (CH4). In recent years, significant greenhouse gas (GHG) emissions from tropical, boreal, and mid-latitude reservoirs have been reported. At a time when hydropower is increasing worldwide, better understanding of seasonal and regional variation in GHG emissions is needed in order to develop a predictive understanding of such fluxes within man-made impoundments. We examined power-producing dam complexes within xeric temperate locations in the northwestern United States. Sampling environments on the Snake (Lower Monumental Dam Complex) and Columbia Rivers (Priest Rapids Dam Complex) includedmore » tributary, mainstem, embayment, forebay, and tailrace areas during winter and summer 2012. At each sampling location, GHG measurement pathways included surface gas flux, degassing as water passed through dams during power generation, ebullition within littoral embayments, and direct sampling of hyporheic pore-water. Measurements were also carried out in a free-flowing reach of the Columbia River to estimate unaltered conditions. Surface flux resulted in very low emissions, with reservoirs acting as a sink for CO2 (up to –262 mg m-2 d-1, which is within the range previously reported for similarly located reservoirs). Surface flux of methane remained below 1 mg CH4 m-2d-1, a value well below fluxes reported previously for temperate reservoirs. Water passing through hydroelectric projects acted as a sink for CO2 during winter and a small source during summer, with mean degassing fluxes of –117 and 4.5 t CO2 d-1, respectively. Degassing of CH4 was minimal, with mean fluxes of 3.1 × 10-6 and –5.6 × 10-4 t CH4 d-1 during winter and summer, respectively. Gas flux due to ebullition was greater in coves located within reservoirs than in coves within the free flowing Hanford Reach–and CH4 flux exceeded that of CO2. Methane emissions varied widely across sampling locations, ranging from 10.5 to 1039 mg CH4 m-2 d-1, with mean fluxes of 324 mg CH4 m-2 d-1in Lower Monumental Dam reservoir and 482 mg CH4 m-2d-1 in the Priest Rapids Dam reservoir. The magnitude of methane flux due to ebullition was unexpectedly high, and falls within the range recently reported for other temperate reservoirs around the world, further suggesting that this methane source should be considered in estimates of global greenhouse gas emissions. Methane flux from sediment pore-water within littoral embayments averaged 4.2 mg m-2 d-1 during winter and 8.1 mg m-2 d-1 during summer, with a peak flux of 19.8 mg m-2d-1 (at the same location where CH4 ebullition was also the greatest). Carbon dioxide flux from sediment pore-water averaged approximately 80 mg m-2d-1 with little difference between winter and summer. Similar to emissions from ebullition, flux from sediment pore-water was higher in reservoirs than in the free flowing reach.« less

Soil-atmosphere exchange of nitrous oxide, nitric oxide, and methane under secondary succession of pasture to forest in the Atlantic lowlands of Costa Rica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keller, M.; Reiners, W.A.

We investigated changes in soil-atmosphere flux of CH{sub 4}, N{sub 2}O, and NO resulting from the succession of pasture to forest in the Atlantic lowlands of Costa Rica. We studied a dozen sites intensively for over one year in order to measure rates and to understand controlling mechanisms for gas exchange. CH{sub 4} flux was controlled primarily by soil moisture content. Soil consumption of atmospheric CH{sub 4} was greatest when soils were relatively dry. Forest soils consumed CH{sub 4} while pasture soils which had poor drainage generally produced CH{sub 4}. The seasonal pattern of N{sub 2}O emissions from forest soilsmore » was related exponentially to soil water-filled pore space. Annual average N{sub 2}O emissions correlated with soil exchangeable NO{sub 3}{sup -} concentrations. Soil-atmosphere NO flux was greatest when soils were relatively dry. We found the largest NO emissions from abandoned pasture sites. Combining these data with those from another study in the Atlantic lowlands of Costa Rica that focused on deforestation, we present a 50-year chronosequence of trace gas emissions that extends from natural conditions, through disturbance and natural recovery. The soil-atmosphere fluxes of CH{sub 4} and N{sub 2}O and NO may be restored to predisturbance rates during secondary succession. The changes in trace gas emissions following deforestation, through pasture use and secondary succession, may be explained conceptually through reference to two major controlling factors, nitrogen availability and soil-atmosphere diffusive exchange of gases as it is influenced by soil moisture content and soil compaction. 59 refs., 6 figs., 3 tabs.« less

Molecular mechanisms of water table lowering and nitrogen deposition in affecting greenhouse gas emissions from a Tibetan alpine wetland.

PubMed

Wang, Hao; Yu, Lingfei; Zhang, Zhenhua; Liu, Wei; Chen, Litong; Cao, Guangmin; Yue, Haowei; Zhou, Jizhong; Yang, Yunfeng; Tang, Yanhong; He, Jin-Sheng

2017-02-01

Rapid climate change and intensified human activities have resulted in water table lowering (WTL) and enhanced nitrogen (N) deposition in Tibetan alpine wetlands. These changes may alter the magnitude and direction of greenhouse gas (GHG) emissions, affecting the climate impact of these fragile ecosystems. We conducted a mesocosm experiment combined with a metagenomics approach (GeoChip 5.0) to elucidate the effects of WTL (-20 cm relative to control) and N deposition (30 kg N ha -1  yr -1 ) on carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) fluxes as well as the underlying mechanisms. Our results showed that WTL reduced CH 4 emissions by 57.4% averaged over three growing seasons compared with no-WTL plots, but had no significant effect on net CO 2 uptake or N 2 O flux. N deposition increased net CO 2 uptake by 25.2% in comparison with no-N deposition plots and turned the mesocosms from N 2 O sinks to N 2 O sources, but had little influence on CH 4 emissions. The interactions between WTL and N deposition were not detected in all GHG emissions. As a result, WTL and N deposition both reduced the global warming potential (GWP) of growing season GHG budgets on a 100-year time horizon, but via different mechanisms. WTL reduced GWP from 337.3 to -480.1 g CO 2 -eq m -2 mostly because of decreased CH 4 emissions, while N deposition reduced GWP from 21.0 to -163.8 g CO 2 -eq m -2 , mainly owing to increased net CO 2 uptake. GeoChip analysis revealed that decreased CH 4 production potential, rather than increased CH 4 oxidation potential, may lead to the reduction in net CH 4 emissions, and decreased nitrification potential and increased denitrification potential affected N 2 O fluxes under WTL conditions. Our study highlights the importance of microbial mechanisms in regulating ecosystem-scale GHG responses to environmental changes. © 2016 John Wiley & Sons Ltd.

Greenhouse Gas Emissions from Reservoir Water Surfaces: A ...

EPA Pesticide Factsheets

Collectively, reservoirs are an important anthropogenic source of greenhouse gases (GHGs) to the atmosphere. Attempts to model reservoir GHG fluxes, however, have been limited by inconsistencies in methodological approaches and data availability. An increase in the number of published reservoir GHG flux estimates during the last 15 years warrants a comprehensive analysis of the magnitude and potential controls on these fluxes. Here we synthesize worldwide reservoir CH4, CO2, and N2O emission data and estimate that GHG emissions from reservoirs account for 80.2 Tmol CO2 equivalents yr-1, thus constituting approximately 5% of anthropogenic radiative forcing. The majority (93%) of these emissions are from CH4, and mainly in the form of bubbles. While age and latitude have historically been linked to reservoir GHG emissions, we found that factors related to reservoir nutrient status and rainfall were better predictors. In particular, nutrient-rich eutrophic reservoirs were found to have an order of magnitude higher per-area CH4 fluxes, on average, than their nutrient-poor oligotrophic counterparts. Therefore, management measures to reduce reservoir eutrophication may result in an important co-benefit, the reduction of GHG emissions to the atmosphere. Greenhouse gas emissions (GHG)

Quantifying the climate-change consequences of shifting land use between forest and agriculture.

PubMed

Kirschbaum, Miko U F; Saggar, Surinder; Tate, Kevin R; Thakur, Kailash P; Giltrap, Donna L

2013-11-01

Land-use change between forestry and agriculture can cause large net emissions of carbon dioxide (CO2), and the respective land uses associated with forest and pasture lead to different on-going emission rates of methane (CH4) and nitrous oxide (N2O) and different surface albedo. Here, we quantify the overall net radiative forcing and consequent temperature change from specified land-use changes. These different radiative agents cause radiative forcing of different magnitudes and with different time profiles. Carbon emission can be very high when forests are cleared. Upon reforestation, the former carbon stocks can be regained, but the rate of carbon sequestration is much slower than the rate of carbon loss from deforestation. A production forest may undergo repeated harvest and regrowth cycles, each involving periods of C emission and release. Agricultural land, especially grazed pastures, have much higher N2O emissions than forests because of their generally higher nitrogen status that can be further enhanced through intensification of the nitrogen cycle by animal excreta. Because of its longevity in the atmosphere, N2O concentrations build up nearly linearly over many decades. CH4 emissions can be very high from ruminant animals grazing on pastures. Because of its short atmospheric longevity, the CH4 concentration from a converted pasture accumulates for only a few decades before reaching a new equilibrium when emission of newly produced CH4 is balanced by the oxidation of previously emitted CH4. Albedo changes generally have the opposite radiative forcing from those of the GHGs and partly negate their radiative forcing. Overall and averaged over 100 years, CO2 is typically responsible for 50% of radiative forcing and CH4 and N2O for 25% each. Albedo changes can negate the radiative forcing by the three greenhouse gases by 20-25%. Copyright © 2013 Elsevier B.V. All rights reserved.

Effects of experimental warming and mowing on greenhouse gas fluxes in an alpine meadow on the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wang, Jinsong; Quan, Quan; Sun, Jian; Niu, Shuli

2017-04-01

Rapid climate change and intensified human activities on the Tibetan Plateau may alter the magnitude and direction of greenhouse gas (GHG) emissions, affecting the climate change impact on these fragile ecosystems. We conducted a controlled experiment to investigate the effects of warming and mowing (simulation of grazing) on soil CO2, CH4 and N2O fluxes in an alpine meadow in eastern Tibetan Plateau between August 2015 and July 2016. Three levels of temperature (C, ambient temperature; W1, < 2 °C warming at 5 cm soil depth by infrared heaters; and W2, > 2 °C warming) were combined with two levels of mowing treatment (UM, un-mowing; and M, mowing). GHG fluxes were measured once an hour using static chamber. Both CO2 emission and CH4 uptake rates showed a seasonal fluctuation, with the maximum value occurred in late summer and the minimum in winter. However, N2O flux did not show a strong seasonal pattern. High level of warming (W2) regardless of mowing significantly increased CO2 emission and CH4 uptake by 15.4 % and 38.2 % averaged over the year, compared with no-warming (C). Moderate warming (W1) did not have significant effects on either CO2 or CH4 fluxes. N2O flux was reduced by 54.1% by W2 and 15.7% by W1 warming. Mowing alone increased CH4 uptake and N2O emission by 18.0 % and 12.7%, respectively, but had no significant effect on CO2 flux. The interactions between warming and mowing were detected in CO2 and CH4 fluxes. Among all treatments, W2UM in general had the highest rates of CO2 emission and CH4 uptake but the lowest rate of N2O flux, while CUM and CM showed the opposite. In addition, warming induced increase in CH4 uptake and decline in N2O release had very limited ability to offset the enhanced CO2 emission, resulting in a net positive feedback of the three GHGs to climate warming. Furthermore, daily CO2 flux increased exponentially with soil temperature at 5 cm. CH4 flux correlated negatively with soil temperature but positively with soil moisture.

Underlying Ecosystem Methane Emissions Exceed Cattle-Derived Methane from Subtropical Lowland Pastures.

NASA Astrophysics Data System (ADS)

Chamberlain, S. D.; Sparks, J. P.

2014-12-01

Grazing cattle are a major methane (CH4) source from pasture ecosystems, however the underlying landscape is a potentially significant CH4 source that has received far less attention. Ecosystem surface emissions of CH4 are poorly quantified, vary widely across time and space, and are easily underestimated if emission hotspots or episodic fluxes are overlooked. We used static chambers, eddy covariance, and mobile cavity-ringdown spectrometry surveys to quantify spatially and temporally variable CH4 emissions from subtropical lowland pastures. We conclude emissions from soil and standing water are the dominant CH4 source, and cattle were responsible for only 13% of annual CH4emissions. The ecosystem emit 33.8 ± 2.2 g CH4 m-2 yr-1, however surface CH4 emissions were highly variable in both time and space. Seasonal flooding of pastures and low-lying landforms (canals, ditches, wetlands) drove high magnitude CH4 emissions. We observed large CH4 emissions from wetlands and, to a lesser extent, the entire landscape during the wet season. In contrast, during the dry season there was no appreciable CH4 accumulation in pastures when cattle were not present, and canals, which comprise 1.7% of the total land area, were responsible 97.7 % of dry season emissions. Ecosystem CH4 fluxes, measured by eddy covariance, varied seasonally and positively correlated to soil and air temperature, topsoil water content, and water table depth. Our work is the first to use mobile spectrometers to map biogenic CH4 emissions at the landscape scale, and demonstrates that soils and water are a strong pasture CH4 source that must be considered in addition to cattle emissions.

Assessment of nitrous oxide and methane emissions for California agriculture

NASA Astrophysics Data System (ADS)

Horwath, W. R.; Burger, M.; Assa, Y.; Wilson, T. J.

2012-12-01

The California Global Warming Solutions Act of 2006 (AB 32) mandates comprehensive strategies to reduce nitrous oxide (N2O) and methane (CH4) emissions. In agriculture crop production, sources of N2O are related to nitrogen fertilization while CH4 emission is associated with rice production. More than half the GHG emissions from agriculture are attributed to N2O production. Currently, baseline N2O emission data for most cropping systems in the State is lacking. Estimates of CH4 emission in rice have been established from previous studies, but a lack of information exists for its expansion into the San Joaquin Delta to address subsidence issues. The paucity of N2O emission data has hampered biogeochemical modeling efforts. The objectives of this assessment are to (1) measure annual N2O and CH4 emissions for major California crops (vineyards, almonds, tomato, wheat, alfalfa, lettuce, and rice) under typical management practices, (2) characterize the effects of environmental factors on the temporal profile of N2O and CH4 emissions, and (3) determine N2O emission factors. The growth of rice in Delta peat soils produced highly variable CH4 emissions depending on tillage intensity. In 2010, standard tillage produced 184 kg CH4-C/ha while in 2011 after deep plowing placing rice residue deeper into the soil, only 26 kg CH4-C/ha was observed. In processing tomato systems, an average 2.5 kg N2O-N/ha was emitted with standard fertilization (160 kg N / ha), similar to background emissions and those from a drip irrigated system, while 4.0 to 5.8 kg N2O-N /ha y-1 was emitted at fertilizer rates of 225 and 300 kg N /ha (see Fig. 1 for example of temporal sources of emissions). About half the annual emissions were emitted within 3 d after the first seasonal rainfall event. In other tomato studies, estimated losses of fertilizer N as N2O were 0.38 ± 0.03 kg/ha y-1 in a drip irrigated system and 1.79 ± 0.21 kg/ha y-1 in furrow irrigated system, which was equivalent to 0.19% and 0.73% of the added fertilizer, respectively. In a lettuce production system, annual N2O emissions were about 1 kg N2O-N /ha y-1. In a wheat system, emissions during the growing season in the rainy season were between 1.0 and 1.5 kg N2O-N, with highest emissions occurring after anhydrous ammonium applications. Older alfalfa fields were larger sources of N2O. This two-year dataset will serve as the basis for developing mitigation practices.igure 1. Nitrous oxide emissions in tomato systems in 2009/10 during the rainy season, between starter and sidedress application of fertilizers, during the growing season and after the first rainfall after harvest.

Tree CH4 fluxes in forestry drained peatland in southern Finland

NASA Astrophysics Data System (ADS)

Haikarainen, Iikka; Putkinen, Anuliina; Pyykkö, Petteri; Halmeenmäki, Elisa; Pihlatie, Mari

2017-04-01

Methane (CH4) is among the most important greenhouse gases and its atmospheric concentration is increasing. Boreal forests are commonly considered a net sink of atmospheric CH4 due to CH4 consuming bacteria in aerated soil layers. Recent studies have, however, demonstrated that trees are capable of emitting CH4 from their stems and shoots by transporting anaerobically produced CH4 from deeper soil layers to the atmosphere. Furthermore, trees may act as independent sources of CH4. We have measured tree stem CH4 exchange of boreal tree species at Lettosuo, a nutrient rich peatland forest in Tammela, southern Finland (60˚ 38' N, 23˚ 57' E), using the static chamber technique. Three species, downy birch (Betula pubescens), Norway spruce (Picea abies) and Scots pine (Pinus sylvestris), were selected under investigation as they represent common boreal tree species. Fluxes of CH4 were measured during 7.6.2016 - 17.10.2016 from in total 25 sample trees growing on two different plots: a treatment plot where all the pines were removed to raise the water table level (WTL) and a control plot. Three birches from the treatment plot were selected to measure CH4 flux variation within vertical profile of the trees. Characterization of microbial communities, quantification of methanogenic and methanotrophic functional genes, and measurements of potential CH4 production and consumption from peat profile and forest floor moss samples were also carried out to obtain insight to the CH4 flux dynamics at the studied sites. The pine removal treatment did not markedly change the average WTL, but it made the WTL more variable with frequently 10-15 cm closer to soil surface compared to the WTL on the control plot. We found small and variable CH4 emissions from the stems of trees on both of the plots, while occasional consumption of CH4 was also present. Generally the CH4 emissions were higher and more dominant at the treatment plot compared to the control plot, and the fluxes were significantly different between the plots (p < 0.001). The CH4 emission rates from the birches at the treatment plot decreased exponentially in the stem vertical profile. Clear seasonal flux dynamics or significant differences in the CH4 flux between the species were not found at either of the plots. Microbial experiments showed that anaerobic CH4 production, CH4 oxidation potential (under 1000 ppm CH4) and the amount of methanogens were higher in the peat of the treatment site. The difference in the CH4 flux rates between the plots indicates that the WTL is a major regulator of tree CH4 emissions on forestry drained peatlands, supporting our hypothesis that the stem emitted CH4 originates from anaerobic soil conditions. This hypothesis is further supported by the results of the microbial analysis and by the observation that more CH4 is emitting from the lower parts of the stems compared to the upper stem.

Supplementation with whole cottonseed causes long-term reduction of methane emissions from lactating dairy cows offered a forage and cereal grain diet.

PubMed

Grainger, C; Williams, R; Clarke, T; Wright, A-D G; Eckard, R J

2010-06-01

The objective of our work was to supplement a forage and cereal diet of lactating dairy cows with whole cottonseed (WCS) for 12 wk and to determine whether the expected reduction in CH(4) would persist. A secondary objective was to determine the effect of supplementing the diet with WCS on milk yield and rumen function over the 12-wk feeding period. Fifty lactating cows were randomly allocated to 1 of 2 diets (control or WCS). The 2 separate groups were each offered, on average, 4.2 kg of DM/cow per day of alfalfa hay (a.m.) and 6.6 kg of DM/cow per day of ryegrass silage (p.m.) on the ground in bare paddocks each day for 12 wk. Cows in each group were also individually offered dietary supplements for 12 wk in a feed trough at milking times of 5.4 kg of DM/cow per day of cracked wheat grain and 0.5 kg of DM/cow per day of cottonseed meal (control) or 2.8 kg of DM/cow per day of cracked wheat grain and 2.61 kg of DM/cow per day of WCS. The 2 diets were formulated to be similar in their concentrations of CP and ME, but the WCS diet was designed to have a higher fat concentration. Samples of rumen fluid were collected per fistula from the rumen approximately 4 h after grain feeding in the morning. Samples were taken from 8 cows (4 cows/diet) on 2 consecutive days in wk 2 of the covariate and wk 3, 6, 10, and 12 of treatment and analyzed for volatile fatty acids, ammonia-N, methanogens, and protozoa. The reduction in CH(4) emissions (g/d) because of WCS supplementation increased from 13% in wk 3 to 23% in wk 12 of treatment. Similarly, the reduction in CH(4) emissions (g/kg of DMI) increased from 5.1% in wk 3 to 14.5% in wk 12 of treatment. It was calculated that the average reduction in CH(4) emissions over the 12-wk period was 2.9% less CH(4) per 1% added fat, increasing from 1.5% in wk 3 to 4.4% less CH(4) in wk 12. There was no effect of WCS supplementation on rumen ammonia-N, rumen volatile fatty acids, rumen methanogens, and rumen protozoa. On average over the 12-wk period, supplementation with WCS decreased the yield of milk (10%), fat (11%), protein (14%), lactose (11%), and fat plus protein (12%) and BW gain (31%). The WCS supplementation had no effect on milk fat concentration but resulted in a decrease in concentration of protein (5%) and lactose (11%). The major finding from this study is that addition of WCS to the diet of lactating dairy cows resulted in a persistent reduction in CH(4) emissions (g of CH(4)/kg of DMI) over a 12-wk period and that these reductions in CH(4) are consistent with previous work that has studied the addition of oilseeds to ruminant diets. 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Environmental and vegetation controls on the spatial variability of CH4 emission from wet-sedge and tussock tundra ecosystems in the Arctic.

PubMed

McEwing, Katherine Rose; Fisher, James Paul; Zona, Donatella

Despite multiple studies investigating the environmental controls on CH 4 fluxes from arctic tundra ecosystems, the high spatial variability of CH 4 emissions is not fully understood. This makes the upscaling of CH 4 fluxes from plot to regional scale, particularly challenging. The goal of this study is to refine our knowledge of the spatial variability and controls on CH 4 emission from tundra ecosystems. CH 4 fluxes were measured in four sites across a variety of wet-sedge and tussock tundra ecosystems in Alaska using chambers and a Los Gatos CO 2 and CH 4 gas analyser. All sites were found to be sources of CH 4 , with northern sites (in Barrow) showing similar CH 4 emission rates to the southernmost site (ca. 300 km south, Ivotuk). Gross primary productivity (GPP), water level and soil temperature were the most important environmental controls on CH 4 emission. Greater vascular plant cover was linked with higher CH 4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH 4 emission in these tundra ecosystems. Overall, this study provides an increased understanding of the fine scale spatial controls on CH 4 flux, in particular the key role that plant cover and GPP play in enhancing CH 4 emissions from tundra soils.

Contribution of Anthropogenic and Natural Emissions to Global CH4 Balances by Utilizing δ13C-CH4 Observations in CarbonTracker Data Assimilation System (CTDAS)

NASA Astrophysics Data System (ADS)

Kangasaho, V. E.; Tsuruta, A.; Aalto, T.; Backman, L. B.; Houweling, S.; Krol, M. C.; Peters, W.; van der Laan-Luijkx, I. T.; Lienert, S.; Joos, F.; Dlugokencky, E. J.; Michael, S.; White, J. W. C.

2017-12-01

The atmospheric burden of CH4 has more than doubled since preindustrial time. Evaluating the contribution from anthropogenic and natural emissions to the global methane budget is of great importance to better understand the significance of different sources at the global scale, and their contribution to changes in growth rate of atmospheric CH4 before and after 2006. In addition, observations of δ13C-CH4 suggest an increase in natural sources after 2006, which matches the observed increase and variation of CH4 abudance. Methane emission sources can be identified using δ13C-CH4, because different sources produce methane with process-specific isotopic signatures. This study focuses on inversion model based estimates of global anthropogenic and natural methane emission rates to evaluate the existing methane emission estimates with a new δ13C-CH4 inversion system. In situ measurements of atmospheric methane and δ13C-CH4 isotopic signature, provided by the NOAA Global Monitoring Division and the Institute of Arctic and Alpine Research, will be assimilated into the CTDAS-13C-CH4. The system uses the TM5 atmospheric transport model as an observation operator, constrained by ECMWF ERA Interim meteorological fields, and off-line TM5 chemistry fields to account for the atmospheric methane sink. LPX-Bern DYPTOP ecosystem model is used for prior natural methane emissions from wetlands, peatlands and mineral soils, GFED v4 for prior fire emissions and EDGAR v4.2 FT2010 inventory for prior anthropogenic emissions. The EDGAR antropogenic emissions are re-divided into enteric fermentation and manure management, landfills and waste water, rice, coal, oil and gas, and residential emissions, and the trend of total emissions is scaled to match optimized anthropogenic emissions from CTE-CH4. In addition to these categories, emissions from termites and oceans are included. Process specific δ13C-CH4 isotopic signatures are assigned to each emission source to estimate 13CH4 fraction in CH4 emissions. Among the priors, anthropogenic and natural emissions are optimized and others are directly imposed from the prior. A detailed emission estimates of antropogenic and natural CH4 emissions will be constructed in order to provide a more comprehensive understanding of methane emission source divisions.

Emission Factors for CO2, CO, CH4, and C2 - C4 Hydrocarbons from the 2011 Great Dismal Swamp, Virginia Fire

NASA Astrophysics Data System (ADS)

Baker, S.; Soja, A. J.; Richardson, M. J.

2012-12-01

With a warming climate, increased dry conditions and drought periods are likely to result in higher fire activity in the wetlands of the eastern and southeastern US. Fires in this fuel type can smolder for months producing significant carbon release and major impacts on air quality. While a comprehensive set of emission factors has been established for most US fuel types, a less complete set is available for emissions where deep layers of organic matter can consume and smolder for days, weeks and months. Lightning started the Lateral West fire in the Great Dismal Swamp National Wildlife Refuge, Virginia on August 4, and it burned slowly through drought-stressed hardwood forest and dry peat soil. The fire produced dense plumes of smoke that mostly dispersed over the Atlantic Ocean, but also affected air quality as far away as Washington, D.C. Fire emissions were sampled August 26, 2011. The fire had burned 6,358 acres. and was smoldering along in the peat, with some brush still igniting. The average emission factors (EF) we measured from the sampling were 1441 g/kg CO2, 192 g/kg CO; and 16.5 g/kg CH4.. Modified combustion efficiency (MCE) was 0.83, produced by the small amount of flaming combustion mixed with smoldering combustion of the peat. The CO2 EF values are similar to those measured from smoldering duff in Alaska in 2003 (1436 g/kg), and the CO EF was lower than Alaska (244 g/kg CO), while the CH4 EF was much higher than Alaska (8.4 g/kg CH4). We will present our complete set of emission factors from the Great Dismal Swamp for CO2, CO, CH4, and C2 - C4 hydrocarbons, and contrast these results with other fuel types. Linear regressions of C1- C4 hydrocarbons vs. CO concentration will presented and compared with other emissions results.

Is there a relationship between genetic merit and enteric methane emission rate of lactating Holstein-Friesian dairy cows?

PubMed

Dong, L F; Yan, T; Ferris, C P; McDowell, D A; Gordon, A

2015-11-01

The present study was undertaken to examine the effect of cow genetic merit on enteric methane (CH4) emission rate. The study used a data set from 32 respiration calorimeter studies undertaken at this Institute between 1992 and 2010, with all studies involving lactating Holstein-Friesian dairy cows. Cow genetic merit was defined as either profit index (PIN) or profitable lifetime index (PLI), with these two United Kingdom genetic indexes expressing the expected improvement in profit associated with an individual cow, compared with the population average. While PIN is based solely on milk production, PLI includes milk production and a number of other functional traits including health, fertility and longevity. The data set had a large range in PIN (n=736 records, -£30 to +£63) and PLI (n=548 records, -£131 to +£184), days in milk (18 to 354), energy corrected milk yield (16.0 to 45.6 kg/day) and CH(4) emission (138 to 598 g/day). The effect of cow genetic merit (PIN or PLI) was evaluated using ANOVA and linear mixed modelling techniques after removing the effects of a number of animal and diet factors. The ANOVA was undertaken by dividing each data set of PIN and PLI into three sub-groups (PIN:£15, PLI:£67) with these being categorised as low, medium and high genetic merit. Within the PIN and PLI data sets there was no significant differences among the three sub-groups in terms of CH(4) emission per kg feed intake or per kg energy corrected milk yield, or CH(4) energy (CH(4)-E) output as a proportion of energy intake. Linear regression using the whole PIN and PLI data sets also demonstrated that there was no significant relationship between either PIN or PLI, and CH(4) emission per kg of feed intake or CH(4)-E output as a proportion of energy intake. These results indicate that cow genetic merit (PIN or PLI) has little effect on enteric CH(4) emissions as a proportion of feed intake. Instead enteric CH(4) production may mainly relate to total feed intake and dietary nutrient composition.

Edge effects on N2O, NO and CH4 fluxes in two temperate forests.

PubMed

Remy, Elyn; Gasche, Rainer; Kiese, Ralf; Wuyts, Karen; Verheyen, Kris; Boeckx, Pascal

2017-01-01

Forest ecosystems may act as sinks or sources of nitrogen (N) and carbon (C) compounds, such as the climate relevant trace gases nitrous oxide (N 2 O), nitric oxide (NO) and methane (CH 4 ). Forest edges, which catch more atmospheric deposition, have become important features in European landscapes and elsewhere. Here, we implemented a fully automated measuring system, comprising static and dynamic measuring chambers determining N 2 O, NO and CH 4 fluxes along an edge-to-interior transect in an oak (Q. robur) and a pine (P. nigra) forest in northern Belgium. Each forest was monitored during a 2-week measurement campaign with continuous measurements every 2h. NO emissions were 9-fold higher than N 2 O emissions. The fluxes of NO and CH 4 differed between forest edge and interior, but not for N 2 O. This edge effect was more pronounced in the oak than in the pine forest. In the oak forest, edges emitted less NO (on average 60%) and took up more CH 4 (on average 177%). This suggests that landscape structure can play a role in the atmospheric budgets of these climate relevant trace gases. Soil moisture variation between forest edge and interior was a key variable explaining the magnitude of NO and CH 4 fluxes in our measurement campaign. To better understand the environmental impact of N and C trace gas fluxes from forest edges, additional and long-term measurements in other forest edges are required. Copyright © 2016 Elsevier B.V. All rights reserved.

Automated CO2, CH4 and N2O Fluxes from Tree Stems and Soils: Magnitudes, Temporal Patterns and Drivers

NASA Astrophysics Data System (ADS)

Barba, J.; Poyatos, R.; Vargas, R.

2017-12-01

The emissions of the main greenhouse gases (GHG; CO2, CH4 and N2O) through tree stems are still an uncertain component of the total GHG balance of forests. Despite that stem CO2 emissions have been studied for several decades, it is still unclear the drivers and spatiotemporal patterns of CH4 and N2O stem emissions. Additionally, it is unknown how stem emissions could be related to soil physiological processes or environmental conditions. We measured CO2, CH4 and N2O emissions hourly from April to July 2017 at two different heights (75 [LStem] and 150cm [HStem]) of bitternut hickory (Carya cordiformis) trees and adjacent soil locations in a forested area in the Mid Atlantic of the USA. We designed an automated system to continuously measure the three greenhouse gases (GHG) in stems and soils. Stem and soil CO2 emissions showed similar seasonal patterns with an average of 6.56±0.09 (soil), 3.72±0.05 (LStem) and 2.47±0.04 µmols m-2 s-1 (HStem) (mean±95% CI). Soil temperature controlled CO2 fluxes at both daily and seasonal scales (R2>0.5 for all cases), but there was no clear effect of soil moisture. The stems were a clear CH4 source with emissions decreasing with height (0.35±0.02 and 0.25±0.01 nmols m-2 s-1 for LStem and HStem, respectively) with no apparent seasonal pattern, and no clear relationship with environmental drivers (e.g., temperature, moisture). In contrast, soil was a CH4 sink throughout the experiment (-0.55±0.02 nmols m-2 s-1) and its seasonal pattern responded to moisture changes. Despite soil and stem N2O emissions did not show a seasonal pattern or apparent dependency on temperature or moisture, they showed net N2O emissions with a decrease in emissions with stem height (0.29±0.05 for soil, 0.38±0.06 for LStem and 0.28±0.05 nmols m-2 s-1 for HStem). The three GHG emissions decreased with stem height at similar rates (33%, 28% and 27% for CO2, CH4 and N2O, respectively). These results suggest that the gases were not produced in the stem but originated in the soil and transported within the stem. At the forest stand level, the CH4 sink capacity of soils could be partially counteracted by the stem emissions. These results indicate the need to measure CO2, CH4 and N2O emissions not only in soil but also in stems to account for the total GHG balance in ecosystems.

Estimating global natural wetland methane emissions using process modelling: spatio-temporal patterns and contributions to atmospheric methane fluctuations

USGS Publications Warehouse

Zhu, Qiuan; Peng, Changhui; Chen, Huai; Fang, Xiuqin; Liu, Jinxun; Jiang, Hong; Yang, Yanzheng; Yang, Gang

2015-01-01

Aim The fluctuations of atmospheric methane (CH4) that have occurred in recent decades are not fully understood, particularly with regard to the contribution from wetlands. The application of spatially explicit parameters has been suggested as an effective method for reducing uncertainties in bottom-up approaches to wetland CH4 emissions, but has not been included in recent studies. Our goal was to estimate spatio-temporal patterns of global wetland CH4 emissions using a process model and then to identify the contribution of wetland emissions to atmospheric CH4fluctuations. Location Global. Methods A process-based model integrated with full descriptions of methanogenesis (TRIPLEX-GHG) was used to simulate global wetland CH4emissions. Results Global annual wetland CH4 emissions ranged from 209 to 245 Tg CH4 year−1 between 1901 and 2012, with peaks occurring in 1991 and 2012. There is a decreasing trend between 1990 and 2010 with a rate of approximately 0.48 Tg CH4 year−1, which was largely caused by emissions from tropical wetlands showing a decreasing trend of 0.44 Tg CH4 year−1 since the 1970s. Emissions from tropical, temperate and high-latitude wetlands comprised 59, 26 and 15% of global emissions, respectively. Main conclusion Global wetland CH4 emissions, the interannual variability of which was primary controlled by tropical wetlands, partially drive the atmosphericCH4 burden. The stable to decreasing trend in wetland CH4 emissions, a result of a balance of emissions from tropical and extratropical wetlands, was a particular factor in slowing the atmospheric CH4 growth rate during the 1990s. The rapid decrease in tropical wetland CH4emissions that began in 2000 was supposed to offset the increase in anthropogenic emissions and resulted in a relatively stable level of atmospheric CH4 from 2000 to 2006. Increasing wetland CH4 emissions, particularly after 2010, should be an important contributor to the growth in atmospheric CH4 seen since 2007.

Greenhouse gas emissions and carbon sequestration potential in restored freshwater marshes in the Sacramento San-Joaquin Delta, California

NASA Astrophysics Data System (ADS)

Knox, S. H.; Sturtevant, C. S.; Oikawa, P. Y.; Matthes, J. H.; Dronova, I.; Anderson, F. E.; Verfaillie, J. G.; Baldocchi, D. D.

2015-12-01

Wetlands can be effective carbon sinks due to limited decomposition rates in anaerobic soil. As such there is a growing interest in the use of restored wetlands as biological carbon sequestration projects for greenhouse gas (GHG) emission reduction programs. However, using wetlands to offset emissions requires accurate accounting of both carbon dioxide (CO2) and methane (CH4) exchange since wetlands are also sources of CH4. To date few studies have quantified CO2 and CH4 exchange from restored wetlands or assessed how these fluxes vary during ecosystem development. In this study, we report on multiple years of eddy covariance measurements of CO2 and CH4 fluxes from two restored freshwater marshes of differing ages (one restored in 1997 and the other in 2010) in the Sacramento-San Joaquin Delta, CA. Measurements at the younger restored wetland started in October 2010 and began in April 2011 at the older site. The younger restored wetland showed considerable year-to-year variability in the first 4 years following restoration, with CO2 uptake ranging from 12 to 420 g C-CO2 m-2 yr-1. Net CO2 uptake at the older wetland was overall greater than at the younger site, ranging from 292 to 585 g C-CO2 m-2 yr-1. Methane emissions were on average higher at the younger wetland (46 g C-CH4 m-2 yr-1) relative to the older one (33 g C-CH4 m-2 yr-1). In terms of the GHG budgets (assuming a global warming potential of 34), the younger wetland was consistently a GHG source, emitting on average 1439 g CO2 eq m-2 yr-1, while the older wetland was a GHG sink in two of the years of measurement (sequestering 651 and 780 g CO2 eq m-2 yr-1 in 2012 and 2013, respectively) and a source of 750 g CO2 eq m-2 yr-1 in 2014. This study highlights how dynamic CO2 and CH4 fluxes are in the first years following wetland restoration and suggests that restored wetlands have the potential to act as GHG sinks but this may depend on time since restoration.

Climate-driven increase of natural wetland methane emissions offset by human-induced wetland reduction in China over the past three decades

USGS Publications Warehouse

Zhu, Qiuan; Peng, Changhui; Liu, Jinxun; Jiang, Hong; Fang, Xiuqin; Chen, Huai; Niu, Zhichun; Gong, Peng; Lin, Guanghui; Wang, Meng; Yang, Yanzheng; Chang, Jie; Ge, Ying; Xiang, Wenhua; Deng, Xiangwen; He, Jin-Sheng

2016-01-01

Both anthropogenic activities and climate change can affect the biogeochemical processes of natural wetland methanogenesis. Quantifying possible impacts of changing climate and wetland area on wetland methane (CH4) emissions in China is important for improving our knowledge on CH4 budgets locally and globally. However, their respective and combined effects are uncertain. We incorporated changes in wetland area derived from remote sensing into a dynamic CH4 model to quantify the human and climate change induced contributions to natural wetland CH4 emissions in China over the past three decades. Here we found that human-induced wetland loss contributed 34.3% to the CH4 emissions reduction (0.92 TgCH4), and climate change contributed 20.4% to the CH4 emissions increase (0.31 TgCH4), suggesting that decreasing CH4 emissions due to human-induced wetland reductions has offset the increasing climate-driven CH4 emissions. With climate change only, temperature was a dominant controlling factor for wetland CH4 emissions in the northeast (high latitude) and Qinghai-Tibet Plateau (high altitude) regions, whereas precipitation had a considerable influence in relative arid north China. The inevitable uncertainties caused by the asynchronous for different regions or periods due to inter-annual or seasonal variations among remote sensing images should be considered in the wetland CH4 emissions estimation.

Climate-driven increase of natural wetland methane emissions offset by human-induced wetland reduction in China over the past three decades

PubMed Central

Zhu, Qiuan; Peng, Changhui; Liu, Jinxun; Jiang, Hong; Fang, Xiuqin; Chen, Huai; Niu, Zhenguo; Gong, Peng; Lin, Guanghui; Wang, Meng; Wang, Han; Yang, Yanzheng; Chang, Jie; Ge, Ying; Xiang, Wenhua; Deng, Xiangwen; He, Jin-Sheng

2016-01-01

Both anthropogenic activities and climate change can affect the biogeochemical processes of natural wetland methanogenesis. Quantifying possible impacts of changing climate and wetland area on wetland methane (CH4) emissions in China is important for improving our knowledge on CH4 budgets locally and globally. However, their respective and combined effects are uncertain. We incorporated changes in wetland area derived from remote sensing into a dynamic CH4 model to quantify the human and climate change induced contributions to natural wetland CH4 emissions in China over the past three decades. Here we found that human-induced wetland loss contributed 34.3% to the CH4 emissions reduction (0.92 TgCH4), and climate change contributed 20.4% to the CH4 emissions increase (0.31 TgCH4), suggesting that decreasing CH4 emissions due to human-induced wetland reductions has offset the increasing climate-driven CH4 emissions. With climate change only, temperature was a dominant controlling factor for wetland CH4 emissions in the northeast (high latitude) and Qinghai-Tibet Plateau (high altitude) regions, whereas precipitation had a considerable influence in relative arid north China. The inevitable uncertainties caused by the asynchronous for different regions or periods due to inter-annual or seasonal variations among remote sensing images should be considered in the wetland CH4 emissions estimation. PMID:27892535

Annual methane and nitrous oxide emissions from rice paddies and inland fish aquaculture wetlands in southeast China

NASA Astrophysics Data System (ADS)

Wu, Shuang; Hu, Zhiqiang; Hu, Tao; Chen, Jie; Yu, Kai; Zou, Jianwen; Liu, Shuwei

2018-02-01

Inland aquaculture ponds have been documented as important sources of atmospheric methane (CH4) and nitrous oxide (N2O), while their regional or global source strength remains unclear due to lack of direct flux measurements by covering more typical habitat-specific aquaculture environments. In this study, we compared the CH4 and N2O fluxes from rice paddies and nearby inland fish aquaculture wetlands that were converted from rice paddies in southeast China. Both CH4 and N2O fluxes were positively related to water temperature and sediment dissolved organic carbon, but negatively related to water dissolved oxygen concentration. More robust response of N2O fluxes to water mineral N was observed than to sediment mineral N. Annual CH4 and N2O fluxes from inland fish aquaculture averaged 0.51 mg m-2 h-1 and 54.78 μg m-2 h-1, amounting to 42.31 kg CH4 ha-1 and 2.99 kg N2O-N ha-1, respectively. The conversion of rice paddies to conventional fish aquaculture significantly reduced CH4 and N2O emissions by 23% and 66%, respectively. The emission factor for N2O was estimated to be 0.46% of total N input in the feed or 1.23 g N2O-N kg-1 aquaculture production. The estimate of sustained-flux global warming potential of annual CH4 and N2O emissions and the net economic profit suggested that such conversion of rice paddies to inland fish aquaculture would help to reconcile the dilemma for simultaneously achieving both low climatic impacts and high economic benefits in China. More solid direct field measurements from inland aquaculture are in urgent need to direct the overall budget of national or global CH4 and N2O fluxes.

Local- and regional-scale measurements of CH4, δ13CH4, and C2H6 in the Uintah Basin using a mobile stable isotope analyzer

NASA Astrophysics Data System (ADS)

Rella, C. W.; Hoffnagle, J.; He, Y.; Tajima, S.

2015-10-01

In this paper, we present an innovative CH4, δ13CH4, and C2H6 instrument based on cavity ring-down spectroscopy (CRDS). The design and performance of the analyzer is presented in detail. The instrument is capable of precision of less than 1 ‰ on δ13CH4 with 1 in. of averaging and about 0.1 ‰ in an hour. Using this instrument, we present a comprehensive approach to atmospheric methane emissions attribution. Field measurements were performed in the Uintah Basin (Utah, USA) in the winter of 2013, using a mobile lab equipped with the CRDS analyzer, a high-accuracy GPS, a sonic anemometer, and an onboard gas storage and playback system. With a small population and almost no other sources of methane and ethane other than oil and gas extraction activities, the Uintah Basin represents an ideal location to investigate and validate new measurement methods of atmospheric methane and ethane. We present the results of measurements of the individual fugitive emissions from 23 natural gas wells and six oil wells in the region. The δ13CH4 and C2H6 signatures that we observe are consistent with the signatures of the gases found in the wells. Furthermore, regional measurements of the atmospheric CH4, δ13CH4, and C2H6 signatures throughout the basin have been made, using continuous sampling into a 450 m long tube and laboratory reanalysis with the CRDS instrument. These measurements suggest that 85 ± 7 % of the total emissions in the basin are from natural gas production.

Spatial and Temporal Variations in the Partial Pressure and Emission of CO2 and CH4 in and Amazon Floodplain Lake

NASA Astrophysics Data System (ADS)

Forsberg, B. R.; Amaral, J. H.; Barbosa, P.; Kasper, D.; MacIntyre, S.; Cortes, A.; Sarmento, H.; Borges, A. V.; Melack, J. M.; Farjalla, V.

2015-12-01

The Amazon floodplain contains a variety of wetland environments which contribute CO2 and CH4 to the regional and global atmospheres. The partial pressure and emission of these greenhouse gases (GHGs) varies: 1) between habitats, 2) seasonally, as the characteristics these habitats changes and 3) diurnally, in response to diurnal stratification. In this study, we investigated the combined influence of these factors on the partial pressure and emission of GHGs in Lago Janauacá, a central Amazon floodplain lake (3o23' S; 60o18' O). All measurements were made between August of 2014 and April of 2015 at two different sites and in three distinct habitats: open water, flooded forest, flooded macrophytes. Concentrations of CO2 and CH4 in air were measured continuously with a cavity enhanced absorption spectrometer, Los Gatos Research´s Ultraportable Greenhouse Gas Analyzer (UGGA). Vertical profiles o pCO2 and pCH4 were measured using the UGGA connected to an electric pump and equilibrator. Diffusive surface emissions were estimated with the UGGA connected to a static floating chamber. To investigate the influence of vertical stratification and mixing on GHG partial pressure and emissions, a meteorological station and submersible sensor chain were deployed at each site. Meteorological sensors included wind speed and direction. The submersible chains included thermistors and oxygen sensors. Depth profiles of partial pressure and diffusive emissions for both CO2 and CH4 varied diurnally, seasonally and between habitats. Both pCO2 and pCH4 were consistently higher in bottom than surface waters with the largest differences occurring at high water when thermal stratification was most stable. Methane emissions and partial pressures were highest at low water while pCO2 and CO2 fluxes were highest during high water periods, with 35% of CO2 fluxes at low water being negative. The highest average surface value of pCO2 (5491 μatm), encountered during rising water, was ~3 times higher than that encountered at low water (1708 μatm). Partial pressures and emissions of both CO2 and CH4 were greatest in open water habitats and consistently higher at night. These patterns reflected the higher levels of wind driven mixing and turbulence in open water environments and higher convective mixing at night which promoted diffusive emission.

Response of CH4 emissions to straw and biochar applications in double-rice cropping systems: Insights from observations and modeling.

PubMed

Chen, Dan; Wang, Cong; Shen, Jianlin; Li, Yong; Wu, Jinshui

2018-04-01

Paddy soil plays an essential role in contributing to the emission of methane (CH 4 ), a potent greenhouse gas, to the atmosphere. This study aimed to demonstrate the effects of straw incorporation and straw-derived biochar amendment on CH 4 emissions from double-rice cropping fields and to explore their potential mechanisms based on in-situ field measurements conducted for a period of three years (2012-2014) and model analysis. The results showed that the improved soil aeration due to biochar amendment resulted in low CH 4 emissions and that sufficient substrate carbon availability in straw amendment treatments caused high CH 4 emissions. The newly developed CH 4 emission module for the water and nitrogen management model (WNMM), a process-based biophysical model, performed well when simulating both daily CH 4 fluxes and the annual cumulative CH 4 emissions under straw incorporation and biochar amendment. Results of our study indicate that the model has a great potential for upscaling and could benefit mechanism analyses about the factors regulating CH 4 emissions. Application of biochar into paddy fields provides a great opportunity to reduce CH 4 emissions, and the decrease in CH 4 emissions following biochar amendment with repeated crop cycles would sustain for a prolonged period. Copyright © 2017 Elsevier Ltd. All rights reserved.

Aerial photography based census of Adélie Penguin and its application in CH4 and N2O budget estimation in Victoria Land, Antarctic.

PubMed

He, Hong; Cheng, Xiao; Li, Xianglan; Zhu, Renbin; Hui, Fengming; Wu, Wenhui; Zhao, Tiancheng; Kang, Jing; Tang, Jianwu

2017-10-11

Penguin guano provides favorable conditions for production and emission of greenhouse gases (GHGs). Many studies have been conducted to determine the GHG fluxes from penguin colonies, however, at regional scale, there is still no accurate estimation of total GHG emissions. We used object-based image analysis (OBIA) method to estimate the Adélie penguin (Pygoscelis adeliae) population based on aerial photography data. A model was developed to estimate total GHG emission potential from Adélie penguin colonies during breeding seasons in 1983 and 2012, respectively. Results indicated that OBIA method was effective for extracting penguin information from aerial photographs. There were 17,120 and 21,183 Adélie penguin breeding pairs on Inexpressible Island in 1983 and 2012, respectively, with overall accuracy of the estimation of 76.8%. The main reasons for the increase in Adélie penguin populations were attributed to increase in temperature, sea ice and phytoplankton. The average estimated CH 4 and N 2 O emissions tended to be increasing during the period from 1983 to 2012 and CH 4 was the main GHG emitted from penguin colonies. Total global warming potential (GWP) of CH 4 and N 2 O emissions was 5303 kg CO 2 -eq in 1983 and 6561 kg CO 2 -eq in 2012, respectively.

Water regime-nitrogen fertilizer incorporation interaction: Field study on methane and nitrous oxide emissions from a rice agroecosystem in Harbin, China.

PubMed

Dong, Wenjun; Guo, Jia; Xu, Lijun; Song, Zhifeng; Zhang, Jun; Tang, Ao; Zhang, Xijuan; Leng, Chunxu; Liu, Youhong; Wang, Lianmin; Wang, Lizhi; Yu, Yang; Yang, Zhongliang; Yu, Yilei; Meng, Ying; Lai, Yongcai

2018-02-01

Water regime and nitrogen (N) fertilizer are two important factors impacting greenhouse gases (GHG) emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane (CH 4 ) emission compared with continuous flooding, however, the decrement was far lower than the global average level. The N 2 O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH 4 emissions at low level (75kgN/ha). But both CH 4 and N 2 O emissions were uninfluenced at the levels of 150kgN/ha and 225kgN/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150kgN/ha. From our results, we recommended that the intermittent irrigation and 150kgN/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields. Copyright © 2017. Published by Elsevier B.V.

Four years of UAS Imagery Reveals Vegetation Change Due to Permafrost Thaw

NASA Astrophysics Data System (ADS)

DelGreco, J. L.; Herrick, C.; Varner, R. K.; McArthur, K. J.; McCalley, C. K.; Garnello, A.; Finnell, D.; Anderson, S. M.; Crill, P. M.; Palace, M. W.

2017-12-01

Warming trends in sub-arctic regions have resulted in thawing of permafrost which in turn induces change in vegetation across peatlands. Collapse of palsas (i.e. permafrost plateaus) has also been correlated to increases in methane (CH4) emissions to the atmosphere. Vegetation change provides new microenvironments that promote CH4 production and emission, specifically through plant interactions and structure. By quantifying the changes in vegetation at the landscape scale, we will be able to understand the impact of thaw on CH4 emissions in these complex and climate sensitive northern ecosystems. We combine field-based measurements of vegetation composition and high resolution Unmanned Aerial Systems (UAS) imagery to characterize vegetation change in a sub-arctic mire. At Stordalen Mire (1 km x 0.5 km), Abisko, Sweden, we flew a fixed-wing UAS in July of each year between 2014 and 2017. High precision GPS ground control points were used to georeference the imagery. Seventy-five randomized square-meter plots were measured for vegetation composition and individually classified into one of five cover types, each representing a different stage of permafrost degradation. With this training data, each year of imagery was classified by cover type. The developed cover type maps were also used to estimate CH4 emissions across the mire based on average flux CH4 rates from each cover type obtained from flux chamber measurements collected at the mire. This four year comparison of vegetation cover and methane emissions has indicated a rapid response to permafrost thaw and changes in emissions. Estimation of vegetation cover types is vital in our understanding of the evolution of northern peatlands and its future role in the global carbon cycle.

Emission of greenhouse gases and soil carbon sequestration in a riparian marsh wetland in central Ohio.

PubMed

Nag, Subir K; Liu, Ruiqiang; Lal, Rattan

2017-10-23

Wetlands are a C sink, but they also account for a large natural source of greenhouse gases (GHG), particularly methane (CH 4 ). Soils of wetlands play an important role in alleviating the global climate change regardless of the emission of CH 4 . However, there are uncertainties about the amount of C stored and emitted from wetlands because of the site specific factors. Therefore, the present study was conducted in a temperate riverine flow-through wetland, part of which was covered with emerging macrophyte Typhus latifolia in central Ohio, USA, with the objective to assess emissions of GHGs (CH 4, CO 2 , N 2 O) and measure C and nitrogen (N) stocks in wetland soil in comparison to a reference upland site. The data revealed that CH 4 emission from the open and vegetated wetland ranged from 1.03-0.51 Mg C/ha/y and that of CO 2 varied from 1.26-1.51 Mg C/ha/y. In comparison, CH 4 emission from reference upland site was negligible (0.01 Mg C/ha/y), but CO 2 emission was much higher (3.24 Mg C/ha/y). The stock of C in wetland soil was 85 to 125 Mg C/ha up to 0.3 m depth. The average rate of emission was 2.15 Mg C/ha/y, but the rate of sequestration was calculated as 5.55 Mg C/ha/y. Thus, the wetland was actually a C sink. Emission of N 2 O was slightly higher in vegetated wetland (0.153 mg N 2 O-N/m 2 /h) than the open wetland and the reference site (0.129 mg N 2 O-N/m 2 /h). Effect of temperature on emission of GHGs from the systems was also studied.

Modeling Impacts of Alternative Practices on Net Global Warming Potential and Greenhouse Gas Intensity from Rice–Wheat Annual Rotation in China

PubMed Central

Wang, Jinyang; Zhang, Xiaolin; Liu, Yinglie; Pan, Xiaojian; Liu, Pingli; Chen, Zhaozhi; Huang, Taiqing; Xiong, Zhengqin

2012-01-01

Background Evaluating the net exchange of greenhouse gas (GHG) emissions in conjunction with soil carbon sequestration may give a comprehensive insight on the role of agricultural production in global warming. Materials and Methods Measured data of methane (CH4) and nitrous oxide (N2O) were utilized to test the applicability of the Denitrification and Decomposition (DNDC) model to a winter wheat – single rice rotation system in southern China. Six alternative scenarios were simulated against the baseline scenario to evaluate their long-term (45-year) impacts on net global warming potential (GWP) and greenhouse gas intensity (GHGI). Principal Results The simulated cumulative CH4 emissions fell within the statistical deviation ranges of the field data, with the exception of N2O emissions during rice-growing season and both gases from the control treatment. Sensitivity tests showed that both CH4 and N2O emissions were significantly affected by changes in both environmental factors and management practices. Compared with the baseline scenario, the long-term simulation had the following results: (1) high straw return and manure amendment scenarios greatly increased CH4 emissions, while other scenarios had similar CH4 emissions, (2) high inorganic N fertilizer increased N2O emissions while manure amendment and reduced inorganic N fertilizer scenarios decreased N2O emissions, (3) the mean annual soil organic carbon sequestration rates (SOCSR) under manure amendment, high straw return, and no-tillage scenarios averaged 0.20 t C ha−1 yr−1, being greater than other scenarios, and (4) the reduced inorganic N fertilizer scenario produced the least N loss from the system, while all the scenarios produced comparable grain yields. Conclusions In terms of net GWP and GHGI for the comprehensive assessment of climate change and crop production, reduced inorganic N fertilizer scenario followed by no-tillage scenario would be advocated for this specified cropping system. PMID:23029173

Using carbon isotopes of methane from porewater to understand methane emissions across a permafrost thaw gradient

NASA Astrophysics Data System (ADS)

Varner, R. K.; McCalley, C. K.; Clarizia, P. E.; Verbeke, B. A.; Werner, S. L.; Burke, S. A.; Malhotra, A.; Rocci, K.

2016-12-01

Methane (CH4) emissions from high latitude ecosystems are controlled in part by the presence/absence of permafrost and concomitant modifications in vegetation composition. Rapid transitions in habitat impact CH4 emissions both by changing the moisture regime as well as the production and emission pathways. Measurement of the isotopic composition of CH4 in porewater in these thawed ecosystems can indicate shifts in production pathways of CH4. We measured CH4 and carbon dioxide (CO2) emission, belowground CH4 concentration and 13CH4 of porewater, vegetative type, and vascular greenness area (VGA) along a thaw gradient during summers 2012-2016 in Stordalen Mire, Sweden. Concentrations of CH4 belowground showed positive correlation with aboveground emissions. Carbon isotopic signatures of CH4 varied varied between sites with more hydrogenotrophic signatures in sites dominated by Sphagnum spp. and acetate fermentation signatures in sedge dominated sites (Carex and Eriophorum spp.). These data indicate that these ecosystems transition from thaw, their 13CH4 emissions will change and therefore need to be accounted for in global atmospheric budgets and models.

Methane emission estimates using chamber and tracer release experiments for a municipal waste water treatment plant

NASA Astrophysics Data System (ADS)

Yver Kwok, C. E.; Müller, D.; Caldow, C.; Lebègue, B.; Mønster, J. G.; Rella, C. W.; Scheutz, C.; Schmidt, M.; Ramonet, M.; Warneke, T.; Broquet, G.; Ciais, P.

2015-07-01

This study presents two methods for estimating methane emissions from a waste water treatment plant (WWTP) along with results from a measurement campaign at a WWTP in Valence, France. These methods, chamber measurements and tracer release, rely on Fourier transform infrared spectroscopy and cavity ring-down spectroscopy instruments. We show that the tracer release method is suitable for quantifying facility- and some process-scale emissions, while the chamber measurements provide insight into individual process emissions. Uncertainties for the two methods are described and discussed. Applying the methods to CH4 emissions of the WWTP, we confirm that the open basins are not a major source of CH4 on the WWTP (about 10 % of the total emissions), but that the pretreatment and sludge treatment are the main emitters. Overall, the waste water treatment plant is representative of an average French WWTP.

Mapping pan-Arctic CH4 emissions using an adjoint method by integrating process-based wetland and lake biogeochemical models and atmospheric CH4 concentrations

NASA Astrophysics Data System (ADS)

Tan, Z.; Zhuang, Q.; Henze, D. K.; Frankenberg, C.; Dlugokencky, E. J.; Sweeney, C.; Turner, A. J.

2015-12-01

Understanding CH4 emissions from wetlands and lakes are critical for the estimation of Arctic carbon balance under fast warming climatic conditions. To date, our knowledge about these two CH4 sources is almost solely built on the upscaling of discontinuous measurements in limited areas to the whole region. Many studies indicated that, the controls of CH4 emissions from wetlands and lakes including soil moisture, lake morphology and substrate content and quality are notoriously heterogeneous, thus the accuracy of those simple estimates could be questionable. Here we apply a high spatial resolution atmospheric inverse model (nested-grid GEOS-Chem Adjoint) over the Arctic by integrating SCIAMACHY and NOAA/ESRL CH4 measurements to constrain the CH4 emissions estimated with process-based wetland and lake biogeochemical models. Our modeling experiments using different wetland CH4 emission schemes and satellite and surface measurements show that the total amount of CH4 emitted from the Arctic wetlands is well constrained, but the spatial distribution of CH4 emissions is sensitive to priors. For CH4 emissions from lakes, our high-resolution inversion shows that the models overestimate CH4 emissions in Alaskan costal lowlands and East Siberian lowlands. Our study also indicates that the precision and coverage of measurements need to be improved to achieve more accurate high-resolution estimates.

Effects of mass air flow rate through an open-circuit gas quantification system when measuring carbon emissions

USDA-ARS?s Scientific Manuscript database

Methane (CH4) and carbon dioxide (CO2) represent 11 and 81%, respectively, of all anthropogenic greenhouse gas emissions. Agricultural CH4 emissions account for approximately 43% of all anthropogenic CH4 emissions. Most agricultural CH4 emissions are attributed to enteric fermentation within rumin...

Response of the global climate to changes in atmospheric chemical composition due to fossil fuel burning

NASA Technical Reports Server (NTRS)

Hameed, S.; Cess, R. D.; Hogan, J. S.

1980-01-01

Recent modeling of atmospheric chemical processes (Logan et al, 1978; Hameed et al, 1979) suggests that tropospheric ozone and methane might significantly increase in the future as the result of increasing anthropogenic emissions of CO, NO(x), and CH4 due to fossil fuel burning. Since O3 and CH4 are both greenhouse gases, increases in their concentrations could augment global warming due to larger future amounts of atmospheric CO2. To test the possible climatic impact of changes in tropospheric chemical composition, a zonal energy-balance climate model has been combined with a vertically averaged tropospheric chemical model. The latter model includes all relevant chemical reactions which affect species derived from H2O, O2, CH4, and NO(x). The climate model correspondingly incorporates changes in the infrared heating of the surface-troposphere system resulting from chemically induced changes in tropospheric ozone and methane. This coupled climate-chemical model indicates that global climate is sensitive to changes in emissions of CO, NO(x) and CH4, and that future increases in these emissions could augment global warming due to increasing atmospheric CO2.

Prediction of enteric methane emissions from sheep offered fresh perennial ryegrass () using data measured in indirect open-circuit respiration chambers.

PubMed

Zhao, Y G; O'Connell, N E; Yan, T

2016-06-01

Development of effective methane (CH) mitigation strategies for grazing sheep requires accurate prediction tools. The present study aimed to identify key parameters influencing enteric CH emissions and develop prediction equations for enteric CH emissions from sheep offered fresh grass. The data used were collected from 82 sheep offered fresh perennial ryegrass () as sole diets in 6 metabolism experiments (data from non-grass-only diets were not used). Sheep were from breeds of Highlander, Texel, Scottish Blackface, and Swaledale at the age of 5 to 18 mo and weighing from 24.5 to 62.7 kg. Grass was harvested daily from 6 swards on contrasting harvest dates (May to December). Before the commencement of each study, the experimental sward was harvested at a residual height of 4 cm and allowed to grow for 2 to 4 wk. The feeding trials commenced when the grass sward was suitable to zero grazing (average grass height = 15 cm), thus offering grass of a quality similar to what grazing animals would receive under routine grazing management. Sheep were housed in individual pens for 14 d and then moved to individual calorimeter chambers for 4 d. Feed intake, fecal and urine outputs, and CH emissions were measured during the final 4 d. Data were analyzed using the REML procedure to develop prediction equations for CH emissions. Linear and multiple prediction equations were developed using BW, DMI, GE intake (GEI), and grass chemical concentrations (DM, OM, water-soluble carbohydrates [WSC], NDF, ADF, nitrogen [N], GE, DE, and ME) as explanatory variables. The mean CH production was 21.1 g/kg DMI or 0.062 MJ/MJ GEI. Dry matter intake and GEI were much more accurate predictors for CH emissions than BW ( < 0.001, = 0.86 and = 0.87 vs. = 0.09, respectively). Adding grass DE and ME concentrations and grass nutrient concentrations (e.g., OM, N, GE, NDF, and WSC) to the relationships between DMI or GEI and CH emissions improved prediction accuracy with values increased to 0.93. Models based on farm-level data, for example, BW and grass nutrient (i.e., DM, GE, OM, and N) concentrations, were also developed and performed satisfactorily ( < 0.001, = 0.63). These models can contribute to improve prediction accuracy for enteric CH emissions from sheep grazing on ryegrass pasture.

Comparison of CH4 Emission from Rice Paddy Soils between Coastal Zone and Inland Regions

NASA Astrophysics Data System (ADS)

Sun, M.; Li, X.

2016-12-01

Numerous measurements of methane (CH4) emission fluxes have been carried out in rice paddy soil between coastal zone and inland regions. However, the differences of CH4 emission from rice paddy soils in these two locations were unavailable. A database of CH4 emission in paddy rice was compiled from previous published references and field observations with major parameters including water regimes, fertilizer application, CH4 fluxes, and environmental variables. Results showed that CH4 emission from inland paddy fields was significantly higher than that in the coastal zone (p < 0.05). Fertilizer application and water management played an important role in CH4 emission. The application of organic fertilizer and continuous flooding significantly promoted CH4 emission from paddy fields. CH4 fluxes showed significantly positive correlations with organic matter, total nitrogen, available potassium and annual temperature (R2 = 0.39, 0.53, 0.27 and 0.23, p < 0.05), and negative correlations with pH and available phosphorus (R2 = 0.29 and 0.37, p < 0.05). Significant differences occurred in available potassium between inland and coastal rice paddy (p < 0.05), which might account for the difference of CH4 emission between inland and coastal rice paddy. The contrasting of CH4 fluxes between inland and coastal wetlands could improve our understanding of the roles of rice paddies in the regional CH4 regulation. Our results also have implications for informing rice paddy management and climate change policy making the efforts being made by agricultural organizations and enterprises to restore coastal rice paddies for mitigating CH4 emissions.

Trace Gas Measurements in Nascent, Aged and Cloud-processed Smoke from Africa Savanna Fires by Airborne Fourier Transform Infrared Spectroscopy (AFTIR)

NASA Technical Reports Server (NTRS)

Yokelson, Robert J.; Bertschi, Isaac T.; Christian, Ted J.; Hobbs, Peter V.; Ward, Darold E.; Hao, Wei Min

2003-01-01

We measured stable and reactive trace gases with an airborne Fourier transform infrared spectrometer (AFTIR) on the University of Washington Convair-580 research aircraft in August/September 2000 during the SAFARI 2000 dry season campaign in Southern Africa. The measurements included vertical profiles of C02, CO, H20, and CH4 up to 5.5 km on six occasions above instrumented ground sites and below the TERRA satellite and ER-2 high-flying research aircraft. We also measured the trace gas emissions from 10 African savanna fires. Five of these fires featured extensive ground-based fuel characterization, and two were in the humid savanna ecosystem that accounts for most African biomass burning. The major constituents we detected in nascent CH3OOH, HCHO, CH30H, HCN, NH3, HCOOH, and C2H2. These are the first quantitative measurements of the initial emissions of oxygenated volatile organic compounds (OVOC), NH3, and HCN from African savanna fires. On average, we measured 5.3 g/kg of OVOC and 3.6 g/kg of hydrocarbons (including CH4) in the initial emissions from the fires. Thus, the OVOC will have profound, largely unexplored effects on tropical tropospheric chemistry. The HCN emission factor was only weakly dependent on fire type; the average value (0.53 g/kg) is about 20 times that of a previous recommendation. HCN may be useful as a tracer for savanna fires. Delta O3/Delta CO and Delta CH3COO/Delta CO increased to as much as 9% in <1 h of photochemical processing downwind of fires. Direct measurements showed that cloud processing of smoke greatly reduced CH30H, NH3, CH3COOH, SO2, and NO2 levels, but significantly increased HCHO and NO.

The effect of regional groundwater on carbon dioxide and methane emissions from a lowland rainforest stream in Costa Rica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oviedo-Vargas, Diana; Genereux, David P.; Dierick, Diego

In the tropical rainforest at La Selva Biological Station in Costa Rica, regional bedrock groundwater high in dissolved carbon discharges into some streams and wetlands, with the potential for multiple cascading effects on ecosystem carbon pools and fluxes. We investigated carbon dioxide (CO 2) and methane (CH 4) degassing from two streams at La Selva: the Arboleda, where ~1/3 of the streamflow is from regional groundwater, and the Taconazo, fed exclusively by local groundwater recharged within the catchment. The regional groundwater inflow to the Arboleda had no measurable effect on stream gas exchange velocity, dissolved CH 4 concentration, or CHmore » 4 emissions but significantly increased stream CO 2 concentration and degassing. CO 2 evasion from the reach of the Arboleda receiving regional groundwater (lower Arboleda) averaged 5.5 mol C m -2 d -1, ~7.5x higher than the average (0.7 mol C m -2 d -1) from the stream reaches with no regional groundwater inflow (the Taconazo and upper Arboleda). Carbon emissions from both streams were dominated by CO 2; CH 4 accounted for only 0.06-1.70% of the total (average of both streams: 5 x10 -3 mol C m -2 d -1). Annual stream degassing fluxes normalized by watershed area were 48 and 299 g C m -2 for the Taconazo and Arboleda, respectively. CO 2 degassing from the Arboleda is a significant carbon flux, similar in magnitude to the average net ecosystem exchange estimated by eddy covariance. As a result, examining the effects of catchment connections to underlying hydrogeological systems can help avoid overestimation of ecosystem respiration and advance our understanding of carbon source/sink status and overall terrestrial ecosystem carbon budgets.« less

The effect of regional groundwater on carbon dioxide and methane emissions from a lowland rainforest stream in Costa Rica

DOE PAGES

Oviedo-Vargas, Diana; Genereux, David P.; Dierick, Diego; ...

2015-12-22

In the tropical rainforest at La Selva Biological Station in Costa Rica, regional bedrock groundwater high in dissolved carbon discharges into some streams and wetlands, with the potential for multiple cascading effects on ecosystem carbon pools and fluxes. We investigated carbon dioxide (CO 2) and methane (CH 4) degassing from two streams at La Selva: the Arboleda, where ~1/3 of the streamflow is from regional groundwater, and the Taconazo, fed exclusively by local groundwater recharged within the catchment. The regional groundwater inflow to the Arboleda had no measurable effect on stream gas exchange velocity, dissolved CH 4 concentration, or CHmore » 4 emissions but significantly increased stream CO 2 concentration and degassing. CO 2 evasion from the reach of the Arboleda receiving regional groundwater (lower Arboleda) averaged 5.5 mol C m -2 d -1, ~7.5x higher than the average (0.7 mol C m -2 d -1) from the stream reaches with no regional groundwater inflow (the Taconazo and upper Arboleda). Carbon emissions from both streams were dominated by CO 2; CH 4 accounted for only 0.06-1.70% of the total (average of both streams: 5 x10 -3 mol C m -2 d -1). Annual stream degassing fluxes normalized by watershed area were 48 and 299 g C m -2 for the Taconazo and Arboleda, respectively. CO 2 degassing from the Arboleda is a significant carbon flux, similar in magnitude to the average net ecosystem exchange estimated by eddy covariance. As a result, examining the effects of catchment connections to underlying hydrogeological systems can help avoid overestimation of ecosystem respiration and advance our understanding of carbon source/sink status and overall terrestrial ecosystem carbon budgets.« less

Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation

USGS Publications Warehouse

Zhu, Qiuan; Peng, Changhui; Ciais, Philippe; Jiang, Hong; Liu, Jinxun; Bousquet, Philippe; Li, Shiqin; Chang, Jie; Fang, Xiuqin; Zhou, Xiaolu; Chen, Huai; Liu, Shirong; Lin, Guanghui; Gong, Peng; Wang, Meng; Wang, Han; Xiang, Wenhua; Chen, Jing

2017-01-01

Methane (CH4) emissions from tropical wetlands contribute 60%–80% of global natural wetland CH4 emissions. Decreased wetland CH4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Niño–Southern Oscillation (ENSO) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño events are expected to become more severe based on climate models’ projections. We use a process-based model of global wetland CH4 emissions to investigate the impacts of the ENSO on CH4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8-month time lag was detected between tropical wetland CH4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Niño events contributed to a lower decadal mean growth rate in atmospheric CH4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH4 concentrations from 1999 to 2006, resulting in negative feedback to global warming.

Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation.

PubMed

Zhu, Qiuan; Peng, Changhui; Ciais, Philippe; Jiang, Hong; Liu, Jinxun; Bousquet, Philippe; Li, Shiqin; Chang, Jie; Fang, Xiuqin; Zhou, Xiaolu; Chen, Huai; Liu, Shirong; Lin, Guanghui; Gong, Peng; Wang, Meng; Wang, Han; Xiang, Wenhua; Chen, Jing

2017-11-01

Methane (CH 4 ) emissions from tropical wetlands contribute 60%-80% of global natural wetland CH 4 emissions. Decreased wetland CH 4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Niño-Southern Oscillation (ENSO) on CH 4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño events are expected to become more severe based on climate models' projections. We use a process-based model of global wetland CH 4 emissions to investigate the impacts of the ENSO on CH 4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH 4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8-month time lag was detected between tropical wetland CH 4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH 4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH 4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Niño events contributed to a lower decadal mean growth rate in atmospheric CH 4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH 4 concentrations from 1999 to 2006, resulting in negative feedback to global warming. © 2017 John Wiley & Sons Ltd.

Estimating methane emissions in California's urban and rural regions using multitower observations

DOE PAGES

Jeong, Seongeun; Newman, Sally; Zhang, Jingsong; ...

2016-11-05

Here, we present an analysis of methane (CH 4) emissions using atmospheric observations from 36 thirteen sites in California during June 2013 – May 2014. A hierarchical Bayesian inversion 37 method is used to estimate CH 4 emissions for spatial regions (0.3° pixels for major regions) by 38 comparing measured CH 4 mixing ratios with transport model (WRF-STILT) predictions based 39 on seasonally varying California-specific CH 4 prior emission models. The transport model is 40 assessed using a combination of meteorological and carbon monoxide (CO) measurements 41 coupled with the gridded California Air Resources Board (CARB) carbon monoxide (CO) 42more » emission inventory. Hierarchical Bayesian inversion suggests that state annual anthropogenic 43 CH 4 emissions are 2.42 ± 0.49 Tg CH 4/yr (at 95% confidence, including transport bias 44 uncertainty), higher (1.2 - 1.8 times) than the CARB current inventory (1.64 Tg CH 4/yr in 2013). 45 We note that the estimated CH 4 emissions drop to 1.0 - 1.6 times the CARB inventory if we 46 correct for the 10% median CH 4 emissions assuming the bias in CO analysis is applicable to 47 CH 4. The CH 4 emissions from the Central Valley and urban regions (San Francisco Bay and 48 South Coast Air Basins) account for ~58% and 26% of the total posterior emissions, 49 respectively. This study suggests that the livestock sector is likely the major contributor to the 50 state total CH 4 emissions, in agreement with CARB’s inventory. Attribution to source sectors for 51 sub-regions of California using additional trace gas species would further improve the 52 quantification of California’s CH 4 emissions and mitigation efforts towards the California Global 53 Warming Solutions Act of 2006 (AB-32).« less

Estimating methane emissions in California's urban and rural regions using multitower observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, Seongeun; Newman, Sally; Zhang, Jingsong

Here, we present an analysis of methane (CH 4) emissions using atmospheric observations from 36 thirteen sites in California during June 2013 – May 2014. A hierarchical Bayesian inversion 37 method is used to estimate CH 4 emissions for spatial regions (0.3° pixels for major regions) by 38 comparing measured CH 4 mixing ratios with transport model (WRF-STILT) predictions based 39 on seasonally varying California-specific CH 4 prior emission models. The transport model is 40 assessed using a combination of meteorological and carbon monoxide (CO) measurements 41 coupled with the gridded California Air Resources Board (CARB) carbon monoxide (CO) 42more » emission inventory. Hierarchical Bayesian inversion suggests that state annual anthropogenic 43 CH 4 emissions are 2.42 ± 0.49 Tg CH 4/yr (at 95% confidence, including transport bias 44 uncertainty), higher (1.2 - 1.8 times) than the CARB current inventory (1.64 Tg CH 4/yr in 2013). 45 We note that the estimated CH 4 emissions drop to 1.0 - 1.6 times the CARB inventory if we 46 correct for the 10% median CH 4 emissions assuming the bias in CO analysis is applicable to 47 CH 4. The CH 4 emissions from the Central Valley and urban regions (San Francisco Bay and 48 South Coast Air Basins) account for ~58% and 26% of the total posterior emissions, 49 respectively. This study suggests that the livestock sector is likely the major contributor to the 50 state total CH 4 emissions, in agreement with CARB’s inventory. Attribution to source sectors for 51 sub-regions of California using additional trace gas species would further improve the 52 quantification of California’s CH 4 emissions and mitigation efforts towards the California Global 53 Warming Solutions Act of 2006 (AB-32).« less

Patterns of in-soil methane production and atmospheric emission among different land covers of a Lake Erie estuarine wetland

NASA Astrophysics Data System (ADS)

Rey Sanchez, C.; Morin, T. H.; Stefanik, K. C.; Angle, J.; Wrighton, K. C.; Bohrer, G.

2017-12-01

Wetland soils store a great amount of carbon, but also accumulate and emit methane (CH4), a powerful greenhouse gas. To better understand the vertical and horizontal spatial variability of CH4 emissions, we monitored production and fluxes of CH4 in Old Woman Creek, an estuarine wetland of Lake Erie, Ohio, during the growing seasons of 2015 and 2016. Our combined observation methods targeted three different scales: 1) the eddy covariance technique provided continuous high frequency observations integrated over a large spatial footprint; 2) monthly chamber measurements provided sparse point measurements of fluxes in four distinct land-cover types in the wetland: open water, emergent vegetation (Typha spp.), floating vegetation (Nelumbo spp.) and mud flats; and 3) in-situ porewater dialysis samplers, "peepers", provided vertical CH4 concentration data in the soil at the same locations and temporal time steps as the chambers. In addition, we studied gene transcripts to quantify methanogenesis activity along the vertical soil profile. Using integrated chamber and EC measurements, we found an average surface emission rate from Typha, the most abundant vegetated land cover, of 219.4 g CH4-C m-2 y-1, which was much higher than rates reported in similar emergent vegetation types in other wetlands. There was large spatial variation of flux rates, with mud flats having the highest rates of CH4 emission, followed by Nelumbo and Typha patches, and with open water having the lowest emissions. Within the soil column, we applied a numerical model to convert soil methane concentrations to emissions rates. We found that, contrary to current ideas of methane production, most methane was being produced in the well-oxygenated surface soils, probably in anoxic microsites within the oxic layer. Our metatranscriptomic data supported these findings, clearly showing nine times greater methanogenic activity in oxic surface soils relative to deeper anoxic soils. Combined, our results provide important insights for the representation of processes of methane production and consumption in models, which can largely affect the estimates of methane emission from wetlands.

Air-water CO2 and CH4 fluxes along a river-reservoir continuum: Case study in the Pengxi River, a tributary of the Yangtze River in the Three Gorges Reservoir, China.

PubMed

Huang, Yang; Yasarer, Lindsey M W; Li, Zhe; Sturm, Belinda S M; Zhang, Zengyu; Guo, Jinsong; Shen, Yu

2017-05-01

Water surface greenhouse gas (GHG) emissions in freshwater reservoirs are closely related to limnological processes in the water column. Affected by both reservoir operation and seasonal changes, variations in the hydro-morphological conditions in the river-reservoir continuum will create distinctive patterns in water surface GHG emissions. A one-year field survey was carried out in the Pengxi River-reservoir continuum, a part of the Three Gorges Reservoir (TGR) immediately after the TGR reached its maximum water level. The annual average water surface CO 2 and CH 4 emissions at the riverine background sampling sites were 6.23 ± 0.93 and 0.025 ± 0.006 mmol h -1  m -2 , respectively. The CO 2 emissions were higher than those in the downstream reservoirs. The development of phytoplankton controlled the downstream decrease in water surface CO 2 emissions. The presence of thermal stratification in the permanent backwater area supported extensive phytoplankton blooms, resulting in a carbon sink during several months of the year. The CH 4 emissions were mainly impacted by water temperature and dissolved organic carbon. The greatest water surface CH 4 emission was detected in the fluctuating backwater area, likely due to a shallower water column and abundant organic matter. The Pengxi River backwater area did not show significant increase in water surface GHG emissions reported in tropical reservoirs. In evaluating the net GHG emissions by the impoundment of TGR, the net change in the carbon budget and the contribution of nitrogen and phosphorus should be taken into consideration in this eutrophic river-reservoir continuum.

Green-house gas emissions from rice fields under different water management

NASA Astrophysics Data System (ADS)

Lagomarsino, Alessandra; Elio Agnelli, Alessandro; Ferrara, Rossana Monica; Adviento-Borbe, Maria Arlene; Linquist, Bruce; Gavina, Giacomo; Ravaglia, Stefano

2013-04-01

During 2012 season, two rice fields have been selected in Italy (Cantaglia farm, Bologna province) and subjected to different water management: one under continuous flooding (WET) and the other under alternate wetting and drying (AWD). In AWD, re-flushing occurred in order to maintain water field capacity over 60 %. Two rice varieties (one commonly cultivated in Italy and one variety from the S.I.S. germoplasm collection) have been considered under WET treatment (Gladio and Zhen Long 13 - abbreviated as ZL13), while only Gladio under AWD. Green house gases (GHGs) sampling have been performed weekly or bi-weekly throughout the growing season. Soluble organic carbon (C), soluble nitrogen (N) and nitrates have been collected through piezometers. Soil sampling have been performed at the beginning and at the end of the growing season and total organic C (TOC), total N (TN), C/N ratio of soil organic matter (SOM), bulk density and water holding capacity were measured. At the end of the growing season rice above- and below-ground biomass have been sampled and C and N content of stem, grain and roots were measured. Methane (CH4) emissions showed a clear trend, following water availability in soils. An initial peak after the first flooding was observed in all soils, while after the second flooding CH4 was emitted only in the WET treatment. Further flooding events in AWD soil did not determine CH4 emissions during the vegetative season. Overall, in 2012 growing season a 98 % reduction of CH4 emissions in AWD soil was observed. In the WET treatment, no significant variations were observed between the two varieties, although on average ZL13 showed lower rates of CH4 emissions. Two peaks of nitrous oxide (N2O) emissions were observed: the first after the initial flooding in all soils; the second one, much greater, 14 days after the fertilization only in AWD soils. These two peaks accounted for 92 % of total N2O emissions in 2012 rice season. Overall, in 2012 growing season N2O emissions were five-fold greater in AWD with respect to WET soils. No significant differences were observed between the two varieties, although ZL13 showed on average lower emission rates. The large difference between the two water management systems indicates that more work is needed to optimize the AWD cultivation method (variety, N management, water management) under Italian conditions before it can be introduced as an instrument to reduce climate impact of the Italian rice crop.

Greenhouse gas emissions from naturally ventilated freestall dairy barns

NASA Astrophysics Data System (ADS)

Joo, H. S.; Ndegwa, P. M.; Heber, A. J.; Ni, J.-Q.; Bogan, B. W.; Ramirez-Dorronsoro, J. C.; Cortus, E.

2015-02-01

Greenhouse gas (GHG) emissions from two naturally-ventilated dairy freestall barns measured for a total of 21 d, one week each in May, July, and September 2009, are presented in this article. The holding capacity of Barn 1 (B1) was 400 Holstein cows, while that for Barn 2 (B2) was 850 cows. Air samples were taken from inlets and outlets of the barns via a custom made multiplexer gas sampling system for measurement of gas concentrations using a photoacoustic infrared multigas analyzer. Barn ventilation rates were based on air velocity measured with arrays of 3-D ultrasonic anemometers at inlets and outlets. Gas concentrations (10 min means) in the barns ranged from: 443-789 ppm for CO2, 0.0-39.4 ppm for CH4, and 0.25-0.39 ppm for N2O; with mean concentrations ranging from 6 to 20%, 0 to 4%, and 26 to 180% above the average background concentrations for CO2, N2O, and CH4, respectively. The correlations between CO2 and CH4 enhanced concentrations were relatively stronger (R of 0.67-0.74) than between CO2 and N2O enhanced concentrations (R of 0.10-0.20). Environmental conditions did not significantly (p = 0.46) impact the enhanced concentrations of N2O in the barns. All three parameters (T, RH, and v) had significant (p < 0.01) influences on CO2 enhanced concentrations; while only T (p < 0.01) and v (p < 0.01) had significant influences on CH4 enhanced concentrations. Enhanced concentrations of CO2 and CH4 correlated negatively with all three parameters. The influence of the temperature-humidity index (THI) on CO2 enhanced concentrations was higher than that of v; while the effect v had on CH4 enhanced concentrations was slightly higher than that of the temperature-humidity index. The average emissions, based on hourly means, ranged from 5.3 to 10.7 kg d-1 AU-1 for CO2; 0.3 to 2.5 g d-1 AU-1 for N2O; and between 67 and 252 g d-1 AU-1 for CH4. Nitrous oxide emissions from the smaller barn, B1 (0.4-2.5 g d-1 AU-1), were significantly higher than from the larger barn, B2 (0.3-0.5 g d-1 AU-1) most probably because 50% of B1 was open (no stalls) loose dirt floor.

Stable carbon isotope ratio of methyl chloride emitted from glasshouse-grown tropical plants and its implication for the global methyl chloride budget

NASA Astrophysics Data System (ADS)

Saito, Takuya; Yokouchi, Yoko

2008-04-01

Stable carbon isotope ratios of methyl chloride (CH3Cl) were measured in foliar emissions from 14 species of tropical plants growing in a glasshouse. The isotopic ratio of CH3Cl (arithmetic mean: -83.2 +/- 15.2‰) ranged from -56‰ to -114‰ that from dipterocarp trees (-87.4 +/- 12.3‰) was on average more depleted in 13C than that from tree ferns (-61.9 +/- 9.7‰). The isotopic ratio was lower than that of CH3Cl produced by other known sources (e.g., biomass burning and salt marshes), with the exception of that by dead leaves. Using the distinctive isotope ratio of CH3Cl emitted from tropical plants together with previously reported isotopic data of CH3Cl sources and sinks to an isotopic mass balance calculation, global CH3Cl emission by tropical plants was estimated to be approximately 1500-3000 Gg yr-1 with uncertainties of 30-60%, which could account for 30-50% of the global emission.

Heat-Wave Effects on Oxygen, Nutrients, and Phytoplankton Can Alter Global Warming Potential of Gases Emitted from a Small Shallow Lake.

PubMed

Bartosiewicz, Maciej; Laurion, Isabelle; Clayer, François; Maranger, Roxane

2016-06-21

Increasing air temperatures may result in stronger lake stratification, potentially altering nutrient and biogenic gas cycling. We assessed the impact of climate forcing by comparing the influence of stratification on oxygen, nutrients, and global-warming potential (GWP) of greenhouse gases (the sum of CH4, CO2, and N2O in CO2 equivalents) emitted from a shallow productive lake during an average versus a heat-wave year. Strong stratification during the heat wave was accompanied by an algal bloom and chemically enhanced carbon uptake. Solar energy trapped at the surface created a colder, isolated hypolimnion, resulting in lower ebullition and overall lower GWP during the hotter-than-average year. Furthermore, the dominant CH4 emission pathway shifted from ebullition to diffusion, with CH4 being produced at surprisingly high rates from sediments (1.2-4.1 mmol m(-2) d(-1)). Accumulated gases trapped in the hypolimnion during the heat wave resulted in a peak efflux to the atmosphere during fall overturn when 70% of total emissions were released, with littoral zones acting as a hot spot. The impact of climate warming on the GWP of shallow lakes is a more complex interplay of phytoplankton dynamics, emission pathways, thermal structure, and chemical conditions, as well as seasonal and spatial variability, than previously reported.

Methane oxidation by termite mounds estimated by the carbon isotopic composition of methane

NASA Astrophysics Data System (ADS)

Sugimoto, Atsuko; Inoue, Tetsushi; Kirtibutr, Nit; Abe, Takuya

1998-12-01

Emission rates and carbon isotope ratios of CH4, emitted by workers of termites, and of CH4, emitted from their mounds, were observed in a dry evergreen forest in Thailand to estimate the proportion of CH4 oxidized during emission through the mound. The δ13C of CH4 emitted from a termite mound (-70.9 to -82.4‰) was higher than that of CH4 emitted by workers in the mound (-85.4 to -97. l‰). Using a fractionation factor (a = 0.987) for oxidation of CH4 which was obtained in the incubation experiment, an emission factor defined as (CH4 emitted from a termite mound/CH4 produced by termites) was calculated. The emission factor obtained in each termite mound was nearly zero for Macrotermes (fungus-growing termites), of which the nest has a thick soil wall and subterrannean termites, and 0.17 to 0.47 for Termitinae (small-mound-making termites). Global CH4 emission by termites was estimated on the basis of the CH4 emission rates by workers and termite biomass with the emission factors. The calculated result was 1.5 to 7.4 Tg/y (0.3 to 1.3% of total source), which is considerably smaller than the estimate by the IPCC [1994].

Methane emission from Minnesota peatlands: Spatial and seasonal variability

NASA Astrophysics Data System (ADS)

Dise, Nancy. B.

1993-03-01

The variability of methane flux with season, year, and habitat type was investigated in northern Minnesota peatlands from September 1988 through September 1990. Average daily fluxes calculated by integration of annual data for an open poor fen, an open bog, a forested bog hollow, a fen lagg in the forested bog and a forested bog hummock were 180,118, 38, 35, and 10 mg CH4 m-2 d-1, respectively. Fluxes among the five ecosystems were significantly different from one another, although emission from all sites was highest in July and lowest in March. Winter fluxes occurred in all sites but the fen lagg. There was no difference in fluxes measured from the same sites in the spring of 1986, 1989, or 1990, but summer fluxes were significantly higher in the wetter year of 1989 than in 1990, and a summer pulse in methane emission occurred in 1989 that was not seen the next year. Concentrations of methane in pore water, reflecting the seasonal balance of production, oxidation, and release, declined during the month of peak flux, then increased to levels of about 500 μM in December. Consistent spatial and temporal differences in flux could be ascribed to differences in water table, temperature, and peat nutrient status, although additional variability remained. Integration gave an annual average flux of 20 g CH4, m-2 ot; for the three bog ecosystems and 39 g CH4, m-2 for the two fen ecosystems. This gives an estimate of 1-2 Tg CH4, yr-1 from peatlands in the Great Lake states of Minnesota, Wisconsin, and Michigan.

Greenhouse Gas Source Detection and Attribution in the San Francisco Bay Area of California Using a Mobile Measurement Platform

NASA Astrophysics Data System (ADS)

Martien, P. T.; Guha, A.; Newman, S.; Young, A.; Bower, J.; Perkins, I.; Randall, S.; Stevenson, E.; Hilken, H.

2017-12-01

The Bay Area Air Quality Management District, the San Francisco Bay Area's air quality regulatory agency, has set a goal to reduce the region's greenhouse gas (GHG) emissions 80% below 1990 levels by 2050, consistent with the State of California's climate goals. Recently, the Air District's governing board adopted a 2017 Clean Air Plan advancing the agency's vision and including actions to put the region on a path to achieving the 2050 goal while also reducing air pollution and related health impacts. The Plan includes GHG rule-making efforts, policy initiatives, local government partnerships, outreach, grants and incentives, encompassing over 250 specific implementation actions across all economic sectors to effect ambitious emission reductions in the region. To support the 2017 Plan, the Air District has built a mobile measurement platform (GHG research van) to perform targeted CH4 emissions hotspot detection and source attribution. Instruments in the van measure CH4, CO2 and N2O in ambient plumes. Coincident measurements of source tracers like isotopic methane (13C - CH4), CO and ethane (C2H6) provide the capability to distinguish between biogenic, combustion-based and fossil-based fugitive methane sources. We report observations of CH4 plumes from source-specific measurements in and around facilities including a wastewater treatment plant, a composting operation, a waste-to-energy anaerobic digestion plant and a few refineries. We performed leak surveys inside several electric utility-operated facilities including a power plant and an underground natural gas storage facility. We sampled exhaust from a roadway tunnel and computed fleet-averaged automobile-related CH4 and N2O emission factors. We used tracer-to-tracer emission ratios to create chemical signatures of emissions from each sampled source category. We compare measurement-based ratios with those used to derive the regional GHG inventory. Data from these and other sources will lead to an improved understanding of GHG emissions from well- and lesser-known CH4 sources in the region, key to resolving the differences between top-down estimates (Fairley and Fischer, 2015; Jeong et al., 2016) and the regional bottom-up inventory.

Seasonal variability in methane and nitrous oxide fluxes from tropical peatlands in the western Amazon basin

NASA Astrophysics Data System (ADS)

Arn Teh, Yit; Murphy, Wayne A.; Berrio, Juan-Carlos; Boom, Arnoud; Page, Susan E.

2017-08-01

The Amazon plays a critical role in global atmospheric budgets of methane (CH4) and nitrous oxide (N2O). However, while we have a relatively good understanding of the continental-scale flux of these greenhouse gases (GHGs), one of the key gaps in knowledge is the specific contribution of peatland ecosystems to the regional budgets of these GHGs. Here we report CH4 and N2O fluxes from lowland tropical peatlands in the Pastaza-Marañón foreland basin (PMFB) in Peru, one of the largest peatland complexes in the Amazon basin. The goal of this research was to quantify the range and magnitude of CH4 and N2O fluxes from this region, assess seasonal trends in trace gas exchange, and determine the role of different environmental variables in driving GHG flux. Trace gas fluxes were determined from the most numerically dominant peatland vegetation types in the region: forested vegetation, forested (short pole) vegetation, Mauritia flexuosa-dominated palm swamp, and mixed palm swamp. Data were collected in both wet and dry seasons over the course of four field campaigns from 2012 to 2014. Diffusive CH4 emissions averaged 36.05 ± 3.09 mg CH4-C m-2 day-1 across the entire dataset, with diffusive CH4 flux varying significantly among vegetation types and between seasons. Net ebullition of CH4 averaged 973.3 ± 161.4 mg CH4-C m-2 day-1 and did not vary significantly among vegetation types or between seasons. Diffusive CH4 flux was greatest for mixed palm swamp (52.0 ± 16.0 mg CH4-C m-2 day-1), followed by M. flexuosa palm swamp (36.7 ± 3.9 mg CH4-C m-2 day-1), forested (short pole) vegetation (31.6 ± 6.6 mg CH4-C m-2 day-1), and forested vegetation (29.8 ± 10.0 mg CH4-C m-2 day-1). Diffusive CH4 flux also showed marked seasonality, with divergent seasonal patterns among ecosystems. Forested vegetation and mixed palm swamp showed significantly higher dry season (47.2 ± 5.4 mg CH4-C m-2 day-1 and 85.5 ± 26.4 mg CH4-C m-2 day-1, respectively) compared to wet season emissions (6.8 ± 1.0 mg CH4-C m-2 day-1 and 5.2 ± 2.7 mg CH4-C m-2 day-1, respectively). In contrast, forested (short pole) vegetation and M. flexuosa palm swamp showed the opposite trend, with dry season flux of 9.6 ± 2.6 and 25.5 ± 2.9 mg CH4-C m-2 day-1, respectively, versus wet season flux of 103.4 ± 13.6 and 53.4 ± 9.8 mg CH4-C m-2 day-1, respectively. These divergent seasonal trends may be linked to very high water tables (> 1 m) in forested vegetation and mixed palm swamp during the wet season, which may have constrained CH4 transport across the soil-atmosphere interface. Diffusive N2O flux was very low (0.70 ± 0.34 µg N2O-N m-2 day-1) and did not vary significantly among ecosystems or between seasons. We conclude that peatlands in the PMFB are large and regionally significant sources of atmospheric CH4 that need to be better accounted for in regional emissions inventories. In contrast, N2O flux was negligible, suggesting that this region does not make a significant contribution to regional atmospheric budgets of N2O. The divergent seasonal pattern in CH4 flux among vegetation types challenges our underlying assumptions of the controls on CH4 flux in tropical peatlands and emphasizes the need for more process-based measurements during periods of high water table.

Top-down methane emissions estimates for the San Francisco Bay Area from 1990 to 2012

DOE PAGES

Fairley, David; Fischer, Marc L.

2015-01-30

Methane is a potent greenhouse gas (GHG) that is now included in both California State and San Francisco Bay Area (SFBA) bottom-up emission inventories as part of California's effort to reduce anthropogenic GHG emissions. Here we provide a top-down estimate of methane (CH 4) emissions from the SFBA by combining atmospheric measurements with the comparatively better estimated emission inventory for carbon monoxide (CO). Local enhancements of CH 4 and CO are estimated using measurements from 14 air quality sites in the SFBA combined together with global background measurements. Mean annual CH 4 emissions are estimated from the product of Baymore » Area Air Quality Management District (BAAQMD) emission inventory CO and the slope of ambient local CH 4 to CO. The resulting top-down estimates of CH 4 emissions are found to decrease slightly from 1990 to 2012, with a mean value of 240 ± 60 GgCH 4 yr⁻¹ (at 95% confidence) in the most recent (2009–2012) period, and correspond to reasonably a constant factor of 1.5–2.0 (at 95% confidence) times larger than the BAAQMD CH 4 emission inventory. However, we note that uncertainty in these emission estimates is dominated by the variation in CH 4:CO enhancement ratios across the observing sites and we expect the estimates could represent a lower-limit on CH 4 emissions because BAAQMD monitoring sites focus on urban air quality and may be biased toward CO rather than CH 4 sources.« less

The positive net radiative greenhouse gas forcing of increasing methane emissions from a thawing boreal forest-wetland landscape.

PubMed

Helbig, Manuel; Chasmer, Laura E; Kljun, NatasCha; Quinton, William L; Treat, Claire C; Sonnentag, Oliver

2017-06-01

At the southern margin of permafrost in North America, climate change causes widespread permafrost thaw. In boreal lowlands, thawing forested permafrost peat plateaus ('forest') lead to expansion of permafrost-free wetlands ('wetland'). Expanding wetland area with saturated and warmer organic soils is expected to increase landscape methane (CH 4 ) emissions. Here, we quantify the thaw-induced increase in CH 4 emissions for a boreal forest-wetland landscape in the southern Taiga Plains, Canada, and evaluate its impact on net radiative forcing relative to potential long-term net carbon dioxide (CO 2 ) exchange. Using nested wetland and landscape eddy covariance net CH 4 flux measurements in combination with flux footprint modeling, we find that landscape CH 4 emissions increase with increasing wetland-to-forest ratio. Landscape CH 4 emissions are most sensitive to this ratio during peak emission periods, when wetland soils are up to 10 °C warmer than forest soils. The cumulative growing season (May-October) wetland CH 4 emission of ~13 g CH 4  m -2 is the dominating contribution to the landscape CH 4 emission of ~7 g CH 4  m -2 . In contrast, forest contributions to landscape CH 4 emissions appear to be negligible. The rapid wetland expansion of 0.26 ± 0.05% yr -1 in this region causes an estimated growing season increase of 0.034 ± 0.007 g CH 4  m -2  yr -1 in landscape CH 4 emissions. A long-term net CO 2 uptake of >200 g CO 2  m -2  yr -1 is required to offset the positive radiative forcing of increasing CH 4 emissions until the end of the 21st century as indicated by an atmospheric CH 4 and CO 2 concentration model. However, long-term apparent carbon accumulation rates in similar boreal forest-wetland landscapes and eddy covariance landscape net CO 2 flux measurements suggest a long-term net CO 2 uptake between 49 and 157 g CO 2  m -2  yr -1 . Thus, thaw-induced CH 4 emission increases likely exert a positive net radiative greenhouse gas forcing through the 21st century. © 2016 John Wiley & Sons Ltd.

Inverse Modeling of Surface CH4 and δ13C-CH4 Measurements to Understand Recent Trends in Global Methane Emissions

NASA Astrophysics Data System (ADS)

Karmakar, S.; Butenhoff, C. L.; Rice, A. L.; Lofdahl, D. B.; Khalil, A. K.

2016-12-01

Methane (CH4) is the second most important greenhouse gas with a radiative forcing of 0.97 W/m2 including both direct and indirect effects and a global warming potential of 28 over a 100-year time horizon. Unlike CO2 whose rate of growth in the atmosphere has remained positive and increased in recent decades, the behavior of atmospheric methane is considerably more complex and is much less understood on account of the spatiotemporal variability of its emissions which include biogenic (e.g. wetlands, ruminants, rice agriculture), thermogenic (fossil fuels), and pyrogenic (i.e. biomass burning) sources. After sustained growth during most of the 20th century, the CH4 growth rate declined falling from 15 ppbv/yr during the 1980s to 6 ppbv/yr in the 1990s to near-zero and even negative values in the early 2000s. With some surprise however, the growth rate rebounded in 2007 and has been on average 6 ppbv/yr during the past 10 years. During this same period the 13CH4/12CH4 ratio of atmospheric CH4 also declined suggesting the recent CH4 growth was caused by an increase in 13CH4-depleted biogenic emissions. Here, we provide additional insight into the recent behavior of atmospheric methane by performing a global three-dimensional Bayesian inversion of surface CH4 and 13CH4/12CH4 ratios over the period 1985-2015 using NOAA Global Monitoring Division (GMD) CH4 measurements and the GEOS-Chem chemical-transport model (CTM) at a horizontal grid resolution of 2ox2.5o. The use of the 3-D model allows us to exploit spatial patterns in the global CH4 and 13CH4/12CH4 fields that provide additional constraints on the retrieval of the time-dependent CH4 fluxes. This work follows up on our previous CH4 inversion where we used a 4ox5o horizontal grid for GEOS-Chem to retrieve fluxes from 1985 to 2009. At higher resolution more information is extracted from the observations due to improved model skill and a smaller number of stations aggregated within model grid cells. This increases the weights of the measurements relative to the a priori fluxes in the inversion producing stronger observational constraints on the optimized fluxes. This work assesses the contribution of spatial heterogeneities in the observed CH4 record to the retrieval of global CH4 fluxes and provides a new look into the causes of the recent growth in atmospheric methane.

Characterizing CH4 and N2O emissions from an intensive dairy operation in summer and fall in China

NASA Astrophysics Data System (ADS)

Zhu, Gaodi; Ma, Xiaoyuan; Gao, Zhiling; Ma, Wenqi; Li, Jianguo; Cai, Zhenjiang

2014-02-01

Evaluation of the global warming potential of the dairy industry both in China and globally necessitates reliable characterization of CH4 and N2O emissions. However, CH4 and N2O emissions from dairy operations differ with feeds, herd structures and manure management practices, and the lack of N2O and CH4 emission measurements for China, especially for intensive dairy operations, causes substantial uncertainty in accounting for GHGs from dairy operation both in China and globally. In this study, CH4 and N2O emissions during summer to fall period from an intensive feedlot in China were characterized to fill the data gap. The diurnal CH4 emission patterns for milking cows and heifers were driven by the feeding activities and the diurnal N2O patterns by the diurnal changes in temperature. The CH4 emission rates of 397 g head-1 d-1 (23.63 L CH4 kg-1 milk) (in summer) and 279 g head-1 d-1 (in fall) for milking cows and heifers accounted for 5.17% and 7.68% of their daily gross energy intakes, whereas the N2O emission rates of 36.7 g head-1 d-1 (0.85 L N2O kg-1 milk) for milking cows and 24.2 g head-1 d-1 for heifers accounted for 4.25% and 6.86% of the daily feed N intake. The CH4 conversion factor and CH4 emission intensity in the measurement season for intensive dairy operations in China are lower than those for collective operations in China, and the CH4 emission intensity is similar to those in developed countries.

An Improved Approach to Estimate Methane Emissions from Coal Mining in China.

PubMed

Zhu, Tao; Bian, Wenjing; Zhang, Shuqing; Di, Pingkuan; Nie, Baisheng

2017-11-07

China, the largest coal producer in the world, is responsible for over 50% of the total global methane (CH 4 ) emissions from coal mining. However, the current emission inventory of CH4 from coal mining has large uncertainties because of the lack of localized emission factors (EFs). In this study, province-level CH4 EFs from coal mining in China were developed based on the data analysis of coal production and corresponding discharged CH4 emissions from 787 coal mines distributed in 25 provinces with different geological and operation conditions. Results show that the spatial distribution of CH 4 EFs is highly variable with values as high as 36 m3/t and as low as 0.74 m3/t. Based on newly developed CH 4 EFs and activity data, an inventory of the province-level CH4 emissions was built for 2005-2010. Results reveal that the total CH 4 emissions in China increased from 11.5 Tg in 2005 to 16.0 Tg in 2010. By constructing a gray forecasting model for CH 4 EFs and a regression model for activity, the province-level CH 4 emissions from coal mining in China are forecasted for the years of 2011-2020. The estimates are compared with other published inventories. Our results have a reasonable agreement with USEPA's inventory and are lower by a factor of 1-2 than those estimated using the IPCC default EFs. This study could help guide CH 4 mitigation policies and practices in China.

Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, Northeast China

NASA Astrophysics Data System (ADS)

Olsson, L.; Ye, S.; Yu, X.; Wei, M.; Krauss, K. W.; Brix, H.

2015-08-01

Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, Northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4 sources emitting 1.2-6.1 g CH4 m-2 yr-1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2. The main controlling factors for the CH4 emissions were water table, temperature, soil organic carbon and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1 mg CH4 m-2 h-1) at soil temperatures < 18 °C. At salinity levels > 18 ppt, the CH4 emission rates were always low (< 1 mg CH4 m-2 h-1) probably because methanogens were out-competed by sulphate-reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities.

Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, Northeast China

NASA Astrophysics Data System (ADS)

Olsson, L.; Ye, S.; Yu, X.; Wei, M.; Krauss, K. W.; Brix, H.

2015-02-01

Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4 sources emitting 1.2-6.1 g CH4 m-2 y-1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2. The main controlling factors for the CH4 emissions were water table, temperature and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1 mg CH4 m-2 h) at soil temperatures <18 °C. At salinity levels > 18 ppt, the CH4 emission rates were always low (< 1 mg CH4 m-2 h-1) probably because methanogens were outcompeted by sulphate reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities.

A simulation model for methane emissions from landfills with interaction of vegetation and cover soil.

PubMed

Bian, Rongxing; Xin, Danhui; Chai, Xiaoli

2018-01-01

Global climate change and ecological problems brought about by greenhouse gas effect have become a severe threat to humanity in the 21st century. Vegetation plays an important role in methane (CH 4 ) transport, oxidation and emissions from municipal solid waste (MSW) landfills as it modifies the physical and chemical properties of the cover soil, and transports CH 4 to the atmosphere directly via their conduits, which are mainly aerenchymatous structures. In this study, a novel 2-D simulation CH 4 emission model was established, based on an interactive mechanism of cover soil and vegetation, to model CH 4 transport, oxidation and emissions in landfill cover soil. Results of the simulation model showed that the distribution of CH 4 concentration and emission fluxes displayed a significant difference between vegetated and non-vegetated areas. CH 4 emission flux was 1-2 orders of magnitude higher than bare areas in simulation conditions. Vegetation play a negative role in CH 4 emissions from landfill cover soil due to the strong CH 4 transport capacity even though vegetation also promotes CH 4 oxidation via changing properties of cover soil and emitting O 2 via root system. The model will be proposed to allow decision makers to reconsider the actual CH 4 emission from vegetated and non-vegetated covered landfills. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of carbon balance in Mediterranean pilot constructed wetlands vegetated with different C4 plant species.

PubMed

Barbera, Antonio C; Borin, Maurizio; Cirelli, Giuseppe L; Toscano, Attilio; Maucieri, Carmelo

2015-02-01

This study investigates carbon dioxide (CO2) and methane (CH4) emissions and carbon (C) budgets in a horizontal subsurface flow pilot-plant constructed wetland (CW) with beds vegetated with Cyperus papyrus L., Chrysopogon zizanioides (L.) Roberty, and Mischantus × giganteus Greef et Deu in the Mediterranean basin (Sicily) during the 1st year of plant growing season. At the end of the vegetative season, M. giganteus showed the higher biomass accumulation (7.4 kg m(-2)) followed by C. zizanioides (5.3 kg m(-2)) and C. papyrus (1.8 kg m(-2)). Significantly higher emissions of CO2 were detected in the summer, while CH4 emissions were maximum during spring. Cumulative CO2 emissions by C. papyrus and C. zizanioides during the monitoring period showed similar trends with final values of about 775 and 1,074 g m(-2), respectively, whereas M. giganteus emitted 3,395 g m(-2). Cumulative CH4 bed emission showed different trends for the three C4 plant species in which total gas release during the study period was for C. papyrus 12.0 g m(-2) and ten times higher for M. giganteus, while C. zizanioides bed showed the greatest CH4 cumulative emission with 240.3 g m(-2). The wastewater organic carbon abatement determined different C flux in the atmosphere. Gas fluxes were influenced both by plant species and monitored months with an average C-emitted-to-C-removed ratio for C. zizanioides, C. papyrus, and M. giganteus of 0.3, 0.5, and 0.9, respectively. The growing season C balances were positive for all vegetated beds with the highest C sequestered in the bed with M. giganteus (4.26 kg m(-2)) followed by C. zizanioides (3.78 kg m(-2)) and C. papyrus (1.89 kg m(-2)). To our knowledge, this is the first paper that presents preliminary results on CO2 and CH4 emissions from CWs vegetated with C4 plant species in Mediterranean basin during vegetative growth.

Estimates of Methane and Ethane Emissions from the Barnett Shale Using Atmospheric Measurements

NASA Astrophysics Data System (ADS)

Karion, A.; Sweeney, C.; Kort, E. A.; Shepson, P. B.; Conley, S. A.; Lauvaux, T.; Davis, K. J.; Deng, A.; Lyon, D. R.; Smith, M. L.

2015-12-01

Recent development of horizontal drilling technology and advances in hydraulic fracturing techniques by the oil and gas industry have dramatically increased onshore U.S. natural gas and oil production in the last several years. The primary component of natural gas is methane (CH4), a powerful greenhouse gas; therefore, natural gas leakage into the atmosphere affects its climate impact. We present estimates of regional methane (CH4) and ethane (C2H6) emissions from oil and natural gas operations in the Barnett Shale, Texas, made in March and October 2013 as part of the Environmental Defense Fund's Barnett Coordinated Campaign. The Barnett is one of the largest production basins in the United States, with 8% of total U.S. natural gas production, and thus, our results represent a crucial step toward determining the greenhouse gas footprint of U.S. onshore natural gas production. Using a mass balance approach on eight different flight days the total CH4 emissions for the region are estimated to be 76 ± 13x 103 kg/hr, or 0.66 ± 0.11 Tg CH4 /yr; (95% CI). Repeated mass balance flights in the same basin on eight different days and two seasons demonstrate the consistency of the mass balance approach. On the basis of airborne C2H6 and CH4 measurements, we find 71-85% of the observed CH4 emissions quantified in the Barnett Shale are derived from fossil sources. The average C2H6 flux was 6.6 ± 0.2 x 103 kg/hr and consistent across six days in spring and fall of 2013. This result is the first demonstration of this approach for C2H6. We estimate that 60±11x103 kg CH4/hr (95% CI) are emitted by natural gas and oil operations, including production, processing, and distribution in the urban areas of Dallas and Fort Worth. This estimate is significantly higher than emissions reported by the EDGAR inventory or by industry to EPA's Greenhouse Gas Reporting Program.

Inverse Estimation of California Methane Emissions and Their Uncertainties using FLEXPART-WRF

NASA Astrophysics Data System (ADS)

Cui, Y.; Brioude, J. F.; Angevine, W. M.; McKeen, S. A.; Peischl, J.; Nowak, J. B.; Henze, D. K.; Bousserez, N.; Fischer, M. L.; Jeong, S.; Liu, Z.; Michelsen, H. A.; Santoni, G.; Daube, B. C.; Kort, E. A.; Frost, G. J.; Ryerson, T. B.; Wofsy, S. C.; Trainer, M.

2015-12-01

Methane (CH4) has a large global warming potential and mediates global tropospheric chemistry. In California, CH4 emissions estimates derived from "top-down" methods based on atmospheric observations have been found to be greater than expected from "bottom-up" population-apportioned national and state inventories. Differences between bottom-up and top-down estimates suggest that the understanding of California's CH4 sources is incomplete, leading to uncertainty in the application of regulations to mitigate regional CH4 emissions. In this study, we use airborne measurements from the California research at the Nexus of Air Quality and Climate Change (CalNex) campaign in 2010 to estimate CH4 emissions in the South Coast Air Basin (SoCAB), which includes California's largest metropolitan area (Los Angeles), and in the Central Valley, California's main agricultural and livestock management area. Measurements from 12 daytime flights, prior information from national and regional official inventories (e.g. US EPA's National Emission Inventory, the California Air Resources Board inventories, the Liu et al. Hybrid Inventory, and the California Greenhouse Gas Emissions Measurement dataset), and the FLEXPART-WRF transport model are used in our mesoscale Bayesian inverse system. We compare our optimized posterior CH4 inventory to the prior bottom-up inventories in terms of total emissions (Mg CH4/hr) and the spatial distribution of the emissions (0.1 degree), and quantify uncertainties in our posterior estimates. Our inversions show that the oil and natural gas industry (extraction, processing and distribution) is the main source accounting for the gap between top-down and bottom-up inventories over the SoCAB, while dairy farms are the largest CH4 source in the Central Valley. CH4 emissions of dairy farms in the San Joaquin Valley and variations of CH4 emissions in the rice-growing regions of Sacramento Valley are quantified and discussed. We also estimate CO and NH3 surface fluxes and use their observed correlation with CH4 mixing ratio to further evaluate our CH4 total emission estimates, and understand the spatial distribution of CH4 emissions.

Anti-methanogenic effects of monensin in dairy and beef cattle: a meta-analysis.

PubMed

Appuhamy, J A D Ranga Niroshan; Strathe, A B; Jayasundara, S; Wagner-Riddle, C; Dijkstra, J; France, J; Kebreab, E

2013-08-01

Monensin is a widely used feed additive with the potential to minimize methane (CH4) emissions from cattle. Several studies have investigated the effects of monensin on CH4, but findings have been inconsistent. The objective of the present study was to conduct meta-analyses to quantitatively summarize the effect of monensin on CH4 production (g/d) and the percentage of dietary gross energy lost as CH4 (Ym) in dairy cows and beef steers. Data from 22 controlled studies were used. Heterogeneity of the monensin effects were estimated using random effect models. Due to significant heterogeneity (>68%) in both dairy and beef studies, the random effect models were then extended to mixed effect models by including fixed effects of DMI, dietary nutrient contents, monensin dose, and length of monensin treatment period. Monensin reduced Ym from 5.97 to 5.43% and diets with greater neutral detergent fiber contents (g/kg of dry matter) tended to enhance the monensin effect on CH4 in beef steers. When adjusted for the neutral detergent fiber effect, monensin supplementation [average 32 mg/kg of dry matter intake (DMI)] reduced CH4 emissions from beef steers by 19±4 g/d. Dietary ether extract content and DMI had a positive and a negative effect on monensin in dairy cows, respectively. When adjusted for these 2 effects in the final mixed-effect model, monensin feeding (average 21 mg/kg of DMI) was associated with a 6±3 g/d reduction in CH4 emissions in dairy cows. When analyzed across dairy and beef cattle studies, DMI or monensin dose (mg/kg of DMI) tended to decrease or increase the effect of monensin in reducing methane emissions, respectively. Methane mitigation effects of monensin in dairy cows (-12±6 g/d) and beef steers (-14±6 g/d) became similar when adjusted for the monensin dose differences between dairy cow and beef steer studies. When adjusted for DMI differences, monensin reduced Ym in dairy cows (-0.23±0.14) and beef steers (-0.33±0.16). Monensin treatment period length did not significantly modify the monensin effects in dairy cow or beef steer studies. Overall, monensin had stronger antimethanogenic effects in beef steers than dairy cows, but the effects in dairy cows could potentially be improved by dietary composition modifications and increasing the monensin dose. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Source apportionment of methane and nitrous oxide in California's San Joaquin Valley at CalNex 2010 via positive matrix factorization

NASA Astrophysics Data System (ADS)

Guha, A.; Gentner, D. R.; Weber, R. J.; Provencal, R.; Goldstein, A. H.

2015-10-01

Sources of methane (CH4) and nitrous oxide (N2O) were investigated using measurements from a site in southeast Bakersfield as part of the CalNex (California at the Nexus of Air Quality and Climate Change) experiment from mid-May to the end of June 2010. Typical daily minimum mixing ratios of CH4 and N2O were higher than daily minima that were simultaneously observed at a mid-oceanic background station (NOAA, Mauna Loa) by approximately 70 ppb and 0.5 ppb, respectively. Substantial enhancements of CH4 and N2O (hourly averages > 500 and > 7 ppb, respectively) were routinely observed, suggesting the presence of large regional sources. Collocated measurements of carbon monoxide (CO) and a range of volatile organic compounds (VOCs) (e.g., straight-chain and branched alkanes, cycloalkanes, chlorinated alkanes, aromatics, alcohols, isoprene, terpenes and ketones) were used with a positive matrix factorization (PMF) source apportionment method to estimate the contribution of regional sources to observed enhancements of CH4 and N2O. The PMF technique provided a "top-down" deconstruction of ambient gas-phase observations into broad source categories, yielding a seven-factor solution. We identified these emission source factors as follows: evaporative and fugitive; motor vehicles; livestock and dairy; agricultural and soil management; daytime light and temperature driven; non-vehicular urban; and nighttime terpene biogenics and anthropogenics. The dairy and livestock factor accounted for the majority of the CH4 (70-90 %) enhancements during the duration of experiments. The dairy and livestock factor was also a principal contributor to the daily enhancements of N2O (60-70 %). Agriculture and soil management accounted for ~ 20-25 % of N2O enhancements over a 24 h cycle, which is not surprising given that organic and synthetic fertilizers are known to be a major source of N2O. The N2O attribution to the agriculture and soil management factor had a high uncertainty in the conducted bootstrapping analysis. This is most likely due to an asynchronous pattern of soil-mediated N2O emissions from fertilizer usage and collocated biogenic emissions from crops from the surrounding agricultural operations that is difficult to apportion statistically when using PMF. The evaporative/fugitive source profile, which resembled a mix of petroleum operation and non-tailpipe evaporative gasoline sources, did not include a PMF resolved-CH4 contribution that was significant (< 2 %) compared to the uncertainty in the livestock-associated CH4 emissions. The uncertainty of the CH4 estimates in this source factor, derived from the bootstrapping analysis, is consistent with the ~ 3 % contribution of fugitive oil and gas emissions to the statewide CH4 inventory. The vehicle emission source factor broadly matched VOC profiles of on-road exhaust sources. This source factor had no statistically significant detected contribution to the N2O signals (confidence interval of 3 % of livestock N2O enhancements) and negligible CH4 (confidence interval of 4 % of livestock CH4 enhancements) in the presence of a dominant dairy and livestock factor. The CalNex PMF study provides a measurement-based assessment of the state CH4 and N2O inventories for the southern San Joaquin Valley (SJV). The state inventory attributes ~ 18 % of total N2O emissions to the transportation sector. Our PMF analysis directly contradicts the state inventory and demonstrates there were no discernible N2O emissions from the transportation sector in the southern SJV region.

Physical and biological controls over patterns of methane flux from wetland soils

NASA Astrophysics Data System (ADS)

Owens, S. M.; von Fischer, J. C.

2006-12-01

While methane (CH4) production and plant-facilitated gas transport both contribute to patterns of CH4 emissions from wetlands, the relative importance of each mechanism is uncertain. In flooded wetland soils, CH4 is produced by anaerobic methanogenic bacteria. In the absence of competing oxidizers (i.e. SO42-, NO3-, O2), CH4 production is limited by the availability of labile carbon, which is supplied from recent plant primary production (e.g. as root exudates) and converted by anaerobic fermenting bacteria into methanogenic substrate (e.g. acetate). Because diffusion of gases through saturated soils is extremely slow, the aerenchymous tissues of wetland plants provide the primary pathway for CH4 emissions in systems dominated by emergent vascular vegetation. Aerenchyma also function to shuttle atmospheric oxygen to belowground plant tissues for respiration. Consequentially, root radial oxygen loss results in an oxidized rhizosphere, which limits CH4 production and provides habitat for aerobic methanotrophic bacteria, potentially reducing CH4 emissions. To test the contribution of recent photosynthates on CH4 emissions, a shading experiment was conducted in a Juncus-dominated wetland in the Colorado Front Range. Shade treatments significantly reduced net ecosystem production (NEE) and gross primary production (GPP) compared to control plots (p=0.0194 and p=0.0551, respectively). While CH4 emissions did not significantly differ between treatments, CH4 flux rates were strongly correlated with NEE (p=0.0063) and GPP (p=0.0020), in support of the hypothesis that labile carbon from recent photosynthesis controls patterns of CH4 emissions. The relative importance of plant gas transport and methane consumption rates on CH4 emissions is not known. Methane flux is more tightly correlated with NEE than GPP, which may be explained by increased CH4 consumption or decreased CH4 production as a result of rhizospheric oxidation. The ability to predict future emissions of this important greenhouse gas will be improved by increased understanding of the controls regulating its emission. Future work will focus on developing a tracer technique using SF6 and 13C-labeled CH4 to determine how plant gas transport properties and CH4 consumption contribute to patterns of methane emissions from wetlands.

Cold season emissions dominate the Arctic tundra methane budget

NASA Astrophysics Data System (ADS)

Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

2016-01-01

Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y-1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

Cold season emissions dominate the Arctic tundra methane budget.

PubMed

Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C; Miller, Charles E; Dinardo, Steven J; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y-W; Henderson, John M; Murphy, Patrick C; Goodrich, Jordan P; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D; Kimball, John S; Lipson, David A; Oechel, Walter C

2016-01-05

Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥ 50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y(-1), ∼ 25% of global emissions from extratropical wetlands, or ∼ 6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

Cold season emissions dominate the Arctic tundra methane budget

PubMed Central

Zona, Donatella; Gioli, Beniamino; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

2016-01-01

Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y−1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming. PMID:26699476

Cold season emissions dominate the Arctic tundra methane budget

DOE PAGES

Zona, Donatella; Gioli, Beniamino; Commane, Róisín; ...

2015-12-22

Arctic terrestrial ecosystems are major global sources of methane (CH 4); hence, it is important to understand the seasonal and climatic controls on CH 4 emissions from these systems. Here, we report year-round CH 4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥ 50% of the annual CH 4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0more » °C. The zero curtain may persist longer than the growing season, and CH 4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH 4 derived from aircraft data demonstrate the large spatial extent of late season CH 4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH 4 y –1, ~25% of global emissions from extratropical wetlands, or ~6% of total global wetland methane emissions. Here, the dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH 4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.« less

Pig feeding strategy coupled with effluent management - fresh or stored slurry, solid phase separation - on methane potential and methane conversion factors during storage

NASA Astrophysics Data System (ADS)

Jarret, Guillaume; Martinez, José; Dourmad, Jean-Yves

2011-11-01

In the guideline for the determination of methane (CH 4) emission from animal manure (IPCC) the amount of CH 4 emitted is generally calculated according to an equation combining the amount of organic matter (OM) or volatile solids excreted, the ultimate CH 4 potential ( B0) of excreta and a system-specific methane conversion factor (MCF, %) that reflects the portion of B0 that is really converted into CH 4. The objective of the present study was to investigate the effect of the modification of dietary crude protein and fibre levels on B0 of pig slurry and on subsequent MCF according to different strategies of slurry management. Five experimental diets differing mainly in their crude protein and fibre content were compared. Two types of measurement of CH 4 emission were performed. The first was the measurement of B0 of slurry using biomethanogene potential (BMP) test. The second consisted in a storage simulation, which was performed on different kinds of effluents: fresh slurry (FSl), stored slurry (SSl), and faeces mixed with water (FaW). The type of diet and the type of effluent affected ( P < 0.001) CH 4 production after 30, 50 and 100 days. Moreover, the interaction between type of effluent and type of diet was significant for CH 4 emission and for MCF. CH 4 production was the highest for BMP, the average production of CH 4 during storage from FaW, FSl and SSl samples representing 77%, 58% and 64% of the B0 value. The dynamic of CH 4 production during BMP tests was rather similar for all dietary treatments whereas it differed for storage simulation studies with significant effects of dietary CP and fibre contents. The results from this study indicate that the type of diet has a significant but rather limited effect on B0 value of effluent. The effect of diet is much more marked on MCF, with lower values for high protein diets, and higher values for high fibre diets. MCF is also affected by manure management, the values measured on separated faeces from urine being much higher than for slurry.

Toward an annual estimate of methane emissions from Lake Erie

NASA Astrophysics Data System (ADS)

Fernandez, J.; Townsend-Small, A.

2017-12-01

Lake Erie is the shallowest, warmest, and most eutrophic of all of the North American Great Lakes. The central basin of Lake Erie exhibits seasonally hypoxic bottom waters, which contributes to biological methane (CH4) production. Leaks from extensive natural gas wells and pipelines in Canadian waters are a potential source of thermogenic CH4 to the lake. The shallow western basin lacks water column hypoxia, but experiences increasingly frequent algal blooms and hypoxic sediments. Our past research, focused on the central basin, indicated that Lake Erie is a positive source of CH4 during late summer (August - September), emitting 1.3 ± 0.6 × 105 kg CH4-C day. Here, we present a seasonal dataset of CH4 fluxes measured throughout a 16-month period starting in the spring of 2015 and ending late summer in 2016 to estimate an annual lake wide CH4 emission. Our results indicate that the western basin experienced the greatest CH4 emissions, and the highest rates of CH4 flux co-occur with the highest rates of nutrient loading and largest algal blooms near the mouth of the Maumee River. Winter CH4 fluxes were minimal and similar throughout the lake, indicating that natural gas wells are a minimal source of CH4 emissions. Emissions were highest in August and tapered off through the fall and winter, rising again in spring. The estimated annual CH4 emission in Lake Erie was 4.41 × 107 kg CH4-C yr-1. We compared this to other CH4 sources in Michigan and Ohio in the USEPA Greenhouse Gas Reporting Program Database, and found that Lake Erie is second largest emitter of CH4 in Ohio (a landfill in Cincinnati is a larger source), and the largest in Michigan. Recent work has shown that eutrophication in lakes such as Lake Erie may be on the rise due to climate change induced increases in precipitation. If so, these large CH4 emissions may have positive feedback consequences to climate warming. Therefore, more research is needed to indicate whether or not these CH4 emissions are increasing.

Environmental control of methane fluxes over a Danish peatland

NASA Astrophysics Data System (ADS)

Herbst, M.; Ringgaard, R.; Friborg, T.; Soegaard, H.

2009-12-01

Reducing the greenhouse gas (GHG) emissions from natural and anthropogenic environments has become a key issue over the last decades. In Denmark the management of the wetlands is playing a key role in these attempts. The wetland area of Skjern Meadows in the western part of Denmark is one of the best known examples of peatland restauration in northern Europe. The valley of the Skjern river was restored in 2002, after it had been drained for about 35 years. A micrometeorological instrument mast was erected in the centre of the 2200 ha large area in the summer of 2008, in order to facilitate continuous eddy covariance measurements of the exchange of carbon dioxide and methane between the peatland and the atmosphere. A sonic anemometer (R3, Gill) was used together with a closed-path CO2 analyzer (LI-7000, Li-Cor) and a closed-path CH4 analyzer (DLT-100, Los Gatos). A measurement height of 7 m above the surface ensures that the observed eddy fluxes represent an average signal from the entire peatland. The first year of data collection confirmed the expectation that the area functions as a moderate CO2 sink, whilst it releases methane into the atmosphere. During a 12-months period starting in September 2008, the wetland removed 119 g CO2-C per m2 from the atmosphere and emitted 6 g CH4-C per m2. If the amount of the emitted CH4 is converted into CO2 equivalents, it remained lower than the annual CO2 uptake (188 versus 437 g CO2). This means that the restored peatland functions as a weak greenhouse gas sink, despite its methane production. Whilst the annual CO2 uptake at Skjern Meadows was similar to that reported by Friborg et al. (2003) for a Siberian wetland, the CH4 emission was much lower. The average CO2 and CH4 flux rates were both lower than those estimated for a Dutch wetland by Hendriks et al. (2007). The CH4 emission showed no particular diurnal pattern, but daily rates varied considerably throughout the year. This variability can be correlated to variations in the soil temperature, the water level and the carbon fixation rates of the vegetation. The highest CH4 emission rates with peak values around 160 mg m-2d-1 were observed in the late summer and early autumn of 2008, after the site had experienced a prolonged period of high rainfall while the temperature was still high. In contrast, CH4 emission rates never exceeded 20 mg m-2d-1 during the winter and the unusually dry spring of 2009. An exponential relationship was found between the soil temperature in 0.2 m depth and the methane flux into the atmosphere. A comparison of this relation with complementary observations from other studies indicates that a general temperature response function for the CH4 emission from northern peatlands can be developed. If such a response function can be validated for other sites as well, it would be a big step towards an improved predictability of the full greenhouse gas budget of northern peatlands in a changing climate. References: Friborg T, Søgaard H, Christensen TR, Lloyd CR, Panikov NS (2003) Siberian wetlands: Where a sink is a source. Geophys. Res. Letters, Vol. 30, No. 21, 2129. Hendriks DMD, van Huissteden J, Dolman AJ, van der Molen MK (2007) The full greenhouse gas balance of an abandoned peat meadow. Biogeosciences 4, 411-424.

Nongrowing season methane emissions-a significant component of annual emissions across northern ecosystems.

PubMed

Treat, Claire C; Bloom, A Anthony; Marushchak, Maija E

2018-03-22

Wetlands are the single largest natural source of atmospheric methane (CH 4 ), a greenhouse gas, and occur extensively in the northern hemisphere. Large discrepancies remain between "bottom-up" and "top-down" estimates of northern CH 4 emissions. To explore whether these discrepancies are due to poor representation of nongrowing season CH 4 emissions, we synthesized nongrowing season and annual CH 4 flux measurements from temperate, boreal, and tundra wetlands and uplands. Median nongrowing season wetland emissions ranged from 0.9 g/m 2 in bogs to 5.2 g/m 2 in marshes and were dependent on moisture, vegetation, and permafrost. Annual wetland emissions ranged from 0.9 g m -2  year -1 in tundra bogs to 78 g m -2  year -1 in temperate marshes. Uplands varied from CH 4 sinks to CH 4 sources with a median annual flux of 0.0 ± 0.2 g m -2  year -1 . The measured fraction of annual CH 4 emissions during the nongrowing season (observed: 13% to 47%) was significantly larger than that was predicted by two process-based model ensembles, especially between 40° and 60°N (modeled: 4% to 17%). Constraining the model ensembles with the measured nongrowing fraction increased total nongrowing season and annual CH 4 emissions. Using this constraint, the modeled nongrowing season wetland CH 4 flux from >40° north was 6.1 ± 1.5 Tg/year, three times greater than the nongrowing season emissions of the unconstrained model ensemble. The annual wetland CH 4 flux was 37 ± 7 Tg/year from the data-constrained model ensemble, 25% larger than the unconstrained ensemble. Considering nongrowing season processes is critical for accurately estimating CH 4 emissions from high-latitude ecosystems, and necessary for constraining the role of wetland emissions in a warming climate. © 2018 John Wiley & Sons Ltd.

Estimating wetland methane emissions from the northern high latitudes from 1990 to 2009 using artificial neural networks

NASA Astrophysics Data System (ADS)

Zhu, Xudong; Zhuang, Qianlai; Qin, Zhangcai; Glagolev, Mikhail; Song, Lulu

2013-04-01

Methane (CH4) emissions from wetland ecosystems in nothern high latitudes provide a potentially positive feedback to global climate warming. Large uncertainties still remain in estimating wetland CH4 emisions at regional scales. Here we develop a statistical model of CH4 emissions using an artificial neural network (ANN) approach and field observations of CH4 fluxes. Six explanatory variables (air temperature, precipitation, water table depth, soil organic carbon, soil total porosity, and soil pH) are included in the development of ANN models, which are then extrapolated to the northern high latitudes to estimate monthly CH4 emissions from 1990 to 2009. We estimate that the annual wetland CH4 source from the northern high latitudes (north of 45°N) is 48.7 Tg CH4 yr-1 (1 Tg = 1012 g) with an uncertainty range of 44.0 53.7 Tg CH4 yr-1. The estimated wetland CH4 emissions show a large spatial variability over the northern high latitudes, due to variations in hydrology, climate, and soil conditions. Significant interannual and seasonal variations of wetland CH4 emissions exist in the past 2 decades, and the emissions in this period are most sensitive to variations in water table position. To improve future assessment of wetland CH4 dynamics in this region, research priorities should be directed to better characterizing hydrological processes of wetlands, including temporal dynamics of water table position and spatial dynamics of wetland areas.

Greenhouse gas emissions of different land uses in the delta region of Red River, Vietnam

NASA Astrophysics Data System (ADS)

Zhou, Minghua; Ha, Thu; An, Ngo The; Brüggemann, Nicolas

2017-04-01

Agricultural activities are responsible for up to a third of total anthropogenic GHG emissions. The subtropical/tropical delta areas of the large rivers in Southeast Asia are long-term history agricultural regions in the world. However, due to lack of field measurements, the estimation of the contribution of agro-ecosystems in the subtropical/tropical delta areas to global greenhouse gas emissions remains largely uncertain. Here, we conducted field experiments since January 2016 to quantify greenhouse gases (CO2, CH4 and N2O) emissions from four agricultural land uses of annual rice-rice, rice-vegetable, continuous vegetable system and fish pond in Red River delta region of Vietnam by using the transparent static chamber-gas chromatography technique. Higher N2O emissions were observed in the rice-vegetable and continuous vegetable systems, while lower N2O emissions were observed in the rice-rice and find pond systems. Compared to rice-rice system the cumulative N2O fluxes were on average twenty-fold higher in the rice-vegetable and continuous vegetable systems but significantly lower (75%) in the fish pond. Overall the net CO2 sinks were observed in the rice-rice system while other three land uses of rice-vegetable, continuous vegetable and fish pond acted as the net CO2 sources. The rice-rice and fish pond showed net CH4 emissions while variations of CH4 emissions (i.e. shifting between sources and sinks) along variations of soil moisture and temperature were observed in rice-vegetable and continuous vegetable systems. Compared to rice-rice system, the cumulative CH4 fluxes were significantly decreased by 100% for continuous vegetable system, 94% for rice-vegetable system and 89% for fish pond. Overall, the data suggest that conversion of traditional rice-rice paddy system to rice-vegetable, continuous vegetable system and find pond, which are currently undergoing driven by the economical requests and environmental changes (e.g., salinity intrusion) in this delta region, could alter CH4, CO2 and N2O emissions.

Effect of water and heat transport processes on methane emissions from paddy soils: a process-based model analysis

NASA Astrophysics Data System (ADS)

Rizzo, Anacleto; Boano, Fulvio; Revelli, Roberto; Ridolfi, Luca

2013-04-01

High CH4 fluxes are emitted from paddy fields worldwide and represent a considerable issue for the rice production eco-sustainability. Water and heat transport fluxes are known to strongly influence biogeochemical cycles in wetland environments, and therefore also CH4 emissions from paddy soils. Water percolation affects the dynamics of many compounds (e.g. DOC, O2) influencing CH4 fate. On the other hand, heat fluxes strongly influence CH4 production in submerged rice crops, and lowering ponding water temperature (LPWT) can reduce microbial activities and consequently decrease CH4 emissions. Moreover, as long as the optimal temperature range for rice growth is maintained, LPWT can lower CH4 emissions without rice yield limitation. Hence, a process-based model is proposed and applied to investigate the role of water flow on CH4 emissions, and to analyse the efficiency of LPWT as mitigation strategy for CH4 production and release. The process-based model relies on a system of partial differential mass balance equations to describe the vertical dynamics of the chemical compounds leading to CH4 production. Many physico-chemical processes and features characteristic of paddy soil are included: paddy soil stratigraphy; spatio-temporal variations of plant-root compartment; water and heat transport; SOC decomposition; heterotrophic reactions in both aerobic and anaerobic conditions; root radial oxygen loss; root solute uptake; DOC root exudation; plant-mediated, ebullition, and diffusion gas exchange pathways. LPWT is included as a temperature shift subtracted directly to the ponding water temperature. Model results confirm the importance of water flow on CH4 emission, since simulations that do not include water fluxes show a considerable overestimation of CH4 emissions due to a different DOC spatio-temporal dynamics. Particularly, when water fluxes are not modeled the overestimation can reach 67 % of the total CH4 emission over the whole growing season. Moreover, model results also suggest that roots influence CH4 dynamics principally due to their solute uptake, while root effect on advective flow plays a minor role. In addition, the analysis of CH4 transport fluxes show the limiting effect of upward dispersive transport fluxes on the downward CH4 percolation. Finally, LPWT is confirmed to be a valid mitigation strategy for CH4 emissions from paddy soils, since the reduction of CH4 emission reach about -50 % with a LPWT equal to only 2°C over the whole growing season.

Understanding the Temporal Variation of CO2 and CH4 Fluxes in a Subtropical Seasonal Wetland

NASA Astrophysics Data System (ADS)

Gomez-Casanovas, N.; DeLucia, N.; DeLucia, E. H.; Boughton, E.; Bernacchi, C.

2017-12-01

The magnitude of the net greenhouse gas (GHG) sink strength of wetlands and mechanisms driving C fluxes remain uncertain, particularly for subtropical and tropical wetlands that are responsible for the majority of wetland CH4 emissions globally. We determined the exchange of CO2 and CH4 fluxes between a subtropical wetland and the atmosphere, and investigated how changes in water table (WT), soil temperature (ST), and Gross Primary Productivity (GPP) alter CH4 fluxes. Measurements were made using the eddy covariance technique from June, 2013 to December, 2015. As GPP was greater than ecosystem respiration, wetland was consistently a net sink of CO2 from the atmosphere (-480 gC m-2 in 2013, -275 gC m-2 in 2014 and -258 gC m-2 in 2015). Though variable among years, wetland was a net source of CH4 to the atmosphere (24.5 gC m-2 in 2013, 26.1 gC m-2 in 2014, 32.7 gC m-2 in 2015). WT and ST were strong drivers of net CH4 fluxes. Fluxes of CH4 exponentially increased with WT near the soil surface, and they were maximal and sustained after 3 days or more of preceding flooding suggesting that flooding duration and intensity drives CH4 emissions in this system. GPP also exerted a strong control on these fluxes, particularly when water was near the soil surface. The system emitted an average of 2 g more C-CH4 m-2 during the wet seasons of 2013 and 2015 than the wet season of 2014 due to higher WT, and increases in flooding days and cumulative GPP for days with water at near-surface (GPPWT). Although WT was higher during the dry season of 2015 than the wet season of 2014, CH4 fluxes were similar likely because of increased ST and GPPWT in the wet season of 2014. The contribution of CH4 fluxes during the dry season to annual fluxes was 41% in 2014 and 48% in 2015. Wetland was a strong sink of C, and it was a net sink of GHGs in 2014 and a net source in 2015 mainly attributable to increases in net CH4 emissions. Climate models predict that subtropical and tropical regions will experience more frequent floods and droughts as well as higher temperatures, conditions that will likely alter ecosystem attributes such as GPP. Our results indicate that CH4 emissions from subtropical wetlands will likely respond to projected changes in precipitation, temperature and productivity, substantially affecting the net GHG sink strength of these systems in future climate scenarios.

Role of regional wetland emissions in atmospheric methane variability

NASA Astrophysics Data System (ADS)

McNorton, J.; Gloor, E.; Wilson, C.; Hayman, G. D.; Gedney, N.; Comyn-Platt, E.; Marthews, T.; Parker, R. J.; Boesch, H.; Chipperfield, M. P.

2016-11-01

Atmospheric methane (CH4) accounts for 20% of the total direct anthropogenic radiative forcing by long-lived greenhouse gases. Surface observations show a pause (1999-2006) followed by a resumption in CH4 growth, which remain largely unexplained. Using a land surface model, we estimate wetland CH4 emissions from 1993 to 2014 and study the regional contributions to changes in atmospheric CH4. Atmospheric model simulations using these emissions, together with other sources, compare well with surface and satellite CH4 data. Modeled global wetland emissions vary by ±3%/yr (σ = 4.8 Tg), mainly due to precipitation-induced changes in wetland area, but the integrated effect makes only a small contribution to the pause in CH4 growth from 1999 to 2006. Increasing temperature, which increases wetland area, drives a long-term trend in wetland CH4 emissions of +0.2%/yr (1999 to 2014). The increased growth post-2006 was partly caused by increased wetland emissions (+3%), mainly from Tropical Asia, Southern Africa, and Australia.

Methane and nitrous oxide emissions from three paddy rice based cultivation systems in Southwest China

NASA Astrophysics Data System (ADS)

Jiang, Changsheng; Wang, Yuesi; Zheng, Xunhua; Zhu, Bo; Huang, Yao; Hao, Qingju

2006-05-01

To understand methane (CH4) and nitrous oxide (N2O) emissions from permanently flooded rice paddy fields and to develop mitigation options, a field experiment was conducted in situ for two years (from late 2002 to early 2005) in three rice-based cultivation systems, which are a permanently flooded rice field cultivated with a single time and followed by a non-rice season (PF), a rice-wheat rotation system (RW) and a rice-rapeseed rotation system (RR) in a hilly area in Southwest China. The results showed that the total CH4 emissions from PF were 646.3±52.1 and 215.0±45.4 kg CH4 hm-2 during the rice-growing period and non-rice period, respectively. Both values were much lower than many previous reports from similar regions in Southwest China. The CH4 emissions in the rice-growing season were more intensive in PF, as compared to RW and RR. Only 33% of the total annual CH4 emission in PF occurred in the non-rice season, though the duration of this season is two times longer than the rice season. The annual mean N2O flux in PF was 4.5±0.6 kg N2O hm-2 yr-1. The N2O emission in the rice-growing season was also more intensive than in the non-rice season, with only 16% of the total annual emission occurring in the non-rice season. The amounts of N2O emission in PF were ignorable compared to the CH4 emission in terms of the global warming potential (GWP). Changing PF to RW or RR not only eliminated CH4 emissions in the non-rice season, but also substantially reduced the CH4 emission during the following rice-growing period (ca. 58%, P<0.05). However, this change in cultivation system substantially increased N2O emissions, especially in the non-rice season, by a factor of 3.7 to 4.5. On the 100-year horizon, the integrated GWP of total annual CH4 and N2O emissions satisfies PF≫RR≈RW. The GWP of PF is higher than that of RW and RR by a factor of 2.6 and 2.7, respectively. Of the total GWP of CH4 and N2O emissions, CH4 emission contributed to 93%, 65% and 59% in PF, RW and RR, respectively. These results suggest that changing PF to RW and RR can substantially reduce not only CH4 emission but also the total GWP of the CH4 and N2O emissions.

Amazon peatlands: quantifying ecosytem's stocks, GHG fluxes and their microbial connections

NASA Astrophysics Data System (ADS)

Cadillo-Quiroz, Hinsby; Lähteenoja, Outi; Buessecker, Steffen; van Haren, Joost

2017-04-01

Reports of hundreds of peatlands across basins in the West and Central Amazon suggest they play an important, previously not considered regional role in organic carbon (OC) and GHG dynamics. Amazon peatlands store ˜3-6 Gt of OC in their waterlogged soils with strong potential for conversion and release of GHG, in fact our recent, and others', efforts have confirmed variable levels of GHG emissions (CO2, N2O, CH4), as well as variable microbial communities across rich to poor soil peatlands. Here, we report early results of quantification of different components making up the aboveground C stocks, the rates and paths for GHG release, and microbial organisms occurring in three ecologically distinct peatland types in the Pastaza-Marañon region of the Peruvian Amazon. Evaluations were done in duplicated continuous monitoring plots established since 2015 at a "palm swamp" (PS), poor "pole forest" (pPF) and a rich "forested" (rF) peatlands. Although overall vegetation "structure" with a few dominant plus several low frequency species was common across the three sites, their botanical composition and tree density was highly contrasting. Aboveground C stocks content showed the following order among sites: rF>PS>pPF, and hence we tested whether this differences can have a direct effect on CH4 emissions rates. CH4 emissions rates from soils were observed in average at 11, 6, and 0.8 mg-C m-2 h-1for rF, PS, and pPF respectively. However, these estimated fluxes needed to be revised when we develop quantifications of CH4 emissions from tree stems. Tree stem fluxes were detected showing a broad variation with nearly nill emissions in some species all the way to maximum fluxes near to ˜90 mg-C m-2 h-1 in other species. Mauritia flexuosa, a highly dominant palm species in PS and ubiquitous to the region, showed the highest ranges of CH4 flux. In the PS site, overall CH4 flux estimate increased by ˜50% when including stem emission weighted by trees' species, density and heights. Flux estimates in p PF did not had a significant change. Analysis across species in the study sites, plus other satellite sites, suggest that in sites stem flux emissions might be conserved with some genera in the Aracaceae, Euphorbiaceae, and Sapotaceae families showing a large emitters capacity. Further characterization also showed that CH4 flux emission from the stems decreases generally with height, suggesting a diffusion constrained stem flux, which seems limited by soil CH4 concentration and wood density. Finally, microbial community composition and methanogenic activity also showed contrasting patterns across sites, with pH being one of the major determinants. GHG producing organisms were detected in different proportions and types across study sites, and importantly methanogenic Archaea closely tracked observed differences of CH4 flux among sites. Nevertheless, the link between vegetation type and density still remain under assessment in our efforts

Methane Emissions from United States Natural Gas Gathering and Processing.

PubMed

Marchese, Anthony J; Vaughn, Timothy L; Zimmerle, Daniel J; Martinez, David M; Williams, Laurie L; Robinson, Allen L; Mitchell, Austin L; Subramanian, R; Tkacik, Daniel S; Roscioli, Joseph R; Herndon, Scott C

2015-09-01

New facility-level methane (CH4) emissions measurements obtained from 114 natural gas gathering facilities and 16 processing plants in 13 U.S. states were combined with facility counts obtained from state and national databases in a Monte Carlo simulation to estimate CH4 emissions from U.S. natural gas gathering and processing operations. Total annual CH4 emissions of 2421 (+245/-237) Gg were estimated for all U.S. gathering and processing operations, which represents a CH4 loss rate of 0.47% (±0.05%) when normalized by 2012 CH4 production. Over 90% of those emissions were attributed to normal operation of gathering facilities (1697 +189/-185 Gg) and processing plants (506 +55/-52 Gg), with the balance attributed to gathering pipelines and processing plant routine maintenance and upsets. The median CH4 emissions estimate for processing plants is a factor of 1.7 lower than the 2012 EPA Greenhouse Gas Inventory (GHGI) estimate, with the difference due largely to fewer reciprocating compressors, and a factor of 3.0 higher than that reported under the EPA Greenhouse Gas Reporting Program. Since gathering operations are currently embedded within the production segment of the EPA GHGI, direct comparison to our results is complicated. However, the study results suggest that CH4 emissions from gathering are substantially higher than the current EPA GHGI estimate and are equivalent to 30% of the total net CH4 emissions in the natural gas systems GHGI. Because CH4 emissions from most gathering facilities are not reported under the current rule and not all source categories are reported for processing plants, the total CH4 emissions from gathering and processing reported under the EPA GHGRP (180 Gg) represents only 14% of that tabulated in the EPA GHGI and 7% of that predicted from this study.

Quantifying greenhouse gas emissions from municipal solid waste dumpsites in Cameroon.

PubMed

Ngwabie, N Martin; Wirlen, Yvette L; Yinda, Godwin S; VanderZaag, Andrew C

2018-03-02

Open dumpsites that receive municipal solid waste are potentially significant sources of greenhouse gas (GHG) emissions into the atmosphere. There is little data available on emissions from these sources, especially in the unique climate and management of central Africa. This research aimed at quantifying CH 4 , N 2 O and CO 2 emissions from two open dumpsites in Cameroon, located in Mussaka-Buea, regional headquarters of the South West Region and in Mbellewa-Bamenda, regional headquarters of the North West Region. Emissions were measured during the wet season (May 2015 and August 2016) at the Mussaka and Mbellewa dumpsites respectively. Dumpsite surfaces were partitioned into several zones for emission measurements, based on the current activity and the age of the waste. Static flux chambers were used to quantify gas emission rates thrice a day (mornings, afternoons and evenings). Average emissions were 96.80 ± 144 mg CH 4 m -2  min -1 , 0.20 ± 0.43 mg N 2 O m -2  min -1 and 224.78 ± 312 mg CO 2 m -2  min -1 in the Mussaka dumpsite, and 213.44 ± 419 mg CH 4 m -2  min -1 , 0.15 ± 0.15 mg N 2 O m -2  min -1 and 1103.82 ± 1194 mg CO 2 m -2  min -1 at the Mbellewa dumpsite. Emissions as high as 1784 mg CH 4 m -2  min -1 , 2.3 mg N 2 O m -2  min -1 and 5448 mg CO 2 m -2  min -1 were measured from both dumpsites. Huge variations observed in emissions between the different zones on the waste surface were likely a result of the heterogeneous nature of the waste, different stages in waste decomposition and different environmental conditions within the waste. Management activities that disturb waste, such as spreading and compressing potentially increase gas emissions, while covering waste with a layer of soil potentially mitigate gas emissions. Recommendations were for dumpsites to be upgraded to sanitary landfills, and biogas production from such landfills should be exploited to reduce CH 4 emissions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Temperate Forest Methane Sink Diminished by Tree Emissions

NASA Astrophysics Data System (ADS)

Megonigal, P.; Pitz, S.

2015-12-01

Global budgets ascribe 4-10% of atmospheric CH4 sinks to upland soils and assume that soils are the sole surface for CH4 exchange between upland forests and the atmosphere. The prevailing dogma that upland forests are sinks of atmospheric CH4 was challenged a decade ago by large discrepancies in bottom-up versus top-down models of CH4 concentrations over upland forests that are still unexplained. Evidence of a novel abiotic mechanism for CH4 production from plant tissue is too small to explain the discrepancy. Alternative hypotheses for this observation have been proposed, but not tested. Here we demonstrate that CH4 is emitted from the stems of dominant tree species in an upland forest. Tree emissions occur throughout the growing season while soils adjacent to the trees are consuming CH4, challenging the concept that forests are uniform sinks of CH4. Scaling by stem surface area showed the forest to be a net CH4 source during a wet sample in June and a reduced CH4 sink by 5% annually. High frequency measurements revealed diurnal cycling in the rate of CH4 emissions, pointing to soils as the CH4 source and transpiration as the most likely pathway for CH4 transport. We propose the forests are smaller CH4 sinks than previously estimated due to stem emissions. Stem emissions may be particularly important in upland tropical forests characterized by high rainfall and transpiration, resolving differences between models and measurements.

Factors influencing CO2 and CH4 emissions from coastal wetlands in the Liaohe Delta, northeast China

USGS Publications Warehouse

Olsson, Linda; Ye, Siyuan; Yu, Xueyang; Wei, Mengjie; Krauss, Ken W.; Brix, Hans

2015-01-01

Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4sources emitting 1.2–6.1 g CH4 m−2 y−1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2. The main controlling factors for the CH4 emissions were water table, temperature and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1 mg CH4 m−2 h) at soil temperatures <18 °C. At salinity levels > 18 ppt, the CH4 emission rates were always low (< 1 mg CH4 m−2 h−1) probably because methanogens were outcompeted by sulphate reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities.

Non-microbial methane emissions from soils

NASA Astrophysics Data System (ADS)

Wang, Bin; Hou, Longyu; Liu, Wei; Wang, Zhiping

2013-12-01

Traditionally, methane (CH4) is anaerobically formed by methanogenic archaea. However, non-microbial CH4 can also be produced from geologic processes, biomass burning, animals, plants, and recently identified soils. Recognition of non-microbial CH4 emissions from soils remains inadequate. To better understand this phenomenon, a series of laboratory incubations were conducted to examine effects of temperature, water, and hydrogen peroxide (H2O2) on CH4 emissions under both aerobic and anaerobic conditions using autoclaved (30 min, 121 °C) soils and aggregates (>2000 μm, A1; 2000-250 μm, A2; 250-53 μm, M1; and <53 μm, M2). Results show that applying autoclaving to pre-treat soils is effective to inhibit methanogenic activity, ensuring the CH4 emitted being non-microbial. Responses of non-microbial CH4 emissions to temperature, water, and H2O2 were almost identical between aerobic and anaerobic conditions. Increasing temperature, water of proper amount, and H2O2 could significantly enhance CH4 emissions. However, the emission rates were inhibited and enhanced by anaerobic conditions without and with the existence of H2O2, respectively. As regards the aggregates, aggregate-based emission presented an order of M1 > A2 > A1 > M2 and C-based emission an order of M2 > M1 > A1 > A2, demonstrating that both organic carbon quantity and property are responsible for CH4 emissions from soils at the scale of aggregate. Whole soil-based order of A2 > A1 > M1 > M2 suggests that non-microbial CH4 release from forest soils is majorly contributed by macro-aggregates (i.e., >250 μm). The underlying mechanism is that organic matter through thermal treatment, photolysis, or reactions with free radicals produce CH4, which, in essence, is identical with mechanisms of other non-microbial sources, indicating that non-microbial CH4 production may be a widespread phenomenon in nature. This work further elucidates the importance of non-microbial CH4 formation which should be distinguished from the well-known microbial CH4 formation in order to define both roles in the atmospheric CH4 global budget.

A global wetland methane emissions and uncertainty dataset for atmospheric chemical transport models (WetCHARTs version 1.0)

NASA Astrophysics Data System (ADS)

Bloom, A. Anthony; Bowman, Kevin W.; Lee, Meemong; Turner, Alexander J.; Schroeder, Ronny; Worden, John R.; Weidner, Richard; McDonald, Kyle C.; Jacob, Daniel J.

2017-06-01

Wetland emissions remain one of the principal sources of uncertainty in the global atmospheric methane (CH4) budget, largely due to poorly constrained process controls on CH4 production in waterlogged soils. Process-based estimates of global wetland CH4 emissions and their associated uncertainties can provide crucial prior information for model-based top-down CH4 emission estimates. Here we construct a global wetland CH4 emission model ensemble for use in atmospheric chemical transport models (WetCHARTs version 1.0). Our 0.5° × 0.5° resolution model ensemble is based on satellite-derived surface water extent and precipitation reanalyses, nine heterotrophic respiration simulations (eight carbon cycle models and a data-constrained terrestrial carbon cycle analysis) and three temperature dependence parameterizations for the period 2009-2010; an extended ensemble subset based solely on precipitation and the data-constrained terrestrial carbon cycle analysis is derived for the period 2001-2015. We incorporate the mean of the full and extended model ensembles into GEOS-Chem and compare the model against surface measurements of atmospheric CH4; the model performance (site-level and zonal mean anomaly residuals) compares favourably against published wetland CH4 emissions scenarios. We find that uncertainties in carbon decomposition rates and the wetland extent together account for more than 80 % of the dominant uncertainty in the timing, magnitude and seasonal variability in wetland CH4 emissions, although uncertainty in the temperature CH4 : C dependence is a significant contributor to seasonal variations in mid-latitude wetland CH4 emissions. The combination of satellite, carbon cycle models and temperature dependence parameterizations provides a physically informed structural a priori uncertainty that is critical for top-down estimates of wetland CH4 fluxes. Specifically, our ensemble can provide enhanced information on the prior CH4 emission uncertainty and the error covariance structure, as well as a means for using posterior flux estimates and their uncertainties to quantitatively constrain the biogeochemical process controls of global wetland CH4 emissions.

Living Trees are a Major Source of Methane in the Temperate Forest

NASA Astrophysics Data System (ADS)

Covey, Kristofer

2017-04-01

Globally, forests sequester about 1.1 ± 0.8 Pg C yr-1, an ecosystem service worth hundreds of billions of dollars annually. Following the COP21 meeting in Paris, an international consensus emerged: The protection and expansion of forests worldwide is a necessary component of climate mitigation strategies to limit warming to less than 2°C. The physiological processes governing sequestration of CO2 in living trees are well studied and the resulting pattern in global forest carbon sequestration is clear. The role living trees play in the production and emission of methane (CH4) remains unclear, despite the fact it has the potential to offset climate benefits of forest CO2 sequestration. A known but largely unexplored pathway of forest CH4 production involves microbial-based methanogenesis in the wood of living trees. In the first regional-scale study of tree trunk gas composition, we examine the ubiquity and potential source strength of this pathway. Trunk methane concentrations were as high as 67.4% by volume (375,000-times atmospheric), with the highest concentrations found in older angiosperms (18,293 μLṡL-1 ± 3,096). Bark flux chambers from 23 living trees show emissions under field conditions, and large static chambers demonstrate high rates of production in felled Acer rubrum trunk sections. Diffusion flux modeling of trunk concentrations suggests wood-based microflora could produce a global CH4 efflux of 26 Tg CH4 yr-1. Applying these fluxes to provide a spatially explicit map of trunk-based CH4 flux, we estimate the potential relationship between carbon sequestration rates and CH4 emission by forest trees in Eastern North America. Methane emissions from the trunk-based methanogenic pathway could reduce the average climate mitigation value of these temperate forests by 10-30%. We highlight the need to improve earth systems models to account for the full complexity of forest climate interactions and provide a data layer useful in reducing large uncertainty in global methane budgets.

Processes controlling the composition of precipitation at a remote southern hemispheric location: Torres del Paine National Park, Chile

NASA Astrophysics Data System (ADS)

Galloway, James N.; Keene, William C.; Likens, Gene E.

1996-03-01

Precipitation composition measured at Torres del Paine National Park, Chile (TdP) (51°10'S, 71°58'W), between 1984 and 1993 was acidic (volume-weighted-average pH of 4.96) with a dilute seawater component. H+ was the dominant non-sea-salt (nss) cation; in decreasing order of abundance, nss anions were HCOO-, Cl-, SO4=, CH3COO-, and NO3-. Relative to lower latitude, remote locations, concentrations and per-event depositions of nss SO4=, NO3-, and NH4+ at TdP were lower; those of HCOOt (HCOO- + HCOOH) and CH3COOHt, (CH3COO- and CH3COOH) were similar; and those of CH3SO3- were higher. Concentrations and deposition fluxes of HCOOt, CH3COOt, nss SO4=, CH3SO3-, and NH4+ varied seasonally with summer maxima and winter minima. Carboxylic acids probably originated from both direct terrestrial emissions and oxidation of hydrocarbons emitted by marine and terrestrial biota. Nss SO4= and CH3SO3- originated primarily from oxidation of biogenic (CH3)2S emitted from the southern Pacific Ocean. Direct emissions of NH3 from upwind terrestrial and marine ecosystems probably accounted for most observed NH4+. NO3- concentrations and depositions were highest during the latter part of austral winter and spring suggesting abiotic controls. Transport of precursors from lightning, biomass burning, and fossil-fuel combustion at lower latitudes and possibly transport of reactive N from the stratosphere apparently contributed oxidized N to the southern Patagonian troposphere. Although the ionic strength of precipitation at TdP is currently among the world's lowest, future changes are likely because of increases in local and regional population and energy and food production.

Global Wetland Contribution to 2000-2012 Atmospheric Methane Growth Rate Dynamics

NASA Technical Reports Server (NTRS)

Poulter, Benjamin; Bousquet, Philippe; Canadell, Josep G.; Ciais, Philippe; Peregon, Anna; Saunois, Marielle; Arora, Vivek K.; Beerling, David J.; Brovkin, Victor; Jones, Chris D.;

Role Of Fires On The Global Methane Budget And Atmospheric Methane Increase Since 2006

NASA Astrophysics Data System (ADS)

Worden, J.; Bloom, A. A.; Jiang, Z.; Pandey, S.; Walker, T. W.; Worden, H. M.

2016-12-01

Since 2006, Methane has increased at an average rate of 7 ppb/year. Satellite based measurements of total column CH4 suggest that 70% of this increase is from N. American (likely fossil fuel) sources whereas surface isotope data attribute the increase almost entirely to emissions from tropical wetlands or agriculture. However, large uncertainties in all components of the methane budget suggest any one source could substantially affect the growth rate of atmospheric methane. Here we examine the role of fires on the recent changes in atmospheric methane. We use satellite measurements of CH4 and CO to show that total land-use related CH4 fire emissions have decreased from 14+/-4 Tg during the 2001-2006 time period to 11+/- 4 Tg for the 2007-2015 time period, consistent with bottom-up estimates. Largest reductions are over S. America and Indonesia, likely as a result of increased rainfall during this time period. Fire emissions of methane are isotopically enhanced relative to fossil fuels and wetlands. Including the effects of fires in a global isotopic box model indicates that fossil fuels can account for 1/3 of the recent increase with the remaining due to biogenic sources.

Greenhouse gas flux and crop productivity after 10 years of reduced and no tillage in a wheat-maize cropping system.

PubMed

Tian, Shenzhong; Wang, Yu; Ning, Tangyuan; Zhao, Hongxiang; Wang, Bingwen; Li, Na; Li, Zengjia; Chi, Shuyun

2013-01-01

Appropriate tillage plays an important role in mitigating the emissions of greenhouse gases (GHG) in regions with higher crop yields, but the emission situations of some reduced tillage systems such as subsoiling, harrow tillage and rotary tillage are not comprehensively studied. The objective of this study was to evaluate the emission characteristics of GHG (CH4 and N2O) under four reduced tillage systems from October 2007 to August 2009 based on a 10-yr tillage experiment in the North China Plain, which included no-tillage (NT) and three reduced tillage systems of subsoil tillage (ST), harrow tillage (HT) and rotary tillage (RT), with the conventional tillage (CT) as the control. The soil under the five tillage systems was an absorption sink for CH4 and an emission source for N2O. The soil temperature positive impacted on the CH4 absorption by the soils of different tillage systems, while a significant negative correlation was observed between the absorption and soil moisture. The main driving factor for increased N2O emission was not the soil temperature but the soil moisture and the content of nitrate. In the two rotation cycle of wheat-maize system (10/2007-10/2008 and 10/2008-10/2009), averaged cumulative uptake fluxes of CH4 under CT, ST, HT, RT and NT systems were approximately 1.67, 1.72, 1.63, 1.77 and 1.17 t ha(-1) year(-1), respectively, and meanwhile, approximately 4.43, 4.38, 4.47, 4.30 and 4.61 t ha(-1) year(-1) of N2O were emitted from soil of these systems, respectively. Moreover, they also gained 33.73, 34.63, 32.62, 34.56 and 27.54 t ha(-1) yields during two crop-rotation periods, respectively. Based on these comparisons, the rotary tillage and subsoiling mitigated the emissions of CH4 and N2O as well as improving crop productivity of a wheat-maize cropping system.

Greenhouse Gas Flux and Crop Productivity after 10 Years of Reduced and No Tillage in a Wheat-Maize Cropping System

PubMed Central

Tian, Shenzhong; Wang, Yu; Ning, Tangyuan; Zhao, Hongxiang; Wang, Bingwen; Li, Na; Li, Zengjia; Chi, Shuyun

2013-01-01

Appropriate tillage plays an important role in mitigating the emissions of greenhouse gases (GHG) in regions with higher crop yields, but the emission situations of some reduced tillage systems such as subsoiling, harrow tillage and rotary tillage are not comprehensively studied. The objective of this study was to evaluate the emission characteristics of GHG (CH4 and N2O) under four reduced tillage systems from October 2007 to August 2009 based on a 10-yr tillage experiment in the North China Plain, which included no-tillage (NT) and three reduced tillage systems of subsoil tillage (ST), harrow tillage (HT) and rotary tillage (RT), with the conventional tillage (CT) as the control. The soil under the five tillage systems was an absorption sink for CH4 and an emission source for N2O. The soil temperature positive impacted on the CH4 absorption by the soils of different tillage systems, while a significant negative correlation was observed between the absorption and soil moisture. The main driving factor for increased N2O emission was not the soil temperature but the soil moisture and the content of nitrate. In the two rotation cycle of wheat-maize system (10/2007–10/2008 and 10/2008–10/2009), averaged cumulative uptake fluxes of CH4 under CT, ST, HT, RT and NT systems were approximately 1.67, 1.72, 1.63, 1.77 and 1.17 t ha−1 year−1, respectively, and meanwhile, approximately 4.43, 4.38, 4.47, 4.30 and 4.61 t ha−1 year−1 of N2O were emitted from soil of these systems, respectively. Moreover, they also gained 33.73, 34.63, 32.62, 34.56 and 27.54 t ha−1 yields during two crop-rotation periods, respectively. Based on these comparisons, the rotary tillage and subsoiling mitigated the emissions of CH4 and N2O as well as improving crop productivity of a wheat-maize cropping system. PMID:24019923

Challenges in global modeling of wetland extent and wetland methane dynamics

NASA Astrophysics Data System (ADS)

Spahni, R.; Melton, J. R.; Wania, R.; Stocker, B. D.; Zürcher, S.; Joos, F.

2012-12-01

Global wetlands are known to be climate sensitive, and are the largest natural emitters of methane (CH4). Increased wetland CH4 emissions could act as a positive feedback to future warming. Modelling of global wetland extent and wetland CH4 dynamics remains a challenge. Here we present results from the Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP) that investigated our present ability to simulate large scale wetland characteristics (e.g. wetland type, water table, carbon cycling, gas transport, etc.) and corresponding CH4 emissions. Ten models participated, covering the spectrum from simple to relatively complex, including models tailored either for regional or global simulations. The WETCHIMP experiments showed that while models disagree in spatial and temporal patterns of simulated CH4 emissions and wetland areal extent, they all do agree on a strong positive response to increased carbon dioxide concentrations. WETCHIMP made clear that we currently lack observation data sets that are adequate to evaluate model CH4 soil-atmosphere fluxes at a spatial scale comparable to model grid cells. Thus there are substantial parameter and structural uncertainties in large-scale CH4 emission models. As an illustration of the implications of CH4 emissions on climate we show results of the LPX-Bern model, as one of the models participating in WETCHIMP. LPX-Bern is forced with observed 20th century climate and climate output from an ensemble of five comprehensive climate models for a low and a high emission scenario till 2100 AD. In the high emission scenario increased substrate availability for methanogenesis due to a strong stimulation of net primary productivity, and faster soil turnover leads to an amplification of CH4 emissions with the sharpest increase in peatlands (+180% compared to present). Combined with prescribed anthropogenic CH4 emissions, simulated atmospheric CH4 concentration reaches ~4500 ppbv by 2100 AD, about 800 ppbv more than in standard IPCC scenarios. This represents a significant contribution to radiative forcing of global climate.

Separating methane emissions from agricultural sources and natural gas: direct measurements of excess columns of CH4, C2H6 and NH3 in the Colorado Front Range

NASA Astrophysics Data System (ADS)

Kille, N.; Chiu, R.; Frey, M.; Hase, F.; Kumar Sha, M.; Blumenstock, T.; Hannigan, J. W.; Volkamer, R. M.

2017-12-01

Methane (CH4) is a major greenhouse gas emitted from biogenic, thermogenic, and pyrogenic sources. Here we demonstrate a novel approach to separate sources of CH4 emissions based on a network of small portable sensors performing column measurements in the Northern Colorado Front Range (NCFR). In the study area CH4 is emitted from biogenic sources such as concentrated animal feeding operations (CAFOs) and natural gas production and storage. In March 2015 we deployed a network of five Fourier Transform Spectrometers (FTS) to characterize the regional scale methane dome in Colorado's Denver-Julesburg Basin based on excess vertical column measurements (the column enhancement inside the dome over background). Three EM27sun FTS measured CH4, oxygen (O2) and water vapor (H2O) columns at Eaton, CO (inside the dome) and at two boundary sites; the CU mobile SOF (Solar Occultation Flux) measured ethane (C2H6), ammonia (NH3), and H2O at Eaton, CO. The column averaged dry air mole fractions XCH4, XC2H6, and XNH3 were determined using O2 columns for air mass factor normalization, and background column was subtracted to derive excess vertical columns of DXCH4, DXC2H6, DXNH3 at Eaton, CO. Eaton is located both near CAFOs and at the northern edge of oil and natural gas production wells. Our approach for source apportioning methane employs a linear regression analysis that explains DXCH4 in terms of DXC2H6 as tracer for natural gas sources, and DXNH3 as tracer for CAFO emissions. The results of the source apportionment are compared with literature values of the NH3/CH4 and C2H6/CH4 ratio to evaluate the method of excess columns, which is independent of boundary layer height.

Optimization of a horizontal-flow biofilm reactor for the removal of methane at low temperatures.

PubMed

Clifford, E; Kennelly, C; Walsh, R; Gerrity, S; Reilly, E O; Collins, G

2012-10-01

Three pilot-scale, horizontal-flow biofilm reactors (HFBRs 1-3) were used to treat methane (CH4)-contaminated air to assess the potential of this technology to manage emissions from agricultural activities, waste and wastewater treatment facilities, and landfills. The study was conducted over two phases (Phase 1, lasting 90 days and Phase 2, lasting 45 days). The reactors were operated at 10 degrees C (typical of ambient air and wastewater temperatures in northern Europe), and were simultaneously dosed with CH4-contaminated air and a synthetic wastewater (SWW). The influent loading rates to the reactors were 8.6 g CH4/m3/hr (4.3 g CH4/m2 TPSA/hr; where TPSA is top plan surface area). Despite the low operating temperatures, an overall average removal of 4.63 g CH4/m3/day was observed during Phase 2. The maximum removal efficiency (RE) for the trial was 88%. Potential (maximum) rates of methane oxidation were measured and indicated that biofilm samples taken from various regions in the HFBRs had mostly equal CH4 removal potential. In situ activity rates were dependent on which part of the reactor samples were obtained. The results indicate the potential of the HFBR, a simple and robust technology, to biologically treat CH4 emissions. The results of this study indicate that the HFBR technology could be effectively applied to the reduction of greenhouse gas emissions from wastewater treatment plants and agricultural facilities at lower temperatures common to northern Europe. This could reduce the carbon footprint of waste treatment and agricultural livestock facilities. Activity tests indicate that methanotrophic communities can be supported at these temperatures. Furthermore, these data can lead to improved reactor design and optimization by allowing conditions to be engineered to allow for improved removal rates, particularly at lower temperatures. The technology is simple to construct and operate, and with some optimization of the liquid phase to improve mass transfer, the HFBR represents a viable, cost-effective solution for these emissions.

Source apportionment of methane and nitrous oxide in California's San Joaquin Valley at CalNex 2010 via positive matrix factorization

NASA Astrophysics Data System (ADS)

Guha, A.; Gentner, D. R.; Weber, R. J.; Provencal, R.; Goldstein, A. H.

2015-03-01

Sources of methane (CH4) and nitrous oxide (N2O) were investigated using measurements from a site in southeast Bakersfield as part of the CalNex (California at the Nexus of Air Quality and Climate Change) experiment from 15 May to 30 June 2010. Typical daily minimum mixing ratios of CH4 and N2O were higher than daily averages that were simultaneously observed at a similar latitude background station (NOAA, Mauna Loa) by approximately 70 and 0.5 ppb, respectively. Substantial enhancements of CH4 and N2O (hourly averages > 500 ppb and > 7 ppb, respectively) were routinely observed suggesting the presence of large regional sources. Collocated measurements of carbon monoxide (CO) and a range of volatile organic compounds (VOCs) (e.g. straight-chain and branched alkanes, cycloalkanes, chlorinated alkanes, aromatics, alcohols, isoprene, terpenes and ketones) were used with a Positive Matrix Factorization (PMF) source apportionment method to estimate the contribution of regional sources to observed enhancements of CH4 and N2O. The PMF technique provided a "top-down" deconstruction of ambient gas-phase observations into broad source categories, yielding a 7-factor solution. We identified these source factors as emissions from evaporative and fugitive; motor vehicles; livestock and dairy; agricultural and soil management; daytime light and temperature driven; non-vehicular urban; and nighttime terpene biogenics and anthropogenics. The dairy and livestock factor accounted for a majority of the CH4 (70-90%) enhancements during the duration of the experiments. Propagation of uncertainties in the PMF-derived factor profiles and time series from bootstrapping analysis resulted in a 29% uncertainty in the CH4 apportionment to this factor. The dairy and livestock factor was also a principal contributor to the daily enhancements of N2O (60-70%) with an uncertainty of 33%. Agriculture and soil management accounted for ~20-25% of N2O enhancements over the course of a day, not surprisingly given that organic and synthetic fertilizers are known to be a major source of N2O. The evaporative/fugitive source profile resembles a mix of petroleum operation and non-tailpipe evaporative gasoline sources, but was not responsible for any observed PMF resolved-CH4 enhancements. The vehicle emission source factor broadly matches VOC profiles of on-road exhaust sources and had no detected contribution to the N2O signals and negligible CH4 in the presence of a dominant dairy and livestock factor. The CalNex PMF study provides a measurement-based assessment of the state CH4 and N2O inventories for the southern San Joaquin valley. The state inventory attributes ~18% of the total N2O emissions to the transportation sector. Our PMF analysis directly contradicts the state inventory and demonstrates there were no discernible N2O emissions from the transportation sector.

Effects of shifting growth stage and regulating temperature on seasonal variation of CH4 emission from rice

NASA Astrophysics Data System (ADS)

Watanabe, Akira; Yamada, Hiromi; Kimura, Makoto

2001-09-01

Seasonal variations in CH4 emission rates from rice paddies have been reported to have one or more maxima during the middle and late periods of rice growth. The factor affecting an appearance of CH4 emission maxima was examined in three types of pot experiments. In the experiment 1, four rice cultivars with difference in length of the period from transplanting to heading were transplanted on the same days. For the experiment 2, a cultivar was transplanted 4 times with interval of two weeks. In these experiments, the heading differed about a month between the earliest and latest treatments, respectively. However, shifting growth stage of rice plants did not shift the CH4 emission maxima, and the CH4 emission maxima often matched the maxima of daily mean air temperature. The effect of variation in temperature on CH4 emission rate was further investigated in the experiment 3 by placing the rice-planted pots under regulated temperature. Besides the first emission peak of CH4 attributable to rice straw (RS) carbon, three emission peaks corresponding to the peaks of air temperature were detected for the RS-applied pots placed outdoors. These three peaks were not observed or much less conspicuous for the RS-applied pots in a phytotron at 30°C. Temporal decreases in CH4 emission were detected both for the pots placed in the phytotron and outdoors just after the topdressing of (NH4)2SO4, which was considered to be a major cause of irregular disagreement between the variations in CH4 emission rates and in air temperature during the middle period of rice growth.

Use of short-term breath measures to estimate daily methane production by cattle.

PubMed

Velazco, J I; Mayer, D G; Zimmerman, S; Hegarty, R S

2016-01-01

Methods to measure enteric methane (CH4) emissions from individual ruminants in their production environment are required to validate emission inventories and verify mitigation claims. Estimates of daily methane production (DMP) based on consolidated short-term emission measurements are developing, but method verification is required. Two cattle experiments were undertaken to test the hypothesis that DMP estimated by averaging multiple short-term breath measures of methane emission rate did not differ from DMP measured in respiration chambers (RC). Short-term emission rates were obtained from a GreenFeed Emissions Monitoring (GEM) unit, which measured emission rate while cattle consumed a dispensed supplement. In experiment 1 (Expt. 1), four non-lactating cattle (LW=518 kg) were adapted for 18 days then measured for six consecutive periods. Each period consisted of 2 days of ad libitum intake and GEM emission measurement followed by 1 day in the RC. A prototype GEM unit releasing water as an attractant (GEM water) was also evaluated in Expt. 1. Experiment 2 (Expt. 2) was a larger study based on similar design with 10 cattle (LW=365 kg), adapted for 21 days and GEM measurement was extended to 3 days in each of the six periods. In Expt. 1, there was no difference in DMP estimated by the GEM unit relative to the RC (209.7 v. 215.1 g CH(4)/day) and no difference between these methods in methane yield (MY, 22.7 v. 23.7 g CH(4)/kg of dry matter intake, DMI). In Expt. 2, the correlation between GEM and RC measures of DMP and MY were assessed using 95% confidence intervals, with no difference in DMP or MY between methods and high correlations between GEM and RC measures for DMP (r=0.85; 215 v. 198 g CH(4)/day SEM=3.0) and for MY (r=0.60; 23.8 v. 22.1 g CH(4)/kg DMI SEM=0.42). When data from both experiments was combined neither DMP nor MY differed between GEM- and RC-based measures (P>0.05). GEM water-based estimates of DMP and MY were lower than RC and GEM (P<0.05). Cattle accessed the GEM water unit with similar frequency to the GEM unit (2.8 v. 3.5 times/day, respectively) but eructation frequency was reduced from 1.31 times/min (GEM) to once every 2.6 min (GEM water). These studies confirm the hypothesis that DMP estimated by averaging multiple short-term breath measures of methane emission rate using GEM does not differ from measures of DMP obtained from RCs. Further, combining many short-term measures of methane production rate during supplement consumption provides an estimate of DMP, which can be usefully applied in estimating MY.

Agricultural peat lands; towards a greenhouse gas sink - a synthesis of a Dutch landscape study

NASA Astrophysics Data System (ADS)

Schrier-Uijl, A. P.; Kroon, P. S.; Hendriks, D. M. D.; Hensen, A.; Van Huissteden, J. C.; Leffelaar, P. A.; Berendse, F.; Veenendaal, E. M.

2013-06-01

It is generally known that managed, drained peatlands act as carbon sources. In this study we examined how mitigation through the reduction of management and through rewetting may affect the greenhouse gas (GHG) emission and the carbon balance of intensively managed, drained, agricultural peatlands. Carbon and GHG balances were determined for three peatlands in the western part of the Netherlands from 2005 to 2008 by considering spatial and temporal variability of emissions (CO2, CH4 and N2O). One area (Oukoop) is an intensively managed grass-on-peatland, including a dairy farm, with the ground water level at an average annual depth of 0.55 m below the soil surface. The second area (Stein) is an extensively managed grass-on-peatland, formerly intensively managed, with a dynamic ground water level at an average annual depth of 0.45 m below the soil surface. The third area is an (since 1998) rewetted former agricultural peatland (Horstermeer), close to Oukoop and Stein, with the average annual ground water level at a depth of 0.2 m below the soil surface. During the measurement campaigns we found that both agriculturally managed sites acted as carbon and GHG sources but the rewetted agricultural peatland acted as a carbon and GHG sink. The terrestrial GHG source strength was 1.4 kg CO2-eq m-2 yr-1 for the intensively managed area and 1.0 kg CO2-eq m-2 yr-1 for the extensively managed area; the unmanaged area acted as a GHG sink of 0.7 kg CO2-eq m-2 yr-1. Water bodies contributed significantly to the terrestrial GHG balance because of a high release of CH4 and the loss of DOC only played a minor role. Adding the farm-based CO2 and CH4 emissions increased the source strength for the managed sites to 2.7 kg CO2-eq m-2 yr-1 for Oukoop and 2.1 kg CO2-eq m-2 yr-1 for Stein. Shifting from intensively managed to extensively managed grass-on-peat reduced GHG emissions mainly because N2O emission and farm-based CH4 emissions decreased. Overall, this study suggests that managed peatlands are large sources of GHG and carbon, but, if appropriate measures are taken they can be turned back into GHG and carbon sinks within 15 yr of abandonment and rewetting.

TA [2] Continuous, regional methane emissions estimates in northern Pennsylvania gas fields using atmospheric inversions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lauvaux, Thomas

Natural Gas (NG) production activities in the northeastern Marcellus shale have significantly increased in the last decade, possibly releasing large amounts of methane (CH 4) into the atmosphere from the operations at the productions sites and during the processing and transmission steps of the natural gas chain. Based on an intensive aircraft survey, leakage rates from the NG production were quantified in May 2015 and found to be in the order of 0.5% of the total production, higher than reported by the Environmental Protection Agency (EPA) but below the usually observed leakage rates over the shale gases in the US.more » Thanks to the high production rates on average at each well, leakage rates normalized by production appeared to be low in the northeastern Marcellus shale. This result confirms that natural gas production using unconventional techniques in this region is emitting relatively less CH 4 into the atmosphere than other shale reservoirs. The low emissions rate can be explained in part by the high productivity of wells drilled across the northeastern Marcellus region. We demonstrated here that atmospheric monitoring techniques can provide an independent quantification of NG leakage rates using aircraft measurements. The CH 4 analyzers were successfully calibrated at four sites across the region, measuring continuously the atmospheric CH 4 mixing ratios and isotopic 13Ch 4. Our preliminary findings confirm the low leakage rates from tower data collected over September 2015 to November 2016 compared to the aircraft mass-balance estimates in may 2015. However, several episodes revealing large releases of natural gas over several weeks showed that temporal variations in the emissions of CH 4 may increase the actual leakage rate over longer time periods.« less

Methane, carbon dioxide, and nitrous oxide emissions from septic tank systems.

PubMed

Diaz-Valbuena, Libia R; Leverenz, Harold L; Cappa, Christopher D; Tchobanoglous, George; Horwath, William R; Darby, Jeannie L

2011-04-01

Emissions of CH4, CO2, and N2O from conventional septic tank systems are known to occur, but there is a dearth of information as to the extent. Mass emission rates of CH4, CO2, and N2O, as measured with a modified flux chamber approach in eight septic tank systems, were determined to be 11, 33.3, and 0.005 g capita(-1) day(-1), respectively, in this research. Existing greenhouse gas (GHG) emission models based on BOD (biochemical oxygen demand) loading have estimated methane emissions to be as high as 27.1 g CH4 capita(-1) day(-1), more than twice the value measured in our study, and concluded that septic tanks are potentially significant sources of GHGs due to the large number of systems currently in use. Based on the measured CH4 emission value, a revised CH4 conversion factor of 0.22 (compared to 0.5) for use in the emissions models is suggested. Emission rates of CH4, CO2, and N2O were also determined from measurements of gas concentrations and flow rates in the septic vent system and were found to be 10.7, 335, and 0.2 g capita(-1)day(-1), respectively. The excellent agreement in the CH4 emission rates between the flux chamber and the vent values indicates the dominant CH4 source is the septic tank.

Emissions of coalbed and natural gas methane from abandoned oil and gas wells in the United States

NASA Astrophysics Data System (ADS)

Townsend-Small, Amy; Ferrara, Thomas W.; Lyon, David R.; Fries, Anastasia E.; Lamb, Brian K.

2016-03-01

Recent work indicates that oil and gas methane (CH4) inventories for the United States are underestimated. Here we present results from direct measurements of CH4 emissions from 138 abandoned oil and gas wells, a source currently missing from inventories. Most abandoned wells do not emit CH4, but 6.5% of wells had measurable CH4 emissions. Twenty-five percent of wells we visited that had not been plugged emitted > 5 g CH4 h-1. Stable isotopes indicate that wells emit natural gas and/or coalbed CH4. We estimate that abandoned wells make a small contribution (<1%) to regional CH4 emissions in our study areas. Additional data are needed to accurately determine the contribution of abandoned wells to national CH4 budgets, particularly measurements in other basins and better characterization of the abundance and regional distribution of high emitters.

[China's rice field greenhouse gas emission under climate change based on DNDC model simulation].

PubMed

Tian, Zhan; Niu, Yi-long; Sun, Lai-xiang; Li, Chang-sheng; Liu, Chun-jiang; Fan, Dong-li

2015-03-01

In contrast to a large body of literature assessing the impact of agriculture greenhouse gas (GHG) emissions on climate change, there is a lack of research examining the impact of climate change on agricultural GHG emissions. This study employed the DNDC v9.5, a state-of-art biogeochemical model, to simulate greenhouse gas emissions in China' s rice-growing fields during 1971-2010. The results showed that owing to temperature rising (on average 0.49 °C higher in the second 20 years than in the first 20 year) and precipitation increase (11 mm more in the second 20 years than in the first 20 years) during the rice growing season, CH4 and N2O emissions in paddy field increased by 0.25 kg C . hm-2 and 0.25 kg N . hm-2, respectively. The rising temperature accelerated CH4 emission and N2O emission increased with precipitation. These results indicated that climate change exerted impact on the mechanism of GHG emissions in paddy field.

40 CFR 98.343 - Calculating GHG emissions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... potential (metric tons CH4/metric ton waste) = MCF × DOC × DOCF × F × 16/12. MCF = Methane correction factor... = Methane emissions from the landfill in the reporting year (metric tons CH4). GCH 4 = Modeled methane...). Emissions = Methane emissions from the landfill in the reporting year (metric tons CH4). R = Quantity of...

Fluxes of carbon dioxide and methane across the water-atmosphere interface of aquaculture shrimp ponds in two subtropical estuaries: The effect of temperature, substrate, salinity and nitrate.

PubMed

Yang, Ping; Zhang, Yifei; Lai, Derrick Y F; Tan, Lishan; Jin, Baoshi; Tong, Chuan

2018-04-20

While aquaculture pond is a dominant land use/cover type and a distinct aquatic ecosystem in the coastal zones of China and southeast Asia, their contributions to the fluxes of greenhouse gases (GHGs) have only been poorly quantified. Fluxes of CO 2 and CH 4 in the shrimp ponds with different salinities were simultaneously measured in situ using the floating chamber technique in two different subtropical estuaries, namely, the Min River Estuary (MRE) and Jiulong River Estuary (JRE). The average CO 2 and CH 4 fluxes in the shrimp ponds over the observation periods varied from -2.09 to 3.37mmol CO 2 m -2 h -1 and from 0.28 to 16.28mmol CH 4 m -2 h -1 , respectively, with higher fluxes being detected during the middle stage of aquaculture. The temporal variation of CO 2 and CH 4 fluxes in both estuaries ponds closely followed the seasonal cycle of temperature. Higher CH 4 emissions were observed in MRE ponds than in JRE ponds because of the lower water salinity and N-NO 3 - concentrations as well as a greater supply of carbon substrates. Our findings suggested that shrimp ponds were CH 4 emission "hotspots" in the subtropical estuaries of China. Based on a new global warming potential model, we conservatively estimated an anuual GHG emission rate of approximately 63.68Tg CO 2 -eq during the culture period from aquaculture ponds across the subtropical estuaries of China. Our results demonstrate the importance of aquaculture ponds as a major GHG source and a contributor to climate warming in the subtropical estuarine regions of China, and call for effective regulation of GHG emissions from these ponds for climate mitigation in future. Copyright © 2018 Elsevier B.V. All rights reserved.

Urea deep placement reduces yield-scaled greenhouse gas (CH4 and N2O) and NO emissions from a ground cover rice production system.

PubMed

Yao, Zhisheng; Zheng, Xunhua; Zhang, Yanan; Liu, Chunyan; Wang, Rui; Lin, Shan; Zuo, Qiang; Butterbach-Bahl, Klaus

2017-09-12

Ground cover rice production system (GCRPS), i.e., paddy soils being covered by thin plastic films with soil moisture being maintained nearly saturated status, is a promising technology as increased yields are achieved with less irrigation water. However, increased soil aeration and temperature under GCRPS may cause pollution swapping in greenhouse gas (GHG) from CH 4 to N 2 O emissions. A 2-year experiment was performed, taking traditional rice cultivation as a reference, to assess the impacts of N-fertilizer placement methods on CH 4 , N 2 O and NO emissions and rice yields under GCRPS. Averaging across all rice seasons and N-fertilizer treatments, the GHG emissions for GCRPS were 1973 kg CO 2 -eq ha -1 (or 256 kg CO 2 -eq Mg -1 ), which is significantly lower than that of traditional cultivation (4186 kg CO 2 -eq ha -1 or 646 kg CO 2 -eq Mg -1 ). Furthermore, if urea was placed at a 10-15 cm soil depth instead of broadcasting, the yield-scaled GHG emissions from GCRPS were further reduced from 377 to 222 kg CO 2 -eq Mg -1 , as N 2 O emissions greatly decreased while yields increased. Urea deep placement also reduced yield-scaled NO emissions by 54%. Therefore, GCRPS with urea deep placement is a climate- and environment-smart management, which allows for maximal rice yields at minimal GHG and NO emissions.

A cool-temperate young larch plantation as a net methane source - A 4-year continuous hyperbolic relaxed eddy accumulation and chamber measurements

NASA Astrophysics Data System (ADS)

Ueyama, Masahito; Yoshikawa, Kota; Takagi, Kentaro

2018-07-01

Upland forests are thought to be methane (CH4) sinks due to oxidation by methanotrophs in aerobic soils. However, CH4 budget for upland forests are not well quantified at the ecosystem scale, when possible CH4 sources, such as small wet areas, exists in the ecosystem. Here, we quantified CH4 fluxes in a cool-temperate larch plantation based on four-year continuous measurements using the hyperbolic relaxed eddy accumulation (HREA) method and dynamic closed chambers with a laser-based analyzer. After filling data gaps for half-hourly data using machine-learning-based regressions, we found that the forest acted as a net CH4 source at the canopy scale: 30 ± 11 mg CH4 m-2 yr-1 in 2014, 56 ± 8 mg CH4 m-2 yr-1 in 2015, 154 ± 5 mg CH4 m-2 yr-1 in 2016, and 132 ± 6 mg CH4 m-2 yr-1 in 2017. Hotspot emissions from the edge of the pond could strongly contribute to the canopy-scale emissions. The magnitude of the hotspot emissions was 10-100 times greater than the order of the canopy-scale and chamber-based CH4 fluxes at the dry soils. The high temperatures with wet conditions stimulated the hotspot emissions, and thus induced canopy-scale CH4 emissions in the summer. Understanding and modeling the dynamics of hotspot emissions are important for quantifying CH4 budgets of upland forests. Micrometeorological measurements at various forests are required for revisiting CH4 budget of upland forests.

Greenhouse gas emissions from waste stabilisation ponds in Western Australia and Quebec (Canada).

PubMed

Glaz, Patricia; Bartosiewicz, Maciej; Laurion, Isabelle; Reichwaldt, Elke S; Maranger, Roxane; Ghadouani, Anas

2016-09-15

Waste stabilisation ponds (WSPs) are highly enriched environments that may emit large quantities of greenhouse gases (GHG), including CO2, CH4 and N2O. However, few studies provide detailed reports on these emissions. In the present study, we investigated GHG emissions from WSPs in Western Australia and Quebec, Canada, and compared emissions to WSPs from other climatic regions and to other types of aquatic ecosystems. Surface water GHG concentrations were related to phytoplankton biomass and nutrients. The CO2 was either emitted or absorbed by WSPs, largely as a function of phytoplankton dynamics and strong stratification in these shallow systems, whereas efflux of CH4 and N2O to the atmosphere was always observed albeit with highly variable emission rates, dependent on treatment phase and time of the day. The total global warming potential index (GWP index, calculated as CO2 equivalent) of emitted GHG from WSPs in Western Australia averaged 12.8 mmol m(-2) d(-1) (median), with CO2, CH4 and N2O respectively contributing 0%, 96.7% and 3.3% of the total emissions, while in Quebec WSPs this index was 194 mmol m(-2) d(-1), with a relative contribution of 93.8, 3.0 and 3.2% respectively. The CO2 fluxes from WSPs were of the same order of magnitude as those reported in hydroelectric reservoirs and constructed wetlands in tropical climates, whereas CH4 fluxes were considerably higher compared to other aquatic ecosystems. N2O fluxes were in the same range of values reported for WSPs in subtropical climate. Copyright © 2016 Elsevier Ltd. All rights reserved.

Variability in methane emissions from West Siberia's shallow boreal lakes on a regional scale and its environmental controls

NASA Astrophysics Data System (ADS)

Sabrekov, Aleksandr F.; Runkle, Benjamin R. K.; Glagolev, Mikhail V.; Terentieva, Irina E.; Stepanenko, Victor M.; Kotsyurbenko, Oleg R.; Maksyutov, Shamil S.; Pokrovsky, Oleg S.

2017-08-01

Small lakes represent an important source of atmospheric CH4 from northern wetlands. However, spatiotemporal variations in flux magnitudes and the lack of knowledge about their main environmental controls contribute large uncertainty into the global CH4 budget. In this study, we measured methane fluxes from small lakes using chambers and bubble traps. Field investigations were carried out in July-August 2014 within the West Siberian middle and southern taiga zones. The average and median of measured methane chamber fluxes were 0.32 and 0.30 mgCH4 m-2 h-1 for middle taiga lakes and 8.6 and 4.1 mgCH4 m-2 h-1 for southern taiga lakes, respectively. Pronounced flux variability was found during measurements on individual lakes, between individual lakes and between zones. To analyze these differences and the influences of environmental controls, we developed a new dynamic process-based model. It shows good performance with emission rates from the southern taiga lakes and poor performance for individual lakes in the middle taiga region. The model shows that, in addition to well-known controls such as temperature, pH and lake depth, there are significant variations in the maximal methane production potential between these climatic zones. In addition, the model shows that variations in gas-filled pore space in lake sediments are capable of controlling the total methane emissions from individual lakes. The CH4 emissions exhibited distinct zonal differences not only in absolute values but also in their probability density functions: the middle taiga lake fluxes were best described by a lognormal distribution while the southern taiga lakes followed a power-law distribution. The latter suggests applicability of self-organized criticality theory for methane emissions from the southern taiga zone, which could help to explain the strong variability within individual lakes.

Carbon dioxide and methane emissions from the scale model of open dairy lots.

PubMed

Ding, Luyu; Cao, Wei; Shi, Zhengxiang; Li, Baoming; Wang, Chaoyuan; Zhang, Guoqiang; Kristensen, Simon

2016-07-01

To investigate the impacts of major factors on carbon loss via gaseous emissions, carbon dioxide (CO2) and methane (CH4) emissions from the ground of open dairy lots were tested by a scale model experiment at various air temperatures (15, 25, and 35 °C), surface velocities (0.4, 0.7, 1.0, and 1.2 m sec(-1)), and floor types (unpaved soil floor and brick-paved floor) in controlled laboratory conditions using the wind tunnel method. Generally, CO2 and CH4 emissions were significantly enhanced with the increase of air temperature and velocity (P < 0.05). Floor type had different effects on the CO2 and CH4 emissions, which were also affected by air temperature and soil characteristics of the floor. Although different patterns were observed on CH4 emission from the soil and brick floors at different air temperature-velocity combinations, statistical analysis showed no significant difference in CH4 emissions from different floors (P > 0.05). For CO2, similar emissions were found from the soil and brick floors at 15 and 25 °C, whereas higher rates were detected from the brick floor at 35 °C (P < 0.05). Results showed that CH4 emission from the scale model was exponentially related to CO2 flux, which might be helpful in CH4 emission estimation from manure management. Gaseous emissions from the open lots are largely dependent on outdoor climate, floor systems, and management practices, which are quite different from those indoors. This study assessed the effects of floor types and air velocities on CO2 and CH4 emissions from the open dairy lots at various temperatures by a wind tunnel. It provided some valuable information for decision-making and further studies on gaseous emissions from open lots.

Quantifying sources of methane using light alkanes in the Los Angeles basin, California

NASA Astrophysics Data System (ADS)

Peischl, J.; Ryerson, T. B.; Brioude, J.; Aikin, K. C.; Andrews, A. E.; Atlas, E.; Blake, D.; Daube, B. C.; de Gouw, J. A.; Dlugokencky, E.; Frost, G. J.; Gentner, D. R.; Gilman, J. B.; Goldstein, A. H.; Harley, R. A.; Holloway, J. S.; Kofler, J.; Kuster, W. C.; Lang, P. M.; Novelli, P. C.; Santoni, G. W.; Trainer, M.; Wofsy, S. C.; Parrish, D. D.

2013-05-01

Methane (CH4), carbon dioxide (CO2), carbon monoxide (CO), and C2-C5 alkanes were measured throughout the Los Angeles (L.A.) basin in May and June 2010. We use these data to show that the emission ratios of CH4/CO and CH4/CO2 in the L.A. basin are larger than expected from population-apportioned bottom-up state inventories, consistent with previously published work. We use experimentally determined CH4/CO and CH4/CO2 emission ratios in combination with annual State of California CO and CO2 inventories to derive a yearly emission rate of CH4 to the L.A. basin. We further use the airborne measurements to directly derive CH4 emission rates from dairy operations in Chino, and from the two largest landfills in the L.A. basin, and show these sources are accurately represented in the California Air Resources Board greenhouse gas inventory for CH4. We then use measurements of C2-C5 alkanes to quantify the relative contribution of other CH4 sources in the L.A. basin, with results differing from those of previous studies. The atmospheric data are consistent with the majority of CH4 emissions in the region coming from fugitive losses from natural gas in pipelines and urban distribution systems and/or geologic seeps, as well as landfills and dairies. The local oil and gas industry also provides a significant source of CH4 in the area. The addition of CH4 emissions from natural gas pipelines and urban distribution systems and/or geologic seeps and from the local oil and gas industry is sufficient to account for the differences between the top-down and bottom-up CH4 inventories identified in previously published work.

Global wetland contribution to 2000–2012 atmospheric methane growth rate dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poulter, Benjamin; Bousquet, Philippe; Canadell, Josep G.

Increasing atmospheric methane (CH 4) concentrations have contributed to approximately 20% of anthropogenic climate change. Despite the importance of CH 4 as a greenhouse gas, its atmospheric growth rate and dynamics over the past two decades, which include a stabilization period (1999–2006), followed by renewed growth starting in 2007, remain poorly understood. We provide an updated estimate of CH 4 emissions from wetlands, the largest natural global CH 4 source, for 2000–2012 using an ensemble of biogeochemical models constrained with remote sensing surface inundation and inventory-based wetland area data. Between 2000–2012, boreal wetland CH 4 emissions increased by 1.2 Tgmore » yr –1 (–0.2–3.5 Tg yr –1), tropical emissions decreased by 0.9 Tg yr –1 (–3.2–1.1 Tg yr –1), yet globally, emissions remained unchanged at 184 ± 22 Tg yr –1. Changing air temperature was responsible for increasing high-latitude emissions whereas declines in low-latitude wetland area decreased tropical emissions; both dynamics are consistent with features of predicted centennial-scale climate change impacts on wetland CH 4 emissions. Despite uncertainties in wetland area mapping, our study shows that global wetland CH 4 emissions have not contributed significantly to the period of renewed atmospheric CH 4 growth, and is consistent with findings from studies that indicate some combination of increasing fossil fuel and agriculture-related CH 4 emissions, and a decrease in the atmospheric oxidative sink.« less

Global wetland contribution to 2000–2012 atmospheric methane growth rate dynamics

DOE PAGES

Poulter, Benjamin; Bousquet, Philippe; Canadell, Josep G.; ...

2017-09-13

Increasing atmospheric methane (CH 4) concentrations have contributed to approximately 20% of anthropogenic climate change. Despite the importance of CH 4 as a greenhouse gas, its atmospheric growth rate and dynamics over the past two decades, which include a stabilization period (1999–2006), followed by renewed growth starting in 2007, remain poorly understood. We provide an updated estimate of CH 4 emissions from wetlands, the largest natural global CH 4 source, for 2000–2012 using an ensemble of biogeochemical models constrained with remote sensing surface inundation and inventory-based wetland area data. Between 2000–2012, boreal wetland CH 4 emissions increased by 1.2 Tgmore » yr –1 (–0.2–3.5 Tg yr –1), tropical emissions decreased by 0.9 Tg yr –1 (–3.2–1.1 Tg yr –1), yet globally, emissions remained unchanged at 184 ± 22 Tg yr –1. Changing air temperature was responsible for increasing high-latitude emissions whereas declines in low-latitude wetland area decreased tropical emissions; both dynamics are consistent with features of predicted centennial-scale climate change impacts on wetland CH 4 emissions. Despite uncertainties in wetland area mapping, our study shows that global wetland CH 4 emissions have not contributed significantly to the period of renewed atmospheric CH 4 growth, and is consistent with findings from studies that indicate some combination of increasing fossil fuel and agriculture-related CH 4 emissions, and a decrease in the atmospheric oxidative sink.« less

Regional landfills methane emission inventory in Malaysia.

PubMed

Abushammala, Mohammed F M; Noor Ezlin Ahmad Basri; Basri, Hassan; Ahmed Hussein El-Shafie; Kadhum, Abdul Amir H

2011-08-01

The decomposition of municipal solid waste (MSW) in landfills under anaerobic conditions produces landfill gas (LFG) containing approximately 50-60% methane (CH(4)) and 30-40% carbon dioxide (CO(2)) by volume. CH(4) has a global warming potential 21 times greater than CO(2); thus, it poses a serious environmental problem. As landfills are the main method for waste disposal in Malaysia, the major aim of this study was to estimate the total CH(4) emissions from landfills in all Malaysian regions and states for the year 2009 using the IPCC, 1996 first-order decay (FOD) model focusing on clean development mechanism (CDM) project applications to initiate emission reductions. Furthermore, the authors attempted to assess, in quantitative terms, the amount of CH(4) that would be emitted from landfills in the period from 1981-2024 using the IPCC 2006 FOD model. The total CH(4) emission using the IPCC 1996 model was estimated to be 318.8 Gg in 2009. The Northern region had the highest CH(4) emission inventory, with 128.8 Gg, whereas the Borneo region had the lowest, with 24.2 Gg. It was estimated that Pulau Penang state produced the highest CH(4) emission, 77.6 Gg, followed by the remaining states with emission values ranging from 38.5 to 1.5 Gg. Based on the IPCC 1996 FOD model, the total Malaysian CH( 4) emission was forecast to be 397.7 Gg by 2020. The IPCC 2006 FOD model estimated a 201 Gg CH(4) emission in 2009, and estimates ranged from 98 Gg in 1981 to 263 Gg in 2024.

Remotely sensed MODIS wetland components for assessing the variability of methane emissions in Indian tropical/subtropical wetlands

NASA Astrophysics Data System (ADS)

Bansal, Sangeeta; Katyal, Deeksha; Saluja, Ridhi; Chakraborty, Monojit; Garg, J. K.

2018-02-01

Temperature and area fluctuations in wetlands greatly influence its various physico-chemical characteristics, nutrients dynamic, rates of biomass generation and decomposition, floral and faunal composition which in turn influence methane (CH4) emission rates. In view of this, the present study attempts to up-scale point CH4 flux from the wetlands of Uttar Pradesh (UP) by modifying two-factor empirical process based CH4 emission model for tropical wetlands by incorporating MODIS derived wetland components viz. wetland areal extent and corresponding temperature factors (Ft). This study further focuses on the utility of remotely sensed temperature response of CH4 emission in terms of Ft. Ft is generated using MODIS land surface temperature products and provides an important semi-empirical input for up-scaling CH4 emissions in wetlands. Results reveal that annual mean Ft values for UP wetlands vary from 0.69 (2010-2011) to 0.71(2011-2012). The total estimated area-wise CH4 emissions from the wetlands of UP varies from 66.47 Gg yr-1with wetland areal extent and Ft value of 2564.04 km2 and 0.69 respectively in 2010-2011 to 88.39 Gg yr-1with wetland areal extent and Ft value of 2720.16 km2 and 0.71 respectively in 2011-2012. Temporal analysis of estimated CH4 emissions showed that in monsoon season estimated CH4 emissions are more sensitive to wetland areal extent while in summer season sensitivity of estimated CH4 emissions is chiefly controlled by augmented methanogenic activities at high wetland surface temperatures.

Global Inverse Modeling of CH4 and δ13C-CH4 Measurements to Understand Recent Trends in Methane Emissions

NASA Astrophysics Data System (ADS)

Karmakar, S.; Butenhoff, C. L.; Rice, A. L.; Khalil, A. K.

2017-12-01

Methane (CH4) is the second most important greenhouse gas with a radiative forcing of 0.97 W/m2 including both direct and indirect effects and a global warming potential of 28 over a 100-year time horizon. After a decades-long period of decline beginning in the 1980s, the methane growth rate rebounded in 2007 for reasons that are of current debate. During this same growth period atmospheric methane became less enriched in the 13CH4 isotope suggesting the recent CH4 growth was caused by an increase in 13CH4-depleted biogenic emissions. Recent papers have attributed this growth to increasing emissions from wetlands, rice agriculture, and ruminants. In this work we provide additional insight into the recent behavior of atmospheric methane and global wetland emissions by performing a three-dimensional Bayesian inversion of surface CH4 and 13CH4/12CH4 ratios using NOAA Global Monitoring Division (GMD) "event-level" CH4 measurements and the GEOS-Chem chemical-transport model (CTM) at a horizontal grid resolution of 2ox2.5o. The spatial pattern of wetland emissions was prescribed using soil moisture and temperature from GEOS-5 meteorology fields and soil carbon pools from the Lund-Potsdam-Jena global vegetation model. In order to reduce the aggregation error caused by a potentially flawed distribution and to account for isotopic measurements that indicate northern high latitude wetlands are isotopically depleted in 13CH4 relative to tropical wetlands we separated our pattern into three latitudinal bands (90-30°N, 30°N-0, 0-90°S). Our preliminary results support previous claims that the recent increase in atmospheric methane is driven by increases in biogenic CH4 emissions. We find that while wetland emissions from northern high latitudes (90-30°N) remained relatively constant during this time, southern hemisphere wetland emissions rebounded from a decade-long decline and began to rise again in 2007 and have remained elevated to the present. Emissions from rice agriculture continue to decline. The use of inverse modeling to exploit the information content of CH4 and 13CH4/12CH4 measurements can provide important constraints on bottom-up estimates of wetland emissions but the method requires choosing numerous model parameters. We explore the sensitivity of our results to a number of these choices.

[Spatiotemporal variations of natural wetland CH4 emissions over China under future climate change].

PubMed

Liu, Jian-gong; Zhu, Qiu-an; Shen, Yan; Yang, Yan-zheng; Luo, Yun-peng; Peng, Chang-hui

2015-11-01

Based on a new process-based model, TRIPLEX-GHG, this paper analyzed the spatio-temporal variations of natural wetland CH4 emissions over China under different future climate change scenarios. When natural wetland distributions were fixed, the amount of CH4 emissions from natural wetland ecosystem over China would increase by 32.0%, 55.3% and 90.8% by the end of 21st century under three representative concentration pathways (RCPs) scenarios, RCP2. 6, RCP4.5 and RCP8.5, respectively, compared with the current level. Southern China would have higher CH4 emissions compared to that from central and northern China. Besides, there would be relatively low emission fluxes in western China while relatively high emission fluxes in eastern China. Spatially, the areas with relatively high CH4 emission fluxes would be concentrated in the middle-lower reaches of the Yangtze River, the Northeast and the coasts of the Pearl River. In the future, most natural wetlands would emit more CH4 for RCP4.5 and RCP8.5 than that of 2005. However, under RCP2.6 scenario, the increasing trend would be curbed and CH4 emissions (especially from the Qinghai-Tibet Plateau) begin to decrease in the late 21st century.

The effects of climate changes on soil methane oxidation in a dry Arctic tundra

NASA Astrophysics Data System (ADS)

D'Imperio, Ludovica

2014-05-01

The effects of climate changes on soil methane oxidation in a dry Arctic tundra. Ludovica D'Imperio1, Anders Michelsen1, Christian J. Jørgensen1, Bo Elberling1 1Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark At Northern latitudes climatic changes are predicted to be most pronounced resulting in increasing active layer depth and changes in growing season length, vegetation cover and nutrient cycling. As a consequence of increased temperature, large stocks of carbon stored in the permafrost-affected soils could become available for microbial transformations and under anoxic conditions result in increasing methane production affecting net methane (CH4) budget. Arctic tundra soils also serves as an important sink of atmospheric CH4 by microbial oxidation under aerobic conditions. While several process studies have documented the mechanisms behind both production and emissions of CH4 in arctic ecosystems, an important knowledge gap exists with respect to the in situ dynamics of microbial-driven uptake of CH4 in arctic dry lands which may be enhanced as a consequence of global warming and thereby counterbalancing CH4 emissions from Arctic wetlands. In-situ methane measurements were made in a dry Arctic tundra in Disko Island, Western Greenland, during the summer 2013 to assess the role of seasonal and inter-annual variations in temperatures and snow cover. The experimental set-up included snow fences installed in 2012, allowed investigations of the emissions of GHGs from soil under increased winter snow deposition and ambient field conditions. The soil fluxes of CH4 and CO2 were measured using closed chambers in manipulated plots with increased summer temperatures and shrub removal with or without increased winter precipitation. At the control plots, the averaged seasonal CH4 oxidation rates ranged between -0.05 mg CH4 m-2 hr-1 (end of August) and -0.32 mg CH4 m-2 hr-1 (end of June). In the plots with increased summer temperatures the rates ranged between -0.08 mg CH4 m-2 hr-1 (end of August) and -0.40 mg CH4 m-2 hr-1 (beginning of July). Preliminary results show a significant effect of increased winter precipitation (p<0.01) over the season as well as a significant warming effect (p<0.05) during July and August. These results suggest that in a warmer climate increasing CH4 uptake rates in dry Arctic soils could become an important factor for net CH4 budget.

Climate change impact of livestock CH4 emission in India: Global temperature change potential (GTP) and surface temperature response.

PubMed

Kumari, Shilpi; Hiloidhari, Moonmoon; Kumari, Nisha; Naik, S N; Dahiya, R P

2018-01-01

Two climate metrics, Global surface Temperature Change Potential (GTP) and the Absolute GTP (AGTP) are used for studying the global surface temperature impact of CH 4 emission from livestock in India. The impact on global surface temperature is estimated for 20 and 100 year time frames due to CH 4 emission. The results show that the CH 4 emission from livestock, worked out to 15.3 Tg in 2012. In terms of climate metrics GTP of livestock-related CH 4 emission in India in 2012 were 1030 Tg CO 2 e (GTP 20 ) and 62 Tg CO 2 e (GTP 100 ) at the 20 and 100 year time horizon, respectively. The study also illustrates that livestock-related CH 4 emissions in India can cause a surface temperature increase of up to 0.7mK and 0.036mK over the 20 and 100 year time periods, respectively. The surface temperature response to a year of Indian livestock emission peaks at 0.9mK in the year 2021 (9 years after the time of emission). The AGTP gives important information in terms of temperature change due to annual CH 4 emissions, which is useful when comparing policies that address multiple gases. Copyright © 2017 Elsevier Inc. All rights reserved.

Testing climate-smart irrigation strategies to reduce methane emissions from rice fields

NASA Astrophysics Data System (ADS)

Runkle, B.; Suvocarev, K.; Reba, M. L.

2017-12-01

Approximately 11% of the global 308 Tg CH4 anthropogenic emissions are currently attributed to rice cultivation. In this study, the impact of water conservation practices on rice field CH4 emissions was evaluated in Arkansas, the leading state in US rice cultivation. While conserving water, the Alternate Wetting and Drying (AWD) irrigation practice can also reduce CH4 emissions through the deliberate, periodic introduction of aerobic conditions. Seasonal CH4emissions from a pair of adjacent, production-sized rice fields were estimated and compared during the 2015 to 2017 growing seasons using the eddy covariance method on each field. The fields were alternately treated with continuous flood (CF) and AWD irrigation. In 2015, the seasonal cumulative carbon losses by CH4 emission were 30.3 ± 6.3 and 141.9 ± 8.6 kg CH4-C ha-1 for the AWD and CF treatments, respectively. Data from 2016 and 2017 will be analyzed and shown within this presentation; an initial view demonstrates consistent findings to 2015. When accounting for differences in field conditions and soils, the AWD practice is attributable to a 36-51% reduction in seasonal emissions. The substantial decrease in CH4 emissions by AWD supports previous chamber-based research and offers strong evidence for the efficacy of AWD in reducing CH4 emissions in Arkansas rice production. The AWD practice has enabled the sale of credits for carbon offsets trading and this new market could encourage CH4 emissions reductions on a national scale. These eddy covariance towers are being placed into a regional perspective including crop and forest land in the three states comprising the Mississippi Delta: Arkansas, Mississippi, and Louisiana.

The nitrogen, carbon and greenhouse gas budget of a grazed, cut and fertilised temperate grassland

NASA Astrophysics Data System (ADS)

Jones, Stephanie K.; Helfter, Carole; Anderson, Margaret; Coyle, Mhairi; Campbell, Claire; Famulari, Daniela; Di Marco, Chiara; van Dijk, Netty; Sim Tang, Y.; Topp, Cairistiona F. E.; Kiese, Ralf; Kindler, Reimo; Siemens, Jan; Schrumpf, Marion; Kaiser, Klaus; Nemitz, Eiko; Levy, Peter E.; Rees, Robert M.; Sutton, Mark A.; Skiba, Ute M.

2017-04-01

Intensively managed grazed grasslands in temperate climates are globally important environments for the exchange of the greenhouse gases (GHGs) carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). We assessed the N and C budget of a mostly grazed and occasionally cut and fertilised grassland in SE Scotland by measuring or modelling all relevant imports and exports to the field as well as changes in soil C and N stocks over time. The N budget was dominated by import from inorganic and organic fertilisers (21.9 g N m-2 a-1) and losses from leaching (5.3 g N m-2 a-1), N2 emissions (2.9 g N m-2 a-1), and NOx and NH3 volatilisation (3.9 g N m-2 a-1), while N2O emission was only 0.6 g N m-2 a-1. The efficiency of N use by animal products (meat and wool) averaged 9.9 % of total N input over only-grazed years (2004-2010). On average over 9 years (2002-2010), the balance of N fluxes suggested that 6.0 ± 5.9 g N m-2 a-1 (mean ± confidence interval at p > 0.95) were stored in the soil. The largest component of the C budget was the net ecosystem exchange of CO2 (NEE), at an average uptake rate of 218 ± 155 g C m-2 a-1 over the 9 years. This sink strength was offset by carbon export from the field mainly as grass offtake for silage (48.9 g C m-2 a-1) and leaching (16.4 g C m-2 a-1). The other export terms, CH4 emissions from the soil, manure applications and enteric fermentation, were negligible and only contributed to 0.02-4.2 % of the total C losses. Only a small fraction of C was incorporated into the body of the grazing animals. Inclusion of these C losses in the budget resulted in a C sink strength of 163 ± 140 g C m-2 a-1. By contrast, soil stock measurements taken in May 2004 and May 2011 indicated that the grassland sequestered N in the 0-60 cm soil layer at 4.51 ± 2.64 g N m-2 a-1 and lost C at a rate of 29.08 ± 38.19 g C m-2 a-1. Potential reasons for the discrepancy between these estimates are probably an underestimation of C losses, especially from leaching fluxes as well as from animal respiration. The average greenhouse gas (GHG) balance of the grassland was -366 ± 601 g CO2 eq. m-2 yr-1 and was strongly affected by CH4 and N2O emissions. The GHG sink strength of the NEE was reduced by 54 % by CH4 and N2O emissions. Estimated enteric fermentation from ruminating sheep proved to be an important CH4 source, exceeding the contribution of N2O to the GHG budget in some years.

CH4 emissions from two floodplain fens of differing nutrient status

NASA Astrophysics Data System (ADS)

Stanley, Kieran; Heppell, Catherine; Belyea, Lisa; Baird, Andrew

2014-05-01

Floodplain fens emit large amounts of CH4 in comparison with ombrotrophic bogs. Little is known about the effect of fluvial nitrogen (N) and phosphorus (P) on CH4 dynamics in fens, although N and P affect carbon (C) dynamics indirectly in other environments by controlling plant growth and root exudate release, as well as by altering microbial biomass and decomposition rates. This study aimed to compare CH4 emissions from two floodplain fen sites which differ in nutrient status, Sutton Fen (52°45'N 001°30'E) and Strumpshaw Fen (52°36'N 001°27'E), in the Norfolk Broadland of England. Sutton and Strumpshaw Fen are under conservation management and both sites have water levels that vary within a few decimetres above and below the surface. The sites are dominated by reed (Phragmites australis). Areas within the fens where the reed was cut in 2009 were chosen for this study. Average plant height and mean aboveground biomass were significantly greater at Strumpshaw (107.2 ± 7.8 cm and 1578 ± 169 g m-2, respectively) than Sutton (56.5 ± 5.1 cm and 435 ± 42 g m-2) as were mean foliar N and P contents (21.8 ± 1.5 g kg-1 and 2.0 ± 0.2 g kg-1 at Strumpshaw, versus 16.3 ± 1.5 g kg-1 and 1.1 ± 0.1 g kg-1 at Sutton). Foliar NPK ratios showed Strumpshaw to be N limited, whereas Sutton was both N and P limited, depending on microsite. Surface peat N and P contents were also greater at Strumpshaw (28.3 ± 0.35 g kg-1 and 0.78 ± 0.02 g kg-1, respectively) than Sutton (18.32 ± 0.87 g kg-1 and 0.43 ± 0.1 g kg-1). These results indicate clear differences in nutrient status between the two sites despite their geographical proximity and other similarities. CH4 emissions were monitored monthly between 19th June 2012 and 2nd September 2013 using tall static chambers and glass funnel-traps, the latter for ebullition. Steady fluxes did not follow a clear seasonal pattern; however, emission was greatest in the summer months. Strumpshaw had a greater range in efflux (0.25 to 134.2 mg CH4 m-2 h-1) than Sutton (0.17 to 29.82 mg CH4 m-2 h-1). Ebullition was generally greater at Sutton throughout the study period, with rates ranging from 0 to 62.09 mg CH4 m-2 h-1 and 0 to 19.30 mg CH4 m-2 h-1 for Sutton and Strumpshaw, respectively. Fluxes were generally within the range of values reported in the literature for ebullition (0 to 466 mg CH4 m-2 h-1) and steady fluxes (0 to 76.83 mg CH4 m-2 h-1). Results show the importance of floodplain fens for CH4 emission, and more research needs to be undertaken to fully understand the factors controlling CH4 fluxes from these systems.

Animal board invited review: genetic possibilities to reduce enteric methane emissions from ruminants.

PubMed

Pickering, N K; Oddy, V H; Basarab, J; Cammack, K; Hayes, B; Hegarty, R S; Lassen, J; McEwan, J C; Miller, S; Pinares-Patiño, C S; de Haas, Y

2015-09-01

Measuring and mitigating methane (CH4) emissions from livestock is of increasing importance for the environment and for policy making. Potentially, the most sustainable way of reducing enteric CH4 emission from ruminants is through the estimation of genomic breeding values to facilitate genetic selection. There is potential for adopting genetic selection and in the future genomic selection, for reduced CH4 emissions from ruminants. From this review it has been observed that both CH4 emissions and production (g/day) are a heritable and repeatable trait. CH4 emissions are strongly related to feed intake both in the short term (minutes to several hours) and over the medium term (days). When measured over the medium term, CH4 yield (MY, g CH4/kg dry matter intake) is a heritable and repeatable trait albeit with less genetic variation than for CH4 emissions. CH4 emissions of individual animals are moderately repeatable across diets, and across feeding levels, when measured in respiration chambers. Repeatability is lower when short term measurements are used, possibly due to variation in time and amount of feed ingested prior to the measurement. However, while repeated measurements add value; it is preferable the measures be separated by at least 3 to 14 days. This temporal separation of measurements needs to be investigated further. Given the above issue can be resolved, short term (over minutes to hours) measurements of CH4 emissions show promise, especially on systems where animals are fed ad libitum and frequency of meals is high. However, we believe that for short-term measurements to be useful for genetic evaluation, a number (between 3 and 20) of measurements will be required over an extended period of time (weeks to months). There are opportunities for using short-term measurements in standardised feeding situations such as breath 'sniffers' attached to milking parlours or total mixed ration feeding bins, to measure CH4. Genomic selection has the potential to reduce both CH4 emissions and MY, but measurements on thousands of individuals will be required. This includes the need for combined resources across countries in an international effort, emphasising the need to acknowledge the impact of animal and production systems on measurement of the CH4 trait during design of experiments.

Quantification of Methane and Ethane Emissions from the San Juan Basin

NASA Astrophysics Data System (ADS)

Smith, M. L.; Kort, E. A.; Karion, A.; Sweeney, C.; Gvakharia, A.

2015-12-01

Methane (CH4), a potent greenhouse gas, and the primary component of natural gas, is emitted from areas of high fossil fuel production and processing. Recently, persistent and large methane emissions (~0.59 Tg yr-1) from the four corners area of the United States have been identified using satellite (SCIAMACHY) observations taken over the years 2003 to 2009. These emissions appear to be the largest CH4 anomaly (positive deviation above background values) in the contiguous U.S., and exceed bottom-up inventory estimates for the area by 1.8 to 3.5 times. The majority of emissions sources expected to contribute to this anomalous CH4 signal are located in the San Juan basin of New Mexico, and include harvesting and processing of natural gas, coal, and coalbed CH4. The magnitude of CH4 emissions from the San Juan basin have not yet been directly quantified using airborne measurements. Additionally, changing fossil fuel-related activities in the basin may have altered the magnitude of CH4 emissions compared to estimates derived from 2003-2009 satellite measurements. Here, we present in-situ airborne observations of CH4 over the San Juan basin, which allow tight quantification of CH4 fluxes using the mass balance method. Observations over the basin were taken for multiple wind directions on multiple days in April, 2015 to obtain a robust estimate of CH4 emissions. The flux of ethane (C2H6), the second most abundant component of natural gas and a tracer species indicative of fossil-derived CH4, was also quantified. Substantial C2H6 emissions may affect regional air quality and chemistry through its influence on tropospheric ozone production.

Seasonal dynamics in methane emissions from the Amazon River floodplain to the troposphere

NASA Technical Reports Server (NTRS)

Devol, Allan H.; Richey, Jeffrey E.; Forsberg, Bruce R.; Martinelli, Luiz A.

1990-01-01

Methane fluxes to the troposphere from the three principal habitats of the floodplain of the Amazon River main stem (open waters, emergent macrophyte beds, and flooded forests) were determined along a 1700-km reach of the river during the low-water period of the annual flood cycle (November-December 1988). Overall, emissions averaged 68 mg CH4/sq m per day and were significantly lower than similar emissions determined previously for the high-water period, 184 mg CH4/sq m per day (July-August 1986). This difference was due to significantly lower emissions from floating macrophyte environments. Low-water emissions from open waters and flooded forest areas were not significantly different than at high water. A monthly time series of methane emission from eight lakes located in the central Amazon basis showed similar results. The data were used to calculate a seasonally weighted annual emission to the troposphere from the Amazon River main stem floodplain of 5.1 Tg/yr, which indicates the importance of the area in global atmospheric chemistry.

Comparison of methods to determine methane emissions from dairy cows in farm conditions.

PubMed

Huhtanen, P; Cabezas-Garcia, E H; Utsumi, S; Zimmerman, S

2015-05-01

Nutritional and animal-selection strategies to mitigate enteric methane (CH4) depend on accurate, cost-effective methods to determine emissions from a large number of animals. The objective of the present study was to compare 2 spot-sampling methods to determine CH4 emissions from dairy cows, using gas quantification equipment installed in concentrate feeders or automatic milking stalls. In the first method (sniffer method), CH4 and carbon dioxide (CO2) concentrations were measured in close proximity to the muzzle of the animal, and average CH4 concentrations or CH4/CO2 ratio was calculated. In the second method (flux method), measurement of CH4 and CO2 concentration was combined with an active airflow inside the feed troughs for capture of emitted gas and measurements of CH4 and CO2 fluxes. A muzzle sensor was used allowing data to be filtered when the muzzle was not near the sampling inlet. In a laboratory study, a model cow head was built that emitted CO2 at a constant rate. It was found that CO2 concentrations using the sniffer method decreased up to 39% when the distance of the muzzle from the sampling inlet increased to 30cm, but no muzzle-position effects were observed for the flux method. The methods were compared in 2 on-farm studies conducted using 32 (experiment 1) or 59 (experiment 2) cows in a switch-back design of 5 (experiment 1) or 4 (experiment 2) periods for replicated comparisons between methods. Between-cow coefficient of variation (CV) in CH4 was smaller for the flux than the sniffer method (experiment 1, CV=11.0 vs. 17.5%, and experiment 2, 17.6 vs. 28.0%). Repeatability of the measurements from both methods were high (0.72-0.88), but the relationship between the sniffer and flux methods was weak (R(2)=0.09 in both experiments). With the flux method CH4 was found to be correlated to dry matter intake or body weight, but this was not the case with the sniffer method. The CH4/CO2 ratio was more highly correlated between the flux and sniffer methods (R(2)=0.30), and CV was similar (6.4-8.8%). In experiment 2, cow muzzle position was highly repeatable (0.82) and influenced sniffer and flux method results when not filtered for muzzle position. It was concluded that the flux method provides more reliable estimates of CH4 emissions than the sniffer method. The sniffer method appears to be affected by variable air-mixing conditions created by geometry of feed trough, muzzle movement, and muzzle position. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Assessing environmental impacts of organic and inorganic fertilizer on daily and seasonal Greenhouse Gases effluxes in rice field

NASA Astrophysics Data System (ADS)

Yuan, Jing; Sha, Zhi-min; Hassani, Danial; Zhao, Zheng; Cao, Lin-kui

2017-04-01

According to the 5th Intergovernmental Panel on Climate Change evaluation report, the average surface temperature of the earth has escalated from 0.69 °C (1901) to 1.08 °C (2012), which is primarily ascribed to the anthropogenic emissions of Greenhouse Gases (GHGs). For the current study, a field experiment with four treatments, including chemical fertilizer, mixed fertilizer (MT), organic fertilizer (OT) and control (CK) was carried out in the Station of Long-term Fertilization Qingpu, Shanghai. The probable impact of fertilization on the average daily and accumulative emissions of GHGs were examined during different growth stages. The results indicated that fertilizer treatments considerably affected emissions of CH4, N2O and CO2. CH4 emitted most in OT, followed by MT, CT and CK, with the emissions of 77.29, 41.64, 30.20 and 17.37 kg ha-1, respectively. As for N2O emissions, there were no significant variations between CT (1.18 kg ha-1) and MT (1.05 kg ha-1), which were both higher than OT (0.66 kg ha-1) and CK (0.23 kg ha-1). CO2 emissions in CT (34 371 kg ha-1) came first, followed by MT (28 929 kg ha-1), OT (19 118 kg ha-1) and CK (11 533 kg ha-1), independently. Soil nutrients or fertility (humid acid, carbon, nitrogen, phosphorus, potassium and C: N) may perhaps speed up CH4 emissions, whilst drainage implicated could alleviate its production. Furthermore, applying substantial organic fertilizer at once might accelerate sudden and huge release of N2O. In addition, despite the inconsistencies among different years observed, the trend that organic fertilizer made the biggest amount of contribution to warming potential was alike. Consequently, the utilization of organic fertilizer should be mitigated, by applying some other inorganic fertilizers.

Methane Feedbacks to the Global Climate System in a Warmer World

NASA Astrophysics Data System (ADS)

Dean, Joshua F.; Middelburg, Jack J.; Röckmann, Thomas; Aerts, Rien; Blauw, Luke G.; Egger, Matthias; Jetten, Mike S. M.; de Jong, Anniek E. E.; Meisel, Ove H.; Rasigraf, Olivia; Slomp, Caroline P.; in't Zandt, Michiel H.; Dolman, A. J.

2018-03-01

Methane (CH4) is produced in many natural systems that are vulnerable to change under a warming climate, yet current CH4 budgets, as well as future shifts in CH4 emissions, have high uncertainties. Climate change has the potential to increase CH4 emissions from critical systems such as wetlands, marine and freshwater systems, permafrost, and methane hydrates, through shifts in temperature, hydrology, vegetation, landscape disturbance, and sea level rise. Increased CH4 emissions from these systems would in turn induce further climate change, resulting in a positive climate feedback. Here we synthesize biological, geochemical, and physically focused CH4 climate feedback literature, bringing together the key findings of these disciplines. We discuss environment-specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate, and present the current state of knowledge of CH4 climate feedbacks in the immediate and distant future. The important linkages between microbial activity and climate warming are discussed with the aim to better constrain the sensitivity of the CH4 cycle to future climate predictions. We determine that wetlands will form the majority of the CH4 climate feedback up to 2100. Beyond this timescale, CH4 emissions from marine and freshwater systems and permafrost environments could become more important. Significant CH4 emissions to the atmosphere from the dissociation of methane hydrates are not expected in the near future. Our key findings highlight the importance of quantifying whether CH4 consumption can counterbalance CH4 production under future climate scenarios.

Methane and Environmental Change during the Paleocene-Eocene Thermal Maximum (PETM): Modeling the PETM Onset as a Two-stage Event

NASA Technical Reports Server (NTRS)

Carozza, David A.; Mysak, Lawrence A.; Schmidt, Gavin A.

2011-01-01

An atmospheric CH4 box model coupled to a global carbon cycle box model is used to constrain the carbon emission associated with the PETM and assess the role of CH4 during this event. A range of atmospheric and oceanic emission scenarios representing different amounts, rates, and isotopic signatures of emitted carbon are used to model the PETM onset. The first 3 kyr of the onset, a pre-isotope excursion stage, is simulated by the atmospheric release of 900 to 1100 Pg C CH4 with a delta C-13 of -22 to - 30 %. For a global average warming of 3 deg C, a release of CO2 to the ocean and CH4 to the atmosphere totalling 900 to 1400 Pg C, with a delta C-13 of -50 to -60%, simulates the subsequent 1 -kyr isotope excursion stage. To explain the observations, the carbon must have been released over at most 500 years. The first stage results cannot be associated with any known PETM hypothesis. However, the second stage results are consistent with a methane hydrate source. More than a single source of carbon is required to explain the PETM onset.

Methane Emissions from Conventional and Unconventional Natural Gas Production Sites in the Marcellus Shale Basin.

PubMed

Omara, Mark; Sullivan, Melissa R; Li, Xiang; Subramanian, R; Robinson, Allen L; Presto, Albert A

2016-02-16

There is a need for continued assessment of methane (CH4) emissions associated with natural gas (NG) production, especially as recent advancements in horizontal drilling combined with staged hydraulic fracturing technologies have dramatically increased NG production (we refer to these wells as "unconventional" NG wells). In this study, we measured facility-level CH4 emissions rates from the NG production sector in the Marcellus region, and compared CH4 emissions between unconventional NG (UNG) well pad sites and the relatively smaller and older "conventional" NG (CvNG) sites that consist of wells drilled vertically into permeable geologic formations. A top-down tracer-flux CH4 measurement approach utilizing mobile downwind intercepts of CH4, ethane, and tracer (nitrous oxide and acetylene) plumes was performed at 18 CvNG sites (19 individual wells) and 17 UNG sites (88 individual wells). The 17 UNG sites included four sites undergoing completion flowback (FB). The mean facility-level CH4 emission rate among UNG well pad sites in routine production (18.8 kg/h (95% confidence interval (CI) on the mean of 12.0-26.8 kg/h)) was 23 times greater than the mean CH4 emissions from CvNG sites. These differences were attributed, in part, to the large size (based on number of wells and ancillary NG production equipment) and the significantly higher production rate of UNG sites. However, CvNG sites generally had much higher production-normalized CH4 emission rates (median: 11%; range: 0.35-91%) compared to UNG sites (median: 0.13%, range: 0.01-1.2%), likely resulting from a greater prevalence of avoidable process operating conditions (e.g., unresolved equipment maintenance issues). At the regional scale, we estimate that total annual CH4 emissions from 88 500 combined CvNG well pads in Pennsylvania and West Virginia (660 Gg (95% CI: 500 to 800 Gg)) exceeded that from 3390 UNG well pads by 170 Gg, reflecting the large number of CvNG wells and the comparably large fraction of CH4 lost per unit production. The new emissions data suggest that the recently instituted Pennsylvania CH4 emissions inventory substantially underestimates measured facility-level CH4 emissions by >10-40 times for five UNG sites in this study.

Alternate wetting and drying practice for reducing greenhouse gas emissions in flooded rice agroecosystems

NASA Astrophysics Data System (ADS)

Adviento-Borbe, A.; Anders, M. M.; Runkle, B.; Reba, M. L.; Suvocarev, K.; Massey, J. H.; Linquist, B.

2017-12-01

Alternate wetting and drying management (AWD) practices which minimize flooding times have been shown to reduce both CH4 emissions and water use but effects on N2O emissions and grain yields are variable. Grain yield and seasonal CH4 and N2O emissions were measured from AWD treatments with various soil water thresholds and conventionally flooded water treatment in two commercial farms in Arkansas and in an experimental field in Biggs, CA during 2015 and 2016 crop seasons. Methane and N2O emissions were measured using vented flux chamber and gas chromatography methods. Grain yields ( 10 Mg ha-1) were similar in AWD and conventional water treatments. Total CH4 emissions ranged from 21 to 338 kg CH4-C ha-1 season-1. The AWD practice reduced growing season CH4 emissions by 44-73% while N2O emissions remained low and represented only <2% of the total seasonal global warming potential in all treatments. The long aerobic periods and proper implementation of AWD drain events showed greatest CH4 reduction. However, N2O emissions can increase if soil inorganic N levels are potentially high prior to initiating the dry cycle. Our results showed that AWD can reduce CH4 and N2O emissions while maintaining optimal grain yields. However, adoption of AWD to mitigate greenhouse gas emissions (GHG) in commercial farms requires proper implementation of AWD to avoid risk of yield loss and high GHG emissions.

Quantifying sources of methane and light alkanes in the Los Angeles Basin, California

NASA Astrophysics Data System (ADS)

Peischl, Jeff; Ryerson, Thomas; Atlas, Elliot; Blake, Donald; Brioude, Jerome; Daube, Bruce; de Gouw, Joost; Frost, Gregory; Gentner, Drew; Gilman, Jessica; Goldstein, Allen; Harley, Robert; Holloway, John; Kuster, William; Santoni, Gregory; Trainer, Michael; Wofsy, Steven; Parrish, David

2013-04-01

We use ambient measurements to apportion the relative contributions of different source sectors to the methane (CH4) emissions budget of a U.S. megacity. This approach uses ambient measurements of methane and C2-C5 alkanes (ethane through pentanes) and includes source composition information to distinguish between methane emitted from landfills and feedlots, wastewater treatment plants, tailpipe emissions, leaks of dry natural gas in pipelines and/or local seeps, and leaks of locally produced (unprocessed) natural gas. Source composition information can be taken from existing tabulations or developed by direct sampling of emissions using a mobile platform. By including C2-C5 alkane information, a linear combination of these source signatures can be found to match the observed atmospheric enhancement ratios to determine relative emissions strengths. We apply this technique to apportion CH4 emissions in Los Angeles, CA (L.A.) using data from the CalNex field project in 2010. Our analysis of L.A. atmospheric data shows the two largest CH4 sources in the city are emissions of gas from pipelines and/or from geologic seeps (47%), and emissions from landfills (40%). Local oil and gas production is a relatively minor source of CH4, contributing 8% of total CH4 emissions in L.A. Absolute CH4 emissions rates are derived by multiplying the observed CH4/CO enhancement ratio by State of California inventory values for carbon monoxide (CO) emissions in Los Angeles. Apportioning this total suggests that emissions from the combined natural and anthropogenic gas sources account for the differences between top-down and bottom-up CH4 estimates previously published for Los Angeles. Further, total CH4 emission attributed in our analysis to local gas extraction represents 17% of local production. While a derived leak rate of 17% of local production may seem unrealistically high, it is qualitatively consistent with the 12% reported in a recent state inventory survey of the L.A. oil and gas industry.

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to physicochemical limnology and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included Direct Ebullition, Diffusion, Storage flux, and a newly identified Ice-Bubble Storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, but themore » climate warming impact of lake CH 4 emissions was two times higher than that of CO 2. Ebullition and Diffusion were the dominant modes of CH 4 and CO 2 emissions respectively. IBS, ~ 10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, dystrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. Total CH 4 emission was correlated with concentrations of phosphate and total nitrogen in lake water, Secchi depth and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. Our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE PAGES

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.; ...

2014-09-12

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to physicochemical limnology and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included Direct Ebullition, Diffusion, Storage flux, and a newly identified Ice-Bubble Storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, but themore » climate warming impact of lake CH 4 emissions was two times higher than that of CO 2. Ebullition and Diffusion were the dominant modes of CH 4 and CO 2 emissions respectively. IBS, ~ 10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, dystrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. Total CH 4 emission was correlated with concentrations of phosphate and total nitrogen in lake water, Secchi depth and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. Our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

Control of dissolved CH4 in a municipal UASB reactor effluent by means of a desorption - Biofiltration arrangement.

PubMed

Huete, A; de Los Cobos-Vasconcelos, D; Gómez-Borraz, T; Morgan-Sagastume, J M; Noyola, A

2018-06-15

The direct anaerobic treatment of municipal wastewater represents an adapted technology to the conditions of developing countries. In order to get an increased acceptance of this technology, a proper control of dissolved methane in the anaerobic effluents should be considered, as methane is a potent greenhouse gas. In this study, a pilot-scale system was operated for 168 days to recover dissolved methane from an effluent of an upflow anaerobic sludge blanket reactor and then oxidize it in a compost biofilter. The system operated at a constant air (0.9 m 3 /h ±0.09) and two air-to anaerobic effluent ratio (1:1 and 1:2). In both conditions (CH 4 concentration of 2.7 ± 0.87 and 4.3% ± 1.14, respectively) the desorption column recovered 99% of the dissolved CH 4 and approximately 30% ± 8.5 of H 2 S, whose desorption was limited due to the high pH (>8) of the effluent. The biofilter removed 70% ± 8 of the average CH 4 load (60 gCH 4 /m 3 h ± 13) and 100% of the H 2 S load at an empty bed retention time of 23 min. The average temperature inside the biofilter was 42 ± 9 °C due to the CH 4 oxidation reaction, indicating that temperature and moisture control is particularly important for CH 4 removal in compost biofilters. The system may achieve a 54% reduction of greenhouse gas emissions from dissolved CH 4 in this particular case. Copyright © 2017 Elsevier Ltd. All rights reserved.

Emission of methane, carbon monoxide, carbon dioxide and short‐chain hydrocarbons from vegetation foliage under ultraviolet irradiation

PubMed Central

FRASER, WESLEY T.; BLEI, EMANUEL; FRY, STEPHEN C.; NEWMAN, MARK F.; REAY, DAVID S.; SMITH, KEITH A.

2015-01-01

Abstract The original report that plants emit methane (CH 4) under aerobic conditions caused much debate and controversy. Critics questioned experimental techniques, possible mechanisms for CH 4 production and the nature of estimating global emissions. Several studies have now confirmed that aerobic CH 4 emissions can be detected from plant foliage but the extent of the phenomenon in plants and the precise mechanisms and precursors involved remain uncertain. In this study, we investigated the role of environmentally realistic levels of ultraviolet (UV) radiation in causing the emission of CH 4 and other gases from foliage obtained from a wide variety of plant types. We related our measured emissions to the foliar content of methyl esters and lignin and to the epidermal UV absorbance of the species investigated. Our data demonstrate that the terrestrial vegetation foliage sampled did emit CH 4, with a range in emissions of 0.6–31.8 ng CH 4 g−1 leaf DW h−1, which compares favourably with the original reports of experimental work. In addition to CH 4 emissions, our data show that carbon monoxide, ethene and propane are also emitted under UV stress but we detected no significant emissions of carbon dioxide or ethane. PMID:25443986

Windrow composting mitigated CH4 emissions: characterization of methanogenic and methanotrophic communities in manure management.

PubMed

Chen, Ruirui; Wang, Yiming; Wei, Shiping; Wang, Wei; Lin, Xiangui

2014-12-01

With increasing livestock breeding, methane (CH4 ) emissions from manure management will increasingly contribute more to atmospheric CH4 concentration. The dynamics of methanogens and methanotrophs have not yet been studied in the manure environment. The current study combines surface CH4 emissions with methanogenic and methanotrophic community analyses from two management practices, windrow composting (WCOM) and solid storage (SSTO). Our results showed that there was an c. 50% reduction of CH4 emissions with WCOM compared with SSTO over a 50-day period. A sharp decrease in the quantities of both methanogens and methanotrophs in WCOM suggested that CH4 mitigation was mainly due to decreased CH4 production rather than increased CH4 oxidation. Pyrosequencing analysis demonstrated that aeration caused a clear shift of dominant methanogens in the manure, with specifically a significant decrease in Methanosarcina and increase in Methanobrevibacter. The composition of methanogenic community was influenced by manure management and regulated CH4 production. A sharp increase in the quantity of methanotrophs in SSTO suggested that microbial CH4 oxidation is an important sink for the CH4 produced. The increased abundance of Methylococcaceae in SSTO suggested that Type I methanotrophs have an advantage in CH4 oxidation in occupying niches under low CH4 and high O2 conditions. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Boreal forest fire emissions in fresh Canadian smoke plumes: C1-C10 volatile organic compounds (VOCs), CO2, CO, NO2, NO, HCN and CH3CN

NASA Astrophysics Data System (ADS)

Simpson, I. J.; Akagi, S. K.; Barletta, B.; Blake, N. J.; Choi, Y.; Diskin, G. S.; Fried, A.; Fuelberg, H. E.; Meinardi, S.; Rowland, F. S.; Vay, S. A.; Weinheimer, A. J.; Wennberg, P. O.; Wiebring, P.; Wisthaler, A.; Yang, M.; Yokelson, R. J.; Blake, D. R.

2011-03-01

Boreal regions comprise about 17% of the global land area, and they both affect and are influenced by climate change. To better understand boreal forest fire emissions and plume evolution, 947 whole air samples were collected aboard the NASA DC-8 research aircraft in summer 2008 as part of the ARCTAS-B field mission, and analyzed for 79 non-methane volatile organic compounds (NMVOCs) using gas chromatography. Together with simultaneous measurements of CO2, CO, CH4, CH2O, NO2, NO, HCN and CH3CN, these measurements represent the most comprehensive assessment of trace gas emissions from boreal forest fires to date. Based on 105 air samples collected in fresh Canadian smoke plumes, 57 of the 80 measured NMVOCs (including CH2O) were emitted from the fires, including 45 species that were quantified from boreal forest fires for the first time. After CO2, CO and CH4, the largest emission factors (EFs) for individual species were formaldehyde (2.1 ± 0.2 g kg-1), followed by methanol, NO2, HCN, ethene, α-pinene, β-pinene, ethane, benzene, propene, acetone and CH3CN. Globally, we estimate that boreal forest fires release 2.4 ± 0.6 Tg C yr-1 in the form of NMVOCs, with approximately 41% of the carbon released as C1-C2 NMVOCs and 21% as pinenes. These are the first reported field measurements of monoterpene emissions from boreal forest fires, and we speculate that the pinenes, which are relatively heavy molecules, were detected in the fire plumes as the result of distillation of stored terpenes as the vegetation is heated. Their inclusion in smoke chemistry models is expected to improve model predictions of secondary organic aerosol (SOA) formation. The fire-averaged EF of dichloromethane or CH2Cl2, (6.9 ± 8.6) ×10-4 g kg-1, was not significantly different from zero and supports recent findings that its global biomass burning source appears to have been overestimated. Similarly, we found no evidence for emissions of chloroform (CHCl3) or methyl chloroform (CH3CCl3) from boreal forest fires. The speciated hydrocarbon measurements presented here show the importance of carbon released by short-chain NMVOCs, the strong contribution of pinene emissions from boreal forest fires, and the wide range of compound classes in the most abundantly emitted NMVOCs, all of which can be used to improve biomass burning inventories in local/global models and reduce uncertainties in model estimates of trace gas emissions and their impact on the atmosphere.

Boreal forest fire emissions in fresh Canadian smoke plumes: C1-C10 volatile organic compounds (VOCs), CO2, CO, NO2, NO, HCN and CH3CN

NASA Astrophysics Data System (ADS)

Simpson, I. J.; Akagi, S. K.; Barletta, B.; Blake, N. J.; Choi, Y.; Diskin, G. S.; Fried, A.; Fuelberg, H. E.; Meinardi, S.; Rowland, F. S.; Vay, S. A.; Weinheimer, A. J.; Wennberg, P. O.; Wiebring, P.; Wisthaler, A.; Yang, M.; Yokelson, R. J.; Blake, D. R.

2011-07-01

Boreal regions comprise about 17 % of the global land area, and they both affect and are influenced by climate change. To better understand boreal forest fire emissions and plume evolution, 947 whole air samples were collected aboard the NASA DC-8 research aircraft in summer 2008 as part of the ARCTAS-B field mission, and analyzed for 79 non-methane volatile organic compounds (NMVOCs) using gas chromatography. Together with simultaneous measurements of CO2, CO, CH4, CH2O, NO2, NO, HCN and CH3CN, these measurements represent the most comprehensive assessment of trace gas emissions from boreal forest fires to date. Based on 105 air samples collected in fresh Canadian smoke plumes, 57 of the 80 measured NMVOCs (including CH2O) were emitted from the fires, including 45 species that were quantified from boreal forest fires for the first time. After CO2, CO and CH4, the largest emission factors (EFs) for individual species were formaldehyde (2.1 ± 0.2 g kg-1), followed by methanol, NO2, HCN, ethene, α-pinene, β-pinene, ethane, benzene, propene, acetone and CH3CN. Globally, we estimate that boreal forest fires release 2.4 ± 0.6 Tg C yr-1 in the form of NMVOCs, with approximately 41 % of the carbon released as C1-C2 NMVOCs and 21 % as pinenes. These are the first reported field measurements of monoterpene emissions from boreal forest fires, and we speculate that the pinenes, which are relatively heavy molecules, were detected in the fire plumes as the result of distillation of stored terpenes as the vegetation is heated. Their inclusion in smoke chemistry models is expected to improve model predictions of secondary organic aerosol (SOA) formation. The fire-averaged EF of dichloromethane or CH2Cl2, (6.9 ± 8.6) × 10-4 g kg-1, was not significantly different from zero and supports recent findings that its global biomass burning source appears to have been overestimated. Similarly, we found no evidence for emissions of chloroform (CHCl3) or methyl chloroform (CH3CCl3) from boreal forest fires. The speciated hydrocarbon measurements presented here show the importance of carbon released by short-chain NMVOCs, the strong contribution of pinene emissions from boreal forest fires, and the wide range of compound classes in the most abundantly emitted NMVOCs, all of which can be used to improve biomass burning inventories in local/global models and reduce uncertainties in model estimates of trace gas emissions and their impact on the atmosphere.

Measurement and prediction of enteric methane emission

NASA Astrophysics Data System (ADS)

Sejian, Veerasamy; Lal, Rattan; Lakritz, Jeffrey; Ezeji, Thaddeus

2011-01-01

The greenhouse gas (GHG) emissions from the agricultural sector account for about 25.5% of total global anthropogenic emission. While CO2 receives the most attention as a factor relative to global warming, CH4, N2O and chlorofluorocarbons (CFCs) also cause significant radiative forcing. With the relative global warming potential of 25 compared with CO2, CH4 is one of the most important GHGs. This article reviews the prediction models, estimation methodology and strategies for reducing enteric CH4 emissions. Emission of CH4 in ruminants differs among developed and developing countries, depending on factors like animal species, breed, pH of rumen fluid, ratio of acetate:propionate, methanogen population, composition of diet and amount of concentrate fed. Among the ruminant animals, cattle contribute the most towards the greenhouse effect through methane emission followed by sheep, goats and buffalos, respectively. The estimated CH4 emission rate per cattle, buffaloe, sheep and goat in developed countries are 150.7, 137, 21.9 and 13.7 (g/animal/day) respectively. However, the estimated rates in developing countries are significantly lower at 95.9 and 13.7 (g/animal/day) per cattle and sheep, respectively. There exists a strong interest in developing new and improving the existing CH4 prediction models to identify mitigation strategies for reducing the overall CH4 emissions. A synthesis of the available literature suggests that the mechanistic models are superior to empirical models in accurately predicting the CH4 emission from dairy farms. The latest development in prediction model is the integrated farm system model which is a process-based whole-farm simulation technique. Several techniques are used to quantify enteric CH4 emissions starting from whole animal chambers to sulfur hexafluoride (SF6) tracer techniques. The latest technology developed to estimate CH4 more accurately is the micrometeorological mass difference technique. Because the conditions under which animals are managed vary greatly by country, CH4 emissions reduction strategies must be tailored to country-specific circumstances. Strategies that are cost effective, improve productivity, and have limited potential negative effects on livestock production hold a greater chance of being adopted by producers. It is also important to evaluate CH4 mitigation strategies in terms of the total GHG budget and to consider the economics of various strategies. Although reductions in GHG emissions from livestock industries are seen as high priorities, strategies for reducing emissions should not reduce the economic viability of enterprises.

Sources and sinks of methane in the African Savanna. CH4 emissions from biomass burning

NASA Astrophysics Data System (ADS)

Delmas, R. A.; Marenco, A.; Tathy, J. P.; Cros, B.; Baudet, J. G. R.

1991-04-01

Sources and sinks of atmospheric methane are studied in savanna regions of west and central Africa. Flux measured over dry savanna soils, using static chambers, is always negative the average uptake rate being 2×1010 molecules/cm2/s. In these regions, sources are linked to biomass burning. Methane and CO2 emission from combustion of savanna plants and wood is studied by both field experiments and laboratory experiments using a combustion chamber. For savanna plants most of the carbon (85%) contained in the biomaterial is volatilized as CO2 and 0.1 to 0.25% as methane. For graminaceous plants like loudetia simplex the ratio C-CH4/C-CO2 is 0.11%; it is 0.28% for hyparrhenia the other main type of savanna plants and it attains 1.4% for the combustion of wood. In natural fire plumes this ratio is around 0.26% for savanna fires and 0.56 to 2.22% for forest fires. These results show that methane release is highly dependent on the type of combustion. Methane to CO2 ratios are also studied in vertical profiles in the troposphere taken during the TROPOZ I campaign, an aerial research expedition carried out over west Africa during the bushfire period. Within polluted layers, the average ratio of CH4 to CO2 excess over ambient air concentration is 0.34%. These results show that biomass burning in tropical Africa constitutes an important source of atmospheric methane estimated to about 9.2×106 T(CH4)/yr.

HIMMELI v1.0: HelsinkI Model of MEthane buiLd-up and emIssion for peatlands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raivonen, Maarit; Smolander, Sampo; Backman, Leif

Wetlands are one of the most significant natural sources of methane (CH 4) to the atmosphere. They emit CH 4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH 4, in addition to carbon dioxide (CO 2). Production of CH 4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH 4 emissions are thus needed for upscaling observations to estimate present CH 4 emissions and for producing scenarios of future atmospheric CH 4 concentrations. Aiming at a CH 4 model that can bemore » added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH 4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH 4, CO 2, and oxygen (O 2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH 4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH 4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH 4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH 4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O 2 concentrations that affect the CH 4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH 4 emissions in this model version.« less

HIMMELI v1.0: HelsinkI Model of MEthane buiLd-up and emIssion for peatlands

NASA Astrophysics Data System (ADS)

Raivonen, Maarit; Smolander, Sampo; Backman, Leif; Susiluoto, Jouni; Aalto, Tuula; Markkanen, Tiina; Mäkelä, Jarmo; Rinne, Janne; Peltola, Olli; Aurela, Mika; Lohila, Annalea; Tomasic, Marin; Li, Xuefei; Larmola, Tuula; Juutinen, Sari; Tuittila, Eeva-Stiina; Heimann, Martin; Sevanto, Sanna; Kleinen, Thomas; Brovkin, Victor; Vesala, Timo

2017-12-01

Wetlands are one of the most significant natural sources of methane (CH4) to the atmosphere. They emit CH4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH4, in addition to carbon dioxide (CO2). Production of CH4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH4 emissions are thus needed for upscaling observations to estimate present CH4 emissions and for producing scenarios of future atmospheric CH4 concentrations. Aiming at a CH4 model that can be added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH4, CO2, and oxygen (O2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O2 concentrations that affect the CH4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH4 emissions in this model version.

HIMMELI v1.0: HelsinkI Model of MEthane buiLd-up and emIssion for peatlands

DOE PAGES

Raivonen, Maarit; Smolander, Sampo; Backman, Leif; ...

2017-12-22

Wetlands are one of the most significant natural sources of methane (CH 4) to the atmosphere. They emit CH 4 because decomposition of soil organic matter in waterlogged anoxic conditions produces CH 4, in addition to carbon dioxide (CO 2). Production of CH 4 and how much of it escapes to the atmosphere depend on a multitude of environmental drivers. Models simulating the processes leading to CH 4 emissions are thus needed for upscaling observations to estimate present CH 4 emissions and for producing scenarios of future atmospheric CH 4 concentrations. Aiming at a CH 4 model that can bemore » added to models describing peatland carbon cycling, we composed a model called HIMMELI that describes CH 4 build-up in and emissions from peatland soils. It is not a full peatland carbon cycle model but it requires the rate of anoxic soil respiration as input. Driven by soil temperature, leaf area index (LAI) of aerenchymatous peatland vegetation, and water table depth (WTD), it simulates the concentrations and transport of CH 4, CO 2, and oxygen (O 2) in a layered one-dimensional peat column. Here, we present the HIMMELI model structure and results of tests on the model sensitivity to the input data and to the description of the peat column (peat depth and layer thickness), and demonstrate that HIMMELI outputs realistic fluxes by comparing modeled and measured fluxes at two peatland sites. As HIMMELI describes only the CH 4-related processes, not the full carbon cycle, our analysis revealed mechanisms and dependencies that may remain hidden when testing CH 4 models connected to complete peatland carbon models, which is usually the case. Our results indicated that (1) the model is flexible and robust and thus suitable for different environments; (2) the simulated CH 4 emissions largely depend on the prescribed rate of anoxic respiration; (3) the sensitivity of the total CH 4 emission to other input variables is mainly mediated via the concentrations of dissolved gases, in particular, the O 2 concentrations that affect the CH 4 production and oxidation rates; (4) with given input respiration, the peat column description does not significantly affect the simulated CH 4 emissions in this model version.« less

A 21st-century shift from fossil-fuel to biogenic methane emissions indicated by ¹³CH₄.

PubMed

Schaefer, Hinrich; Mikaloff Fletcher, Sara E; Veidt, Cordelia; Lassey, Keith R; Brailsford, Gordon W; Bromley, Tony M; Dlugokencky, Edward J; Michel, Sylvia E; Miller, John B; Levin, Ingeborg; Lowe, Dave C; Martin, Ross J; Vaughn, Bruce H; White, James W C

2016-04-01

Between 1999 and 2006, a plateau interrupted the otherwise continuous increase of atmospheric methane concentration [CH4] since preindustrial times. Causes could be sink variability or a temporary reduction in industrial or climate-sensitive sources. We reconstructed the global history of [CH4] and its stable carbon isotopes from ice cores, archived air, and a global network of monitoring stations. A box-model analysis suggests that diminishing thermogenic emissions, probably from the fossil-fuel industry, and/or variations in the hydroxyl CH4 sink caused the [CH4] plateau. Thermogenic emissions did not resume to cause the renewed [CH4] rise after 2006, which contradicts emission inventories. Post-2006 source increases are predominantly biogenic, outside the Arctic, and arguably more consistent with agriculture than wetlands. If so, mitigating CH4 emissions must be balanced with the need for food production. Copyright © 2016, American Association for the Advancement of Science.

Transport of Methane in Trees

NASA Astrophysics Data System (ADS)

Kutschera, E.; Khalil, A. K.; Shearer, M. J.; Rosenstiel, T.; Rice, A. L.

2011-12-01

Although overall methane (CH4) emissions for croplands, wetlands, and forests have been measured, the exact dynamics of CH4 transport through trees is not well understood. What roles transport mechanisms play in emission rates has been thoroughly investigated for rice, but is fairly unknown for trees. Better defined plant transport mechanisms yield more accurate determination of greenhouse gas flux and its variations, contributing to a comprehensive theory quantifying greenhouse gas emissions globally. CH4 emissions from the common wetland tree species black cottonwood (Populus trichocarpa) native to the Pacific Northwest have been measured under hydroponic conditions in order to separate plant transport processes from the influence of soil processes. Canopy emissions of CH4 have been measured via canopy enclosure. Measurements of CH4 flux from each of 16 trees have indicated that emissions are normally constant over the half-hour sampling period. Samples for stable carbon isotope composition have been taken during these experiments and measured on a mass spectrometer. Compared to the isotopic composition of root water CH4, canopy CH4 is depleted in 13C; this indicates that CH4 moving through the tree is not following a bulk flow pathway (where no depletion would occur), but instead moves either diffusively or through other cell or tissue barriers. No correlation was found to exist between leaf area and CH4 emission; this is vital to upscaling tree-level emissions to the global scale since leaf area index (LAI) cannot be treated as an appropriate parameter to upscale flux. Correctly informing global-scale CH4 fluxes from plants requires an association between the role plant physiology plays in the production and transport of CH4 and magnitudes of flux. This research was supported by the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG02-08ER64515. Supported in part through NASA / Oregon Space Grant Consortium, grant NNG05GJ85H.

Enhanced winter soil frost reduces methane emission during the subsequent growing season in a boreal peatland.

PubMed

Zhao, Junbin; Peichl, Matthias; Nilsson, Mats B

2016-02-01

Winter climate change may result in reduced snow cover and could, consequently, alter the soil frost regime and biogeochemical processes underlying the exchange of methane (CH4 ) in boreal peatlands. In this study, we investigated the short-term (1-3 years) vs. long-term (11 years) effects of intensified winter soil frost (induced by experimental snow exclusion) on CH4 exchange during the following growing season in a boreal peatland. In the first 3 years (2004-2006), lower CH4 emissions in the treatment plots relative to the control coincided with delayed soil temperature increase in the treatment plots at the beginning of the growing season (May). After 11 treatment years (in 2014), CH4 emissions were lower in the treatment plots relative to the control over the entire growing season, resulting in a reduction in total growing season CH4 emission by 27%. From May to July 2014, reduced sedge leaf area coincided with lower CH4 emissions in the treatment plots compared to the control. From July to August, lower dissolved organic carbon concentrations in the pore water of the treatment plots explained 72% of the differences in CH4 emission between control and treatment. In addition, greater Sphagnum moss growth in the treatment plots resulted in a larger distance between the moss surface and the water table (i.e., increasing the oxic layer) which may have enhanced the CH4 oxidation potential in the treatment plots relative to the control in 2014. The differences in vegetation might also explain the lower temperature sensitivity of CH4 emission observed in the treatment plots relative to the control. Overall, this study suggests that greater soil frost, associated with future winter climate change, might substantially reduce the growing season CH4 emission in boreal peatlands through altering vegetation dynamics and subsequently causing vegetation-mediated effects on CH4 exchange. © 2015 John Wiley & Sons Ltd.

Temperature and hydrology affect methane emissions from Prairie Pothole Wetlands

USGS Publications Warehouse

Bansal, Sheel; Tangen, Brian; Finocchiaro, Raymond

2016-01-01

The Prairie Pothole Region (PPR) in central North America consists of millions of depressional wetlands that each have considerable potential to emit methane (CH4). Changes in temperature and hydrology in the PPR from climate change may affect methane fluxes from these wetlands. To assess the potential effects of changes in climate on methane emissions, we examined the relationships between flux rates and temperature or water depth using six years of bi-weekly flux measurements during the snow-free period from six temporarily ponded and six permanently ponded wetlands in North Dakota, USA. Methane flux rates were among the highest reported for freshwater wetlands, and had considerable spatial and temporal variation. Methane flux rates increased with increasing temperature and water depth, and were especially high when conditions were warmer and wetter than average (163 ± 28 mg CH4 m−2 h−1) compared to warmer and drier (37 ± 7 mg CH4 m−2 h−1). Methane emission rates from permanent wetlands were less sensitive to changes in temperature and water depth compared to temporary wetlands, likely due to higher sulfate concentrations in permanent wetlands. While the predicted increase in temperature with climate change will likely increase methane emission rates from PPR wetlands, drier conditions could moderate these increases.

Methane efflux measured by eddy covariance in Alaskan upland tundra undergoing permafrost degradation

NASA Astrophysics Data System (ADS)

Taylor, M.; Celis, G.; Ledman, J.; Bracho, R. G.; Schuur, E.

2017-12-01

Permafrost thaw can increase landscape heterogeneity, leading to wetter and drier soil conditions that affect the magnitude and form (carbon dioxide - CO2 and methane - CH4) of carbon produced via microbial decomposition. Environmental controls on CH4 emissions, especially in drier upland tundra systems, are not well understood. In degrading upland tundra permafrost, cold season CH4 fluxes may contribute significantly to annual emissions from CH4 production within unfrozen layers deep in the soil profile. Eight Mile Lake (EML), located in Interior Alaska near Denali National Park, is a moist acidic tussock tundra ecosystem undergoing permafrost degradation. Perennially frozen soils have warmed between 1985 and 2016 from -1.2 to -0.75˚C resulting in a deeper active layer depth from 61 to 70 cm between 2004-2016. Depth from the soil/moss surface to the water table perched on the permafrost surface has decreased from 30 to 20 cm over the same interval. Here we present the first year of continuous CH4 flux measurements made at EML (May 2016 - May 2017). The site was a net source of low-level CH4 emissions throughout the year. Annual CH4 emissions (1.3 g C yr-1) made up 8.8% of total annual C emissions (14.7 g m-2yr-1). Methane flux is related with soil temperatures during both summer and non-summer seasons. Emissions increased throughout the summer season as thaw depth and soil temperatures increased. In contrast with wetland sites where water table is at or above the soil surface for much of the growing season, EML is relatively dry and there was no relationship between soil moisture and emissions. Non-summer season CH4 emissions are related to increases in atmospheric and shallow soil temperatures. Winter season emissions account for 37% of the annual CH4 budget, the bulk of which occurred between October and January when deep soils remained thawed. Non-summer season CH4 and CO2 pulses appear to be coupled, suggesting a similar mechanism for release. We hypothesize that this relationship is the result of surface soils warming and cracking, allowing for the escape of microbially produced gases at depth. While annual CH4 emissions made up 8.8% of total annual C emissions at this site, taking into account the greenhouse warming potential of CH4 relative to CO2, the climate impact of CH4 is 15.6 g m-2yr-1, or 69% of the C budget.

Leachate treatment in landfills is a significant N2O source.

PubMed

Wang, Xiaojun; Jia, Mingsheng; Zhang, Chengliang; Chen, Shaohua; Cai, Zucong

2017-10-15

The importance of methane (CH 4 ) emissions from landfills has been extensively documented, while the nitrous oxide (N 2 O) emissions from landfills are considered negligible. In this study, three landfills were selected to measure CH 4 and N 2 O emissions using the static chamber method. Dongbu (DB) and Dongfu (DF) landfills, both located in Xiamen city, Fujian Province, were classified as sanitary. The former started to receive solid waste from Xiamen city in 2009, and the latter was closed in 2009. Nanjing (NJ) landfill, located in Nanjing county, Fujian Province, was classified as managed. Results showed that for the landfill reservoirs, CH 4 emissions were significant, while N 2 O emissions occurred mainly in operating areas (on average, 16.3 and 19.0mgN 2 Om -2 h -1 for DB and NJ landfills, respectively) and made a negligible contribution to the total greenhouse gas emissions in term of CO 2 equivalent. However, significant N 2 O emissions were observed in the leachate treatment systems of sanitary landfills and contributed 72.8% and 45.6% of total emissions in term of CO 2 equivalent in DB and DF landfills, respectively. The N 2 O emission factor (EF) of the leachate treatment systems was in the range of 8.9-11.9% of the removed nitrogen. The total N 2 O emissions from the leachate treatment systems of landfills in Xiamen city were estimated to be as high as 8.55gN 2 O-Ncapita -1 yr -1 . These results indicated that N 2 O emissions from leachate treatment systems of sanitary landfills were not negligible and should be included in national and/or local inventories of greenhouse gas emissions. Copyright © 2017 Elsevier B.V. All rights reserved.

Assessing Methane Fluxes in a Small Run-of-River Reservoir: The Importance of Adjacent Marshland

NASA Astrophysics Data System (ADS)

McGinnis, D. F.; Flury, S.; Fietzek, P.; Bilsley, N. A.; Bodmer, P.; Premke, K.; Maeck, A.; Lorke, A.; Schmidt, M.

2013-12-01

We investigate methane (CH4) emissions from a small run-of-river impoundment, the Schwentine River in Kiel, Germany. Small dammed rivers, while important regions for carbon transformation, are presently not considered in the terrestrial carbon budget and are under-represented in CH4 emission studies. Using state-of-the-art monitoring techniques, we determine that 1) the CH4 emissions well-exceed those reported for temperate reservoirs and 2) the hydrodynamic linkage to bordering marshland (consisting of reed belts, sidebays and creeks) is an important CH4 source for Schwentine River CH4. During our study, the Schwentine River discharged into the Kieler Fjord at 3 - 12 m3/s. CH4 measurements included 1) a moored sensor near the dam discharge, 2) discrete water sampling, and 3) real time surface flux measurements with floating chambers. We observed that the CH4 concentration increased nearly linearly from 2.5 km upstream towards the dam. The CH4 concentration near the dam discharge was logged and reported every 30 minutes nearly continuously from 11 July - 28 Sept 2011, and varied from 500 μmol/L to 2,200 μmol/L. Surprisingly, the CH4 mass discharge from the dam - ranging from 4 to 20 kg/day - increased with both temperature and flowrate, suggesting a flow-dependent CH4 source. We found that the bordering and numerous inundated reed belts, sidebays and small creeks, had significantly elevated CH4 concentrations. These marshland regions are relatively productive and quiescent compared to the main river, and trap organic and particulate matter, leading to enhanced CH4 production. As the river flowrate increases, the lateral exchange with these adjacent areas also increases. Using the CH4 concentration time series, measured surface diffusive and ebullition fluxes, and sediment CH4 porewater profiles, we estimate the relative contributions of CH4 in the main branch due to 1) sediment diffusion, 2) dissolution from sediment CH4 bubble release, and 3) lateral fluxes from the marshland. Damming of the rivers potentially creates or increases adjacent marshland, leading to methane production/emission hotspots. Considering only the main branch, the Schwentine River CH4 emission rate is similar to tropical reservoirs. However, including bubble and diffusive emissions from the reed belts and many small side bays and streams could significantly increase this estimate. As millions of such small river impoundments exist worldwide, we discuss the hydrodynamic alterations promoting CH4 production/emission hotspots, illustrate the importance of collecting high-resolution time series data for assessing emissions, and finally estimate the potential contribution of these small aquatic systems to the global terrestrial carbon balance.

Contribution of photosynthesized carbon to the methane emitted from paddy fields

NASA Astrophysics Data System (ADS)

Minoda, T.; Kimura, M.

1994-09-01

Emission rates of CH4 from paddy soil with and without rice straw applications were measured with pot experiments to estimate the contribution of rice straw to total CH4 emissions during the growing season. The CH4 derived from rice straw was calculated to be 50.4% of the total emission. 13CO2 uptake experiments were carried out three times from Aug. 8 to Sept. 18 to estimate the contribution of photosynthesized carbon to CH4 emission. The contribution percentages of photosynthesized carbon to the total CH4 emitted to the atmosphere were 72-110% around Aug. 8, 29-36% around Aug. 30, and 13-17% around Sept. 18, 1993.

Increased importance of methane reduction for a 1.5 degree target

NASA Astrophysics Data System (ADS)

Collins, William J.; Webber, Christopher P.; Cox, Peter M.; Huntingford, Chris; Lowe, Jason; Sitch, Stephen; Chadburn, Sarah E.; Comyn-Platt, Edward; Harper, Anna B.; Hayman, Garry; Powell, Tom

2018-04-01

To understand the importance of methane on the levels of carbon emission reductions required to achieve temperature goals, a processed-based approach is necessary rather than reliance on the transient climate response to emissions. We show that plausible levels of methane (CH4) mitigation can make a substantial difference to the feasibility of achieving the Paris climate targets through increasing the allowable carbon emissions. This benefit is enhanced by the indirect effects of CH4 on ozone (O3). Here the differing effects of CH4 and CO2 on land carbon storage, including the effects of surface O3, lead to an additional increase in the allowable carbon emissions with CH4 mitigation. We find a simple robust relationship between the change in the 2100 CH4 concentration and the extra allowable cumulative carbon emissions between now and 2100 (0.27 ± 0.05 GtC per ppb CH4). This relationship is independent of modelled climate sensitivity and precise temperature target, although later mitigation of CH4 reduces its value and thus methane reduction effectiveness. Up to 12% of this increase in allowable emissions is due to the effect of surface ozone. We conclude early mitigation of CH4 emissions would significantly increase the feasibility of stabilising global warming below 1.5 °C, alongside having co-benefits for human and ecosystem health.

Winter fluxes of CO2 and CH4 from subalpine soils in Rocky Mountain National Park, Colorado

USGS Publications Warehouse

Mast, M. Alisa; Wickland, Kimberly P.; Striegl, Robert G.; Clow, David W.

1998-01-01

Fluxes of CO2 and CH4 through a seasonal snowpack were measured in and adjacent to a subalpine wetland in Rocky Mountain National Park, Colorado. Gas diffusion through the snow was controlled by gas production or consumption in the soil and by physical snowpack properties. The snowpack insulated soils from cold midwinter air temperatures allowing microbial activity to continue through the winter. All soil types studied were net sources of CO2 to the atmosphere through the winter, whereas saturated soils in the wetland center were net emitters of CH4 and soils adjacent to the wetland were net CH4 consumers. Most sites showed similar temporal patterns in winter gas fluxes; the lowest fluxes occurred in early winter, and maximum fluxes occurred at the onset of snowmelt. Temporal changes in fluxes probably were related to changes in soil-moisture conditions and hydrology because soil temperatures were relatively constant under the snowpack. Average winter CO2 fluxes were 42.3, 31.2, and 14.6 mmol m−2 d−1 over dry, moist, and saturated soils, respectively, which accounted for 8 to 23% of the gross annual CO2emissions from these soils. Average winter CH4 fluxes were −0.016, 0.274, and 2.87 mmol m−2 d−1over dry, moist, and saturated soils, respectively. Microbial activity under snow cover accounted for 12% of the annual CH4 consumption in dry soils and 58 and 12% of the annual CH4 emitted from moist and saturated soils, respectively. The observed ranges in CO2 and CH4 flux through snow indicated that winter fluxes are an important part of the annual carbon budget in seasonally snow-covered terrains.

Factors Related with CH4 and N2O Emissions from a Paddy Field: Clues for Management implications

PubMed Central

Wang, Chun; Lai, Derrick Y. F.; Sardans, Jordi; Wang, Weiqi; Zeng, Congsheng; Peñuelas, Josep

2017-01-01

Paddy fields are major sources of global atmospheric greenhouse gases, including methane (CH4) and nitrous oxide (N2O). The different phases previous to emission (production, transport, diffusion, dissolution in pore water and ebullition) despite well-established have rarely been measured in field conditions. We examined them and their relationships with temperature, soil traits and plant biomass in a paddy field in Fujian, southeastern China. CH4 emission was positively correlated with CH4 production, plant-mediated transport, ebullition, diffusion, and concentration of dissolved CH4 in porewater and negatively correlated with sulfate concentration, suggesting the potential use of sulfate fertilizers to mitigate CH4 release. Air temperature and humidity, plant stem biomass, and concentrations of soil sulfate, available N, and DOC together accounted for 92% of the variance in CH4 emission, and Eh, pH, and the concentrations of available N and Fe3+, leaf biomass, and air temperature 95% of the N2O emission. Given the positive correlations between CH4 emission and DOC content and plant biomass, reduce the addition of a carbon substrate such as straw and the development of smaller but higher yielding rice genotypes could be viable options for reducing the release of greenhouse gases from paddy fields to the atmosphere. PMID:28081161

Net emissions of CH4 and CO2 in Alaska: Implications for the region's greenhouse gas budget

USGS Publications Warehouse

Zhuang, Q.; Melillo, J.M.; McGuire, A.D.; Kicklighter, D.W.; Prinn, R.G.; Steudler, P.A.; Felzer, B.S.; Hu, S.

2007-01-01

We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to study the net methane (CH4) fluxes between Alaskan ecosystems and the atmosphere. We estimated that the current net emissions of CH4 (emissions minus consumption) from Alaskan soils are ???3 Tg CH 4/yr. Wet tundra ecosystems are responsible for 75% of the region's net emissions, while dry tundra and upland boreal forests are responsible for 50% and 45% of total consumption over the region, respectively. In response to climate change over the 21st century, our simulations indicated that CH 4 emissions from wet soils would be enhanced more than consumption by dry soils of tundra and boreal forests. As a consequence, we projected that net CH4 emissions will almost double by the end of the century in response to high-latitude warming and associated climate changes. When we placed these CH4 emissions in the context of the projected carbon budget (carbon dioxide [CO2] and CH4) for Alaska at the end of the 21st century, we estimated that Alaska will be a net source of greenhouse gases to the atmosphere of 69 Tg CO2 equivalents/yr, that is, a balance between net methane emissions of 131 Tg CO2 equivalents/yr and carbon sequestration of 17 Tg C/yr (62 Tg CO2 equivalents/yr). ?? 2007 by the Ecological Society of America.

Short communication: Development of an equation for estimating methane emissions of dairy cows from milk Fourier transform mid-infrared spectra by using reference data obtained exclusively from respiration chambers.

PubMed

Vanlierde, A; Soyeurt, H; Gengler, N; Colinet, F G; Froidmont, E; Kreuzer, M; Grandl, F; Bell, M; Lund, P; Olijhoek, D W; Eugène, M; Martin, C; Kuhla, B; Dehareng, F

2018-05-09

Evaluation and mitigation of enteric methane (CH 4 ) emissions from ruminant livestock, in particular from dairy cows, have acquired global importance for sustainable, climate-smart cattle production. Based on CH 4 reference measurements obtained with the SF 6 tracer technique to determine ruminal CH 4 production, a current equation permits evaluation of individual daily CH 4 emissions of dairy cows based on milk Fourier transform mid-infrared (FT-MIR) spectra. However, the respiration chamber (RC) technique is considered to be more accurate than SF 6 to measure CH 4 production from cattle. This study aimed to develop an equation that allows estimating CH 4 emissions of lactating cows recorded in an RC from corresponding milk FT-MIR spectra and to challenge its robustness and relevance through validation processes and its application on a milk spectral database. This would permit confirming the conclusions drawn with the existing equation based on SF 6 reference measurements regarding the potential to estimate daily CH 4 emissions of dairy cows from milk FT-MIR spectra. A total of 584 RC reference CH 4 measurements (mean ± standard deviation of 400 ± 72 g of CH 4 /d) and corresponding standardized milk mid-infrared spectra were obtained from 148 individual lactating cows between 7 and 321 d in milk in 5 European countries (Germany, Switzerland, Denmark, France, and Northern Ireland). The developed equation based on RC measurements showed calibration and cross-validation coefficients of determination of 0.65 and 0.57, respectively, which is lower than those obtained earlier by the equation based on 532 SF 6 measurements (0.74 and 0.70, respectively). This means that the RC-based model is unable to explain the variability observed in the corresponding reference data as well as the SF 6 -based model. The standard errors of calibration and cross-validation were lower for the RC model (43 and 47 g/d vs. 66 and 70 g/d for the SF 6 version, respectively), indicating that the model based on RC data was closer to actual values. The root mean squared error (RMSE) of calibration of 42 g/d represents only 10% of the overall daily CH 4 production, which is 23 g/d lower than the RMSE for the SF 6 -based equation. During the external validation step an RMSE of 62 g/d was observed. When the RC equation was applied to a standardized spectral database of milk recordings collected in the Walloon region of Belgium between January 2012 and December 2017 (1,515,137 spectra from 132,658 lactating cows in 1,176 different herds), an average ± standard deviation of 446 ± 51 g of CH 4 /d was estimated, which is consistent with the range of the values measured using both RC and SF 6 techniques. This study confirmed that milk FT-MIR spectra could be used as a potential proxy to estimate daily CH 4 emissions from dairy cows provided that the variability to predict is covered by the model. The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Warmer and drier conditions and nitrogen fertilizer application altered methanotroph abundance and methane emissions in a vegetable soil.

PubMed

Ran, Yu; Xie, Jianli; Xu, Xiaoya; Li, Yong; Liu, Yapeng; Zhang, Qichun; Li, Zheng; Xu, Jianming; Di, Hongjie

2017-01-01

Methane (CH 4 ) is a potent greenhouse gas, and soil can both be a source and sink for atmospheric CH 4 . It is not clear how future climate change may affect soil CH 4 emissions and related microbial communities. The aim of this study was to determine the interactive effects of a simulated warmer and drier climate scenarios and the application of different nitrogen (N) sources (urea and manure) on CH 4 emissions and related microbial community abundance in a vegetable soil. Greenhouses were used to control simulated climate conditions which gave 2.99 °C warmer and 6.2% lower water content conditions. The field experiment was divided into two phases. At the beginning of phase II, half of the greenhouses were removed to study possible legacy effects of the simulated warmer and drier conditions. The responses in methanogen and methanotroph abundance to a simulated climate change scenario were determined using real-time PCR. The results showed that the simulated warmer and drier conditions in the greenhouses significantly decreased CH 4 emissions largely due to the lower soil moisture content. For the same reason, CH 4 emissions of treatments in phase I were much lower than the same treatments in phase II. The abundance of methanotrophs showed a more significant response than methanogens to the simulated climate change scenario, increasing under simulated drier conditions. Methanogenic community abundance remained low, except where manure was applied which provided a source of organic C that stimulated methanogen growth. Soil moisture content was a major driver for methanotroph abundance and strongly affected CH 4 emissions. The application of N source decreased CH 4 emissions probably because of increased methanotrophic activity. CH 4 emissions were positively correlated to methanogenic abundance and negatively correlated to methanotrophic abundance. These results demonstrate that projected future climate change conditions can have a feedback impact on CH 4 emissions from the soil by altering soil conditions (particularly soil moisture) and related microbial communities.

Effect of Alum Additions to Poultry Litter on In-House Ammonia and Greenhouse Gas Concentrations and Emissions.

PubMed

Eugene, Branly; Moore, Philip A; Li, Hong; Miles, Dana; Trabue, Steven; Burns, Robert; Buser, Michael

2015-09-01

Alum [Al(SO4) ·14HO] addition to poultry litter has been shown to reduce ammonia (NH) concentrations in poultry houses; however, its effects on greenhouse gas (GHG; NO, CH, and CO) emissions is unknown. The objectives of this study were to determine the effects of alum additions on (i) in-house NH and GHG concentrations, (ii) NH and GHG emissions, and (iii) litter chemical properties. Two identical broiler houses located in northwest Arkansas were used for this study: one house was a control and the other was treated with alum between each flock of birds. Ventilation rates were coupled with in-house NH and GHG measurements to determine emission rates. Overall, alum additions significantly reduced the daily average in-house NH concentration by 42% (8.9 vs. 15.4 μL L), and the overall NH emission rate was reduced by 47% (7.2 vs. 13.4 kg d house). The average cumulative NH emission for the three flocks was 330 kg house flock for the alum-treated house and 617 kg house flock for the control. Concentrations and emissions of nitrous oxide (NO) and methane (CH) from the alum-treated house were not significantly different than the untreated house. However, carbon dioxide (CO) emissions were significantly higher from the untreated house than the alum-treated house. Alum also significantly increased litter N content and reduced the C/N ratio. These results indicate that the addition of alum to poultry litter is not only an effective management practice for reducing in-house NH concentrations and emissions but also significantly reduces CO emissions from poultry facilities. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Technical note: Comparison of methane ebullition modelling approaches used in terrestrial wetland models

NASA Astrophysics Data System (ADS)

Peltola, Olli; Raivonen, Maarit; Li, Xuefei; Vesala, Timo

2018-02-01

Emission via bubbling, i.e. ebullition, is one of the main methane (CH4) emission pathways from wetlands to the atmosphere. Direct measurement of gas bubble formation, growth and release in the peat-water matrix is challenging and in consequence these processes are relatively unknown and are coarsely represented in current wetland CH4 emission models. In this study we aimed to evaluate three ebullition modelling approaches and their effect on model performance. This was achieved by implementing the three approaches in one process-based CH4 emission model. All the approaches were based on some kind of threshold: either on CH4 pore water concentration (ECT), pressure (EPT) or free-phase gas volume (EBG) threshold. The model was run using 4 years of data from a boreal sedge fen and the results were compared with eddy covariance measurements of CH4 fluxes.

Modelled annual CH4 emissions were largely unaffected by the different ebullition modelling approaches; however, temporal variability in CH4 emissions varied an order of magnitude between the approaches. Hence the ebullition modelling approach drives the temporal variability in modelled CH4 emissions and therefore significantly impacts, for instance, high-frequency (daily scale) model comparison and calibration against measurements. The modelling approach based on the most recent knowledge of the ebullition process (volume threshold, EBG) agreed the best with the measured fluxes (R2 = 0.63) and hence produced the most reasonable results, although there was a scale mismatch between the measurements (ecosystem scale with heterogeneous ebullition locations) and model results (single horizontally homogeneous peat column). The approach should be favoured over the two other more widely used ebullition modelling approaches and researchers are encouraged to implement it into their CH4 emission models.

Methane emissions from an alpine wetland on the Tibetan Plateau: Neglected but vital contribution of the nongrowing season

NASA Astrophysics Data System (ADS)

Song, Weimin; Wang, Hao; Wang, Guangshuai; Chen, Litong; Jin, Zhenong; Zhuang, Qianlai; He, Jin-Sheng

2015-08-01

The vast wetlands on the Tibetan Plateau are expected to be an important natural source of methane (CH4) to the atmosphere. The magnitude, patterns and environmental controls of CH4 emissions on different timescales, especially during the nongrowing season, remain poorly understood, because of technical limitations and the harsh environments. We conducted the first study on year-round CH4 fluxes in an alpine wetland using the newly developed LI-COR LI-7700 open-path gas analyzer. We found that the total annual CH4 emissions were 26.4 and 33.8 g CH4 m-2 in 2012 and 2013, respectively, and the nongrowing season CH4 emissions accounted for 43.2-46.1% of the annual emissions, highlighting an indispensable contribution that was often overlooked by previous studies. A two-peak seasonal variation in CH4 fluxes was observed, with a small peak in the spring thawing period and a large one in the peak growing season. We detected a significant difference in the diurnal variation of CH4 fluxes between the two seasons, with two peaks in the growing season and one peak in the nongrowing season. We found that the CH4 fluxes during the growing season were well correlated with soil temperature, water table depth and gross primary production, whereas the CH4 fluxes during the nongrowing season were highly correlated with soil temperature. Our results suggested that the CH4 emission during the nongrowing season cannot be ignored and the vast wetlands on the Tibetan plateau will have the potential to exert a positive feedback on climate considering the increasing warming, particularly in the nongrowing season in this region.

Turn on, fade out - methane exchange in a coastal fen over a period of six years after rewetting

NASA Astrophysics Data System (ADS)

Jurasinski, Gerald; Glatzel, Stephan; Hahn, Juliane; Koch, Stefan; Koch, Marian; Koebsch, Franziska

2016-04-01

The rewetting of drained peatlands is widely regarded as an adequate measure for the mitigation of greenhouse gas emissions. Therefore, especially in NE Germany, many peatlands are being rewetted. Our knowledge about greenhouse gas exchange associated with rewetting is mainly based on short-term experiments or space-for-time substitutions. These approaches do not consider the transient character of ecosystem acclimatization to flooding by rewetting. Moreover data in this regard on coastal peatland ecosystems are sparse. Here, we present 7 years of data on CH4-exchange in a coastal fen after rewetting by flooding. On the site „Rodewiese", which is located within the NSG "Hütelmoor und Heiligensee" in the Northeast of Rostock, NE Germany, we have established a long term research observatory addressing atmospheric C-exchange. The site is part of the TERENO network. Since summer 2009 we determine CH4 fluxes with closed chambers distributed widely across the study site and CO2-exchange with eddy covariance as well as ancillary data on vegetation, hydrology, and biogeochemistry. This talk addresses the CH4-exchange over time whereas CO2-exchange data are presented by Koebsch et al. in the same session. Rewetting turned the site from a summer dry fen with mean annual water levels of around -0.08m into a shallow lake with water levels up to 0.60m. In the first year after flooding, we observed a substantial die-back of vegetation, especially in stands of Carex acutiformis. Flooding increased methane release rates to extremely high levels of up to 4.3 t ha-1 a-1 for sedge stands and 2.7 t ha-1 a-1 on average, which amounts to 75.6 t ha-1 a-1 in CO2-equivalents. Thereafter, the averaged annual CH4 emissions decreased asymptotically and where at an average of 0.5 t ha-1 a-1 (14 t ha-1 a-1 in CO2-equivalents) in 2015. Factoring in the NEE of the growing season (from Eddy measurements) suggests that the system may be slightly above neutral with respect to the greenhouse warming potential of its atmospheric C-exchange 7 years after flooding. Analyses of peat and water biochemistry showed that the system had been destabilized in the first year following flooding and repeated vegetation analysis combined with remote sensing reveal strong and directed change in vegetation patterns. The successional development in atmospheric C-exchange in the 6 years after flooding hint at an adaptation of ecosystem functioning to the flooded conditions associated with reaching desirable annual rates of C-exchange and vegetation development during an acceptable time frame. However, high CH4 emissions and a slow recovery to lower CH4 emissions that likely occur directly after rewetting by flooding should be considered when forecasting the overall effect of rewetting on GHG exchange of a particular site.

Greenhouse Gas Emission from Beef Cattle Grazing Systems on Temperate Grasslands

NASA Astrophysics Data System (ADS)

Rice, C. W.; Rivera-Zayas, J.

2017-12-01

At a global scale, cattle production is responsible for 65% of GHG emissions. During 2014 cattle management was the largest emitters of methane (CH4) representing a 23.2% of the total CH4 from anthropogenic activities. Since 2014, gas samples have been gathered and analyzed for carbon dioxide (CO2), CH4 and nitrous oxide (N2O) from three grazing areas under three different burning regimes at the temperate grassland of Konza Prairie Biological Station in Kansas. Burning regimes included one site in annually burned, and two sites with patch burned every three years on offset years. Burning regimes showed no effect in N2O emissions (p<0.05). Annual burning lowered CO2 emissions relative to patch burned. There was a significant effect of interaction between emissions and season. Maximum CO2 and CH4 fluxes were gathered during summer and fall; which coincided with high biomass seasons. Weather and edaphological conditions during fall and winter increase N2O emissions. A decrease in CO2 and CH4 fluxes, and N2O and CH4 soil uptake occurred during winter. Data gathered since 2014 implies CH4 and N2O are consumed on grazed grassland soils; with an increase in consumption with patch burning. Results quantify the role of temperate grasslands as a sink of CH4, and a possible sink of N2O. This experiment evidence CO2, CH4 and N2O emissions behavior as a consequence of burning regimes, and quantify the role of temperate grasslands as a sink of CH4 and N2O in order to understand best practice for resilience of beef cattle management.

Atmospheric emissivity with clear sky computed by E-Trans/HITRAN

NASA Astrophysics Data System (ADS)

Mendoza, Víctor M.; Villanueva, Elba E.; Garduño, René; Sánchez-Meneses, Oscar

2017-04-01

The vertical profiles of temperature and pressure from the International Standard Atmosphere, together with the mixing ratio profiles of the main greenhouse effect gases (GG), namely water vapour, CO2 , CH4 , N2 O and stratospheric O3 , are used to determine the downward emissivity of long wave radiation by cloudless atmosphere, by means of the spectral calculator E-Trans with the HITRAN (high-resolution transmission) database. We make a review of emissivity parameterizations, reported by several authors, in terms of the surface vapour pressure and surface air temperature. We compute vertically weighted averages of temperature and pressure, also parameterize the CH4 , N2 O and O3 mixing ratio profiles, in order to adapt these variables as required by the E-Trans/HITRAN. Our results of emissivity for the corresponding vapour pressures agree well with those obtained by the reviewed authors. With this method, the emissivity can be computed at a regional scale and towards the future global warming, according to the IPCC temperature projections that will also increase the atmospheric humidity, from the emission scenarios of GG.

Methane emission from global livestock sector during 1890-2014: Magnitude, trends and spatiotemporal patterns.

PubMed

Dangal, Shree R S; Tian, Hanqin; Zhang, Bowen; Pan, Shufen; Lu, Chaoqun; Yang, Jia

2017-10-01

Human demand for livestock products has increased rapidly during the past few decades largely due to dietary transition and population growth, with significant impact on climate and the environment. The contribution of ruminant livestock to greenhouse gas (GHG) emissions has been investigated extensively at various scales from regional to global, but the long-term trend, regional variation and drivers of methane (CH 4 ) emission remain unclear. In this study, we use Intergovernmental Panel on Climate Change (IPCC) Tier II guidelines to quantify the evolution of CH 4 emissions from ruminant livestock during 1890-2014. We estimate that total CH 4 emissions in 2014 was 97.1 million tonnes (MT) CH 4 or 2.72 Gigatonnes (Gt) CO 2 -eq (1 MT = 10 12 g, 1 Gt = 10 15 g) from ruminant livestock, which accounted for 47%-54% of all non-CO 2 GHG emissions from the agricultural sector. Our estimate shows that CH 4 emissions from the ruminant livestock had increased by 332% (73.6 MT CH 4 or 2.06 Gt CO 2 -eq) since the 1890s. Our results further indicate that livestock sector in drylands had 36% higher emission intensity (CH 4 emissions/km 2 ) compared to that in nondrylands in 2014, due to the combined effect of higher rate of increase in livestock population and low feed quality. We also find that the contribution of developing regions (Africa, Asia and Latin America) to the total CH 4 emissions had increased from 51.7% in the 1890s to 72.5% in the 2010s. These changes were driven by increases in livestock numbers (LU units) by up to 121% in developing regions, but decreases in livestock numbers and emission intensity (emission/km 2 ) by up to 47% and 32%, respectively, in developed regions. Our results indicate that future increases in livestock production would likely contribute to higher CH 4 emissions, unless effective strategies to mitigate GHG emissions in livestock system are implemented. © 2017 John Wiley & Sons Ltd.

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, butmore » the climate warming impact of lake CH 4 emissions was 2 times higher than that of CO 2. Ebullition and diffusion were the dominant modes of CH 4 and CO 2 emissions, respectively. IBS, ~10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO 2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO 2 emissions (e.g., catchment waters, pH equilibrium). Total CH 4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. In conclusion, our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

Methane and carbon dioxide emissions from 40 lakes along a north–south latitudinal transect in Alaska

DOE PAGES

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K.; ...

2015-06-02

Uncertainties in the magnitude and seasonality of various gas emission modes, particularly among different lake types, limit our ability to estimate methane (CH 4) and carbon dioxide (CO 2) emissions from northern lakes. Here we assessed the relationship between CH 4 and CO 2 emission modes in 40 lakes along a latitudinal transect in Alaska to lakes' physicochemical properties and geographic characteristics, including permafrost soil type surrounding lakes. Emission modes included direct ebullition, diffusion, storage flux, and a newly identified ice-bubble storage (IBS) flux. We found that all lakes were net sources of atmospheric CH 4 and CO 2, butmore » the climate warming impact of lake CH 4 emissions was 2 times higher than that of CO 2. Ebullition and diffusion were the dominant modes of CH 4 and CO 2 emissions, respectively. IBS, ~10% of total annual CH 4 emissions, is the release to the atmosphere of seasonally ice-trapped bubbles when lake ice confining bubbles begins to melt in spring. IBS, which has not been explicitly accounted for in regional studies, increased the estimate of springtime emissions from our study lakes by 320%. Geographically, CH 4 emissions from stratified, mixotrophic interior Alaska thermokarst (thaw) lakes formed in icy, organic-rich yedoma permafrost soils were 6-fold higher than from non-yedoma lakes throughout the rest of Alaska. The relationship between CO 2 emissions and geographic parameters was weak, suggesting high variability among sources and sinks that regulate CO 2 emissions (e.g., catchment waters, pH equilibrium). Total CH 4 emission was correlated with concentrations of soluble reactive phosphorus and total nitrogen in lake water, Secchi depth, and lake area, with yedoma lakes having higher nutrient concentrations, shallower Secchi depth, and smaller lake areas. In conclusion, our findings suggest that permafrost type plays important roles in determining CH 4 emissions from lakes by both supplying organic matter to methanogenesis directly from thawing permafrost and by enhancing nutrient availability to primary production, which can also fuel decomposition and methanogenesis.« less

40 CFR 98.353 - Calculating GHG emissions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... anaerobic reactor and anaerobic lagoon from which biogas is not recovered, estimate annual CH4 emissions... wastewater treatment process n from which biogas is not recovered (metric tons). CH4Gn = Annual mass of CH4... biogas is recovered, estimate the annual mass of CH4 recovered according to the requirements in...

Recent Advances in Measurement and Dietary Mitigation of Enteric Methane Emissions in Ruminants

PubMed Central

Patra, Amlan K.

2016-01-01

Methane (CH4) emission, which is mainly produced during normal fermentation of feeds by the rumen microorganisms, represents a major contributor to the greenhouse gas (GHG) emissions. Several enteric CH4 mitigation technologies have been explored recently. A number of new techniques have also been developed and existing techniques have been improved in order to evaluate CH4 mitigation technologies and prepare an inventory of GHG emissions precisely. The aim of this review is to discuss different CH4 measuring and mitigation technologies, which have been recently developed. Respiration chamber technique is still considered as a gold standard technique due to its greater precision and reproducibility in CH4 measurements. With the adoption of recent recommendations for improving the technique, the SF6 method can be used with a high level of precision similar to the chamber technique. Short-term measurement techniques of CH4 measurements generally invite considerable within- and between-animal variations. Among the short-term measuring techniques, Greenfeed and methane hood systems are likely more suitable for evaluation of CH4 mitigation studies, if measurements could be obtained at different times of the day relative to the diurnal cycle of the CH4 production. Carbon dioxide and CH4 ratio, sniffer, and other short-term breath analysis techniques are more suitable for on farm screening of large number of animals to generate the data of low CH4-producing animals for genetic selection purposes. Different indirect measuring techniques are also investigated in recent years. Several new dietary CH4 mitigation technologies have been explored, but only a few of them are practical and cost-effective. Future research should be directed toward both the medium- and long-term mitigation strategies, which could be utilized on farms to accomplish substantial reductions of CH4 emissions and to profitably reduce carbon footprint of livestock production systems. This review presents recent developments and critical analysis on different measurements and dietary mitigation of enteric CH4 emissions technologies. PMID:27243027

Recent Advances in Measurement and Dietary Mitigation of Enteric Methane Emissions in Ruminants.

PubMed

Patra, Amlan K

2016-01-01

Methane (CH4) emission, which is mainly produced during normal fermentation of feeds by the rumen microorganisms, represents a major contributor to the greenhouse gas (GHG) emissions. Several enteric CH4 mitigation technologies have been explored recently. A number of new techniques have also been developed and existing techniques have been improved in order to evaluate CH4 mitigation technologies and prepare an inventory of GHG emissions precisely. The aim of this review is to discuss different CH4 measuring and mitigation technologies, which have been recently developed. Respiration chamber technique is still considered as a gold standard technique due to its greater precision and reproducibility in CH4 measurements. With the adoption of recent recommendations for improving the technique, the SF6 method can be used with a high level of precision similar to the chamber technique. Short-term measurement techniques of CH4 measurements generally invite considerable within- and between-animal variations. Among the short-term measuring techniques, Greenfeed and methane hood systems are likely more suitable for evaluation of CH4 mitigation studies, if measurements could be obtained at different times of the day relative to the diurnal cycle of the CH4 production. Carbon dioxide and CH4 ratio, sniffer, and other short-term breath analysis techniques are more suitable for on farm screening of large number of animals to generate the data of low CH4-producing animals for genetic selection purposes. Different indirect measuring techniques are also investigated in recent years. Several new dietary CH4 mitigation technologies have been explored, but only a few of them are practical and cost-effective. Future research should be directed toward both the medium- and long-term mitigation strategies, which could be utilized on farms to accomplish substantial reductions of CH4 emissions and to profitably reduce carbon footprint of livestock production systems. This review presents recent developments and critical analysis on different measurements and dietary mitigation of enteric CH4 emissions technologies.

Verification of Agricultural Methane Emission Inventories

NASA Astrophysics Data System (ADS)

Desjardins, R. L.; Pattey, E.; Worth, D. E.; VanderZaag, A.; Mauder, M.; Srinivasan, R.; Worthy, D.; Sweeney, C.; Metzger, S.

2017-12-01

It is estimated that agriculture contributes more than 40% of anthropogenic methane (CH4) emissions in North America. However, these estimates, which are either based on the Intergovernmental Panel on Climate Change (IPCC) methodology or inverse modeling techniques, are poorly validated due to the challenges of separating interspersed CH4 sources within agroecosystems. A flux aircraft, instrumented with a fast-response Picarro CH4 analyzer for the eddy covariance (EC) technique and a sampling system for the relaxed eddy accumulation technique (REA), was flown at an altitude of about 150 m along several 20-km transects over an agricultural region in Eastern Canada. For all flight days, the top-down CH4 flux density measurements were compared to the footprint adjusted bottom-up estimates based on an IPCC Tier II methodology. Information on the animal population, land use type and atmospheric and surface variables were available for each transect. Top-down and bottom-up estimates of CH4 emissions were found to be poorly correlated, and wetlands were the most frequent confounding source of CH4; however, there were other sources such as waste treatment plants and biodigesters. Spatially resolved wavelet covariance estimates of CH4 emissions helped identify the contribution of wetlands to the overall CH4 flux, and the dependence of these emissions on temperature. When wetland contribution in the flux footprint was minimized, top-down and bottom-up estimates agreed to within measurement error. This research demonstrates that although existing aircraft-based technology can be used to verify regional ( 100 km2) agricultural CH4 emissions, it remains challenging due to diverse sources of CH4 present in many regions. The use of wavelet covariance to generate spatially-resolved flux estimates was found to be the best way to separate interspersed sources of CH4.

Primary production control of methane emission from wetlands

NASA Technical Reports Server (NTRS)

Whiting, G. J.; Chanton, J. P.

1993-01-01

Based on simultaneous measurements of CO2 and CH4 exchange in wetlands extending from subarctic peatlands to subtropical marshes, a positive correlation between CH4 emission and net ecosystem production is reported. It is suggested that net ecosystem production is a master variable integrating many factors which control CH4 emission in vegetated wetlands. It is found that about 3 percent of the daily net ecosystem production is emitted back to the atmosphere as CH4. With projected stimulation of primary production and soil microbial activity in wetlands associated with elevated atmospheric CO2 concentration, the potential for increasing CH4 emission from inundated wetlands, further enhancing the greenhouse effect, is examined.

[Emission of CH4, N2O and NH3 from vegetable field applied with animal manure composts].

PubMed

Wan, He-Feng; Zhao, Chen-Yang; Zhong, Jia; Ge, Zhen; Wei, Yuan-Song; Zheng, Jia-Xi; Wu, Yu-Long; Han, Sheng-Hui; Zheng, Bo-Fu; Li, Hong-Mei

2014-03-01

Greenhouse gas (GHG) emission from vegetable land is of great concern recently because agriculture land is one of the major sources contributing to global GHG emission. In this study, an experiment of Lactuca sativa L. land applied with different animal manure composts was carried out in a greenhouse vegetable land located in the surburb of Beijing to monitor the emission of GHG (CH4 and N2O) and ammonia in situ, and to analyze the affecting factors of GHG and ammonia emission. Results showed that the emission factors (EFs) of CH4 from Treatment NRM, RM and CF were 0.2%, 0.027% and 0.004%, respectively,the EFs of N2O from these three treatments were 0.18%, 0.63% and 0.74%, respectively, and the EFs of ammonia were 2.00%, 3.98% and 2.53%, respectively. CH4 emission flux was significantly affected by soil temperature and humidity, while N2O emission flux was related to soil temperature, surface temperature and humidity. The emission fluxes of CH4, N2O and NH3 were significantly affected by soil moisture, but there was little relation between CH4, N2O and NH3 emissions and the ambient temperature in the greenhouse.

Modeling methane and nitrous oxide emissions from direct-seeded rice systems

NASA Astrophysics Data System (ADS)

Simmonds, Maegen B.; Li, Changsheng; Lee, Juhwan; Six, Johan; van Kessel, Chris; Linquist, Bruce A.

2015-10-01

Process-based modeling of CH4 and N2O emissions from rice fields is a practical tool for conducting greenhouse gas inventories and estimating mitigation potentials of alternative practices at the scale of management and policy making. However, the accuracy of these models in simulating CH4 and N2O emissions in direct-seeded rice systems under various management practices remains a question. We empirically evaluated the denitrification-decomposition model for estimating CH4 and N2O fluxes in California rice systems. Five and nine site-year combinations were used for calibration and validation, respectively. The model was parameterized for two cultivars, M206 and Koshihikari, and able to simulate 30% and 78% of the variation in measured yields, respectively. Overall, modeled and observed seasonal CH4 emissions were similar (R2 = 0.85), but there was poor correspondence in fallow period CH4 emissions and in seasonal and fallow period N2O emissions. Furthermore, management effects on seasonal CH4 emissions were highly variable and not well represented by the model (0.2-465% absolute relative deviation). Specifically, simulated CH4 emissions were oversensitive to fertilizer N rate but lacked sensitivity to the type of seeding system (dry seeding versus water seeding) and prior fallow period straw management. Additionally, N2O emissions were oversensitive to fertilizer N rate and field drainage. Sensitivity analysis showed that CH4 emissions were highly sensitive to changes in the root to total plant biomass ratio, suggesting that it is a significant source of model uncertainty. These findings have implications for model-directed field research that could improve model representation of paddy soils for application at larger spatial scales.

GLOBAL METHANE EMISSIONS FROM MINOR ANTHROPOGENIC SOURCES AND BIOFUEL COMBUSTION IN RESIDENTIAL STOVES (JOURNAL)

EPA Science Inventory

Most global methane (CH4) budgets have failed to include emissions from a diverse group of minor anthropogenic sources. Individually, these minor sources emit small quantities of CH4, but collectively, their contributions to the budget may be significant. In this paper, CH4 emiss...

HIGH METHANE EMISSIONS FROM A MID-LATITUDE AGRICULTURAL RESERVOIR

EPA Science Inventory

To assess the magnitude of methane (CH4) emissions from reservoirs in agricultural regions, we measured CH4 emission rates from William H. Harsha Lake, located in southwestern Ohio, USA, over a thirteen month period. The reservoir was a strong source of CH4¬ throughout the year,...

Nutrient Controls on Methane Emissions in a Permafrost Thaw Subarctic Peatland

NASA Astrophysics Data System (ADS)

Kashi, N. N.; Perryman, C. R.; Malhotra, A.; Marek, E. A.; Giesler, R.; Varner, R. K.

2015-12-01

Permafrost peatlands in northern latitudes are large reservoirs of sequestered carbon that are vulnerable to climate change. While peatlands account for a small fraction of total global land surfaces, their potential to release sequestered carbon in response to higher temperatures is of concern. Of particular relevance is the conversion of these carbon stores into methane (CH4), a strong greenhouse gas with a global warming potential 20 times greater than that of CO2 over a 100-year time frame. Here, we explore how key nutrients impact the consumption of CH4 at the Stordalen Mire in Abisko, Sweden, a discontinuous permafrost peatland with expanding thaw over the last century. Peatland CH4 emissions are highly spatially variable due to multiple emission pathways and strong dependence on several environmental factors. Among controls on CH4 emissions, such as temperature and water table depth, primary production of wetland vegetation is also a strong factor in the variability of CH4 emissions. Plant community shifts among permafrost thaw stages subsequently change nutrient cycling and availability, which in turn impacts primary production. Early stages of permafrost thaw are mosaicked with a variety of vascular plants and mosses. We analyzed potential enzymatic activities of chitinase, glucosidase, and phosphatase as proxies for organic nitrogen, carbon, and phosphorus cycling, respectively, in tandem with potential CH4 oxidation rates. In addition, stoichiometric ratios of carbon, nitrogen, and phosphorus concentrations are used to illustrate nutrient limitation controls on CH4 oxidation rates. While CH4 emissions are low throughout initial thaw stages, < 7 CH4 mg m-2 day-1, we found they had the highest rates of potential CH4 oxidation. These permafrost thaw-induced CH4 oxidation rates are 5 and 11 times higher, in the surface and depth of the peat profile respectively, than subsequent aerobic permafrost thaw stages. As CH4 emissions are low in intact permafrost peatlands, these high rates of potential CH4 oxidation indicate the importance of plant communities and the methanotrophic microbes they harbor.

CarbonSat -Quantification of natural and man-made greenhouse gas surface fluxes from satellite observations of atmospheric CO2 and CH4 column amounts

NASA Astrophysics Data System (ADS)

Bovensmann, Heinrich; Buchwitz, M.; Burrows, J. P.; Notholt, J.; Bovensmann, H.; Reuter, M.; Trautmann, T.; Ehret, G.; Heimann, M.; Monks, P.; B&Ü, H.; Sch; Harding, R.; Quegan, S.; Rayner, P.; Breon, F. M.; Bergam-O Aschi, P.; Dittus, H. J.; Erzinger, J.; Crisp, D.

Surprisingly and in spite of their exceptional driving role in climate change, our knowledge about the variable sources and sinks of the greenhouse gases CO2 and CH4 is currently inadequate. For example, the ability of the Earth-atmosphere system to buffer increasing anthropogenic emissions into the atmosphere has large uncertainties and emissions from many sources (geo-logic, anthropogenic, biogenic) are to a large degree uncertain. An adequate knowledge of the sources and sinks of CO2 and CH4 and their response to a changing climate is a pre-requisite for the accurate prediction of the regional variation of the climate of our planet. CarbonSat is a new mission concept to quantify and monitor CO2 and CH4 sources and sinks at the regional to local scale. The data will allow a better understanding of the processes that control the Carbon Cycle dynamics and an independent estimate of local greenhouse gas emissions (fossil fuel, geological CO2 and CH4, etc.). This will be achieved by a unique combination of high spatial resolution passive and active compact remote sensing with inverse modeling techniques. CarbonSat will accurately measure column-averaged mixing ratios of CO2 and CH4, i.e., XCO2 and XCH4, at a spatial resolution of 2 x 2 km2 (500 km continuous swath) with 0.5 percent goal (1 percent threshold) single measurement precision and global coverage within 3-6 days. Beside the quantification of sources and sinks on the regional scale, one key and innovative aim of the CarbonSat mission is to go a step forward towards quantifying local emission hot spots (fossil fuel emissions by power plants, gas/oil production, geological sources etc.). The core sensor will be a compact Imaging NIR/SWIR spectrometer (SCIAMACHY, OCO her-itage) whose measurements yield global data sets of XCO2 and XCH4 with at least one order of magnitude higher number of cloud free measurements than GOSAT and OCO and one order of magnitude better spatial coverage than OCO, due to CarbonSat's 500 km swath continuous across track coverage with 2 x 2 km2 spatial resolution. Ideally, the imaging spectrometer will be accompanied by a compact CH4 Lidar, to derive complementary accurate XCH4 -especially in high northern latitudes -as well as information on clouds and vegetation height. The overall mission concept will be presented.

CarbonSat - Quantification of natural and man-made greenhouse gas surface fluxes from satellite observations of atmospheric CO2 and CH4 column amounts

NASA Astrophysics Data System (ADS)

Bovensmann, Heinrich; Buchwitz, Michael

2010-05-01

Surprisingly and in spite of their exceptional driving role in climate change, our knowledge about the variable sources and sinks of the greenhouse gases CO2 and CH4 is currently inadequate. For example, the ability of the Earth-atmosphere system to buffer increasing anthropogenic emissions into the atmosphere has large uncertainties and emissions from many sources (geologic, anthropogenic, biogenic) are to a large degree uncertain. An adequate knowledge of the sources and sinks of CO2 and CH4 and their response to a changing climate is a pre-requisite for the accurate prediction of the regional variation of the climate of our planet. CarbonSat is a new mission concept to quantify and monitor CO2 and CH4 sources and sinks at the regional to local scale. The data will allow a better understanding of the processes that control the Carbon Cycle dynamics and an independent estimate of local greenhouse gas emissions (fossil fuel, geological CO2 and CH4, etc.). This will be achieved by a unique combination of high spatial resolution passive and active compact remote sensing with inverse modeling techniques. CarbonSat will accurately measure column-averaged mixing ratios of CO2 and CH4, i.e., XCO2 and XCH4, at a spatial resolution of 2 x 2 km2 (500 km continuous swath) with 0.5% goal (1%, threshold) single measurement precision and global coverage within 3-6 days. Beside the quantification of sources and sinks on the regional scale, one key and innovative aim of the CarbonSat mission is to go a step forward towards quantifying local emission hot spots (fossil fuel emissions by power plants, gas/oil production, geological sources etc.). The core sensor will be a compact Imaging NIR/SWIR spectrometer (SCIAMACHY, OCO heritage) whose measurements yield global data sets of XCO2 and XCH4 with at least one order of magnitude higher number of cloud free measurements than GOSAT and OCO and one order of magnitude better spatial coverage than OCO, due to CarbonSat's 500 km swath continuous across track coverage with 2 x 2 km2 spatial resolution. Ideally, the imaging spectrometer will be accompanied by a compact CH4 Lidar, to derive complementary accurate XCH4 - especially in high northern latitudes - as well as information on clouds and vegetation height. The overall mission concept, the expected data quality and selected application areas will be presented.

Emission of greenhouse gases from controlled incineration of cattle manure.

PubMed

Oshita, Kazuyuki; Sun, Xiucui; Taniguchi, Miki; Takaoka, Masaki; Matsukawa, Kazutsugu; Fujiwara, Taku

2012-01-01

Greenhouse gas emission is a potential limiting factor in livestock farming development. While incineration is one approach to minimize livestock manure, there are concerns about significant levels of nitrogen and organic compounds in manure as potential sources of greenhouse gas emissions (N2O and CH4). In this study, the effects of various incineration conditions, such as the furnace temperature and air ratio on N2O and CH4 formation behaviour, of cattle manure (as a representative livestock manure) were investigated in a pilot rotary kiln furnace. The results revealed that N2O emissions decreased with increasing temperature and decreasing air ratio. In addition, CH4 emissions tended to be high above 800 degrees C at a low air ratio. The emission factors for N2O and CH4 under the general conditions (combustion temperature of 800-850 degrees C and air ratio of 1.4) were determined to be 1.9-6.0% g-N2O-N/g-N and 0.0046-0.26% g-CH4/g-burning object, respectively. The emission factor for CH4 differed slightly from the published values between 0.16 and 0.38% g-CH4/g-burning object. However, the emission factor for N2O was much higher than the currently accepted value of 0.7% g-N2O-N/g-N and, therefore, it is necessary to revise the N2O emission factor for the incineration of livestock manure.

High Resolution CH4 Emissions and Dissolved CH4 Measurements Elucidate Surface Gas Exchange Processes in Toolik Lake, Arctic Alaska

NASA Astrophysics Data System (ADS)

Del Sontro, T.; Sollberger, S.; Kling, G. W.; Shaver, G. R.; Eugster, W.

2013-12-01

Approximately 14% of the Alaskan North Slope is covered in lakes of various sizes and depths. Diffusive carbon emissions (CH4 and CO2) from these lakes offset the tundra sink by ~20 %, but the offset would substantially increase if ebullitive CH4 emissions were also considered. Ultimately, arctic lake CH4 emissions are not insignificant in the global CH4 budget and their contribution is bound to increase due to impacts from climate change. Here we present high resolution CH4 emission data as measured via eddy covariance and a Los Gatos gas analyzer during the ice free period from Toolik Lake, a deep (20 m) Arctic lake located on the Alaskan North Slope, over the last few summers. Emissions are relatively low (< 25 mg CH4 m-2 d-1) with little variation over the summer. Diurnal variations regularly occur, however, with up to 3 times higher fluxes at night. Gas exchange is a relatively difficult process to estimate, but is normally done so as the product of the CH4 gradient across the air-water interface and the gas transfer velocity, k. Typically, k is determined based on the turbulence on the water side of the interface, which is most commonly approximated by wind speed; however, it has become increasingly apparent that this assumption does not remain valid across all water bodies. Dissolved CH4 profiles in Toolik revealed a subsurface peak in CH4 at the thermocline of up to 3 times as much CH4 as in the surface water. We hypothesize that convective mixing at night due to cooling surface waters brings the subsurface CH4 to the surface and causes the higher night fluxes. In addition to high resolution flux emission estimates, we also acquired high resolution data for dissolved CH4 in surface waters of Toolik Lake during the last two summers using a CH4 equilibrator system connected to a Los Gatos gas analyzer. Thus, having both the flux and the CH4 gradient across the air-water interface measured directly, we can calculate k and investigate the processes influencing CH4 gas exchange in this lake. Preliminary results indicate that there are two regimes in wind speed that impact k - one at low wind speeds up to ~5 m s-1 and another at higher wind speeds (max ~10 m s-1). The differential wind speeds during night and day may compound the effect of convective mixing and cause the diurnal variation in observed fluxes.

Investigation of Biogenic and Non-biogenic Methane Sources in Texas

NASA Astrophysics Data System (ADS)

Yang, S.; Talbot, R. W.; Liu, L.; Lan, X.

2016-12-01

Methane (CH4) is a potent greenhouse gas with its mixing ratio increasing in the global atmosphere. Texas is one of the significant areas where underestimation of CH4 emissions by the U.S. inventories are pronounced. This study focused on two areas of Texas: Houston, the energy capital of the world, and the Barnett Shale area which is one of the largest onshore natural gas fields in the United States. The investigation of background CH4 and the fingerprints of CH4 emissions are critical to understanding potential impacts of extensive nature gas operations in these two areas. One-year of stationary CH4 measurements were studied to deduce the regional background CH4 characteristics and to identify the principle CH4 sources in Houston. Key information concerning CH4 sources can be obtained through the stable carbon isotope δ13CH4 during two field campaigns using a state-of-the-art mobile laboratory. CH4 mixing ratio and δ13C in CH4 were sampled by two cavity ring-down spectrometers (CRDS), one of which is coupled to a custom air core 13C sampling device which can supply more than 600 measurements for each plume analysis. Here, we report results of the overall δ13CH4 values and CH4 emission signatures derived from thirty-three sources in the two studied areas, ranging from oil production and processing, waste managements and landfills, to livestock. δ13CH4 signatures of these sources vary from -76‰ to -23‰. Several repeated measurements were sampled to investigate the variability of source signatures. We investigated a case of unexpected massive CH4 leaking detected near the San Jacinto River Fleet site. At the regional scale, the comparison of background δ13CH4 signatures were conducted to obtain the difference of dominate CH4 sources in two study areas. At the local scale, the combination of tower and mobile lab measurements were used to estimate and characterize CH4 emissions in Houston. The results and findings can supply valuable references for the local emission inventory and atmospheric model inputs.

Quantification of Greenhouse Gas Emissions from the Predisposal Stage of Municipal Solid Waste Management.

PubMed

Zhou, Chuanbin; Jiang, Daqian; Zhao, Zhilan

2017-01-03

Municipal solid waste (MSW) disposal represents one of the largest sources of anthropogenic greenhouse gas (GHG) emissions. However, the biogenic GHG emissions in the predisposal stage of MSW management (i.e., the time from waste being dropped off in community or household garbage bins to being transported to disposal sites) are excluded from the IPCC inventory methodology and rarely discussed in academic literature. Herein, we quantify the effluxes of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) from garbage bins in five communities along the urban-rural gradient in Beijing in four seasons. We find that the annual average CO 2 , CH 4 , and N 2 O effluxes in the predisposal stage were (1.6 ± 0.9)10 3 , 0.049 ± 0.016, and 0.94 ± 0.54 mg kg -1 h -1 (dry matter basis) and had significant seasonal differences (24- to 159-fold) that were strongly correlated with temperature. According to our estimate, the N 2 O emission in the MSW predisposal stage amounts to 20% of that in the disposal stage in Beijing, making the predisposal stage a nontrivial source of waste-induced N 2 O emissions. Furthermore, the CO 2 and CH 4 emissions in the MSW predisposal account for 5% (maximum 10% in summer) of the total carbon contents in a Beijing's household food waste stream, which has significance in the assessment of MSW-related renewable energy potential and urban carbon cycles.

Role of atmospheric oxidation in recent methane growth

PubMed Central

Rigby, Matthew; Montzka, Stephen A.; Prinn, Ronald G.; White, James W. C.; Young, Dickon; Lunt, Mark F.; Ganesan, Anita L.; Manning, Alistair J.; Simmonds, Peter G.; Salameh, Peter K.; Harth, Christina M.; Mühle, Jens; Weiss, Ray F.; Fraser, Paul J.; Steele, L. Paul; McCulloch, Archie; Park, Sunyoung

2017-01-01

The growth in global methane (CH4) concentration, which had been ongoing since the industrial revolution, stalled around the year 2000 before resuming globally in 2007. We evaluate the role of the hydroxyl radical (OH), the major CH4 sink, in the recent CH4 growth. We also examine the influence of systematic uncertainties in OH concentrations on CH4 emissions inferred from atmospheric observations. We use observations of 1,1,1-trichloroethane (CH3CCl3), which is lost primarily through reaction with OH, to estimate OH levels as well as CH3CC3 emissions, which have uncertainty that previously limited the accuracy of OH estimates. We find a 64–70% probability that a decline in OH has contributed to the post-2007 methane rise. Our median solution suggests that CH4 emissions increased relatively steadily during the late 1990s and early 2000s, after which growth was more modest. This solution obviates the need for a sudden statistically significant change in total CH4 emissions around the year 2007 to explain the atmospheric observations and can explain some of the decline in the atmospheric 13CH4/12CH4 ratio and the recent growth in C2H6. Our approach indicates that significant OH-related uncertainties in the CH4 budget remain, and we find that it is not possible to implicate, with a high degree of confidence, rapid global CH4 emissions changes as the primary driver of recent trends when our inferred OH trends and these uncertainties are considered. PMID:28416657

Can we explain the observed methane variability after the Mount Pinatubo eruption?

NASA Astrophysics Data System (ADS)

Bândă, N.; Krol, M.; van Weele, M.; van Noije, T.; Le Sager, P.; Röckmann, T.

2015-07-01

The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr-1 in the growth rate over the course of 1992 was reported and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as ENSO and biomass burning events. Emissions of CO, NOX and NMVOCs also affected CH4 concentrations indirectly by influencing tropospheric OH levels. Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 8-10 ppb yr-1 CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6-9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.

Characterization of methane emissions in Los Angeles with airborne hyperspectral imaging

NASA Astrophysics Data System (ADS)

Saad, K.; Tratt, D. M.; Buckland, K. N.; Roehl, C. M.; Wennberg, P. O.; Wunch, D.

2017-12-01

As urban areas develop regulations to limit atmospheric methane (CH4), accurate quantification of anthropogenic emissions will be critical for program development and evaluation. However, relating emissions derived from process-level metadata to those determined from assimilating atmospheric observations of CH4 concentrations into models is particularly difficult. Non-methane hydrocarbons (NMHCs) can help differentiate between thermogenic and biogenic CH4 emissions, as they are primarily co-emitted with the former; however, these trace gases are subject to the same limitations as CH4. Remotely-sensed hyperspectral imaging bridges these approaches by measuring emissions plumes directly with spatial coverage on the order of 10 km2 min-1. We identify the sources of and evaluate emissions plumes measured by airborne infrared hyperspectral imagers flown over the Los Angeles (LA) metropolitan area, which encompasses various CH4 sources, including petroleum and natural gas wells and facilities. We quantify total CH4 and NMHC emissions, as well as their relative column densities, at the point-source level to create fingerprints of source types. We aggregate these analyses to estimate the range of variability in chemical composition across source types. These CH4 and NMHC emissions factors are additionally compared to their tropospheric column abundances measured by the Total Carbon Column Observing Network (TCCON) Pasadena Fourier transform infrared spectrometer, which provides a footprint for the LA basin.

Integrating Source Apportionment Tracers into a Bottom-up Inventory of Methane Emissions in the Barnett Shale Hydraulic Fracturing Region.

PubMed

Townsend-Small, Amy; Marrero, Josette E; Lyon, David R; Simpson, Isobel J; Meinardi, Simone; Blake, Donald R

2015-07-07

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.

Characteristics of greenhouse gas emission in three full-scale wastewater treatment processes.

PubMed

Yan, Xu; Li, Lin; Liu, Junxin

2014-02-01

Three full-scale wastewater treatment processes, Orbal oxidation ditch, anoxic/anaerobic/aerobic (reversed A2O) and anaerobic/anoxic/aerobic (A2O), were selected to investigate the emission characteristics of greenhouse gases (GHG), including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Results showed that although the processes were different, the units presenting high GHG emission fluxes were remarkably similar, namely the highest CO2 and N2O emission fluxes occurred in the aerobic areas, and the highest CH4 emission fluxes occurred in the grit tanks. The GHG emission amount of each unit can be calculated from its area and GHG emission flux. The calculation results revealed that the maximum emission amounts of CO2, CH4 and N2O in the three wastewater treatment processes appeared in the aerobic areas in all cases. Theoretically, CH4 should be produced in anaerobic conditions, rather than aerobic conditions. However, results in this study showed that the CH4 emission fluxes in the forepart of the aerobic area were distinctly higher than in the anaerobic area. The situation for N2O was similar to that of CH4: the N2O emission flux in the aerobic area was also higher than that in the anoxic area. Through analysis of the GHG mass balance, it was found that the flow of dissolved GHG in the wastewater treatment processes and aerators may be the main reason for this phenomenon. Based on the monitoring and calculation results, GHG emission factors for the three wastewater treatment processes were determined. The A2O process had the highest CO2 emission factor of 319.3 g CO2/kg COD(removed), and the highest CH4 and N2O emission factors of 3.3 g CH4/kg COD(removed) and 3.6 g N2O/kg TN(removed) were observed in the Orbal oxidation ditch process.

Regional emission and loss budgets of atmospheric methane (2002-2012)

NASA Astrophysics Data System (ADS)

Saeki, T.; Patra, P. K.; Dlugokencky, E. J.; Ishijima, K.; Umezawa, T.; Ito, A.; Aoki, S.; Morimoto, S.; Kort, E. A.; Crotwell, A. M.; Ravi Kumar, K.; Nakazawa, T.

2015-12-01

Methane (CH4) plays important roles in atmospheric chemistry and short-term forcing of climate. Clear understanding of atmospheric CH4's budget of emissions and losses is required to aid sustainable development of Earth's future environment. We used an atmospheric chemistry-transport model (JAMSTEC's ACTM) for simulating atmospheric CH4. An inverse modeling system has been developed for estimating CH4 emissions (7 ensemble cases) from 53 land regions for 2002-2012 using measurements at 39 sites. Global net CH4 emissions varied between 505-509 and 524-545 Tg/yr during 2002-2004 and 2010-2012, respectively (ranges based on 6 inversion cases), with a step like increase in 2007 in agreement with atmospheric measurement. The inversion system did not account for interannual variations in radicals reacting with CH4 in atmosphere. Our results suggest that the recent update of EDGAR inventory (version 4.2FT2010) overestimated global total emissions by at least 25 Tg/yr in 2010. Increase in CH4 emission since 2004 originated in the tropical and southern hemisphere regions, with timing consistent with an increase of non-dairy cattle stocks by ~10% in 2012 from 1056 million heads in 2002, leading to ~10 Tg/yr increase in emissions from enteric fermentation. All 7 inversions robustly estimated the interannual variations in emissions, but poorly constrained the seasonal cycle amplitude or phase consistently for all regions due to sparse observational network. Forward simulation results using both the a priori and a posteriori emissions are compared with independent aircraft measurements for validation. By doing that we are able to reject the upper limit (545 Tg/yr) of global total emissions as 14 Tg/yr too high during 2008-2012, which allows us to further conclude that CH4 emission increase rate over the East Asia (China mainly) region was 7-8 Tg/yr between the 2002-2006 and 2008-2012 periods, contrary to 1-17 Tg/yr in the a priori emissions.

[Discussion on reduction potential of CH4 emission intensity for early off-take practice of grazing yak].

PubMed

Wang, Shi-Ping; Wilkes, Andreas; Wang, Ya-Yun; Bai, Ling

2014-08-01

The case study preliminarily compared the CH4 reduction potential and CH4 emission intensity of 7 year-old and 4 year-old grazing yak after early off-take practice based on the 2006 IPCC GHG inventory guidelines and under the premise of equal herbage consumption. Our results showed that the total CH4 emission was greater by about 86.3 kg for 2.1 4-year yaks compared with 7 years old yak during their life assuming that their total herbage consumption was the same, because total herbage consumption for a 7-year yak was equal to that of 2.1 4-year yaks. However, CH4 emission per unit body weight (1.374 kg x kg(-1)) for a 7-year yak (i. e. emission intensity) was higher than that of 2.1 4-year yaks (0.973 kg x kg(-1)) because total body weight of 2.1 4-year yaks was higher by 192 kg than that of a 7-year yak. According to CH4 emission intensity, change of the early off-take practice from 7-year to 4-year yak could reduce 77 kg CH4 if producing 192 kg body weight through 2.1 4-year yaks compared with a 7-year yak, i. e. reduction potential was about 1 600 kg CO2 equivalent under the same consuming forage. Therefore, for grassland-based animal husbandry, early off-take practice for grazing animals had a great reduction potential in the intensity of greenhouse gases (GHGs) emissions per unit output rather than total emissions of GHGs.

Contribution of rice straw carbon to CH4 emission from rice paddies using 13C-enriched rice straw

NASA Astrophysics Data System (ADS)

Watanabe, Akira; Yoshida, Mariko; Kimura, Makoto

1998-04-01

It is generally recognized that the application of rice straw (RS) increases CH4 emission from rice paddies. To estimate the contribution of RS carbon to CH4 emission, a pot experiment was conducted using 13C-enriched RS. The percentage contributions of RS carbon to CH4 emission throughout the rice growth period were 10±1, 32±3, and 43±3% for the treatments with RS applied at the rates of 2, 4, and 6 g kg-1 soil, respectively. The increase in the rate of application of RS increased CH4 emission derived from both RS carbon and other carbon sources. The percentage contribution of RS carbon to CH4 emission was larger in the earlier period (maximum 96%) when the decomposition rate of RS was larger. After RS decomposition had slowed, CH4 emission derived from RS carbon decreased. However, the δ13C values of CH4 emitted from the pots with 13C-enriched RS applied at rates of 4 and 6 g kg-1 soil were significantly higher than those from the pots with natural RS until the harvesting stage. An increased atom-13C% of roots of rice plants growing in the pots with 6 g kg-1 of 13C-enriched RS at around the maximum tiller number stage and a decrease during the following 2 months suggested that rice plants assimilated RS carbon once and then released a portion of it. This supply of RS carbon from roots may be one of the sources of CH4 in the late period of rice growth.

Static Vented Chamber and Eddy Covariance Methane Flux Comparisons in Mid-South US Rice

NASA Astrophysics Data System (ADS)

Reba, M. L.; Fong, B.; Adviento-Borbe, A.; Runkle, B.; Suvocarev, K.; Rival, I.

2017-12-01

Rice cultivation contributes higher amounts of GHG emissions (CO2 and CH4) due to flooded field conditions. A comparison between eddy covariance and static vented flux chamber measurement techniques is presented. Rice GHG emissions originating from plot level chambers may not accurately describe the aggregate effects of all the soil and micrometeorological variations across a production field. Eddy covariance (EC) is a direct, integrated field measurement of field scale trace gases. Flux measurements were collected in NE Arkansas production size rice fields (16 ha, 40 ac) during the 2015 and 2016 production seasons (June-August) in continuous flood (CF) irrigation. The study objectives included quantifying the difference between chamber and EC measurements, and categorizing flux behavior to growth stage and field history. EC daily average emissions correlated with chamber measurements (R2=0.27-0.54) more than average from 09:00-12:00 which encompassed chamber measurement times (R2=0.23-0.32). Maximum methane emissions occurred in the late afternoon from 14:00-18:00 which corresponded with maximum soil heat flux and air temperature. The total emissions from the study fields ranged from 27-117 kg CH4-C ha-1 season-1. The emission profile was lower in 2015, most likely due to higher rainfall and cooler temperatures during the growing season compared to 2016. These findings improve our understanding of GHG emissions at the field scale under typical production practices and validity of chamber and EC flux measurement techniques.

Mangroves act as a small methane source: an investigation on 5 pathways of methane emissions from mangroves

NASA Astrophysics Data System (ADS)

Chen, H.; Peng, C.; Guan, W.; Liao, B.; Hu, J.

2017-12-01

The methane (CH4) source strength of mangroves is not well understood, especially for integrating all CH4 pathways. This study measured CH4 fluxes by five pathways (sediments, pneumatophores, water surface, leaves, and stems) from four typical mangrove forests in Changning River of Hainan Island, China, including Kandelia candel , Sonneratia apetala, Laguncularia racemosa and Bruguiera gymnoihiza-Bruguiera sexangula. The CH4 fluxes (mean ± SE) from sediments were 4.82 ± 1.46 mg CH4 m-2 h-1 for those without pneumatophores and 1.36 ± 0.17 mg CH4 m-2 h-1 for those with pneumatophores. Among the three communities with pneumatophores, S. apetala community had significantly greater emission rate than the other two. Pneumatophores in S. apetala were found to significantly decrease CH4 emission from sediments (P < 0.01), while those in B. gymnoihiza-B. sexangula significantly enhanced it (P < 0.05). The CH4 fluxes (mean ± SE) from waters were 3.48 ± 1.11 mg CH4 m-2 h-1, with the highest emission rate in the K. candel community with duck farming. Leaves of mangroves except for K. candel were a weak CH4 sink while stems a weak source. As a whole the 72 ha of mangroves in the Changning river basin emitted about 8.10 Gg CH4 yr-1 with a weighted emission rate of about 1.29 mg CH4 m-2 h-1, therefore only a small methane source to the atmosphere compared to other reported ones. Keywords: Greenhouse Gases; Biogeochemistry; Tropical ecosystems; Methane budget

Top-down estimate of methane emissions in California using a mesoscale inverse modeling technique: The South Coast Air Basin

DOE PAGES

Cui, Yu Yan; Brioude, Jerome; McKeen, Stuart A.; ...

2015-07-28

Methane (CH 4) is the primary component of natural gas and has a larger global warming potential than CO 2. Some recent top-down studies based on observations showed CH 4 emissions in California's South Coast Air Basin (SoCAB) were greater than those expected from population-apportioned bottom-up state inventories. In this study, we quantify CH 4 emissions with an advanced mesoscale inverse modeling system at a resolution of 8 km × 8 km, using aircraft measurements in the SoCAB during the 2010 Nexus of Air Quality and Climate Change campaign to constrain the inversion. To simulate atmospheric transport, we use themore » FLEXible PARTicle-Weather Research and Forecasting (FLEXPART-WRF) Lagrangian particle dispersion model driven by three configurations of the Weather Research and Forecasting (WRF) mesoscale model. We determine surface fluxes of CH 4 using a Bayesian least squares method in a four-dimensional inversion. Simulated CH4 concentrations with the posterior emission inventory achieve much better correlations with the measurements (R2 = 0.7) than using the prior inventory (U.S. Environmental Protection Agency's National Emission Inventory 2005, R 2 = 0.5). The emission estimates for CH 4 in the posterior, 46.3 ± 9.2 Mg CH 4/h, are consistent with published observation-based estimates. Changes in the spatial distribution of CH 4 emissions in the SoCAB between the prior and posterior inventories are discussed. Missing or underestimated emissions from dairies, the oil/gas system, and landfills in the SoCAB seem to explain the differences between the prior and posterior inventories. Furthermore, we estimate that dairies contributed 5.9 ± 1.7 Mg CH 4/h and the two sectors of oil and gas industries (production and downstream) and landfills together contributed 39.6 ± 8.1 Mg CH 4/h in the SoCAB.« less

Agricultural peatlands: towards a greenhouse gas sink - a synthesis of a Dutch landscape study

NASA Astrophysics Data System (ADS)

Schrier-Uijl, A. P.; Kroon, P. S.; Hendriks, D. M. D.; Hensen, A.; Van Huissteden, J.; Berendse, F.; Veenendaal, E. M.

2014-08-01

It is generally known that managed, drained peatlands act as carbon (C) sources. In this study we examined how mitigation through the reduction of the intensity of land management and through rewetting may affect the greenhouse gas (GHG) emission and the C balance of intensively managed, drained, agricultural peatlands. Carbon and GHG balances were determined for three peatlands in the western part of the Netherlands from 2005 to 2008 by considering spatial and temporal variability of emissions (CO2, CH4 and N2O). One area (Oukoop) is an intensively managed grass-on-peatland area, including a dairy farm, with the ground water level at an average annual depth of 0.55 (±0.37) m below the soil surface. The second area (Stein) is an extensively managed grass-on-peatland area, formerly intensively managed, with a dynamic ground water level at an average annual depth of 0.45 (±0.35) m below the soil surface. The third area is a (since 1998) rewetted former agricultural peatland (Horstermeer), close to Oukoop and Stein, with the average annual ground water level at a depth of 0.2 (±0.20) m below the soil surface. During the measurement campaigns we found that both agriculturally managed sites acted as C and GHG sources and the rewetted former agricultural peatland acted as a C and GHG sink. The ecosystem (fields and ditches) total GHG balance, including CO2, CH4 and N2O, amounted to 3.9 (±0.4), 1.3 (±0.5) and -1.7 (±1.8) g CO2-eq m-2 d-1 for Oukoop, Stein and Horstermeer, respectively. Adding the farm-based emissions to Oukoop and Stein resulted in a total GHG emission of 8.3 (±1.0) and 6.6 (±1.3) g CO2-eq m-2 d-1, respectively. For Horstermeer the GHG balance remained the same since no farm-based emissions exist. Considering the C balance (uncertainty range 40-60%), the total C release in Oukoop and Stein is 5270 and 6258 kg C ha-1 yr-1, respectively (including ecosystem and management fluxes), and the total C uptake in Horstermeer is 3538 kg C ha-1 yr-1. Water bodies contributed significantly to the terrestrial GHG balance because of a high release of CH4. Overall, this study suggests that managed peatlands are large sources of GHGs and C, but, if appropriate measures are taken, they can be turned back into GHG and C sinks within 15 years of abandonment and rewetting. The shift from an intensively managed grass-on-peat area (Oukoop) to an extensively managed one (Stein) reduced the GHG emissions mainly because N2O emission and farm-based CH4 emissions decreased.

40 CFR 98.353 - Calculating GHG emissions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... anaerobic reactor and anaerobic lagoon from which biogas is not recovered, estimate annual CH4 emissions... wastewater treatment process n from which biogas is not recovered (metric tons). CH4Gn = Annual mass of CH4... some biogas is recovered, estimate the annual mass of CH4 recovered according to the requirements in...

40 CFR 98.353 - Calculating GHG emissions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... anaerobic reactor and anaerobic lagoon from which biogas is not recovered, estimate annual CH4 emissions... wastewater treatment process n from which biogas is not recovered (metric tons). CH4Gn = Annual mass of CH4... some biogas is recovered, estimate the annual mass of CH4 recovered according to the requirements in...

40 CFR 98.353 - Calculating GHG emissions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... anaerobic reactor and anaerobic lagoon from which biogas is not recovered, estimate annual CH4 emissions... wastewater treatment process n from which biogas is not recovered (metric tons). CH4Gn = Annual mass of CH4... some biogas is recovered, estimate the annual mass of CH4 recovered according to the requirements in...

Exploring sub-daily to seasonal variations in methane exchange in a single-crop rice paddy in central Japan

NASA Astrophysics Data System (ADS)

Iwata, Hiroki; Mano, Masayoshi; Ono, Keisuke; Tokida, Takeshi; Kawazoe, Takahiro; Kosugi, Yoshiko; Sakabe, Ayaka; Takahashi, Kenshi; Miyata, Akira

2018-04-01

Season-long methane (CH4) exchange was observed in a rice paddy field in central Japan (Kanto Region) using the eddy covariance technique to clarify the variations in environmental controls on CH4 exchange in different stages of cultivation. Before heading of rice plant, the CH4 emission depended on wind speed and soil temperature. The soil temperature dependence can be due to an increase in CH4 production, higher molecular diffusion, and higher conductance within rice plant at higher soil temperature. An occurrence of ebullitive emission was also suggested from the wind speed dependence. After heading was completed, relative humidity and water temperature influenced CH4 emission. The amplitude of the diurnal variation in emission increased from 0.03 μmolm-2s-1 in the late pre-heading stage to 0.13 μmolm-2s-1 in the post-heading stage. Induced convective throughflow within the rice aerenchyma after the change in plant structure was attributable to this variation in environmental controls after the heading. After drainage, CH4 emission was confined to short periods after strong rain events. The water level controlled the timing of emission, most likely by influencing the diffusion efficiency from the anoxic soil to the atmosphere and CH4 oxidation in the surface oxic zone. The variation in the dominant transport pathway needs to be accounted for in terrestrial ecosystem models to accurately predict CH4 emission from rice paddies.

A multi-year estimate of methane fluxes in Alaska from CARVE atmospheric observations

PubMed Central

Miller, Scot M.; Miller, Charles E.; Commane, Roisin; Chang, Rachel Y.-W.; Dinardo, Steven J.; Henderson, John M.; Karion, Anna; Lindaas, Jakob; Melton, Joe R.; Miller, John B.; Sweeney, Colm; Wofsy, Steven C.; Michalak, Anna M.

2016-01-01

Methane (CH4) fluxes from Alaska and other arctic regions may be sensitive to thawing permafrost and future climate change, but estimates of both current and future fluxes from the region are uncertain. This study estimates CH4 fluxes across Alaska for 2012–2014 using aircraft observations from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and a geostatistical inverse model (GIM). We find that a simple flux model based on a daily soil temperature map and a static map of wetland extent reproduces the atmospheric CH4 observations at the state-wide, multi-year scale more effectively than global-scale, state-of-the-art process-based models. This result points to a simple and effective way of representing CH4 flux patterns across Alaska. It further suggests that contemporary process-based models can improve their representation of key processes that control fluxes at regional scales, and that more complex processes included in these models cannot be evaluated given the information content of available atmospheric CH4 observations. In addition, we find that CH4 emissions from the North Slope of Alaska account for 24% of the total statewide flux of 1.74 ± 0.44 Tg CH4 (for May–Oct.). Contemporary global-scale process models only attribute an average of 3% of the total flux to this region. This mismatch occurs for two reasons: process models likely underestimate wetland area in regions without visible surface water, and these models prematurely shut down CH4 fluxes at soil temperatures near 0°C. As a consequence, wetlands covered by vegetation and wetlands with persistently cold soils could be larger contributors to natural CH4 fluxes than in process estimates. Lastly, we find that the seasonality of CH4 fluxes varied during 2012–2014, but that total emissions did not differ significantly among years, despite substantial differences in soil temperature and precipitation; year-to-year variability in these environmental conditions did not affect obvious changes in total CH4 fluxes from the state. PMID:28066129

A multi-year estimate of methane fluxes in Alaska from CARVE atmospheric observations.

PubMed

Miller, Scot M; Miller, Charles E; Commane, Roisin; Chang, Rachel Y-W; Dinardo, Steven J; Henderson, John M; Karion, Anna; Lindaas, Jakob; Melton, Joe R; Miller, John B; Sweeney, Colm; Wofsy, Steven C; Michalak, Anna M

2016-10-01

Methane (CH 4 ) fluxes from Alaska and other arctic regions may be sensitive to thawing permafrost and future climate change, but estimates of both current and future fluxes from the region are uncertain. This study estimates CH 4 fluxes across Alaska for 2012-2014 using aircraft observations from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and a geostatistical inverse model (GIM). We find that a simple flux model based on a daily soil temperature map and a static map of wetland extent reproduces the atmospheric CH 4 observations at the state-wide, multi-year scale more effectively than global-scale, state-of-the-art process-based models. This result points to a simple and effective way of representing CH 4 flux patterns across Alaska. It further suggests that contemporary process-based models can improve their representation of key processes that control fluxes at regional scales, and that more complex processes included in these models cannot be evaluated given the information content of available atmospheric CH 4 observations. In addition, we find that CH 4 emissions from the North Slope of Alaska account for 24% of the total statewide flux of 1.74 ± 0.44 Tg CH 4 ( for May-Oct.). Contemporary global-scale process models only attribute an average of 3% of the total flux to this region. This mismatch occurs for two reasons: process models likely underestimate wetland area in regions without visible surface water, and these models prematurely shut down CH 4 fluxes at soil temperatures near 0°C. As a consequence, wetlands covered by vegetation and wetlands with persistently cold soils could be larger contributors to natural CH 4 fluxes than in process estimates. Lastly, we find that the seasonality of CH 4 fluxes varied during 2012-2014, but that total emissions did not differ significantly among years, despite substantial differences in soil temperature and precipitation; year-to-year variability in these environmental conditions did not affect obvious changes in total CH 4 fluxes from the state.

Long-term effect of linseed plus nitrate fed to dairy cows on enteric methane emission and nitrate and nitrite residuals in milk.

PubMed

Guyader, J; Doreau, M; Morgavi, D P; Gérard, C; Loncke, C; Martin, C

2016-07-01

A previous study showed the additive methane (CH4)-mitigating effect of nitrate and linseed fed to non-lactating cows. Before practical application, the use of this new strategy in dairy cows requires further investigation in terms of persistency of methanogenesis reduction and absence of residuals in milk products. The objective of this experiment was to study the long-term effect of linseed plus nitrate on enteric CH4 emission and performance in dairy cows. We also assessed the effect of this feeding strategy on the presence of nitrate residuals in milk products, total tract digestibility, nitrogen (N) balance and rumen fermentation. A total of 16 lactating Holstein cows were allocated to two groups in a randomised design conducted in parallel for 17 weeks. Diets were on a dry matter (DM) basis: (1) control (54% maize silage, 6% hay and 40% concentrate; CON) or (2) control plus 3.5% added fat from linseed and 1.8% nitrate (LIN+NIT). Diets were equivalent in terms of CP (16%), starch (28%) and NDF (33%), and were offered twice daily. Cows were fed ad libitum, except during weeks 5, 16 and 17 in which feed was restricted to 95% of dry matter intake (DMI) to ensure complete consumption of meals during measurement periods. Milk production and DMI were measured weekly. Nitrate and nitrite concentrations in milk and milk products were determined monthly. Daily CH4 emission was quantified in open circuit respiration chambers (weeks 5 and 16). Total tract apparent digestibility, N balance and rumen fermentation parameters were determined in week 17. Daily DMI tended to be lower with LIN+NIT from week 4 to 16 (-5.1 kg/day on average). The LIN+NIT diet decreased milk production during 6 non-consecutive weeks (-2.5 kg/day on average). Nitrate or nitrite residuals were not detected in milk and associated products. The LIN+NIT diet reduced CH4 emission to a similar extent at the beginning and end of the trial (-47%, g/day; -30%, g/kg DMI; -33%, g/kg fat- and protein-corrected milk, on average). Diets did not affect N efficiency and nutrients digestibility. In the rumen, LIN+NIT did not affect protozoa number but reduced total volatile fatty acid (-12%) and propionate (-31%) concentrations. We concluded that linseed plus nitrate may have a long-term CH4-mitigating effect in dairy cows and that consuming milk products from cows fed nitrate may be safe in terms of nitrate and nitrite residuals. Further work is required to optimise the doses of linseed plus nitrate to avoid reduced cows performance.

Seasonal variation in CH4 emissions and production and oxidation potentials at microsites on an oligotrophic pine fen.

PubMed

Saarnio, S; Alm, Jukka; Silvola, Jouko; Lohila, Annalea; Nykänen, Hannu; Martikainen, Pertti J

1997-04-01

 Temporal and spatial variation in CH 4 emissions was studied at hummock, Eriophorum lawn, flark and Carex lawn microsites in an oligotrophic pine fen over the growing season using a static chamber method, and CH 4 production and oxidation potentials in peat profiles from hummock and flark were determined in laboratory incubation experiments. Emissions were lowest in the hummocks, and decreased with increasing hummock height, while in the lawns and flarks they increased with increasing sedge cover. Statistical response functions with water table and peat temperature as independent variables were calculated in order to reconstruct seasonal CH 4 emissions by reference to the time series for peat temperature and water table specific to each microsite type. Mean CH 4 emissions in the whole area in the snow-free period of 1993, weighted in terms of the proportions of the microsites, were 1.7 mol CH 4 m -2 . Potential CH 4 production and oxidation rates were very low in the hummocks rising above the groundwater table, but were relatively similar when expressed per dry weight of peat both in the hummocks and flarks below the water table. The CH 4 production potential increased in autumn at both microsites and CH 4 oxidation potential seemed to decrease. The decrease in temperature in autumn certainly reduced in situ decomposition processes, possibly leaving unused substrates in the peat, which would explain the increase in CH 4 production potential.

Continuous multi-plot measurements of CO2, CH4, N2O and H2O in a managed boreal forest - The importance of accounting for all greenhouse gases

NASA Astrophysics Data System (ADS)

Vestin, P.; Mölder, M.; Sundqvist, E.; Båth, A.; Lehner, I.; Weslien, P.; Klemedtsson, L.; Lindroth, A.

2015-12-01

In order to assess the effects of different management practices on the exchange of greenhouse gases (GHG), it is desirable to perform repeated and parallel measurements on both experimental and control plots. Here we demonstrate how a system system combining eddy covariance and gradient techniques can be used to perform this assessment in a managed forest ecosystem.The net effects of clear-cutting and stump harvesting on GHG fluxes were studied at the ICOS site Norunda, Sweden. Micrometeorological measurements (i.e., flux-gradient measurements in 3 m tall towers) allowed for quantification of CO2, CH4 and H2O fluxes (from May 2010) as well as N2O and H2O fluxes (from June 2011) at two stump harvested plots and two control plots. There was one wetter and one drier plot of each treatment. Air was continuously sampled at two heights in the towers and gas concentrations were analyzed for CH4, CO2, H2O (LGR DLT-100, Los Gatos Research) and N2O, H2O (QCL Mini Monitor, Aerodyne Research). Friction velocities and sensible heat fluxes were measured by sonic anemometers (Gill Windmaster, Gill Instruments Ltd). Automatic chamber measurements (CO2, CH4, H2O) were carried out in the adjacent forest stand and at the clear-cut during 2010.Average CO2 emissions for the first year ranged between 14.4-20.2 ton CO2 ha-1 yr-1. The clear-cut became waterlogged after harvest and a comparison of flux-gradient data and chamber data (from the adjacent forest stand) indicated a switch from a weak CH4 sink to a significant source at all plots. The CH4 emissions ranged between 0.8-4.5 ton CO2-eq. ha-1 yr-1. N2O emissions ranged between 0.4-2.6 ton CO2-eq. ha-1 yr-1. Enhanced N2O emission on the drier stump harvested plot was the only clear treatment effect on GHG fluxes that was observed. Mean CH4 and N2O emissions for the first year of measurements amounted up to 29% and 20% of the mean annual CO2 emissions, respectively. This highlights the importance of including all GHGs when assessing the climate impacts of different forest management options. Our results show that continuous multi-plot measurements of the main GHGs are possible also at sites where GHG fluxes are low, at a reasonable cost and with reduced plot inter-comparison uncertainties.

Isotopic insights into methane production, oxidation, and emissions in Arctic polygon tundra.

PubMed

Vaughn, Lydia J S; Conrad, Mark E; Bill, Markus; Torn, Margaret S

2016-10-01

Arctic wetlands are currently net sources of atmospheric CH4 . Due to their complex biogeochemical controls and high spatial and temporal variability, current net CH4 emissions and gross CH4 processes have been difficult to quantify, and their predicted responses to climate change remain uncertain. We investigated CH4 production, oxidation, and surface emissions in Arctic polygon tundra, across a wet-to-dry permafrost degradation gradient from low-centered (intact) to flat- and high-centered (degraded) polygons. From 3 microtopographic positions (polygon centers, rims, and troughs) along the permafrost degradation gradient, we measured surface CH4 and CO2 fluxes, concentrations and stable isotope compositions of CH4 and DIC at three depths in the soil, and soil moisture and temperature. More degraded sites had lower CH4 emissions, a different primary methanogenic pathway, and greater CH4 oxidation than did intact permafrost sites, to a greater degree than soil moisture or temperature could explain. Surface CH4 flux decreased from 64 nmol m(-2)  s(-1) in intact polygons to 7 nmol m(-2)  s(-1) in degraded polygons, and stable isotope signatures of CH4 and DIC showed that acetate cleavage dominated CH4 production in low-centered polygons, while CO2 reduction was the primary pathway in degraded polygons. We see evidence that differences in water flow and vegetation between intact and degraded polygons contributed to these observations. In contrast to many previous studies, these findings document a mechanism whereby permafrost degradation can lead to local decreases in tundra CH4 emissions. © 2016 John Wiley & Sons Ltd.

Influence of vehicular emissions on atmospheric CH4 and NMHC mixing ratios and its correlation with CO and other VOCs tracers in Mexico City

NASA Astrophysics Data System (ADS)

Solano-Murillo, M.; Torres-Jardón, R.; Ruiz-Suárez, L. G.; Barrera-Huertas, H.; Hernandez-Solis, J. M.

2016-12-01

The Mexico City Metropolitan Area (MCMA) is one of the world's largest and most polluted urban areas. A recent GHC emission inventory for MCMA suggests that vehicular emissions contribute with around 37% of CH4, followed by landfills and dump garbage areas (30%) and construction and manufacturing (27%). Contrary to other urban areas, natural gas is not the main fuel used in MCMA, neither for domestic and industrial heating, nor for transportation. Therefore, there is a great uncertainty about who is the main contributor of CH4 emissions. An intensive monitoring campaign of methane (CH4), Non-methane hydrocarbons (NMHC) and carbon monoxide (CO) was performed between February and March 2015 in southwest MCMA. Methane concentrations showed sometimes a diurnal pattern similar to those of CO and to NMHC but most of the time this similarity was lost (CH4 vs CO, R2 = 0.27; CH4 vs NMHC, R2 = 0.28). However, NMHC correlated well with CO (R2 = 0.75). The intercepts of the CH4-CO correlation resulted in [CH4] 1.8 ppm and that of the CO-NMHC correlation in [CO] 0.080 ppb. The lack of agreement between CH4 and CO indicates these species do not come from the same sources. The results suggest that vehicular emissions are not significant contributors to atmospheric CH4 and that the background methane concentration has not change significantly in 25 years. An attempt to correlate some tracers COVs tracers of vehicular and biomass burning with CH4, NMHC and CH4 is done.

Factors affecting variation in CH4 emission from paddy soils grown with different rice cultivars: A pot experiment

NASA Astrophysics Data System (ADS)

Watanabe, Akira; Kimura, Makoto

1998-08-01

The growth of rice plants greatly influences CH4 emission from paddy fields through the supply of organic materials such as root exudates and sloughed tissues, the release of oxygen to the root environment, and the transfer of CH4 from the rhizosphere into the atmosphere through the aerenchyma. In the present pot experiments, the effects of the release of water-soluble organic substances from roots, the air space in roots, and the CH4-oxidizing capacity of roots on intervarietal differences in CH4 emission were examined using three Japonica type cultivars (Norin 25, Nipponbare, and Aoinokaze), which differ in morphological properties. The CH4 emission rates varied among the cultivars from mid-July (tillering stage) to the beginning of September (heading stage).Total CH4 emission throughout the rice growth period was largest for Norin 25, followed by Nipponbare, and Aoinokaze. In August, the rate of release of water-soluble organic substances from roots was largest for Norin 25. The air space in roots was also largest in Norin 25 and least in Aoinokaze. The stable carbon isotopic ratios (δ13C) of CH4 in roots were 3-10‰ higher than those in soil in August. The difference in δ13C values of CH4 between roots and soil was largest for Aoinokaze and smallest for Norin 25. In September, the difference in δ13C values of CH4 between roots and soil became small (2-3‰). These findings suggest that the proportion of CH4 oxidation in the rhizosphere was largest in the cultivar which emitted the smallest amount of CH4 and that the proportion became smaller with continued plant growth.

Unregulated pollutant emissions from on-road vehicles in China, 1999-2014.

PubMed

Lang, Jianlei; Zhou, Ying; Cheng, Shuiyuan; Zhang, Yanyun; Dong, Meng; Li, Shengyue; Wang, Gang; Zhang, Yonglin

2016-12-15

Multi-year (1999-2014) vehicular unregulated pollutants emissions in China, including SO 2 , CH 4 , N 2 O, NH 3 , Indeno(1,2,3-cd)pyrene (IPY), Benzo(k)fluoranthene (BkF), Benzo(b)fluoranthene (BbF), Benzo(a)pyrene (BaP), dioxins and furans, were estimated based on emission factors calculated by COPERT. The inter-annual trends, correlation with GDP and population, spatial distribution characteristics, contributions from various vehicle types for the ten pollutants emissions were analyzed. Results showed that the emissions of the above ten pollutants changed from approximately 576.9Gg, 130.0Gg, 8.1Gg, 2.1Gg, 1.0Mg, 1.1Mg, 1.4Mg, 0.5Mg, 7.4g and 15.6g in 1999 to 193.8Gg, 171.1Gg, 79.1Gg, 117.8Gg, 3.5Mg, 6.7Mg, 6.8Mg, 2.9Mg, 37.6g and 79.1g in 2014, respectively. Implementation of stringent sulfur content limit during the past decade reduced approximately 94.4% of the SO 2 emission in 2014. CH 4 and N 2 O increased from 1999 to 2011, but began to decrease since 2012; NH 3 emission had the highest annual average change rate (35.5%) from 1999 to 2014; PAHs, dioxins and furans increased continuously during the past decade. The vehicular emissions were higher in Guangdong, Shandong, Henan, Jiangsu, Zhejiang and Hebei. Good linear correlation between vehicular emissions and GDP was found (except SO 2 ); in the provinces/municipalities with higher population density, the emission density was also larger, indicating more significant vehicular emissions' potential damage on human health. HDT and PC, PC and MC, PC and BUS were the major contributors to SO 2 , CH 4 , N 2 O emissions, respectively. In 2014, PC was the dominant contributor to NH 3 emission; PC, BUS and HDT had higher fraction in the total IPY and BaP emissions; HDT was the major contributor to BkF and BbF emissions. In addition, the uncertainties of estimated emissions were also analyzed based on Monte Carlo simulation. Copyright © 2016 Elsevier B.V. All rights reserved.

Use of a portable, automated, open-circuit gas quantification system and the sulfur hexafluoride tracer technique for measuring enteric methane emissions in Holstein cows fed ad libitum or restricted

USDA-ARS?s Scientific Manuscript database

The sulfur hexafluoride tracer technique (SF**6) is a commonly used method for measuring CH**4 enteric emissions in ruminants. Studies using SF**6 have shown large variation in CH**4 emissions data, inconsistencies in CH**4 emissions across studies, and potential methodological errors. Therefore, th...

The variation of methane flux rates from boreal tree species at the beginning of the growing season

NASA Astrophysics Data System (ADS)

Haikarainen, Iikka; Halmeenmäki, Elisa; Machacova, Katerina; Pihlatie, Mari

2016-04-01

Boreal forests are considered as net sink for atmospheric methane (CH4) because of the CH4 oxidizing bacteria in the aerobic soil layer. However, within the last decades it has become more evident that trees play an important role in the global CH4 budget by offering pathways for anaerobically produced CH4 from deeper soil layers to the atmosphere. Furthermore, trees may also act as independent sources of CH4. To confirm magnitude, variability and the origin of the tree mediated CH4 emissions more research is needed, especially in boreal forests which have been in a minority in such investigation. We measured tree stem and shoot CH4 exchange of three boreal tree species at the beginning of the growing season (13.4.-13.6.2015) at SMEAR II station in Hyytiälä, located in southern Finland (61° 51'N, 24° 17'E, 181 asl). The fluxes were measured from silver birch (Betula pendula), downy birch (B. pubescens) and Norway spruce (Picea abies) on two sites with differing soil type and characteristics (paludified and mineral soil), vegetation and forest structure by using the static chamber technique. Scaffold towers were used for measurements at multiple stem heights and shoots. The aim was to study the vertical profile of CH4 fluxes at stem and shoot level and compare these fluxes among the studied species, and to observe temporal changes in CH4 flux over the beginning of the growing season. We found that all the trees emitted CH4 from their stems and shoots. Overall, the birches showed higher emissions compared to the spruces. The emission rates were considerably larger in the lower parts of the birch stems than upper parts, and these emissions increased during the growing season. The spruces had more variation in the stem CH4 flux, but the emission rates of the upper parts of the stem exceeded the birch emissions at the same height. The shoot fluxes of all the studied trees indicated variable CH4 emissions without a clear pattern regarding the vertical profile and progress of the growing season.

Effects of warming and nitrogen fertilization on GHG flux in the permafrost region of an alpine meadow

NASA Astrophysics Data System (ADS)

Chen, Xiaopeng; Wang, Genxu; Zhang, Tao; Mao, Tianxu; Wei, Da; Hu, Zhaoyong; Song, Chunlin

2017-05-01

The limited number of in situ measurements of greenhouse gas (GHG) flux during soil freeze-thaw cycles in permafrost regions limits our ability to accurately predict how the alpine ecosystem carbon sink or source function will vary under future warming and increased nitrogen (N) deposition. An alpine meadow in the permafrost region of the Qinghai-Tibet Plateau was selected, and a simulated warming with N fertilization experiment was carried out to investigate the key GHG fluxes (ecosystem respiration [Re], CH4 and N2O) in the early (EG), mid (MG) and late (LG) growing seasons. The results showed that: (i) warming (4.5 °C) increased the average seasonal Re, CH4 uptake and N2O emission by 73.5%, 65.9% and 431.6%, respectively. N fertilization (4 g N m-2) alone had no significant effect on GHG flux; the interaction of warming and N fertilization enhanced CH4 uptake by 10.3% and N2O emissions by 27.2% than warming, while there was no significant effect on the Re; (ii) the average seasonal fluxes of Re, CH4 and N2O were MG > LG > EG, and Re and CH4 uptake were most sensitive to the soil freezing process instead of soil thawing process; (iii) surface soil temperature was the main driving factor of the Re and CH4 fluxes, and the N2O flux was mainly affected by daily rainfall; (iv) in the growing season, warming increased greenhouse warming potential (GWP) of the alpine meadow by 74.5%, the N fertilization decreased GWP of the warming plots by 13.9% but it was not statistically significant. These results indicate that (i) relative to future climate warming (or permafrost thawing), there could be a hysteresis of GHG flux in the alpine meadow of permafrost region; (ii) under the scenario of climate warming, increasing N deposition has limited impacts on the feedback of GHG flux of the alpine meadow.

The role of forest floor and trees to the ecosystem scale methane budget of boreal forests

NASA Astrophysics Data System (ADS)

Pihlatie, Mari; Halmeenmäki, Elisa; Peltola, Olli; Haikarainen, Iikka; Heinonsalo, Jussi; Santalahti, Minna; Putkinen, Anuliina; Fritze, Hannu; Urban, Otmar; Machacova, Katerina

2016-04-01

Boreal forests are considered as a sink of atmospheric methane (CH4) due to the activity of CH4 oxidizing bacteria (methanotrophs) in the soil. This soil CH4 sink is especially strong for upland forest soils, whereas forests growing on organic soils may act as small sources due to the domination of CH4 production by methanogens in the anaerobic parts of the soil. The role of trees to the ecosystem-scale CH4 fluxes has until recently been neglected due to the perception that trees do not contribute to the CH4 exchange, and also due to difficulties in measuring the CH4 exchange from trees. Findings of aerobic CH4 formation in plants and emissions from tree-stems in temperate and tropical forests during the past decade demonstrate that our understanding of CH4 cycling in forest ecosystems is not complete. Especially the role of forest canopies still remain unresolved, and very little is known of CH4 fluxes from trees in boreal region. We measured the CH4 exchange of tree-stems and tree-canopies from pine (Pinus sylvestris), spruce (Picea abies) and birch (Betula pubescens, Betula pendula) trees growing in Southern Finland (SMEAR II station) on varying soil conditions, from upland mineral soils to paludified soil. We compared the CH4 fluxes from trees to forest-floor CH4 exchange, both measured by static chambers, and to CH4 fluxes measured above the forest canopy by a flux gradient technique. We link the CH4 fluxes from trees and forest floor to physiological activity of the trees, such as transpiration, sap-flow, CO2 net ecosystem exchange (NEE), soil properties such as temperature and moisture, and to the presence of CH4 producing methanogens and CH4 oxidizing methanotrophs in trees or soil. The above canopy CH4 flux measurements show that the whole forest ecosystem was a small source of CH4 over extended periods in the spring and summer 2012, 2014 and 2015. Throughout the 2013-2014 measurements, the forest floor was in total a net sink of CH4, with variation between high CH4 uptake in the dominating dry upland areas and high emissions from the few wet spots of the forest. All the studied tree species emitted small amounts of CH4 from the stems and shoots, with emission rates depending on the season, tree species and soil conditions. Especially, CH4 emissions from birch canopies were high and can therefore contribute significantly to the ecosystem-scale CH4 fluxes. Processes behind the canopy and stem CH4emission remain unresolved, however, ongoing analysis of the methanogens and methanotrophs within the plant-soil systems will reveal whether CH4 production or consumption is of microbial origin. Also, comparison of the CH4 fluxes from trees and forest floor to sap-flow, transpiration, and NEE as well as soil parameters will help to explain the seasonality and mechanisms involved in the CH4 emissions.

Water-saving ground cover rice production system reduces net greenhouse gas fluxes in an annual rice-based cropping system

NASA Astrophysics Data System (ADS)

Yao, Z.; Du, Y.; Tao, Y.; Zheng, X.; Liu, C.; Lin, S.; Butterbach-Bahl, K.

2014-11-01

To safeguard food security and preserve precious water resources, the technology of water-saving ground cover rice production system (GCRPS) is being increasingly adopted for rice cultivation. However, changes in soil water status and temperature under GCRPS may affect soil biogeochemical processes that control the biosphere-atmosphere exchanges of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2). The overall goal of this study is to better understand how net ecosystem greenhouse gas exchanges (NEGE) and grain yields are affected by GCRPS in an annual rice-based cropping system. Our evaluation was based on measurements of the CH4 and N2O fluxes and soil heterotrophic respiration (CO2 emissions) over a complete year, and the estimated soil carbon sequestration intensity for six different fertilizer treatments for conventional paddy and GCRPS. The fertilizer treatments included urea application and no N fertilization for both conventional paddy (CUN and CNN) and GCRPS (GUN and GNN), and solely chicken manure (GCM) and combined urea and chicken manure applications (GUM) for GCRPS. Averaging across all the fertilizer treatments, GCRPS increased annual N2O emission and grain yield by 40 and 9%, respectively, and decreased annual CH4 emission by 69%, while GCRPS did not affect soil CO2 emissions relative to the conventional paddy. The annual direct emission factors of N2O were 4.01, 0.09 and 0.50% for GUN, GCM and GUM, respectively, and 1.52% for the conventional paddy (CUN). The annual soil carbon sequestration intensity under GCRPS was estimated to be an average of -1.33 Mg C ha-1 yr-1, which is approximately 44% higher than the conventional paddy. The annual NEGE were 10.80-11.02 Mg CO2-eq ha-1 yr-1 for the conventional paddy and 3.05-9.37 Mg CO2-eq ha-1 yr-1 for the GCRPS, suggesting the potential feasibility of GCRPS in reducing net greenhouse effects from rice cultivation. Using organic fertilizers for GCRPS considerably reduced annual emissions of CH4 and N2O and increased soil carbon sequestration, resulting in the lowest NEGE (3.05-5.00 Mg CO2-eq ha-1 yr-1). Accordingly, water-saving GCRPS with organic fertilizer amendments was considered the most promising management regime for simultaneously achieving relatively high grain yield and reduced net greenhouse gas emission.

Water-saving ground cover rice production system reduces net greenhouse gas fluxes in an annual rice-based cropping system

NASA Astrophysics Data System (ADS)

Yao, Z.; Du, Y.; Tao, Y.; Zheng, X.; Liu, C.; Lin, S.; Butterbach-Bahl, K.

2014-06-01

To safeguard food security and preserve precious water resources, the technology of water-saving ground cover rice production system (GCRPS) is being increasingly adopted for the rice cultivation. However, changes in soil water status and temperature under GCRPS may affect soil biogeochemical processes that control the biosphere-atmosphere exchanges of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2). The overall goal of this study is to better understand how net ecosystem greenhouse gas exchanges (NEGE) and grain yields are affected by GCRPS in an annual rice-based cropping system. Our evaluation was based on measurements of the CH4 and N2O fluxes and soil heterotrophic respiration (CO2 emission) over a complete year, as well as the estimated soil carbon sequestration intensity for six different fertilizer treatments for conventional paddy and GCRPS. The fertilizer treatments included urea application and no N fertilization for both conventional paddy (CUN and CNN) and GCRPS (GUN and GNN), solely chicken manure (GCM) and combined urea and chicken manure applications (GUM) for GCRPS. Averaging across all the fertilizer treatments, GCRPS increased annual N2O emission and grain yield by 40% and 9%, respectively, and decreased annual CH4 emission by 69%, while GCRPS did not affect soil CO2 emissions relative to the conventional paddy. The annual direct emission factors of N2O were 4.01, 0.087 and 0.50% for GUN, GCM and GUM, respectively, and 1.52% for the conventional paddy (CUN). The annual soil carbon sequestration intensity under GCRPS was estimated to be an average of -1.33 Mg C ha-1 yr-1, which is approximately 44% higher than the conventional paddy. The annual NEGE were 10.80-11.02 Mg CO2-eq ha-1 yr-1 for the conventional paddy and 3.05-9.37 Mg CO2-eq ha-1 yr-1 for the GCRPS, suggesting the potential feasibility of GCRPS in reducing net greenhouse effect from rice cultivation. Using organic fertilizers for GCRPS considerably reduced annual emissions of CH4 and N2O and increased soil carbon sequestration, resulting in the lowest NEGE (3.05-5.00 Mg CO2-eq ha-1 yr-1). Accordingly, water-saving GCRPS with organic fertilizer amendments was considered the most promising management regime for simultaneously achieving relatively high grain yield and reduced net greenhouse gas emission.

Mitigation of Methane and Odor using a Pilot-Scale Engineered Biocover at a Landfill, South Korea

NASA Astrophysics Data System (ADS)

Bomin, K.; O, G. C.; Ryu, H. W.; Jeon, J. M.; Cho, K. S.

2016-12-01

Landfill is an important anthropogenic source of methane (CH4) and odorous gases. In South Korea, 37% (0.5 Tg/y) of annual anthropogenic CH4 emissions come from landfills, which represent the third largest source of anthropogenic CH4 emissions. Moreover, civil complaints on landfill odor have been gradually increased. Biocovers have been demonstrated as promising solutions to mitigate CH4 and odors from landfills. The pilot-scale biocover (10 m in length x 5 m in width x 1 m in depth) was constructed at a landfill, Gwangyang, South Korea. The mixture of soil and perlite was used as packing materials, and EG microbial agent was used as an inoculum source. Methane removal efficiencies were 21% 72% from Feburary to May. Based on the dilution-to-threshold ratios derived by the air dilution sensory test, the removal efficiencies for complex odor were ranged from 95% to 99%. The packing materials of biocover were sampled from each of the following depth intervals: 0-15 cm, 15-30 cm, and 30-50 cm, and CH4 and DMS degradation rates were measured in serum bottles experiment. CH4 and DMS average degradation rates were the fastest in the 15-30 cm depth. Average degradation rates of CH4 and DMS in the 15-30 cm depth were 208±2.68 and 82±3.04 μg·g dry soil-1·h-1, respectively. Specific degradation rate were calculated excluding the lag time. CH4 specific degradation rate was the fastest in the 0-15 cm depth (329±14.45 μg·g dry soil-1·h-1), while DMS specific degradation rate was the fastest in the 30-50 cm depth (106±6.93 μg·g dry soil-1·h-1). The filling materials of biocover were sampled during winter, spring and summer. And three samples were examined bacterial communities by 16S rRNA pyrosequencing analysis. In order to clarify the relationship between the community structures and CH4/odor concentration, network analysis using extended local similarity analysis (eLSA) was also conducted. According to a phylogenic analysis, Methylobacter (40.4 42.1%) and Flavobacterium (20.2 38.2%) were the most prevalent species in the pilot-scale biocover. Methylobacter (Methanotrophics of Type I) are responsible for methane oxidation and can be identified in the biocover.

CH_{4} production in the deep soil as a source of stem CH_{4} emission in Fagus sylvatica}

NASA Astrophysics Data System (ADS)

Maier, Martin; Machacova, Katerina; Urban, Otmar; Lang, Friederike

2017-04-01

Predicting greenhouse gas (GHG) fluxes on a global scale requires understanding fluxes on the local scale. Understanding GHG processes in soil-plant-atmosphere systems is essential to understand and mitigate GHG fluxes on the local scale. Forests are known to act as carbon sink. Yet, trees at waterlogged sites are known to emit large amounts of CH4, what can offset the positive GHG balance due the CO2 that is sequestered as wood. Generally, upland trees like European beech (Fagus sylvatica L.) are assumed not to emit CH4, and the upland forest soils are regarded as CH4 sinks. Soil-atmosphere fluxes and stem-atmosphere fluxes of CH4 were studied together with soil gas profiles at two upland beech forest sites in Germany and Czech Republic. Soil was a net CH4 sink at both sites. While most trees showed no or low emissions, one beech tree had exorbitant CH4 emissions that were higher than the CH4 sink capacity of the soil. A soil survey showed strong redoximorphic color patterns in the soil adjacent to this tree. Although the soil around the tree was taking up CH4, the soil gas profiles around this tree showed CH4 production at a soil depth >0.3 m. We interpret the coincidence of the production of CH4 in the deep soil below the beech with the large stem emissions as strong hint that there is a transport link between the soil and stem. We think that the root system represents a preferential transport system for CH4 despite the fact that beech roots usually do not have a special gas transport tissue. The observed CH4 stem emissions represent an important CH4 flux in this ecosystem, and, thus, should be considered in future research. Acknowledgement This research was supported by the Czech Academy of Sciences and the German Academic Exchange Service within the project "Methane (CH4) and nitrous oxide (N2O) emissions from Fagus sylvatica trees" (DAAD-15-03), the Czech Science Foundation (17-18112Y), National Programme for Sustainability I (LO1415) and project DFG (MA 5826/2-1). We would like to thank Marek Jakubik, Sinikka Paulus, Ellen Halaburt and Sally Haddad for technical support.

Influence of water table fluctuations on subsurface methane dynamics and surface fluxes in seasonally flooded subtropical pastures.

NASA Astrophysics Data System (ADS)

Chamberlain, S.; Gomez-Casanovas, N.; Boughton, E.; Keel, E.; Walter, M. T.; Groffman, P. M.; Sparks, J. P.

2015-12-01

Seasonally flooded subtropical pastures are major sources of methane (CH4), and periodic flooding drives complex emission dynamics from these ecosystems. Understanding the mechanisms of belowground CH4 dynamics driving soil surface fluxes is needed to better understand emissions from these systems and their response to environmental change. We investigated subsurface CH4 dynamics in relation to net surface fluxes using laboratory water table manipulations and compared these results to eddy covariance-measured fluxes to link within-soil CH4 dynamics to observed ecosystem fluxes. Pronounced hysteresis was observed in ecosystem CH4 fluxes during precipitation driven flooding events. This dynamic was replicated in mesocosm experiments, with maximum CH4 fluxes observed during periods of water table recession. Hysteresis dynamics were best explained by oxygen dynamics during precipitation recharge events and the oxidation of CH4 produced in organic soil horizons during water table recession. We observed distinct CH4 dynamics between surface organic and deeper mineral soil horizons. In surface organic soil horizons, high levels of CH4 production were temporally linked to observed surface emissions. In contrast, high concentrations of CH4 observed in deeper mineral soils did not contribute to surface fluxes. Methane production potentials in surface organic soils were orders of magnitude higher than in mineral soils, suggesting that over longer flooding regimes CH4 produced in mineral horizons is unlikely to be a significant component of net surface emissions. Our results demonstrate that distinct CH4 dynamics may be stratified by depth, and flooding of the near-surface organic soils drives the high magnitude CH4 fluxes observed from subtropical pastures. These results suggest that relatively small changes in pasture water table dynamics can drive large changes in net CH4 emissions if surface organic soils remain saturated over longer time scales.

Inter-Annual Variability of Area-Scaled Gaseous Carbon Emissions from Wetland Soils in the Liaohe Delta, China.

PubMed

Ye, Siyuan; Krauss, Ken W; Brix, Hans; Wei, Mengjie; Olsson, Linda; Yu, Xueyang; Ma, Xueying; Wang, Jin; Yuan, Hongming; Zhao, Guangming; Ding, Xigui; Moss, Rebecca F

2016-01-01

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO2 and CH4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO2 and CH4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km2. One percent is Suaeda salsa, 24% is Phragmites australis, and 75% is rice. While S. salsa wetlands are under somewhat natural tidal influence, P. australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO2 and CH4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO2 (~98%). Photosynthetic uptake of CO2 would mitigate most of the soil CO2 emissions, but CH4 emissions would persist. Overall, CH4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling.

Inter-Annual Variability of Area-Scaled Gaseous Carbon Emissions from Wetland Soils in the Liaohe Delta, China

PubMed Central

Ye, Siyuan; Krauss, Ken W.; Brix, Hans; Wei, Mengjie; Olsson, Linda; Yu, Xueyang; Ma, Xueying; Wang, Jin; Yuan, Hongming; Zhao, Guangming; Ding, Xigui; Moss, Rebecca F.

2016-01-01

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO2 and CH4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO2 and CH4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km2. One percent is Suaeda salsa, 24% is Phragmites australis, and 75% is rice. While S. salsa wetlands are under somewhat natural tidal influence, P. australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO2 and CH4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO2 (~98%). Photosynthetic uptake of CO2 would mitigate most of the soil CO2 emissions, but CH4 emissions would persist. Overall, CH4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling. PMID:27501148

Top-down estimates of methane and nitrogen oxide emissions from shale gas production regions using aircraft measurements and a mesoscale Bayesian inversion system together with a flux ratio inversion technique

NASA Astrophysics Data System (ADS)

Cui, Y.; Brioude, J. F.; Angevine, W. M.; McKeen, S. A.; Henze, D. K.; Bousserez, N.; Liu, Z.; McDonald, B.; Peischl, J.; Ryerson, T. B.; Frost, G. J.; Trainer, M.

2016-12-01

Production of unconventional natural gas grew rapidly during the past ten years in the US which led to an increase in emissions of methane (CH4) and, depending on the shale region, nitrogen oxides (NOx). In terms of radiative forcing, CH4 is the second most important greenhouse gas after CO2. NOx is a precursor of ozone (O3) in the troposphere and nitrate particles, both of which are regulated by the US Clean Air Act. Emission estimates of CH4 and NOx from the shale regions are still highly uncertain. We present top-down estimates of CH4 and NOx surface fluxes from the Haynesville and Fayetteville shale production regions using aircraft data collected during the Southeast Nexus of Climate Change and Air Quality (SENEX) field campaign (June-July, 2013) and the Shale Oil and Natural Gas Nexus (SONGNEX) field campaign (March-May, 2015) within a mesoscale inversion framework. The inversion method is based on a mesoscale Bayesian inversion system using multiple transport models. EPA's 2011 National CH4 and NOx Emission Inventories are used as prior information to optimize CH4 and NOx emissions. Furthermore, the posterior CH4 emission estimates are used to constrain NOx emission estimates using a flux ratio inversion technique. Sensitivity of the posterior estimates to the use of off-diagonal terms in the error covariance matrices, the transport models, and prior estimates is discussed. Compared to the ground-based in-situ observations, the optimized CH4 and NOx inventories improve ground level CH4 and O3 concentrations calculated by the Weather Research and Forecasting mesoscale model coupled with chemistry (WRF-Chem).

Simulated nitrogen deposition reduces CH4 uptake and increases N2O emission from a subtropical plantation forest soil in southern China.

PubMed

Wang, Yongsheng; Cheng, Shulan; Fang, Huajun; Yu, Guirui; Xu, Minjie; Dang, Xusheng; Li, Linsen; Wang, Lei

2014-01-01

To date, few studies are conducted to quantify the effects of reduced ammonium (NH4+) and oxidized nitrate (NO3-) on soil CH4 uptake and N2O emission in the subtropical forests. In this study, NH4Cl and NaNO3 fertilizers were applied at three rates: 0, 40 and 120 kg N ha(-1) yr(-1). Soil CH4 and N2O fluxes were determined twice a week using the static chamber technique and gas chromatography. Soil temperature and moisture were simultaneously measured. Soil dissolved N concentration in 0-20 cm depth was measured weekly to examine the regulation to soil CH4 and N2O fluxes. Our results showed that one year of N addition did not affect soil temperature, soil moisture, soil total dissolved N (TDN) and NH4+-N concentrations, but high levels of applied NH4Cl and NaNO3 fertilizers significantly increased soil NO3(-)-N concentration by 124% and 157%, respectively. Nitrogen addition tended to inhibit soil CH4 uptake, but significantly promoted soil N2O emission by 403% to 762%. Furthermore, NH4+-N fertilizer application had a stronger inhibition to soil CH4 uptake and a stronger promotion to soil N2O emission than NO3(-)-N application. Also, both soil CH4 and N2O fluxes were driven by soil temperature and moisture, but soil inorganic N availability was a key integrator of soil CH4 uptake and N2O emission. These results suggest that the subtropical plantation soil sensitively responses to atmospheric N deposition, and inorganic N rather than organic N is the regulator to soil CH4 uptake and N2O emission.

Methane emissions from floodplains in the Amazon Basin: towards a process-based model for global applications

NASA Astrophysics Data System (ADS)

Ringeval, B.; Houweling, S.; van Bodegom, P. M.; Spahni, R.; van Beek, R.; Joos, F.; Röckmann, T.

2013-10-01

Tropical wetlands are estimated to represent about 50% of the natural wetland emissions and explain a large fraction of the observed CH4 variability on time scales ranging from glacial-interglacial cycles to the currently observed year-to-year variability. Despite their importance, however, tropical wetlands are poorly represented in global models aiming to predict global CH4 emissions. This study documents the first regional-scale, process-based model of CH4 emissions from tropical floodplains. The LPX-Bern Dynamic Global Vegetation Model (LPX hereafter) was modified to represent floodplain hydrology, vegetation and associated CH4 emissions. The extent of tropical floodplains was prescribed using output from the spatially-explicit hydrology model PCR-GLOBWB. We introduced new Plant Functional Types (PFTs) that explicitly represent floodplain vegetation. The PFT parameterizations were evaluated against available remote sensing datasets (GLC2000 land cover and MODIS Net Primary Productivity). Simulated CH4 flux densities were evaluated against field observations and regional flux inventories. Simulated CH4 emissions at Amazon Basin scale were compared to model simulations performed in the WETCHIMP intercomparison project. We found that LPX simulated CH4 flux densities are in reasonable agreement with observations at the field scale but with a~tendency to overestimate the flux observed at specific sites. In addition, the model did not reproduce between-site variations or between-year variations within a site. Unfortunately, site informations are too limited to attest or disprove some model features. At the Amazon Basin scale, our results underline the large uncertainty in the magnitude of wetland CH4 emissions. In particular, uncertainties in floodplain extent (i.e., difference between GLC2000 and PCR-GLOBWB output) modulate the simulated emissions by a factor of about 2. Our best estimates, using PCR-GLOBWB in combination with GLC2000, lead to simulated Amazon-integrated emissions of 44.4 ± 4.8 Tg yr-1. Additionally, the LPX emissions are highly sensitive to vegetation distribution. Two simulations with the same mean PFT cover, but different spatial distributions of grasslands within the basin modulated emissions by about 20%. Correcting the LPX simulated NPP using MODIS reduces the Amazon emissions by 11.3%. Finally, due to an intrinsic limitation of LPX to account for seasonality in floodplain extent, the model failed to reproduce the seasonality in CH4 emissions. The Inter Annual Variability (IAV) of the emissions increases by 90% if the IAV in floodplain extent is account for, but still remains lower than in most of WETCHIMP models. While our model includes more mechanisms specific to tropical floodplains, we were unable to reduce the uncertainty in the magnitude of wetland CH4 emissions of the Amazon Basin. Our results stress the need for more research to constrain floodplain CH4 emissions and their temporal variability.

On the methane paradox: Transport from shallow water zones rather than in situ methanogenesis is the major source of CH4 in the open surface water of lakes

NASA Astrophysics Data System (ADS)

Encinas Fernández, Jorge; Peeters, Frank; Hofmann, Hilmar

2016-10-01

Estimates of global methane (CH4) emissions from lakes and the contributions of different pathways are currently under debate. In situ methanogenesis linked to algae growth was recently suggested to be the major source of CH4 fluxes from aquatic systems. However, based on our very large data set on CH4 distributions within lakes, we demonstrate here that methane-enriched water from shallow water zones is the most likely source of the basin-wide mean CH4 concentrations in the surface water of lakes. Consistently, the mean surface CH4 concentrations are significantly correlated with the ratio between the surface area of the shallow water zone and the entire lake, fA,s/t, but not with the total surface area. The categorization of CH4 fluxes according to fA,s/t may therefore improve global estimates of CH4 emissions from lakes. Furthermore, CH4 concentrations increase substantially with water temperature, indicating that seasonally resolved data are required to accurately estimate annual CH4 emissions.

A black alder plantation improves the greenhouse gas balance of a degraded moist peat grassland

NASA Astrophysics Data System (ADS)

Bereswill, Sarah; Hoffmann, Mathias; Huth, Vytas; Popova, Yulia; Zak, Dominik; Augustin, Jürgen

2017-04-01

Drained peatlands are among the strongest terrestrial sources of the greenhouse gases (GHG) CO2 and N2O. Therefore, activities of peatland revitalisation through rewetting, often combined with the implementation of peat forming vegetation, aim to restore the GHG sink function that is characteristic for pristine peatlands. Black alder (Alnus glutinosa) naturally occurs in temperate marshes and minerotrophic peatlands (= fens) and is also suitable for paludiculture, the cultivation of biomass on wet or rewetted peatlands. However, only little information exists, if a black alder plantation can reduce the climate impact of restored peatlands. Therefore, we investigated the effect of a newly established black alder plantation on the net GHG balance of a degraded fen in north-eastern Germany during a two-year study (August 2010 - August 2012). We compared the alder plantation (Awet) with an extensively used meadow (Mwet) both characterized by very moist soil conditions and a drier reference meadow (Mdry) characterized by moderately moist soil conditions. CO2, CH4 and N2O fluxes were measured monthly to bi-monthly with the manual closed chamber method. Fluxes were calculated using a modular R script and gap filled to obtain continuous daily fluxes. Awet was a net GHG sink of -4.8 t CO2-eq ha-1 yr-1, Mwet was climate neutral (-0.03 t CO2-eq ha-1 yr-1), and Mdry was a net GHG source of 15.7 t CO2-eq ha-1 yr-1. This was mainly caused by CO2 uptake at the two very moist sites and a high CO2 release at the drier reference site. In addition, Awet was a larger CO2 sink than Mwet, likely caused by an additional CO2 uptake of the alder stand. All sites were significant CH4 sources. Due to inundation following extraordinarily heavy precipitation in summer 2011 remarkable CH4emission peaks were found on all sites which accounted for up to 70 % of the cumulated two-year CH4emissions. However, overall Awet emitted significantly lesser CH4(4.9 g C m-2 yr-1). We assume that the black alders decreased the CH4emissions due to their effective O2 transport mechanism. N2O emissions were negligible at all three sites. Our results indicate that rewetting and planting black alders significantly improve the GHG balances of formerly drained fens already in the first two years after plantation. Furthermore, only one wet summer significantly increased the CH4 emissions of our study site, despite two-year average groundwater levels (GWL) of -0.2 to -0.35 m. This highlights the importance of acknowledging extreme precipitation events and groundwater fluctuations for the derivation of reliable GHG emission factors.

Enhanced Oxidation Capacity from Photolytic HOx/NOx Recycling: Implications for CH4 Growth

NASA Astrophysics Data System (ADS)

Madronich, S.

2017-12-01

Oxidation by OH radicals converts many emitted compounds (CO, CH4, VOCs as well as NOx, SO2, HCFCs, and others) to more soluble forms that can be removed rapidly from the atmosphere, e.g., by deposition. In a chemically stable atmosphere (without runaway concentration growth) the rate of OH production must generally exceed the emission rates of the reduced compounds, but secondary chemistry complicates OH budgets. If emission rates (e.g., E for CH4) increase, OH concentrations can either decrease or increase depending on NOx conditions, causing a non-linear dependence of CH4 concentrations on its emissions, [CH4] Ef where f, the methane feedback factor, is currently estimated in global 3d models to be 1.3-1.4. This feature is robust among models, and can be reproduced in simpler box models with the canonical Ox-HOx-NOx chemistry, in which global OH is increased by NOx emissions and decreased by CO, CH4, and VOC emissions. Scenarios with lower NOx emissions but higher CH4 emissions point to substantially lower global oxidation capacity in the future. Several newly hypothesized processes have attracted attention in recent years, including the photolytic recycling of OH from biogenic VOCs, and the photolysis of particulate nitrates to regenerate NOx. The latter process could be particularly significant in regions far from NOx emissions, where low NOx levels are more efficient at generating O3 and OH. To the extent that these processes do occur, they may provide some buffering of global OH against CH4 variations (f nearer 1), and more generally against anthropogenic perturbations. However, critical measurements from both lab and field are needed to assess the importance of these proposed processes.

Effective Suppression of Methane Emission by 2-Bromoethanesulfonate during Rice Cultivation.

PubMed

Waghmode, Tatoba R; Haque, Md Mozammel; Kim, Sang Yoon; Kim, Pil Joo

2015-01-01

2-bromoethanesulfonate (BES) is a structural analogue of coenzyme M (Co-M) and potent inhibitor of methanogenesis. Several studies confirmed, BES can inhibit CH4 prodcution in rice soil, but the suppressing effectiveness of BES application on CH4 emission under rice cultivation has not been studied. In this pot experiment, different levels of BES (0, 20, 40 and 80 mg kg-1) were applied to study its effect on CH4 emission and plant growth during rice cultivation. Application of BES effectively suppressed CH4 emission when compared with control soil during rice cultivation. The CH4 emission rates were significantly (P<0.001) decreased by BES application possibly due to significant (P<0.001) reduction of methnaogenic biomarkers like Co-M concentration and mcrA gene copy number (i.e. methanogenic abunadance). BES significantly (P<0.001) reduced methanogen activity, while it did not affect soil dehydrogenase activity during rice cultivation. A rice plant growth and yield parameters were not affected by BES application. The maximum CH4 reduction (49% reduction over control) was found at 80 mg kg-1 BES application during rice cultivation. It is, therefore, concluded that BES could be a suitable soil amendment for reducing CH4 emission without affecting rice plant growth and productivity during rice cultivation.

Inter-seasonal and spatial distribution of ground-level greenhouse gases (CO2, CH4, N2O) over Nagpur in India and their management roadmap.

PubMed

Majumdar, Deepanjan; Rao, Padma; Maske, Nilam

2017-03-01

Ground-level concentrations of carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) were monitored over three seasons, i.e., post-monsoon (September-October), winter (January-February), and summer (May-June) for 1 year during 2013-2014 in Nagpur City in India. The selected gases had moderate to high variation both spatially (residential, commercial, traffic intersections, residential cum commercial sites) and temporally (at 7:00, 13:00, 18:00, and 23:00 hours in all three seasons). Concentrations of gases were randomly distributed diurnally over city in all seasons, and there was no specific increasing or decreasing trend with time in a day. Average CO 2 and N 2 O concentrations in winter were higher over post-monsoon and summer while CH 4 had highest average concentration in summer. Observed concentrations of CO 2 were predominantly above global average of 400 ppmv while N 2 O and CH 4 concentrations frequently dropped down below global average of 327 ppbv and 1.8 ppmv, respectively. Two-tailed Student's t test indicated that post-monsoon CO 2 concentrations were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). CH 4 concentrations in all seasons were statistically at par to each other. In case of N 2 O, concentrations in post-monsoon were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). Average ground-level concentrations of the gases calculated for three seasons together were higher in commercial areas. Environmental management priorities vis a vis greenhouse gas emissions in the city are also discussed.

Variability and Quasi-Decadal Changes in the Methane Budget over the Period 2000-2012

NASA Technical Reports Server (NTRS)

Saunois, Marielle; Bousquet, Philippe; Poulter, Ben; Peregon, Anna; Ciais, Philippe; Canadell, Josep G.; Dlugokencky, Edward J.; Etiope, Giuseppe; Bastviken, David; Houweling, Sander;

Variability and quasi-decadal changes in the methane budget over the period 2000-2012

NASA Astrophysics Data System (ADS)

Saunois, Marielle; Bousquet, Philippe; Poulter, Ben; Peregon, Anna; Ciais, Philippe; Canadell, Josep G.; Dlugokencky, Edward J.; Etiope, Giuseppe; Bastviken, David; Houweling, Sander; Janssens-Maenhout, Greet; Tubiello, Francesco N.; Castaldi, Simona; Jackson, Robert B.; Alexe, Mihai; Arora, Vivek K.; Beerling, David J.; Bergamaschi, Peter; Blake, Donald R.; Brailsford, Gordon; Bruhwiler, Lori; Crevoisier, Cyril; Crill, Patrick; Covey, Kristofer; Frankenberg, Christian; Gedney, Nicola; Höglund-Isaksson, Lena; Ishizawa, Misa; Ito, Akihiko; Joos, Fortunat; Kim, Heon-Sook; Kleinen, Thomas; Krummel, Paul; Lamarque, Jean-François; Langenfelds, Ray; Locatelli, Robin; Machida, Toshinobu; Maksyutov, Shamil; Melton, Joe R.; Morino, Isamu; Naik, Vaishali; O'Doherty, Simon; Parmentier, Frans-Jan W.; Patra, Prabir K.; Peng, Changhui; Peng, Shushi; Peters, Glen P.; Pison, Isabelle; Prinn, Ronald; Ramonet, Michel; Riley, William J.; Saito, Makoto; Santini, Monia; Schroeder, Ronny; Simpson, Isobel J.; Spahni, Renato; Takizawa, Atsushi; Thornton, Brett F.; Tian, Hanqin; Tohjima, Yasunori; Viovy, Nicolas; Voulgarakis, Apostolos; Weiss, Ray; Wilton, David J.; Wiltshire, Andy; Worthy, Doug; Wunch, Debra; Xu, Xiyan; Yoshida, Yukio; Zhang, Bowen; Zhang, Zhen; Zhu, Qiuan

2017-09-01

Following the recent Global Carbon Project (GCP) synthesis of the decadal methane (CH4) budget over 2000-2012 (Saunois et al., 2016), we analyse here the same dataset with a focus on quasi-decadal and inter-annual variability in CH4 emissions. The GCP dataset integrates results from top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up models (including process-based models for estimating land surface emissions and atmospheric chemistry), inventories of anthropogenic emissions, and data-driven approaches. The annual global methane emissions from top-down studies, which by construction match the observed methane growth rate within their uncertainties, all show an increase in total methane emissions over the period 2000-2012, but this increase is not linear over the 13 years. Despite differences between individual studies, the mean emission anomaly of the top-down ensemble shows no significant trend in total methane emissions over the period 2000-2006, during the plateau of atmospheric methane mole fractions, and also over the period 2008-2012, during the renewed atmospheric methane increase. However, the top-down ensemble mean produces an emission shift between 2006 and 2008, leading to 22 [16-32] Tg CH4 yr-1 higher methane emissions over the period 2008-2012 compared to 2002-2006. This emission increase mostly originated from the tropics, with a smaller contribution from mid-latitudes and no significant change from boreal regions. The regional contributions remain uncertain in top-down studies. Tropical South America and South and East Asia seem to contribute the most to the emission increase in the tropics. However, these two regions have only limited atmospheric measurements and remain therefore poorly constrained. The sectorial partitioning of this emission increase between the periods 2002-2006 and 2008-2012 differs from one atmospheric inversion study to another. However, all top-down studies suggest smaller changes in fossil fuel emissions (from oil, gas, and coal industries) compared to the mean of the bottom-up inventories included in this study. This difference is partly driven by a smaller emission change in China from the top-down studies compared to the estimate in the Emission Database for Global Atmospheric Research (EDGARv4.2) inventory, which should be revised to smaller values in a near future. We apply isotopic signatures to the emission changes estimated for individual studies based on five emission sectors and find that for six individual top-down studies (out of eight) the average isotopic signature of the emission changes is not consistent with the observed change in atmospheric 13CH4. However, the partitioning in emission change derived from the ensemble mean is consistent with this isotopic constraint. At the global scale, the top-down ensemble mean suggests that the dominant contribution to the resumed atmospheric CH4 growth after 2006 comes from microbial sources (more from agriculture and waste sectors than from natural wetlands), with an uncertain but smaller contribution from fossil CH4 emissions. In addition, a decrease in biomass burning emissions (in agreement with the biomass burning emission databases) makes the balance of sources consistent with atmospheric 13CH4 observations. In most of the top-down studies included here, OH concentrations are considered constant over the years (seasonal variations but without any inter-annual variability). As a result, the methane loss (in particular through OH oxidation) varies mainly through the change in methane concentrations and not its oxidants. For these reasons, changes in the methane loss could not be properly investigated in this study, although it may play a significant role in the recent atmospheric methane changes as briefly discussed at the end of the paper.

Observations of the birth of a small coronal hole

NASA Technical Reports Server (NTRS)

Solodyna, C. V.; Krieger, A. S.; Nolte, J. T.

1977-01-01

Using soft X-ray data from the S-054 X-ray spectrographic telescope aboard Skylab, we observed temporal changes in the emission structure of the X-ray corona associated with the birth of a small coronal hole. Designated as CH6, this coronal hole was born near the equator in a time interval less than 9-1/2 hr. By constructing a light curve for a point near the center of CH6, we observed a sudden 40% decrease in X-ray emission associated with the birth of this coronal hole. On a time scale of hours, the growth of CH6 in area proceeded faster than the average rate predicted by the diffusion of solar fields. The short term decay of CH6 followed the diffusive rate to within experimental uncertainty. On a time scale of one rotation, the subsequent development of CH6 was not consistent with steady growth at the average rate predicted by diffusion.

Identification, Comparison, and Validation of Robust Rumen Microbial Biomarkers for Methane Emissions Using Diverse Bos Taurus Breeds and Basal Diets

PubMed Central

Auffret, Marc D.; Stewart, Robert; Dewhurst, Richard J.; Duthie, Carol-Anne; Rooke, John A.; Wallace, Robert J.; Freeman, Tom C.; Snelling, Timothy J.; Watson, Mick; Roehe, Rainer

2018-01-01

Previous shotgun metagenomic analyses of ruminal digesta identified some microbial information that might be useful as biomarkers to select cattle that emit less methane (CH4), which is a potent greenhouse gas. It is known that methane production (g/kgDMI) and to an extent the microbial community is heritable and therefore biomarkers can offer a method of selecting cattle for low methane emitting phenotypes. In this study a wider range of Bos Taurus cattle, varying in breed and diet, was investigated to determine microbial communities and genetic markers associated with high/low CH4 emissions. Digesta samples were taken from 50 beef cattle, comprising four cattle breeds, receiving two basal diets containing different proportions of concentrate and also including feed additives (nitrate or lipid), that may influence methane emissions. A combination of partial least square analysis and network analysis enabled the identification of the most significant and robust biomarkers of CH4 emissions (VIP > 0.8) across diets and breeds when comparing all potential biomarkers together. Genes associated with the hydrogenotrophic methanogenesis pathway converting carbon dioxide to methane, provided the dominant biomarkers of CH4 emissions and methanogens were the microbial populations most closely correlated with CH4 emissions and identified by metagenomics. Moreover, these genes grouped together as confirmed by network analysis for each independent experiment and when combined. Finally, the genes involved in the methane synthesis pathway explained a higher proportion of variation in CH4 emissions by PLS analysis compared to phylogenetic parameters or functional genes. These results confirmed the reproducibility of the analysis and the advantage to use these genes as robust biomarkers of CH4 emissions. Volatile fatty acid concentrations and ratios were significantly correlated with CH4, but these factors were not identified as robust enough for predictive purposes. Moreover, the methanotrophic Methylomonas genus was found to be negatively correlated with CH4. Finally, this study confirmed the importance of using robust and applicable biomarkers from the microbiome as a proxy of CH4 emissions across diverse production systems and environments. PMID:29375511

Identification, Comparison, and Validation of Robust Rumen Microbial Biomarkers for Methane Emissions Using Diverse Bos Taurus Breeds and Basal Diets.

PubMed

Auffret, Marc D; Stewart, Robert; Dewhurst, Richard J; Duthie, Carol-Anne; Rooke, John A; Wallace, Robert J; Freeman, Tom C; Snelling, Timothy J; Watson, Mick; Roehe, Rainer

2017-01-01

Previous shotgun metagenomic analyses of ruminal digesta identified some microbial information that might be useful as biomarkers to select cattle that emit less methane (CH 4 ), which is a potent greenhouse gas. It is known that methane production (g/kgDMI) and to an extent the microbial community is heritable and therefore biomarkers can offer a method of selecting cattle for low methane emitting phenotypes. In this study a wider range of Bos Taurus cattle, varying in breed and diet, was investigated to determine microbial communities and genetic markers associated with high/low CH 4 emissions. Digesta samples were taken from 50 beef cattle, comprising four cattle breeds, receiving two basal diets containing different proportions of concentrate and also including feed additives (nitrate or lipid), that may influence methane emissions. A combination of partial least square analysis and network analysis enabled the identification of the most significant and robust biomarkers of CH 4 emissions (VIP > 0.8) across diets and breeds when comparing all potential biomarkers together. Genes associated with the hydrogenotrophic methanogenesis pathway converting carbon dioxide to methane, provided the dominant biomarkers of CH 4 emissions and methanogens were the microbial populations most closely correlated with CH 4 emissions and identified by metagenomics. Moreover, these genes grouped together as confirmed by network analysis for each independent experiment and when combined. Finally, the genes involved in the methane synthesis pathway explained a higher proportion of variation in CH 4 emissions by PLS analysis compared to phylogenetic parameters or functional genes. These results confirmed the reproducibility of the analysis and the advantage to use these genes as robust biomarkers of CH 4 emissions. Volatile fatty acid concentrations and ratios were significantly correlated with CH 4 , but these factors were not identified as robust enough for predictive purposes. Moreover, the methanotrophic Methylomonas genus was found to be negatively correlated with CH 4 . Finally, this study confirmed the importance of using robust and applicable biomarkers from the microbiome as a proxy of CH 4 emissions across diverse production systems and environments.

More CH4 is emitted during the fallow than during the growing season in a Mediterranean rice agrosystems

NASA Astrophysics Data System (ADS)

Martínez-Eixarch, Maite; Ibàñez, Carles; Alcaraz, Carles; Viñas, Marc; Aranda, Xavier; Saldaña, J. Antonio

2017-04-01

Paddy rice fields are an important source of greenhouse gas emissions (GHG) as they contribute 5 to 20 % of the global anthropogenic CH4 emissions. The Ebre Delta (Catalonia, NE Spain) is one of the most important wetland complexes in the Western Mediterranean with 65 % of its area covered by rice fields. The results herein presented assess the annual pattern of CH4 emissions from paddy rice in Ebre Delta, including the growing and fallow seasons as well as the major environmental variables modulating such emissions. Fifteen rice fields covering the geo-physical variability of the Ebre Delta were selected for GHG monitoring. Common agronomic management was practiced: water direct-seeding, permanent flooding and moderate mineral fertilization during the growing season and straw incorporation, progressive drainage of the fields after the harvest. Fields are left fallow during the winter. GHG were monthly sampled, from May to December in 2015. In each field, three closed chambers were used; from each of these, four gas samples were taken over a 30-minute period. Simultaneously, hydrological regime, soil physic-chemical parameters and plant cover were measured. GHG were analysed by gas chromatography. A Generalized linear model analysis (GLM) was performed to assess the most important influencing factors on CH4 emissions. An information-theoretic approach was used to find the best approximating models. Overall, the CH4 emissions showed a bi-modal pattern, with peaks in July-August and in October. Emissions rates ranged from 2.1 ± 0.5 to 7.5 ± 1.4 mg C-CH4 m-2 h-1 in the growing season (May to September) and from 25.0 ± 5.7 to 20.1 ± 3.3 mg C-CH4 m-2 h-1 at post-harvest (October to December). In total, 314 kg C-CH4 ha-1 were emitted from Ebre Delta rice fields, of which 70 % during post-harvest. Larger off-season emissions were likely induced by straw incorporation. The results of the GLM-IT analysis revealed that during the growing season, soil Eh and water level were the most important factors influencing CH4 emissions, followed by soil temperature and plant cover, with similar degree of importance. During the fallow season, soil redox and water level were also the most important factors, along with air temperature. Throughout the growing and fallow seasons, soil Eh was negatively related to CH4 emissions whereas temperature and plant cover positively. Interestingly, water level showed a contrasting effect on CH4 emissions: positive during the growing season and negative the fallow. Traditionally, most of the research on GHG mitigation options in paddy rice has been focused on the rice growing period and less attention has been paid to the post-harvest season. The higher contribution of the fallow season to the total annual CH4 emissions evidenced in our study suggests that more effort should be made on this season when aiming at mitigating CH4 emissions, being water and straw management the key factors. Accordingly, we also recommend the inclusion of the fallow season for GHG inventories from paddy rice, usually neglected, to avoid CH4 emissions underestimations.

Impact of elevated CO2, water table, and temperature changes on CO2 and CH4 fluxes from arctic tundra soils

NASA Astrophysics Data System (ADS)

Zona, Donatella; Haynes, Katherine; Deutschman, Douglas; Bryant, Emma; McEwing, Katherine; Davidson, Scott; Oechel, Walter

2015-04-01

Large uncertainties still exist on the response of tundra C emissions to future climate due, in part, to the lack of understanding of the interactive effects of potentially controlling variables on C emissions from Arctic ecosystems. In this study we subjected 48 soil cores (without active vegetation) from dominant arctic wetland vegetation types, to a laboratory manipulation of elevated atmospheric CO2, elevated temperature, and altered water table, representing current and future conditions in the Arctic for two growing seasons. To our knowledge this experiment comprised the most extensively replicated manipulation of intact soil cores in the Arctic. The hydrological status of the soil was the most dominant control on both soil CO2 and CH4 emissions. Despite higher soil CO2 emission occurring in the drier plots, substantial CO2 respiration occurred under flooded conditions, suggesting significant anaerobic respirations in these arctic tundra ecosystems. Importantly, a critical control on soil CO2 and CH4 fluxes was the original vascular plant cover. The dissolved organic carbon (DOC) concentration was correlated with cumulative CH4 emissions but not with cumulative CO2 suggesting C quality influenced CH4 production but not soil CO2 emissions. An interactive effect between increased temperature and elevated CO2 on soil CO2 emissions suggested a potential shift of the soils microbial community towards more efficient soil organic matter degraders with warming and elevated CO2. Methane emissions did not decrease over the course of the experiment, even with no input from vegetation. This result indicated that CH4 emissions are not carbon limited in these C rich soils. Overall CH4 emissions represented about 49% of the sum of total C (C-CO2 + C-CH4) emission in the wet treatments, and 15% in the dry treatments, representing a dominant component of the overall C balance from arctic soils.

Comprehensive effects of a sedge plant on CH4 and N2O emissions in an estuarine marsh

NASA Astrophysics Data System (ADS)

Li, Yangjie; Wang, Dongqi; Chen, Zhenlou; Hu, Hong

2018-05-01

Although there have been numerous studies focusing on plants' roles in methane (CH4) emissions, the influencing mechanism of wetland plants on nitrous oxide (N2O) emissions has rarely been studied. Here, we test whether wetland plants also play an important role in N2O emissions. Gas fluxes were determined using the in situ static flux chamber technique. We also carried out pore-water extractions, sedge removal experiments and tests of N2O transportation. The brackish marsh acted as a net source of both CH4 and N2O. However, sedge plants played the opposite role in CH4 and N2O emissions. The removal of the sedges led to reduced CH4 emissions and increased accumulation of CH4 inside the sediment. Apart from being a conduit for CH4 transport, the sedges made a greater contribution to CH4 oxidation than CH4 production. The sedges exerted inhibitory effects on the release of N2O. The N2O was barely detectable inside the sediment in both vegetated and vegetation-removed plots. The denitrification measurements and nitrogen addition (the addition rates were equal to 0.028, 0.056 and 0.112 g m-2) experiments suggest that denitrification associated with N2O production occurred mainly in the surface sediment layer. The vascular sedge could transport atmospheric N2O downward into the rhizosphere. The rhizospheric sediment, together with the vascular sedge, became an effective sink of atmospheric N2O.

Discrepant responses of methane emissions to additions with different organic compound classes of rice straw in paddy soil.

PubMed

Tan, Wenbing; Yu, Hanxia; Huang, Caihong; Li, Dan; Zhang, Hui; Jia, Yufu; Wang, Guoan; Xi, Beidou

2018-07-15

Crop straw incorporation has become a prevailing agricultural practice that guarantees the food production and security. There is a significant body of work on the effects of straw incorporation on the methane (CH 4 ) emissions in paddy fields. However, it is unclear whether there are diverse links between CH 4 emission dynamics and incorporations of different organic compound classes of straw to paddy fields. In this study, soil incubations were conducted to assess the respective effect of incorporations of hydrolysable amino acid (HAA), dilute-acid extractable carbohydrate (DAC), lipid and acid-insoluble organic matter (AIOM) fractions of rice straw on the CH 4 emission in paddy soil. It is revealed that incorporations of HAA and DAC fractions exert the greatest intensities to stimulate the CH 4 emissions, which mainly takes place in the early period of incubation; on contrary, the incorporation of lipid fraction exerts the lowest intensity and mainly takes place in the late period. The pattern of CH 4 emission after incorporation of AIOM fraction occurs peaks both in the early and late periods of incubation. Our findings highlight that the time of occurrence and intensity of effects of rice straw incorporation on CH 4 emissions vary significantly depending on the different organic compound classes of rice straw, which may be key to proposing a promising management strategy for mitigating CH 4 emissions in paddy fields in the context of straw incorporation. Copyright © 2018 Elsevier B.V. All rights reserved.

Invited Review: Measuring the respiratory gas exchange by grazing cattle using the GreenFeed emissions monitoring system

USDA-ARS?s Scientific Manuscript database

Ruminants are a source of enteric methane (CH4), which has been identified as a greenhouse gas that contributes to climate change. With interest in developing technologies to decrease enteric CH4 emission, systems are currently being developed to measure the CH4 emission by cattle. An issue with g...

Modelling methane emissions from natural wetlands by development and application of the TRIPLEX-GHG model

USGS Publications Warehouse

Zhu, Qing; Liu, Jinxun; Peng, C.; Chen, H.; Fang, X.; Jiang, H.; Yang, G.; Zhu, D.; Wang, W.; Zhou, X.

2014-01-01

A new process-based model TRIPLEX-GHG was developed based on the Integrated Biosphere Simulator (IBIS), coupled with a new methane (CH4) biogeochemistry module (incorporating CH4 production, oxidation, and transportation processes) and a water table module to investigate CH4 emission processes and dynamics that occur in natural wetlands. Sensitivity analysis indicates that the most sensitive parameters to evaluate CH4 emission processes from wetlands are r (defined as the CH4 to CO2 release ratio) and Q10 in the CH4 production process. These two parameters were subsequently calibrated to data obtained from 19 sites collected from approximately 35 studies across different wetlands globally. Being heterogeneously spatially distributed, r ranged from 0.1 to 0.7 with a mean value of 0.23, and the Q10 for CH4 production ranged from 1.6 to 4.5 with a mean value of 2.48. The model performed well when simulating magnitude and capturing temporal patterns in CH4 emissions from natural wetlands. Results suggest that the model is able to be applied to different wetlands under varying conditions and is also applicable for global-scale simulations.

[Effects of filamentous macroalgae on the methane emission from urban river: a review].

PubMed

Zhang, Xiu-Yun; Liang, Xia; He, Chi-Quan

2013-05-01

The global warming caused by greenhouse gases emission has raised serious concerns. Recent studies found that the carbon dioxide (CO2) and methane (CH4) emissions from river ecosystem can partly offset the carbon sequestration by terrestrial ecosystem, leading to a rethink of the effects of river ecosystem on the global carbon balance and greenhouse gases emission inventory. As an important primary producer in urban river ecosystem, filamentous macroalgae can deeply affect the carbon cycle process of river system through changing the abiotic and biotic factors in the interface of water-sediment. This paper reviewed the effects of filamentous macroalgae on the CH4 emission from urban river system from the aspects of 1) the effects of urbanization on the river ecosystem and its CH4 emission flux, 2) the effects of filamentous macroalgae on the CH4 generation and emission process in natural river systems, and 3) the effects of filamentous macroalgae on the primary productivity and CH4 emission process in urban river systems. The current problems and future directions in related researches were discussed and prospected.

The impact of water management practices and associated methane emissions on subtropical pasture greenhouse gas budgets and ecosystem service payments

NASA Astrophysics Data System (ADS)

Chamberlain, S.; Groffman, P. M.; Boughton, E.; Gomez-Casanovas, N.; DeLucia, E. H.; Bernacchi, C.; Sparks, J. P.

2016-12-01

Pastures are an extensive land cover type, however patterns in pasture greenhouse gas (GHG) exchange vary widely depending on climate and land management. Understanding this variation is important, as pastures may be a net GHG source or sink depending on these factors. We quantified carbon dioxide (CO2) and methane (CH4) fluxes from subtropical pastures in south Florida for three years using eddy covariance, and estimated annual budgets of CO2, CH4, and GHG equivalent emissions. We also explored the influence of water retention practices on pasture GHG budgets by combining data from a multi-year pasture water retention experiment with CH4 flux data from our eddy covariance tower to 1) estimate the influence of water retention on surface soil flooding, and 2) estimate the influence of extended surface soil flooding on CH4 emissions. These findings were then used to assess the impact of CH4 emissions on stakeholder payments for water retention services in a carbon market framework. The pastures were net CO2 sinks sequestering up to 163 ± 54 g CO2-C m-2 yr-1, but were also strong CH4 sources emitting up to 23.5 ± 2.1 g CH4-C m-2 yr-1. Accounting for the global warming potential of CH4, the pastures were strong GHG sources emitting up to 584 ± 78 g CO2 eq. m-2 yr-1. Our analysis suggests CH4 emissions due to increased flooding from water management practices is a small component of the pasture GHG budget, and water retention likely contributes 2-11% of pasture GHG emissions. These emissions could reduce water retention payments by up to 12% if stakeholders were required to pay for current GHG emissions in a carbon market. It would require at least 93.7 kg CH4-C emissions per acre-foot water storage for carbon market costs to exceed water retention payments, and this scenario is highly unlikely as we estimate current practices are responsible for 11.3 ± 7.2 kg CH4-C emissions per acre-foot of water storage. Our results demonstrate that water retention practices aimed at reducing nutrient loading to the Everglades are likely responsible for only a minor increase in pasture GHG emissions and would have a small economic consequence in a carbon market.

Are closed landfills free of CH_{4} emissions? A case study of Arico's landfill, Tenerife, Canary Islands

NASA Astrophysics Data System (ADS)

Barrancos, José; Cook, Jenny; Phillips, Victoria; Asensio-Ramos, María; Melián, Gladys; Hernández, Pedro A.; Pérez, Nemesio M.

2016-04-01

Landfills are authentic chemical and biological reactors that introduce in the environment a wide amount of gas pollutants (CO2, CH4, volatile organic compounds, etc.) and leachates. Even after years of being closed, a significant amount of landfill gas could be released to the atmosphere through the surface in a diffuse form, also known as non-controlled emission. The study of the spatial-temporal distribution of diffuse emissions provides information of how a landfill degassing takes place. The main objective of this study was to estimate the diffuse uncontrolled emission of CH4 into the atmosphere from the closed Arico's landfill (0.3 km2) in Tenerife Island, Spain. To do so, a non-controlled biogenic gas emission survey of nearly 450 sampling sites was carried out during August 2015. Surface gas sampling and surface landfill CO2 efflux measurements were carried out at each sampling site by means of a portable non-dispersive infrared spectrophotometer (NDIR) model LICOR Li800 following the accumulation chamber method. Landfill gases, CO2 and CH4, were analyzed using a double channel VARIAN 4900 micro-GC. The CH4 efflux was computed combining CO2 efflux and CH4/CO2 ratio in the landfill's surface gas. To quantify the total CH4 emission, CH4 efflux contour map was constructed using sequential Gaussian simulation (sGs) as interpolation method. The total diffuse CH4 emission was estimated in 2.2 t d-1, with CH4 efflux values ranging from 0-922 mg m-2 d-1. This type of studies provides knowledge of how a landfill degasses and serves to public and private entities to establish effective systems for extraction of biogas. This aims not only to achieve higher levels of controlled gas release from landfills resulting in a higher level of energy production but also will contribute to minimize air pollution caused by them.

Improving and Assessing Aircraft-based Greenhouse Gas Emission Rate Measurements at Indianapolis as part of the INFLUX project.

NASA Astrophysics Data System (ADS)

Heimburger, A. M. F.; Shepson, P. B.; Stirm, B. H.; Susdorf, C.; Cambaliza, M. O. L.

2015-12-01

Since the Copenhagen accord in 2009, several countries have affirmed their commitment to reduce their greenhouse gas emissions. The United States and Canada committed to reduce their emissions by 17% below 2005 levels, by 2020, Europe by 14% and China by ~40%. To achieve such targets, coherent and effective strategies in mitigating atmospheric carbon emissions must be implemented in the next decades. Whether such goals are actually achieved, they require that reductions are "measurable", "reportable", and "verifiable". Management of greenhouse gas emissions must focus on urban environments since ~74% of CO2 emissions worldwide will be from cities, while measurement approaches are highly uncertain (~50% to >100%). The Indianapolis Flux Experiment (INFLUX) was established to develop, assess and improve top-down and bottom-up quantifications of urban greenhouse gas emissions. Based on an aircraft mass balance approach, we performed a series of experiments focused on the improvement of CO2, CH4 and CO emission rates quantification from Indianapolis, our final objective being to drastically improve the method overall uncertainty from the previous estimate of 50%. In November-December 2014, we conducted nine methodologically identical mass balance experiments in a short period of time (24 days, one downwind distance) for assumed constant total emission rate conditions, as a means to obtain an improved standard deviation of the mean determination. By averaging the individual emission rate determinations, we were able to obtain a method precision of 17% and 16% for CO2 and CO, respectively, at the 95%C.L. CH4 emission rates are highly variable day to day, leading to precision of 60%. Our results show that repetitive sampling can enable improvement in precision of the aircraft top-down methods through averaging.

Diurnal and seasonal variations of greenhouse gas emissions from a naturally ventilated dairy barn in a cold region

NASA Astrophysics Data System (ADS)

Huang, Dandan; Guo, Huiqing

2018-01-01

Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions were quantified for a naturally ventilated free-stall dairy barn in the Canadian Prairies climate through continuous measurements for a year from February 2015 to January 2016, with ventilation rate estimated by a CO2 mass balance method. The results were categorized into seasonal emission profiles with monthly data measured on a typical day, and diurnal profiles in cold (January), warm (July), and mild seasons (October) of all three gases. Seasonal CO2, CH4, and N2O concentrations greatly fluctuated within ranges of 593-2433 ppm, 15-152 ppm, and 0.32-0.40 ppm, respectively, with obviously higher concentrations in the cold season. Emission factors of the three gases were summarized: seasonal N2O emission varied between 0.5 and 10 μg s-1 AU-1 with lower emission in the cold season, while seasonal CO2 and CH4 emissions were within narrow ranges of 112-119 mg s-1 AU-1 and 2.5-3.5 mg s-1 AU-1. The result suggested a lower enteric CH4 emission for dairy cows than that estimated by Environment Canada (2014). Significant diurnal effects (P < 0.05) were observed for CH4 emissions in all seasons with higher emissions in the afternoons and evenings. The total greenhouse gas (GHG) emission, which was calculated by summing the three GHG in CO2 equivalent, was mainly contributed by CO2 and CH4 emissions and showed no significant seasonal variations (P > 0.05), but obvious diurnal variations in all seasons. In comparison with previous studies, it was found that the dairy barn in a cold region climate with smaller vent openings had relatively higher indoor CO2 and CH4 concentrations, but comparable CO2 and CH4 emissions to most previous studies. Besides, ventilation rate, temperature, and relative humidity all significantly affected the three gas concentrations with the outdoor temperature being the most relevant factor (P < 0.01); however, they showed less or no statistical relations to emissions.

Testing a biofilter cover design to mitigate dairy effluent pond methane emissions.

PubMed

Pratt, Chris; Deslippe, Julie; Tate, Kevin R

2013-01-02

Biofiltration, whereby CH(4) is oxidized by methanotrophic bacteria, is a potentially effective strategy for mitigating CH(4) emissions from anaerobic dairy effluent lagoons/ponds, which typically produce insufficient biogas for energy recovery. This study reports on the effectiveness of a biofilter cover design at oxidizing CH(4) produced by dairy effluent ponds. Three substrates, a volcanic pumice soil, a garden-waste compost, and a mixture of the two, were tested as media for the biofilters. All substrates were suspended as 5 cm covers overlying simulated dairy effluent ponds. Methane fluxes supplied to the filters were commensurate with emission rates from typical dairy effluent ponds. All substrates oxidized more than 95% of the CH(4) influx (13.9 g CH(4) m(-3) h(-1)) after two months and continued to display high oxidation rates for the remaining one month of the trial. The volcanic soil biofilters exhibited the highest oxidation rates (99% removal). When the influx CH(4) dose was doubled for a month, CH(4) removal rates remained >90% for all substrates (maximum = 98%, for the volcanic soil), suggesting that biofilters have a high capacity to respond to increases in CH(4) loads. Nitrous oxide emissions from the biofilters were negligible (maximum = 19.9 mg N(2)O m(-3) h(-1)) compared with CH(4) oxidation rates, particularly from the volcanic soil that had a much lower microbial-N (75 mg kg(-1)) content than the compost-based filters (>240 mg kg(-1)). The high and sustained CH(4) oxidation rates observed in this laboratory study indicate that a biofilter cover design is a potentially efficient method to mitigate CH(4) emissions from dairy effluent ponds. The design should now be tested under field conditions.

Deep peat warming increases surface methane and carbon dioxide emissions in a black spruce-dominated ombrotrophic bog.

PubMed

Gill, Allison L; Giasson, Marc-André; Yu, Rieka; Finzi, Adrien C

2017-12-01

Boreal peatlands contain approximately 500 Pg carbon (C) in the soil, emit globally significant quantities of methane (CH 4 ), and are highly sensitive to climate change. Warming associated with global climate change is likely to increase the rate of the temperature-sensitive processes that decompose stored organic carbon and release carbon dioxide (CO 2 ) and CH 4 . Variation in the temperature sensitivity of CO 2 and CH 4 production and increased peat aerobicity due to enhanced growing-season evapotranspiration may alter the nature of peatland trace gas emission. As CH 4 is a powerful greenhouse gas with 34 times the warming potential of CO 2 , it is critical to understand how factors associated with global change will influence surface CO 2 and CH 4 fluxes. Here, we leverage the Spruce and Peatland Responses Under Changing Environments (SPRUCE) climate change manipulation experiment to understand the impact of a 0-9°C gradient in deep belowground warming ("Deep Peat Heat", DPH) on peat surface CO 2 and CH 4 fluxes. We find that DPH treatments increased both CO 2 and CH 4 emission. Methane production was more sensitive to warming than CO 2 production, decreasing the C-CO 2 :C-CH 4 of the respired carbon. Methane production is dominated by hydrogenotrophic methanogenesis but deep peat warming increased the δ 13 C of CH 4 suggesting an increasing contribution of acetoclastic methanogenesis to total CH 4 production with warming. Although the total quantity of C emitted from the SPRUCE Bog as CH 4 is <2%, CH 4 represents >50% of seasonal C emissions in the highest-warming treatments when adjusted for CO 2 equivalents on a 100-year timescale. These results suggest that warming in boreal regions may increase CH 4 emissions from peatlands and result in a positive feedback to ongoing warming. © 2017 John Wiley & Sons Ltd.

Methane emission from ruminants and solid waste: A critical analysis of baseline and mitigation projections for climate and policy studies

NASA Astrophysics Data System (ADS)

Matthews, E.

2012-12-01

Current and projected estimates of methane (CH4) emission from anthropogenic sources are numerous but largely unexamined or compared. Presented here is a critical appraisal of CH4 projections used in climate-chemistry and policy studies. We compare emissions for major CH4 sources from several groups, including our own new data and RCP projections developed for climate-chemistry models for the next IPCC Assessment Report (AR5). We focus on current and projected baseline and mitigation emissions from ruminant animals and solid waste that are both predicted to rise dramatically in coming decades, driven primarily by developing countries. For waste, drivers include increasing urban populations, higher per capita waste generation due to economic growth and increasing landfilling rates. Analysis of a new global data base detailing waste composition, collection and disposal indicates that IPCC-based methodologies and default data overestimate CH4 emission for the current period which cascades into substantial overestimates in future projections. CH4 emission from solid waste is estimated to be ~10-15 Tg CH4/yr currently rather than the ~35 Tg/yr often reported in the literature. Moreover, emissions from developing countries are unlikely to rise rapidly in coming decades because new management approaches, such as sanitary landfills, that would increase emissions are maladapted to infrastructures in these countries and therefore unlikely to be implemented. The low current emission associated with solid waste (~10 Tg), together with future modest growth, implies that mitigation of waste-related CH4 emission is a poor candidate for slowing global warming. In the case of ruminant animals (~90 Tg CH4/yr currently), the dominant assumption driving future trajectories of CH4 emission is a substantial increase in meat and dairy consumption in developing countries to be satisfied by growing animal populations. Unlike solid waste, current ruminant emissions among studies exhibit a narrow range that does not necessarily signal low uncertainty but rather a reliance on similar animal statistics and emission factors. The UN Food and Agriculture Organization (FAO) projects 2000-2030 growth rates of livestock for most developing countries at 2% to >3% annually. However, the assumption of rapidly rising meat consumption is not supported by current trends nor by resource availability. For example, increased meat consumption in China and other developing countries is poultry and pork that do not affect CH4 emissions, suggesting that the rapid growth projected for all animals, boosting growth in CH4 emission, will not occur. From a resource standpoint, large increases in cattle, sheep and goat populations, especially for African countries (~60% by 2030), are not supportable on arid grazing lands that require very low stocking rates and semi-nomadic management. Increases projected for African animal populations would require either that about 2/3 more animals are grazed on increasingly drier lands or that all non-forested areas become grazing lands. Similar to solid waste, future methane emission from ruminant animals is likely to grow modestly although animals are not a likely candidate for CH4 mitigation due to their dispersed distribution throughout widely varying agricultural systems under very local management.

Effects of Different Vegetation Zones on CH4 and N2O Emissions in Coastal Wetlands: A Model Case Study

PubMed Central

Liu, Yuhong; Wang, Lixin; Bao, Shumei; Liu, Huamin; Yu, Junbao; Wang, Yu; Shao, Hongbo; Ouyang, Yan; An, Shuqing

2014-01-01

The coastal wetland ecosystems are important in the global carbon and nitrogen cycle and global climate change. For higher fragility of coastal wetlands induced by human activities, the roles of coastal wetland ecosystems in CH4 and N2O emissions are becoming more important. This study used a DNDC model to simulate current and future CH4 and N2O emissions of coastal wetlands in four sites along the latitude in China. The simulation results showed that different vegetation zones, including bare beach, Spartina beach, and Phragmites beach, produced different emissions of CH4 and N2O in the same latitude region. Correlation analysis indicated that vegetation types, water level, temperature, and soil organic carbon content are the main factors affecting emissions of CH4 and N2O in coastal wetlands. PMID:24892044

Can we explain the observed methane variability after the Mount Pinatubo eruption?

NASA Astrophysics Data System (ADS)

Bândă, N.; Krol, M.; van Weele, M.; van Noije, T.; Le Sager, P.; Röckmann, T.

2016-01-01

The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr-1 in the growth rate over the course of 1992 was reported, and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as El Niño-Southern Oscillation (ENSO) and biomass burning events. Emissions of CO, NOX and non-methane volatile organic compounds (NMVOCs) also affected CH4 concentrations indirectly by influencing tropospheric OH levels.

Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 8-10 ppb yr-1 CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6&nash;9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.

Management practices and controls on methane emissions from sub-tropical wetlands

NASA Astrophysics Data System (ADS)

DeLucia, Nicholas; Casa-Nova Gomez, Nuri; Bernacchi, Carl

2015-04-01

It is well documented that green house gas concentrations have risen at unequivocal rates since the industrial revolution but the disparity between anthropogenic sources and natural sources is uncertain. Wetlands are one example of a natural ecosystem that can be a substantial source or sink for methane (CH4) depending on any combination of climate conditions, natural and anthropogenic disturbances, or ecosystem perturbations. Due to strict anaerobic conditions required for CH4-generating microorganisms, natural wetlands are the main source for biogenic CH4. Although wetlands occupy less than 5% of total land surface area, they contribute approximately 20% of total CH4 emissions to the atmosphere. CH4 is one of the most damaging green house gases with current emission estimates ranging from 55 to 231 Tg CH4 yr-1. The processes regulating CH4 emissions are sensitive to land use and management practices of areas surrounding wetlands. Variation in adjacent vegetation or grazing intensity by livestock can, for example, alter CH4 fluxes from wetland soils by altering nutrient balance, carbon inputs and hydrology. Therefore, understanding how these changes will affect wetland source strength is essential to understand the impact of wetland management practices on the global climate system. In this study we quantify wetland methane fluxes from subtropical wetlands on a working cattle ranch in central Florida near Okeechobee Lake (27o10'52.04"N, 81o21'8.56"W). To determine differences in CH4 fluxes associated with land use and management, a replicated (n = 4) full factorial experiment was designed for wetlands where the surrounding vegetation was (1) grazed or un-grazed and (2) composed of native vegetation or improved pasture. Net exchange of CH4 and CO2 between the land surface and the atmosphere were sampled with a LICOR Li-7700 open path CH4 analyzer and Li-7500A open path CO2/H20 analyzer mounted in a 1-m3 static gas-exchange chamber. Our results showed and verified that CH4 emissions from subtropical wetlands were larger when high soil moisture was coupled with high temperatures. Grazing alone, does not appear to alter net ecosystem CH4 emissions from subtropical semi-native and improved wetlands. Pasture type is a stronger indicator of wetland methane potential. Wetlands embedded in improved pastures exhibited periods of increased methane emission that was particularly noticeable during the wet season (July- Nov). These results help quantify GHG emissions from subtropical wetlands under different management practices while demonstrating the differences in these fluxes based on the surrounding ecosystem.

Methane airborne measurements and comparison to global models during BARCA

NASA Astrophysics Data System (ADS)

Beck, Veronika; Chen, Huilin; Gerbig, Christoph; Bergamaschi, Peter; Bruhwiler, Lori; Houweling, Sander; Röckmann, Thomas; Kolle, Olaf; Steinbach, Julia; Koch, Thomas; Sapart, Célia J.; van der Veen, Carina; Frankenberg, Christian; Andreae, Meinrat O.; Artaxo, Paulo; Longo, Karla M.; Wofsy, Steven C.

2012-08-01

Tropical regions, especially the Amazon region, account for large emissions of methane (CH4). Here, we present CH4 observations from two airborne campaigns conducted within the BARCA (Balanço Atmosférico Regional de Carbono na Amazônia) project in the Amazon basin in November 2008 (end of the dry season) and May 2009 (end of the wet season). We performed continuous measurements of CH4 onboard an aircraft for the first time in the Amazon region, covering the whole Amazon basin with over 150 vertical profiles between altitudes of 500 m and 4000 m. The observations support the finding of previous ground-based, airborne, and satellite measurements that the Amazon basin is a large source of atmospheric CH4. Isotope analysis verified that the majority of emissions can be attributed to CH4 emissions from wetlands, while urban CH4 emissions could be also traced back to biogenic origin. A comparison of five TM5 based global CH4 inversions with the observations clearly indicates that the inversions using SCIAMACHY observations represent the BARCA observations best. The calculated CH4 flux estimate obtained from the mismatch between observations and TM5-modeled CH4 fields ranges from 36 to 43 mg m-2 d-1 for the Amazon lowland region.

Modeling methane emissions by cattle production systems in Mexico

NASA Astrophysics Data System (ADS)

Castelan-Ortega, O. A.; Ku Vera, J.; Molina, L. T.

2013-12-01

Methane emissions from livestock is one of the largest sources of methane in Mexico. The purpose of the present paper is to provide a realistic estimate of the national inventory of methane produced by the enteric fermentation of cattle, based on an integrated simulation model, and to provide estimates of CH4 produced by cattle fed typical diets from the tropical and temperate climates of Mexico. The Mexican cattle population of 23.3 million heads was divided in two groups. The first group (7.8 million heads), represents cattle of the tropical climate regions. The second group (15.5 million heads), are the cattle in the temperate climate regions. This approach allows incorporating the effect of diet on CH4 production into the analysis because the quality of forages is lower in the tropics than in temperate regions. Cattle population in every group was subdivided into two categories: cows (COW) and other type of cattle (OTHE), which included calves, heifers, steers and bulls. The daily CH4 production by each category of animal along an average production cycle of 365 days was simulated, instead of using a default emission factor as in Tier 1 approach. Daily milk yield, live weight changes associated with the lactation, and dry matter intake, were simulated for the entire production cycle. The Moe and Tyrrell (1979) model was used to simulate CH4 production for the COW category, the linear model of Mills et al. (2003) for the OTHE category in temperate regions and the Kurihara et al. (1999) model for the OTHE category in the tropical regions as it has been developed for cattle fed tropical diets. All models were integrated with a cow submodel to form an Integrated Simulation Model (ISM). The AFRC (1993) equations and the lactation curve model of Morant and Gnanasakthy (1989) were used to construct the cow submodel. The ISM simulates on a daily basis the CH4 production, milk yield, live weight changes associated with lactation and dry matter intake. The total daily CH4 emission per region was calculated by multiplying the number of heads of cattle in each region by their corresponding simulated emission factor, either COW or OTHE, as predicted by the ISM. The total CH4 emissions from the Mexican cattle population was then calculated by adding up the daily emissions from each region. The predicted total emission of methane produced by the 23.3 million heads of cattle in Mexico is approximately 2.02 Tg/year, from which 1.28 Tg is produced by cattle in temperate regions and the rest by cattle in the tropics. It was concluded that the modeling approach was suitable in producing a better estimate of the national methane inventory for cattle. It is flexible enough to incorporate more cattle groups or classification schemes and productivity levels.

Mitigation of nitrous oxide (N2 O) emission from swine wastewater treatment in an aerobic bioreactor packed with carbon fibers.

PubMed

Yamashita, Takahiro; Yamamoto-Ikemoto, Ryoko; Yokoyama, Hiroshi; Kawahara, Hirofumi; Ogino, Akifumi; Osada, Takashi

2015-03-01

Mitigation of nitrous oxide (N2 O) emission from swine wastewater treatment was demonstrated in an aerobic bioreactor packed with carbon fibers (CF reactor). The CF reactor had a demonstrated advantage in mitigating N2 O emission and avoiding NOx (NO3  + NO2 ) accumulation. The N2 O emission factor was 0.0003 g N2 O-N/gTN-load in the CF bioreactor compared to 0.03 gN2 O-N/gTN-load in an activated sludge reactor (AS reactor). N2 O and CH4 emissions from the CF reactor were 42 g-CO2 eq/m(3) /day, while those from the AS reactor were 725 g-CO2 eq/m(3) /day. The dissolved inorganic nitrogen (DIN) in the CF reactor removed an average of 156 mg/L of the NH4 -N, and accumulated an average of 14 mg/L of the NO3 -N. In contrast, the DIN in the AS reactor removed an average 144 mg/L of the NH4 -N and accumulated an average 183 mg/L of the NO3 -N. NO2 -N was almost undetectable in both reactors. © 2014 Japanese Society of Animal Science.

Mitigation of methane emissions in cities: How new measurements and partnerships can contribute to emissions reduction strategies

DOE PAGES

Hopkins, Francesca M.; Ehleringer, James R.; Bush, Susan E.; ...

2016-09-10

Cities generate 70% of anthropogenic greenhouse gas emissions, a fraction that is grow-ing with global urbanization. While cities play an important role in climate change mitigation, there has been little focus on reducing urban methane (CH4) emissions. Here, we develop a conceptual framework for CH 4 mitigation in cities by describing emission processes, the role of measurements, and a need for new institutional partnerships. Urban CH 4 emissions are likely to grow with expanding use of natural gas and organic waste disposal systems in growing population centers; however, we currently lack the ability to quantify this increase. We also lackmore » systematic knowledge of the relative contribution of these distinct source sectors on emissions. We present new observations from four North American cities to demonstrate that CH4 emissions vary in magnitude and sector from city to city and hence require different mitigation strategies. Detections of fugitive emissions from these systems suggest that current mitiga- tion approaches are absent or ineffective. These findings illustrate that tackling urban CH 4 emissions will require research efforts to identify mitigation targets, develop and implement new mitigation strategies, and monitor atmospheric CH 4 levels to ensure the success of mitigation efforts. This research will require a variety of techniques to achieve these objectives and should be deployed in cities globally. In conclusion, we suggest that metropolitan scale partnerships may effectively coordinate systematic measurements and actions focused on emission reduction goals.« less

Mitigation of methane emissions in cities: How new measurements and partnerships can contribute to emissions reduction strategies

NASA Astrophysics Data System (ADS)

Hopkins, Francesca M.; Ehleringer, James R.; Bush, Susan E.; Duren, Riley M.; Miller, Charles E.; Lai, Chun-Ta; Hsu, Ying-Kuang; Carranza, Valerie; Randerson, James T.

2016-09-01

Cities generate 70% of anthropogenic greenhouse gas emissions, a fraction that is growing with global urbanization. While cities play an important role in climate change mitigation, there has been little focus on reducing urban methane (CH4) emissions. Here, we develop a conceptual framework for CH4 mitigation in cities by describing emission processes, the role of measurements, and a need for new institutional partnerships. Urban CH4 emissions are likely to grow with expanding use of natural gas and organic waste disposal systems in growing population centers; however, we currently lack the ability to quantify this increase. We also lack systematic knowledge of the relative contribution of these distinct source sectors on emissions. We present new observations from four North American cities to demonstrate that CH4 emissions vary in magnitude and sector from city to city and hence require different mitigation strategies. Detections of fugitive emissions from these systems suggest that current mitigation approaches are absent or ineffective. These findings illustrate that tackling urban CH4 emissions will require research efforts to identify mitigation targets, develop and implement new mitigation strategies, and monitor atmospheric CH4 levels to ensure the success of mitigation efforts. This research will require a variety of techniques to achieve these objectives and should be deployed in cities globally. We suggest that metropolitan scale partnerships may effectively coordinate systematic measurements and actions focused on emission reduction goals.

Mitigation of methane emissions in cities: How new measurements and partnerships can contribute to emissions reduction strategies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hopkins, Francesca M.; Ehleringer, James R.; Bush, Susan E.

Cities generate 70% of anthropogenic greenhouse gas emissions, a fraction that is grow-ing with global urbanization. While cities play an important role in climate change mitigation, there has been little focus on reducing urban methane (CH4) emissions. Here, we develop a conceptual framework for CH 4 mitigation in cities by describing emission processes, the role of measurements, and a need for new institutional partnerships. Urban CH 4 emissions are likely to grow with expanding use of natural gas and organic waste disposal systems in growing population centers; however, we currently lack the ability to quantify this increase. We also lackmore » systematic knowledge of the relative contribution of these distinct source sectors on emissions. We present new observations from four North American cities to demonstrate that CH4 emissions vary in magnitude and sector from city to city and hence require different mitigation strategies. Detections of fugitive emissions from these systems suggest that current mitiga- tion approaches are absent or ineffective. These findings illustrate that tackling urban CH 4 emissions will require research efforts to identify mitigation targets, develop and implement new mitigation strategies, and monitor atmospheric CH 4 levels to ensure the success of mitigation efforts. This research will require a variety of techniques to achieve these objectives and should be deployed in cities globally. In conclusion, we suggest that metropolitan scale partnerships may effectively coordinate systematic measurements and actions focused on emission reduction goals.« less

Aviation NOx-induced CH4 effect: Fixed mixing ratio boundary conditions versus flux boundary conditions

NASA Astrophysics Data System (ADS)

Khodayari, Arezoo; Olsen, Seth C.; Wuebbles, Donald J.; Phoenix, Daniel B.

2015-07-01

Atmospheric chemistry-climate models are often used to calculate the effect of aviation NOx emissions on atmospheric ozone (O3) and methane (CH4). Due to the long (∼10 yr) atmospheric lifetime of methane, model simulations must be run for long time periods, typically for more than 40 simulation years, to reach steady-state if using CH4 emission fluxes. Because of the computational expense of such long runs, studies have traditionally used specified CH4 mixing ratio lower boundary conditions (BCs) and then applied a simple parameterization based on the change in CH4 lifetime between the control and NOx-perturbed simulations to estimate the change in CH4 concentration induced by NOx emissions. In this parameterization a feedback factor (typically a value of 1.4) is used to account for the feedback of CH4 concentrations on its lifetime. Modeling studies comparing simulations using CH4 surface fluxes and fixed mixing ratio BCs are used to examine the validity of this parameterization. The latest version of the Community Earth System Model (CESM), with the CAM5 atmospheric model, was used for this study. Aviation NOx emissions for 2006 were obtained from the AEDT (Aviation Environmental Design Tool) global commercial aircraft emissions. Results show a 31.4 ppb change in CH4 concentration when estimated using the parameterization and a 1.4 feedback factor, and a 28.9 ppb change when the concentration was directly calculated in the CH4 flux simulations. The model calculated value for CH4 feedback on its own lifetime agrees well with the 1.4 feedback factor. Systematic comparisons between the separate runs indicated that the parameterization technique overestimates the CH4 concentration by 8.6%. Therefore, it is concluded that the estimation technique is good to within ∼10% and decreases the computational requirements in our simulations by nearly a factor of 8.

Biotechnologies for greenhouse gases (CH₄, N₂O, and CO₂) abatement: state of the art and challenges.

PubMed

López, Juan C; Quijano, Guillermo; Souza, Theo S O; Estrada, José M; Lebrero, Raquel; Muñoz, Raúl

2013-03-01

Today, methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions represent approximately 98 % of the total greenhouse gas (GHG) inventory worldwide, and their share is expected to increase significantly in this twenty-first century. CO2 represents the most important GHG with approximately 77 % of the total GHG emissions (considering its global warming potential) worldwide, while CH4 and N2O are emitted to a lesser extent (14 and 8 %, respectively) but exhibit global warming potentials 23 and 298 times higher than that of CO2, respectively. Most members of the United Nations, based on the urgent need to maintain the global average temperature 2 °C above preindustrial levels, have committed themselves to significantly reduce their GHG emissions. In this context, an active abatement of these emissions will help to achieve these target emission cuts without compromising industrial growth. Nowadays, there are sufficient empirical evidence to support that biological technologies can become, if properly tailored, a low-cost and environmentally friendly alternative to physical/chemical methods for the abatement of GHGs. This study constitutes a state-of-the-art review of the microbiology (biochemistry, kinetics, and waste-to-value processes) and bioreactor technology of CH4, N2O, and CO2 abatement. The potential and limitations of biological GHG degradation processes are critically discussed, and the current knowledge gaps and technology niches in the field are identified.

Occasional large emissions of nitrous oxide and methane observed in stormwater biofiltration systems.

PubMed

Grover, Samantha P P; Cohan, Amanda; Chan, Hon Sen; Livesley, Stephen J; Beringer, Jason; Daly, Edoardo

2013-11-01

Designed, green infrastructures are becoming a customary feature of the urban landscape. Sustainable technologies for stormwater management, and biofilters in particular, are increasingly used to reduce stormwater runoff volumes and peaks as well as improve the water quality of runoff discharged into urban water bodies. Although a lot of research has been devoted to these technologies, their effect in terms of greenhouse gas fluxes in urban areas has not been yet investigated. We present the first study aimed at quantifying greenhouse gas fluxes between the soil of stormwater biofilters and the atmosphere. N2O, CH4, and CO2 were measured periodically over a year in two operational vegetated biofiltration cells at Monash University in Melbourne, Australia. One cell had a saturated zone at the bottom, and compost and hardwood mulch added to the sandy loam filter media. The other cell had no saturated zone and was composed of sandy loam. Similar sedges were planted in both cells. The biofilter soil was a small N2O source and a sink for CH4 for most measurement events, with occasional large emissions of both N2O and CH4 under very wet conditions. Average N2O fluxes from the cell with the saturated zone were almost five-fold greater (65.6 μg N2O-N m(-2) h(-1)) than from the other cell (13.7 μg N2O-N m(-2) h(-1)), with peaks up to 1100 μg N2O-N m(-2) h(-1). These N2O fluxes are of similar magnitude to those measured in other urban soils, but with larger peak emissions. The CH4 sink strength of the cell with the saturated zone (-3.8 μg CH4-C m(-2) h(-1)) was lower than the other cell (-18.3 μg CH4-C m(-2) h(-1)). Both cells of the biofilter appeared to take up CH4 at similar rates to other urban lawn systems; however, the biofilter cells displayed occasional large CH4 emissions following inflow events, which were not seen in other urban systems. CO2 fluxes increased with soil temperature in both cells, and in the cell without the saturated zone CO2 fluxes decreased as soil moisture increased. Other studies of CO2 fluxes from urban soils have found both similar and larger CO2 emissions than those measured in the biofilter. The results of this study suggest that the greenhouse gas footprint of stormwater treatment warrant consideration in the planning and implementation of engineered green infrastructures. Copyright © 2013 Elsevier B.V. All rights reserved.

N2O and CH4 emissions from N-fertilized rice paddy soil can be mitigated by wood vinegar application at an appropriate rate

NASA Astrophysics Data System (ADS)

Sun, Haijun; Feng, Yanfang; Ji, Yang; Shi, Weiming; Yang, Linzhang; Xing, Baoshan

2018-07-01

To understand the impacts of wood vinegar (WV), a by-product of biochar production, on N2O and CH4 emissions and their total global warming potential (GWPt) from N-fertilized rice paddy soil, a soil column experiment was conducted using three treatments: 240 kg urea-N ha-1 accompanied with 0, 5, and 10 t WV ha-1, respectively. Results showed that N2O and CH4 emission flux patterns were dominated by water regime of rice growth cycle, which was independent with WV application. The total N2O, CH4 emission loads and GWPt over rice season of three N received treatments were 6.41-8.85 kg ha-1, 127.7-405.0 kg ha-1, and 5.24-12.03 t CO2-e ha-1, respectively. Rice seasonal N2O and CH4 emissions were synchronously mitigated by 22.4% and 36.4%, respectively, when WV was applied at 5 t ha-1. Consequently, 5 t ha-1 WV treatment reduced 31.5% of GWPt compared with the urea treatment. In addition, 10 t ha-1 WV treatment exerted a more positive effect on suppressing N2O with 27.6% reduction. However, it increased GWPt by 57.2% because its CH4 emission load was increased by 101.8%. In conclusion, WV amendment applied at an appropriate rate (5 t ha-1) or combination with other CH4 control technologies were suggested to reduce both N2O and CH4 emissions and thereby the GWPt in N-fertilized rice paddy soil.

Assessing fugitive emissions of CH4 from high-pressure gas pipelines

NASA Astrophysics Data System (ADS)

Worrall, Fred; Boothroyd, Ian; Davies, Richard

2017-04-01

The impact of unconventional natural gas production using hydraulic fracturing methods from shale gas basins has been assessed using life-cycle emissions inventories, covering areas such as pre-production, production and transmission processes. The transmission of natural gas from well pad to processing plants and its transport to domestic sites is an important source of fugitive CH4, yet emissions factors and fluxes from transmission processes are often based upon ver out of date measurements. It is important to determine accurate measurements of natural gas losses when compressed and transported between production and processing facilities so as to accurately determine life-cycle CH4 emissions. This study considers CH4 emissions from the UK National Transmission System (NTS) of high pressure natural gas pipelines. Mobile surveys of CH4 emissions using a Picarro Surveyor cavity-ring-down spectrometer were conducted across four areas in the UK, with routes bisecting high pressure pipelines and separate control routes away from the pipelines. A manual survey of soil gas measurements was also conducted along one of the high pressure pipelines using a tunable diode laser. When wind adjusted 92 km of high pressure pipeline and 72 km of control route were drive over a 10 day period. When wind and distance adjusted CH4 fluxes were significantly greater on routes with a pipeline than those without. The smallest leak detectable was 3% above ambient (1.03 relative concentration) with any leaks below 3% above ambient assumed ambient. The number of leaks detected along the pipelines correlate to the estimated length of pipe joints, inferring that there are constant fugitive CH4 emissions from these joints. When scaled up to the UK's National Transmission System pipeline length of 7600 km gives a fugitive CH4 flux of 4700 ± 2864 kt CH4/yr - this fugitive emission from high pressure pipelines is 0.016% of the annual gas supply.

Effects of ferric iron reduction and regeneration on nitrous oxide and methane emissions in a rice soil.

PubMed

Huang, Bin; Yu, Kewei; Gambrell, Robert P

2009-01-01

A laboratory soil slurry experiment and an outdoor pot experiment were conducted to study effects of ferric iron (Fe(III)) reduction and regeneration on nitrous oxide (N(2)O) and methane (CH(4)) emissions in a rice (Oryza sativa L.) soil. The anoxic slurry experiment showed that enhancing microbial Fe(III) reduction by ferrihydrite amendment (40 mol Fe g(-1)) transitionally stimulated N(2)O production and lowered CH(4) production by 16% during an initial 33-day incubation. Increased regeneration of Fe(III) through a 4-day aeration period in the Fe-amended slurry compared to the control slurry reduced CH(4) emission by 30% in the subsequent 15-day anaerobic incubation. The pot experiment showed that ferrihydrite amendment (63 micromol Fe g(-1)) stimulated N(2)O fluxes in the days following flooding. The Fe amendment suppression on CH(4) emission was obscured in the early season but became significant upon reflooding in the mid- and late-seasons. As a result, seasonal CH(4) emission in Fe-amended pots was 26% lower than the control with a single 2-day drainage and 69% lower with a double 2-day drainage. The reduction in CH(4) emission upon reflooding from the Fe-amended pots was mainly attributed to the increased Fe(III) regeneration during drainage showing a mechanism of Fe(III) regeneration in mitigating CH(4) emission by short-term drainage in flooded soils.

Diurnal variability of CO2 and CH4 emissions from tropical reservoirs

NASA Astrophysics Data System (ADS)

Linkhorst, Annika; Reinaldo Paranaíba, José; Barros, Nathan; DelSontro, Tonya; Isidorova, Anastasija; Mendonça, Raquel; Sobek, Sebastian

2017-04-01

Reservoirs are important atmospheric sources of carbon dioxide (CO2) and methane (CH4) with CH4 being a greenhouse gas (GHG) at least 28 times more potent than CO2. Reservoir GHG emissions tend to be heterogeneous, however, and thus current emission estimates are likely conservative since they often overlook emission hot spots and hot moments, especially for CH4 ebullition. For CO2, diffusion is the dominant flux pathway, and diurnal patterns in CO2 emissions can largely be linked to photosynthesis. In contrast, ebullition, the release of gases through bubbles that are formed in the sediments and travel through the water column, is a major emission pathway for CH4 in shallow waters. We visually observed a change in quantity and size of bubbles at different times of the day, and therefore conducted a diurnal study in four different Brazilian reservoirs of different size, age, climatic and geographic characteristics. We hypothesized that sub-daily trends in CH4 ebullition occur in Brazilian reservoirs as bubble release depends on physical factors such as turbulence and hydrostatic pressure, which can exhibit sub-daily patterns in large, managed reservoirs. In each reservoir, we performed measurements of CO2 and CH4 fluxes at one location over 24 hours. CH4 ebullition was tracked continuously by an echosounder, and 13 anchored bubble traps per reservoir were sampled every three hours. Further, a custom-built equilibrator monitored dissolved CH4 and CO2 concentrations, and diffusive and total fluxes of CO2 and CH4 were measured using floating chambers in triplicates every 30 minutes during the same period. We observed that CH4 ebullition as well as CH4 and CO2 diffusion peaked during the day, with peak fluxes being up to four times higher than low fluxes. However, the exact timing and magnitude varied for the different sampling events, and could in part be linked to biological and physical properties of the respective reservoir. This study combined different state-of-the-art techniques to show, for the first time, short-scale temporal variability for both diffusion and ebullition of CO2 and CH4 in different tropical reservoirs. It shows substantial and non-negligable diurnal variability in GHG emission from tropical reservoirs. Further studies are needed to find out if the pattern of low flux during night needs to be accounted for in estimations of GHG emission from reservoirs.

Quantifying direct carbon dioxide emissions from wastewater treatment units by nondispersive infrared sensor (NDIR) - A pilot study.

PubMed

Kosse, Pascal; Kleeberg, Tasja; Lübken, Manfred; Matschullat, Jörg; Wichern, Marc

2018-08-15

Treatment of nutrient-rich wastewater potentially results in direct release of greenhouse gases (GHGs) such as CO 2 , N 2 O or CH 4 - and thus affects Waste Water Treatment Plant's carbon footprint. Accurate CO 2 quantification is challenging due to various chemical, physical and operational conditions. A floating chamber equipped with a nondispersive infrared, single beam, dual wavelength sensor has been evaluated for a pilot approach to quantify fugitive CO 2 emissions above different wastewater treatment units. Total average CO 2 flux was 1182gCO 2 ·m -2 ·d -1 with minimum and maximum fluxes of 829gCO 2 ·m -2 ·d -1 and 1493gCO 2 ·m -2 ·d -1 , respectively. Total observed CO 2 emissions were in 7 to 17kgCO 2 ·PE -1 ·a -1 (average 12kgCO 2 ·PE -1 ·a -1 ). The nitrification tank accounted for about 94.3% of the emissions, followed by secondary clarification (ca. 4.3%) and denitrification (ca. 1.4%), based on those average annual CO 2 emissions per population equivalent (PE). Copyright © 2018 Elsevier B.V. All rights reserved.

Drainage and tillage practices in the winter fallow season mitigate CH4 and N2O emissions from a double-rice field in China

NASA Astrophysics Data System (ADS)

Zhang, Guangbin; Yu, Haiyang; Fan, Xianfang; Yang, Yuting; Ma, Jing; Xu, Hua

2016-09-01

Traditional land management (no tillage, no drainage, NTND) during the winter fallow season results in substantial CH4 and N2O emissions from double-rice fields in China. A field experiment was conducted to investigate the effects of drainage and tillage during the winter fallow season on CH4 and N2O emissions and to develop mitigation options. The experiment had four treatments: NTND, NTD (drainage but no tillage), TND (tillage but no drainage), and TD (both drainage and tillage). The study was conducted from 2010 to 2014 in a Chinese double-rice field. During winter, total precipitation and mean daily temperature significantly affected CH4 emission. Compared to NTND, drainage and tillage decreased annual CH4 emissions in early- and late-rice seasons by 54 and 33 kg CH4 ha-1 yr-1, respectively. Drainage and tillage increased N2O emissions in the winter fallow season but reduced it in early- and late-rice seasons, resulting in no annual change in N2O emission. Global warming potentials of CH4 and N2O emissions were decreased by 1.49 and 0.92 t CO2 eq. ha-1 yr-1, respectively, and were reduced more by combining drainage with tillage, providing a mitigation potential of 1.96 t CO2 eq. ha-1 yr-1. A low total C content and high C / N ratio in rice residues showed that tillage in the winter fallow season reduced CH4 and N2O emissions in both early- and late-rice seasons. Drainage and tillage significantly decreased the abundance of methanogens in paddy soil, and this may explain the decrease of CH4 emissions. Greenhouse gas intensity was significantly decreased by drainage and tillage separately, and the reduction was greater by combining drainage with tillage, resulting in a reduction of 0.17 t CO2 eq. t-1. The results indicate that drainage combined with tillage during the winter fallow season is an effective strategy for mitigating greenhouse gas releases from double-rice fields.

Natural gas pipeline leaks across Washington, DC.

PubMed

Jackson, Robert B; Down, Adrian; Phillips, Nathan G; Ackley, Robert C; Cook, Charles W; Plata, Desiree L; Zhao, Kaiguang

2014-01-01

Pipeline safety in the United States has increased in recent decades, but incidents involving natural gas pipelines still cause an average of 17 fatalities and $133 M in property damage annually. Natural gas leaks are also the largest anthropogenic source of the greenhouse gas methane (CH4) in the U.S. To reduce pipeline leakage and increase consumer safety, we deployed a Picarro G2301 Cavity Ring-Down Spectrometer in a car, mapping 5893 natural gas leaks (2.5 to 88.6 ppm CH4) across 1500 road miles of Washington, DC. The δ(13)C-isotopic signatures of the methane (-38.2‰ ± 3.9‰ s.d.) and ethane (-36.5 ± 1.1 s.d.) and the CH4:C2H6 ratios (25.5 ± 8.9 s.d.) closely matched the pipeline gas (-39.0‰ and -36.2‰ for methane and ethane; 19.0 for CH4/C2H6). Emissions from four street leaks ranged from 9200 to 38,200 L CH4 day(-1) each, comparable to natural gas used by 1.7 to 7.0 homes, respectively. At 19 tested locations, 12 potentially explosive (Grade 1) methane concentrations of 50,000 to 500,000 ppm were detected in manholes. Financial incentives and targeted programs among companies, public utility commissions, and scientists to reduce leaks and replace old cast-iron pipes will improve consumer safety and air quality, save money, and lower greenhouse gas emissions.

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

NASA Astrophysics Data System (ADS)

Hartery, Sean; Commane, Róisín; Lindaas, Jakob; Sweeney, Colm; Henderson, John; Mountain, Marikate; Steiner, Nicholas; McDonald, Kyle; Dinardo, Steven J.; Miller, Charles E.; Wofsy, Steven C.; Chang, Rachel Y.-W.

2018-01-01

Methane (CH4) is the second most important greenhouse gas but its emissions from northern regions are still poorly constrained. In this study, we analyze a subset of in situ CH4 aircraft observations made over Alaska during the growing seasons of 2012-2014 as part of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE). Net surface CH4 fluxes are estimated using a Lagrangian particle dispersion model which quantitatively links surface emissions from Alaska and the western Yukon with observations of enhanced CH4 in the mixed layer. We estimate that between May and September, net CH4 emissions from the region of interest were 2.2 ± 0.5 Tg, 1.9 ± 0.4 Tg, and 2.3 ± 0.6 Tg of CH4 for 2012, 2013, and 2014, respectively. If emissions are only attributed to two biogenic eco-regions within our domain, then tundra regions were the predominant source, accounting for over half of the overall budget despite only representing 18 % of the total surface area. Boreal regions, which cover a large part of the study region, accounted for the remainder of the emissions. Simple multiple linear regression analysis revealed that, overall, CH4 fluxes were largely driven by soil temperature and elevation. In regions specifically dominated by wetlands, soil temperature and moisture at 10 cm depth were important explanatory variables while in regions that were not wetlands, soil temperature and moisture at 40 cm depth were more important, suggesting deeper methanogenesis in drier soils. Although similar environmental drivers have been found in the past to control CH4 emissions at local scales, this study shows that they can be used to generate a statistical model to estimate the regional-scale net CH4 budget.

Tidal variability of CO2 and CH4 emissions from the water column within a Rhizophora mangrove forest (New Caledonia).

PubMed

Jacotot, Adrien; Marchand, Cyril; Allenbach, Michel

2018-08-01

We performed a preliminary study to quantify CO 2 and CH 4 emissions from the water column within a Rhizophora spp. mangrove forest. Mean CO 2 and CH 4 emissions during the studied period were 3.35±3.62mmolCm -2 h -1 and 18.30±27.72μmolCm -2 h -1 , respectively. CO 2 and CH 4 emissions were highly variable and mainly driven by tides (flow/ebb, water column thickness, neap/spring). Indeed, an inverse relationship between the magnitude of the emissions and the thickness of the water column above the mangrove soil was observed. δ 13 CO 2 values ranged from -26.88‰ to -8.6‰, suggesting a mixing between CO 2 -enriched pore waters and lagoon incoming waters. In addition, CO 2 and CH 4 emissions were significantly higher during ebb tides, mainly due to the progressive enrichment of the water column by diffusive fluxes as its residence time over the forest floor increased. Eventually, we observed higher CO 2 and CH 4 emissions during spring tides than during neap tides, combined to depleted δ 13 CO 2 values, suggesting a higher contribution of soil-produced gases to the emissions. These higher emissions may result from higher renewable of the electron acceptor and enhanced exchange surface between the soil and the water column. This study shows that CO 2 and CH 4 emissions from the water column were not negligible and must be considered in future carbon budgets in mangroves. Copyright © 2018 Elsevier B.V. All rights reserved.

Inter-annual variability of area-scaled gaseous carbon emissions from wetland soils in the Liaohe Delta, China

USGS Publications Warehouse

Ye, Siyuan; Krauss, Ken W.; Brix, Hans; Wei, Mengjie; Olsson, Linda; Yu, Xueyang; Ma, Yueying; Wang, Jin; Yuan, Hongming; Zhao, Guangming; Ding, Xigui; Moss, Rebecca

2016-01-01

Global management of wetlands to suppress greenhouse gas (GHG) emissions, facilitate carbon (C) sequestration, and reduce atmospheric CO2 concentrations while simultaneously promoting agricultural gains is paramount. However, studies that relate variability in CO2 and CH4 emissions at large spatial scales are limited. We investigated three-year emissions of soil CO2 and CH4 from the primary wetland types of the Liaohe Delta, China, by focusing on a total wetland area of 3287 km2. One percent is Suaeda salsa, 24% is Phragmites australis, and 75% is rice. While S. salsa wetlands are under somewhat natural tidal influence, P. australis and rice are managed hydrologically for paper and food, respectively. Total C emissions from CO2 and CH4 from these wetland soils were 2.9 Tg C/year, ranging from 2.5 to 3.3 Tg C/year depending on the year assessed. Primary emissions were from CO2 (~98%). Photosynthetic uptake of CO2 would mitigate most of the soil CO2 emissions, but CH4 emissions would persist. Overall, CH4 fluxes were high when soil temperatures were >18°C and pore water salinity <18 PSU. CH4 emissions from rice habitat alone in the Liaohe Delta represent 0.2% of CH4 carbon emissions globally from rice. With such a large area and interannual sensitivity in soil GHG fluxes, management practices in the Delta and similar wetlands around the world have the potential not only to influence local C budgeting, but also to influence global biogeochemical cycling.

Subsoil methanogenesis as source of stem CH4 emission in upland forest trees: preferential CH4 transport via the root system?

NASA Astrophysics Data System (ADS)

Maier, M.; Machacova, K.; Urban, O.; Friederike, L.

2016-12-01

Quantifying and understanding green house gas fluxes in natural soil-plant-atmosphere systems are crucial to predicting global climate change. Wetland species or trees at waterlogged sites are known to emit large amounts of CH4. Yet upland forest soils are regarded as CH4 sinks and tree species like upland European beech (Fagus sylvatica, L.) are assumed not to emit CH4. We studied the soil-atmosphere and stem-atmosphere fluxes of CH4, and soil gas profiles at two upland beech forest sites in Central Europe. Soil was a net CH4 sink at both. Unusually there was one beech tree with substantial CH4 emissions that were higher than the CH4 sink of the soil. The soil gas profile at this tree indicated CH4 production at a soil depth >0.3 m, despite the net uptake of CH4 observed at the soil surface adjacent to the tree. Field soil assessment showed strong redoximorphic color patterns in the adjacent soil. We think that there is a transport link between the soil and stem via the root system representing a preferential transport mechanism for CH4 despite the fact that beech roots usually do not bear aerenchyma. The gas transport process , either via dissolved CH4 in the xylem water or in the root gas phase, is not yet clear. The observed CH4 stem emissions represent an important CH4flux in this ecosystem, und thus should be considered in future research. AcknowledgementThis research was financially supported by the Czech Academy of Sciences and the German Academic Exchange Service within the project "Methane (CH4) and nitrous oxide (N2O) emissions from Fagus sylvatica trees" (DAAD-15-03), National Programme for Sustainability I (LO1415) and project DFG (MA 5826/2-1). We would like to thank Marek Jakubik, Katerina Svobodova, Sinikka Paulus, Ellen Halaburt and Sally Haddad for technical support.

Cross continental increase in methane ebullition under climate change.

PubMed

Aben, Ralf C H; Barros, Nathan; van Donk, Ellen; Frenken, Thijs; Hilt, Sabine; Kazanjian, Garabet; Lamers, Leon P M; Peeters, Edwin T H M; Roelofs, Jan G M; de Senerpont Domis, Lisette N; Stephan, Susanne; Velthuis, Mandy; Van de Waal, Dedmer B; Wik, Martin; Thornton, Brett F; Wilkinson, Jeremy; DelSontro, Tonya; Kosten, Sarian

2017-11-22

Methane (CH 4 ) strongly contributes to observed global warming. As natural CH 4 emissions mainly originate from wet ecosystems, it is important to unravel how climate change may affect these emissions. This is especially true for ebullition (bubble flux from sediments), a pathway that has long been underestimated but generally dominates emissions. Here we show a remarkably strong relationship between CH 4 ebullition and temperature across a wide range of freshwater ecosystems on different continents using multi-seasonal CH 4 ebullition data from the literature. As these temperature-ebullition relationships may have been affected by seasonal variation in organic matter availability, we also conducted a controlled year-round mesocosm experiment. Here 4 °C warming led to 51% higher total annual CH 4 ebullition, while diffusion was not affected. Our combined findings suggest that global warming will strongly enhance freshwater CH 4 emissions through a disproportional increase in ebullition (6-20% per 1 °C increase), contributing to global warming.

Estimating Sources and Sinks of Methane from Soils in the Contiguous United States (CONUS)

NASA Astrophysics Data System (ADS)

Shu, S.; Jain, A. K.; Kheshgi, H. S.

2017-12-01

The global methane (CH4) budget estimated based on state-of-the-art models remains highly uncertain. Sources and sinks of CH4 from soils, including wetlands, are the most important source of uncertainty. Soils are estimated to account for about 45% of global CH4 emissions. At the same time oxidation of CH4 by soils is a significant sink, representing about 10% of the total sink. However, most regional and global scale modeling studies of soil CH4 fluxes have ignored the sink through soil oxidation and the source of CH4 emissions from the wet soils with shallow water tables. In this study, we link a bottom-up soil gas diffusion and CH4 biogeochemistry model to a land surface model, ISAM, to calculate the sources, emissions from both wetlands and non-wetlands, and sinks, soil oxidation, of CH4 from soils for the CONUS over the period 1900-2100. The newly developed soil CH4 model framework consists of a gas diffusion module with the vertically resolved soil hydrology (depth up to 3.5 m soil) and soil organic carbon (SOC) and CH4 biogeochemistry module. SOC profile is estimated by modeling vertical soil mixing and thus can represent the deep SOC content and estimate CH4 production from the deep non-wetland soil. For the diffusion calculations, we separately consider both the dissolved and gaseous O2 and CH4 at each soil layer. For CH4 biogeochemistry, we parameterize the production, soil oxidation, ebullition and aerenchyma transportation of CH4 for both seasonal/permanent wetland and wet soil. The SWAMP inundated fraction dataset with 8-day temporal resolution is incorporated to prescribe the extent of permanent and seasonal wetland extent for the recent decade. The model is first evaluated using a compilation of published CH4 site measurement data for CONUS. We then perform two different model experiments: 1) forced by the CRUNCEP climate data from 1900 to 2010 to estimate the contemporary CH4 emission and 2) forced by a climate projection of IPCC's highest representative concentration pathway (RCP8.5) from 2011 to 2100. Our study shows that soil oxidation has an important role attenuating the estimated natural CH4 source. We also find a wetter and warmer climate affects the dry soil CH4 sink and wet soil CH4 emissions and increases the estimated CH4 source over the CONUS.

Substrate lability and plant activity controls greenhouse gas release from Neotropical peatland

NASA Astrophysics Data System (ADS)

Sjogersten, Sofie; Hoyos, Jorge; Lomax, Barry; Turner, Ben; Wright, Emma

2014-05-01

Almost one third of global CO2 emissions resulting from land use change and substantial CH4 emissions originate from tropical peatlands. However, our understanding of the controls of CO2 and CH4 release from tropical peatlands are limited. The aim of this study was to investigate the role of peat lability and the activity of the vegetation on gas release using a combination of field and laboratory experiments. We demonstrated that peat lability constrained CH4 production to the surface peat under anaerobic conditions. The presence of plants shifted the C balance from a C source to a C sink with respect to CO2 while the activity of the root system strongly influenced CH4 emissions through its impact on soil O2 inputs. Both field and laboratory data suggest a coupling between the photosynthetic activity of the vegetation and the release of both CO2 and CH4 following the circadian rhythm of the dominant plant functional types. Forest clearance for agriculture resulted in elevated CH4 release, which we attribute in part to the cessation of root O2 inputs to the peat. We conclude that high emissions of CO2 and CH4 from forested tropical peatlands are likely driven by labile C inputs from the vegetation but that root O2 release may limit CH4 emissions.

Sunlight stimulates methane uptake and nitrous oxide emission from the High Arctic tundra.

PubMed

Li, Fangfang; Zhu, Renbin; Bao, Tao; Wang, Qing; Xu, Hua

2016-12-01

Many environmental factors affecting methane (CH 4 ) and nitrous oxide (N 2 O) fluxes have been investigated during the processes of carbon and nitrogen transformation in the boreal tundra. However, effects of sunlight on CH 4 and N 2 O fluxes and their budgets were neglected in the boreal tundra. Here, summertime CH 4 and N 2 O fluxes in the presence and total absence of sunlight were investigated at the six tundra sites (DM1-DM6) on Ny-Ålesund in the High Arctic. The mean CH 4 fluxes at the tundra sites ranged from -4.7 to -158.6μg CH 4 m -2 h -1 in the presence of light, indicating that a large CH 4 sink occurred in the tundra soils. However, enhanced CH 4 emission in total absence of light occurred at all the tundra sites. The mean N 2 O fluxes ranged from 7.4 to 14.6μg N 2 O m -2 h -1 in the presence of light, whereas in the absence of light all the tundra sites generally released less N 2 O, and even significant N 2 O uptake occurred there. Soil temperature, chamber temperature and soil moisture showed no significant correlations with tundra CH 4 and N 2 O flux. The presence of sunlight increased tundra CH 4 uptake by 114.2μg CH 4 m -2 h -1 and N 2 O emission by 10.9μg N 2 O m -2 h -1 compared with total absence of light. Overall our results showed that tundra ecosystem switched from CH 4 sink and N 2 O emission source in the presence of light to CH 4 emission source and N 2 O sink in the absence of light. Therefore sunlight had an important effect on CH 4 and N 2 O budgets in the High Arctic tundra. The exclusion of sunlight might overestimate CH 4 budgets, but underestimate N 2 O budgets in the Arctic tundra ecosystem. Copyright © 2016 Elsevier B.V. All rights reserved.

Gas-geochemical condition and ecological functions of urban soils in areas with gas generating grounds

NASA Astrophysics Data System (ADS)

Mozharova, Nadezhda; Lebed-Sharlevich, Iana; Kulachkova, Svetlana

2014-05-01

Rapid urbanization and expansion of city borders lead to development of new areas, often following with relief changes, covering of gully-ravine systems and river beds with technogenic grounds containing construction and municipal waste. Decomposition of organic matter in these grounds is a source of methane and carbon dioxide. Intensive generation and accumulation of CO2 and CH4 into grounds may cause a fire and explosion risk for constructed objects. Gases emission to the atmosphere changes the global balance of GHGs and negatively influences on human health. The aim of this investigation is to study gas-geochemical condition and ecological functions of urban soils in areas with gas generating grounds. Studied areas are the gully-ravine systems or river beds, covered with technogenic grounds during land development. Stratigraphic columns of these grounds are 5-17 meters of man-made loamy material with inclusion of construction waste. Gas generating layer with increased content of organic matter, reductive conditions and high methanogenic activity (up to 1.0 ng*g-1*h-1) is situated at the certain depth. Maximum CH4 and CO2 concentrations in this layer reach dangerous values (2-10% and 11%, respectively) in the current standards. In case of disturbance of ground layer (e.g. well-drilling) methane is rapidly transferred by convective flux to atmosphere. The rate of CH4 emission reaches 100 mg*m-2*h-1 resulting in its atmospheric concentration growth by an order of magnitude compared with background. In normal occurrence of grounds methane gradually diffuses into the upper layers by pore space, consuming on different processes (e.g. formation of organic matter, nitrogen compounds or specific particles of magnetite), and emits to atmosphere. CH4 emission rate varies from 1 to 40 mg*m-2*h-1 increasing with depth of grounds. Carbon dioxide emission is about 100 mg*m-2*h-1. During soil formation on gas generating grounds bacterial oxidation of methane, one of the most important ecological functions of such soils, is initiated. Due to high rate of this process (25-30 ng*g-1*h-1) accumulation of methane in the profile does not observed, its content in soil averages 2-5 ppm. Methane emission from soils is low (0.01-0.03 mg*m-2*h-1) or there is a weak consumption of atmospheric CH4, whereby its concentration in the air corresponds to the average content of this gas. Active methane oxidation and decomposition of organic matter under aerobic conditions result to intensive formation of carbon dioxide and, thus, increase its emission (600 mg*m-2*h-1), concentration in soils (0.2-0.9%) and in atmosphere (up to 0.5%). Fixed concentration of CO2 in the air is dangerous for human health. Thus, presence of gas generating grounds with high content of organic matter leads to methane formation, causing its intensive emission to atmosphere. At upper layers of soils and grounds bacterial oxidation of methane occurs and results in complete CH4 utilization. During this process significant amounts of carbon dioxide are released and accumulated in the atmosphere up to concentration dangerous for people. Carbon dioxide emission increases current level of this gas in the urban atmosphere.

Impact of seabird activity on nitrous oxide and methane fluxes from High Arctic tundra in Svalbard, Norway

NASA Astrophysics Data System (ADS)

Zhu, Renbin; Chen, Qingqing; Ding, Wei; Xu, Hua

2012-12-01

In this study, tundra N2O and CH4 fluxes were measured from one seabird sanctuary (SBT) and two non-seabird colonies (NST-I and NST-II) in Ny-Ålesund (79°55'N, 11°56'E), Svalbard during the summers of 2008 and 2009. N2O and CH4 fluxes from SBT showed large temporal and spatial variations depending on the intensity of seabird activity. High seabird activity sites showed large N2O and CH4 emissions while low N2O and CH4 emissions, even CH4 uptake occurred at medium and low seabird activity sites. Overall the mean fluxes were 18.3 ± 3.6 μg N2O m-2 h-1 and 53.5 ± 20.3 μg CH4 m-2 h-1 from tundra SBT whereas tundra NST-I and NST-II represented a relatively weak N2O source (8.3 ± 13.2 μg N2O m-2 h-1) and strong CH4 sink (-82.8 ± 22.3 μg CH4 m-2 h-1). Seabird activity was the strongest control of N2O and CH4 fluxes compared with soil temperature and moisture, and high N2O and CH4 emissions were created by soil physical and chemical processes (the sufficient supply of nutrients NH4+-N, NO3--N, total nitrogen, total phosphorus and total carbon from seabird guano, seabird tramp and appropriate water content) related to the seabird activity. Our work suggests that tundra ecosystems impacted by seabird activity are the potential "hotspots" for N2O and CH4 emissions although these sources have been largely neglected at present. Furthermore the combination of seabird activity and warming climate will likely further enhance N2O and CH4 emissions from the High Arctic tundra.

Genetic parameters of methane emissions determined using portable accumulation chambers in lambs and ewes grazing pasture and genetic correlations with emissions determined in respiration chambers.

PubMed

Jonker, A; Hickey, S M; Rowe, S J; Janssen, P H; Shackell, G; Elmes, S; Bain, W E; Wing, J; Greer, G J; Bryson, B; MacLean, S; Dodds, K G; Pinares-Patiño, C S; Young, E A; Knowler, K; Pickering, N K; McEwan, J C

2018-05-07

Methane (CH4) emission traits were previously found to be heritable and repeatable in sheep fed alfalfa pellets in respiration chambers (RC). More rapid screening methods are, however, required to increase genetic progress and to provide a cost effective method to the farming industry for maintaining the generation of breeding values in the future. The objective of the current study was to determine CH4 and carbon dioxide (CO2) emissions using several one-hour portable accumulation chamber (PAC) measurements from lambs and again as ewes, while grazing ryegrass based pasture. Many animals with PAC measurements were also measured in RC while fed alfalfa pellets at 2.0 × maintenance metabolizable energy requirements (MEm). Heritability estimates from mixed models for CH4 and CO2 production (g/d) were 0.19 and 0.16, respectively, when measured using PAC with lambs; 0.20 and 0.27, respectively, when measured using PAC with ewes; and 0.23 and 0.34, respectively, when measured using RC with lambs. For measured gas traits, repeatabilities of measurements collected 14 days apart ranged from 0.33 to 0.55 for PAC (combined lambs and ewes) and were greater at 0.65 to 0.76 for the same traits measured using RC. Genetic correlations (rg) between PAC in lambs and ewes were 0.99 for CH4, 0.93 for CH4+CO2 and 0.85 for CH4/(CH4+CO2), suggesting CH4 emissions in lambs and ewes are the same trait. Genetic correlations between PAC and RC measurements were lower, at 0.62 to 0.67 for CH4 and 0.41 to 0.42 for CH4+CO2, likely reflecting different environmental conditions associated with the protocols used with the two measurement methods. The CH4/(CH4+CO2) ratio was the most similar genetic trait measured using PAC (both lambs and ewes, 63 and 66% selection efficiency, respectively) compared with CH4 yield (g/kg DMI) measured using RC. These results suggest that PAC measurements have considerable value as a rapid low cost method to estimate breeding values for CH4 emissions in sheep.

High emissions of greenhouse gases from grasslands on peat and other organic soils.

PubMed

Tiemeyer, Bärbel; Albiac Borraz, Elisa; Augustin, Jürgen; Bechtold, Michel; Beetz, Sascha; Beyer, Colja; Drösler, Matthias; Ebli, Martin; Eickenscheidt, Tim; Fiedler, Sabine; Förster, Christoph; Freibauer, Annette; Giebels, Michael; Glatzel, Stephan; Heinichen, Jan; Hoffmann, Mathias; Höper, Heinrich; Jurasinski, Gerald; Leiber-Sauheitl, Katharina; Peichl-Brak, Mandy; Roßkopf, Niko; Sommer, Michael; Zeitz, Jutta

2016-12-01

Drainage has turned peatlands from a carbon sink into one of the world's largest greenhouse gas (GHG) sources from cultivated soils. We analyzed a unique data set (12 peatlands, 48 sites and 122 annual budgets) of mainly unpublished GHG emissions from grasslands on bog and fen peat as well as other soils rich in soil organic carbon (SOC) in Germany. Emissions and environmental variables were measured with identical methods. Site-averaged GHG budgets were surprisingly variable (29.2 ± 17.4 t CO 2 -eq. ha -1  yr -1 ) and partially higher than all published data and the IPCC default emission factors for GHG inventories. Generally, CO 2 (27.7 ± 17.3 t CO 2  ha -1  yr -1 ) dominated the GHG budget. Nitrous oxide (2.3 ± 2.4 kg N 2 O-N ha -1  yr -1 ) and methane emissions (30.8 ± 69.8 kg CH 4 -C ha -1  yr -1 ) were lower than expected except for CH 4 emissions from nutrient-poor acidic sites. At single peatlands, CO 2 emissions clearly increased with deeper mean water table depth (WTD), but there was no general dependency of CO 2 on WTD for the complete data set. Thus, regionalization of CO 2 emissions by WTD only will remain uncertain. WTD dynamics explained some of the differences between peatlands as sites which became very dry during summer showed lower emissions. We introduced the aerated nitrogen stock (N air ) as a variable combining soil nitrogen stocks with WTD. CO 2 increased with N air across peatlands. Soils with comparatively low SOC concentrations showed as high CO 2 emissions as true peat soils because N air was similar. N 2 O emissions were controlled by the WTD dynamics and the nitrogen content of the topsoil. CH 4 emissions can be well described by WTD and ponding duration during summer. Our results can help both to improve GHG emission reporting and to prioritize and plan emission reduction measures for peat and similar soils at different scales. © 2016 John Wiley & Sons Ltd.

Differences in net global warming potential and greenhouse gas intensity between major rice-based cropping systems in China.

PubMed

Xiong, Zhengqin; Liu, Yinglie; Wu, Zhen; Zhang, Xiaolin; Liu, Pingli; Huang, Taiqing

2015-12-02

Double rice (DR) and upland crop-single rice (UR) systems are the major rice-based cropping systems in China, yet differences in net global warming potential (NGWP) and greenhouse gas intensity (GHGI) between the two systems are poorly documented. Accordingly, a 3-year field experiment was conducted to simultaneously measure methane (CH4) and nitrous oxide (N2O) emissions and changes in soil organic carbon (SOC) in oil rape-rice-rice and wheat-rice (representing DR and UR, respectively) systems with straw incorporation (0, 3 and 6 t/ha) during the rice-growing seasons. Compared with the UR system, the annual CH4, N2O, grain yield and NGWP were significantly increased in the DR system, though little effect on SOC sequestration or GHGI was observed without straw incorporation. Straw incorporation increased CH4 emission and SOC sequestration but had no significant effect on N2O emission in both systems. Averaged over the three study years, straw incorporation had no significant effect on NGWP and GHGI in the UR system, whereas these parameters were greatly increased in the DR system, i.e., by 108% (3 t/ha) and 180% (6 t/ha) for NGWP and 103% (3 t/ha) and 168% (6 t/ha) for GHGI.

Differences in net global warming potential and greenhouse gas intensity between major rice-based cropping systems in China

PubMed Central

Xiong, Zhengqin; Liu, Yinglie; Wu, Zhen; Zhang, Xiaolin; Liu, Pingli; Huang, Taiqing

2015-01-01

Double rice (DR) and upland crop-single rice (UR) systems are the major rice-based cropping systems in China, yet differences in net global warming potential (NGWP) and greenhouse gas intensity (GHGI) between the two systems are poorly documented. Accordingly, a 3-year field experiment was conducted to simultaneously measure methane (CH4) and nitrous oxide (N2O) emissions and changes in soil organic carbon (SOC) in oil rape-rice-rice and wheat-rice (representing DR and UR, respectively) systems with straw incorporation (0, 3 and 6 t/ha) during the rice-growing seasons. Compared with the UR system, the annual CH4, N2O, grain yield and NGWP were significantly increased in the DR system, though little effect on SOC sequestration or GHGI was observed without straw incorporation. Straw incorporation increased CH4 emission and SOC sequestration but had no significant effect on N2O emission in both systems. Averaged over the three study years, straw incorporation had no significant effect on NGWP and GHGI in the UR system, whereas these parameters were greatly increased in the DR system, i.e., by 108% (3 t/ha) and 180% (6 t/ha) for NGWP and 103% (3 t/ha) and 168% (6 t/ha) for GHGI. PMID:26626733

Differences in net global warming potential and greenhouse gas intensity between major rice-based cropping systems in China

NASA Astrophysics Data System (ADS)

Xiong, Zhengqin; Liu, Yinglie; Wu, Zhen; Zhang, Xiaolin; Liu, Pingli; Huang, Taiqing

2015-12-01

Double rice (DR) and upland crop-single rice (UR) systems are the major rice-based cropping systems in China, yet differences in net global warming potential (NGWP) and greenhouse gas intensity (GHGI) between the two systems are poorly documented. Accordingly, a 3-year field experiment was conducted to simultaneously measure methane (CH4) and nitrous oxide (N2O) emissions and changes in soil organic carbon (SOC) in oil rape-rice-rice and wheat-rice (representing DR and UR, respectively) systems with straw incorporation (0, 3 and 6 t/ha) during the rice-growing seasons. Compared with the UR system, the annual CH4, N2O, grain yield and NGWP were significantly increased in the DR system, though little effect on SOC sequestration or GHGI was observed without straw incorporation. Straw incorporation increased CH4 emission and SOC sequestration but had no significant effect on N2O emission in both systems. Averaged over the three study years, straw incorporation had no significant effect on NGWP and GHGI in the UR system, whereas these parameters were greatly increased in the DR system, i.e., by 108% (3 t/ha) and 180% (6 t/ha) for NGWP and 103% (3 t/ha) and 168% (6 t/ha) for GHGI.

Comparison of different modeling approaches to better evaluate greenhouse gas emissions from whole wastewater treatment plants.

PubMed

Corominas, Lluís; Flores-Alsina, Xavier; Snip, Laura; Vanrolleghem, Peter A

2012-11-01

New tools are being developed to estimate greenhouse gas (GHG) emissions from wastewater treatment plants (WWTPs). There is a trend to move from empirical factors to simple comprehensive and more complex process-based models. Thus, the main objective of this study is to demonstrate the importance of using process-based dynamic models to better evaluate GHG emissions. This is tackled by defining a virtual case study based on the whole plant Benchmark Simulation Model Platform No. 2 (BSM2) and estimating GHG emissions using two approaches: (1) a combination of simple comprehensive models based on empirical assumptions and (2) a more sophisticated approach, which describes the mechanistic production of nitrous oxide (N(2) O) in the biological reactor (ASMN) and the generation of carbon dioxide (CO(2) ) and methane (CH(4) ) from the Anaerobic Digestion Model 1 (ADM1). Models already presented in literature are used, but modifications compared to the previously published ASMN model have been made. Also model interfaces between the ASMN and the ADM1 models have been developed. The results show that the use of the different approaches leads to significant differences in the N(2) O emissions (a factor of 3) but not in the CH(4) emissions (about 4%). Estimations of GHG emissions are also compared for steady-state and dynamic simulations. Averaged values for GHG emissions obtained with steady-state and dynamic simulations are rather similar. However, when looking at the dynamics of N(2) O emissions, large variability (3-6 ton CO(2) e day(-1) ) is observed due to changes in the influent wastewater C/N ratio and temperature which would not be captured by a steady-state analysis (4.4 ton CO(2) e day(-1) ). Finally, this study also shows the effect of changing the anaerobic digestion volume on the total GHG emissions. Decreasing the anaerobic digester volume resulted in a slight reduction in CH(4) emissions (about 5%), but significantly decreased N(2) O emissions in the water line (by 14%). Copyright © 2012 Wiley Periodicals, Inc.

Estimates of reservoir methane emissions based on a spatially ...

EPA Pesticide Factsheets

Global estimates of methane (CH4) emissions from reservoirs are poorly constrained, partly due to the challenges of accounting for intra-reservoir spatial variability. Reservoir-scale emission rates are often estimated by extrapolating from measurement made at a few locations; however, error and bias associated with this approach can be large and difficult to quantify. Here we use a generalized random tessellation survey (GRTS) design to generate estimates of central tendency and variance at multiple spatial scales in a reservoir. GRTS survey designs are probabilistic and spatially balanced which eliminates bias associated with expert judgment in site selection. GRTS surveys also allow for variance estimates that account for spatial pattern in emission rates. Total CH4 emission rates (i.e. sum of ebullition and diffusive emissions) were 4.8 (±2.1), 33.0 (±10.7), and 8.3 (±2.2) mg CH4 m-2 h-1 in open-waters, tributary associated areas, and the entire reservoir for the period in August 2014 during which 115 sites were sampled across an 7.98 km2 reservoir in Southwestern, Ohio, USA. Tributary areas occupy 12% of the reservoir surface, but were the source of 41% of total CH4 emissions, highlighting the importance of riverine-lacustrine transition zones. Ebullition accounted for >90% of CH4 emission at all spatial scales. Confidence interval estimates that incorporated spatial pattern in CH4 emissions were up to 29% narrower than when spatial independence

Methane production and emissions from four reclaimed and pristine wetlands of Southeastern United States

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schipper, L.A.; Reddy, K.R.

Wetlands are significant contributors to global CH[sub 4] emission. We measured CH[sub 4] emissions at two pristine wetlands [Okefenokee swamp and the Everglades (Water Conservation Area 2A)] and two reclaimed wetlands (Sunny Hill Farm and Apopka Marsh) in Southeastern USA, and we attempted to relate emissions to CH[sub 4] production rates of the soil and the soil's biological and chemical properties. Methane emissions through cattail [Typha sp.] and waterilly [Nymphaea ordorata (L.)] ranged from 0.09 to 1.7 g CH[sub 4] m[sup [minus]2] d[sup [minus]1] and exhibited high spatial and temporal variability. Diffusive flux of CH[sub 4] was calculated using dissolvedmore » CH[sub 4] profiles in the soil pore water and accounted for <5% of the plant-mediated emissions. Potential CH[sub 4] production rates were measured as a function of depth using soil samples obtained at 2-cm increments. Methane production rates were the same order of magnitude at all sites (<1-70 ng CH[sub 4]-C g[sup [minus]1] soil C d[sup [minus]1]) and were highest in the surface soils (0-6 cm) at three of the wetland sites, indicating that the predominant source of C available to methanogens was in the surface soils. Methane production rates in the top 24 cm ranged from 0.3 to 1.1 g CH[sub 4] m[sup [minus]2] d[sup [minus]1] and annual C losses due to anaerobic decomposition accounted for between 0.68 and 3.7% of the total C in the surface 24-cm soil depth. 36 refs., 3 figs., 3 tabs.« less

Spatial variability of greenhouse gases emissions (CO2, CH4, N2O) in a tropical hydroelectric reservoir flooding primary forest (Petit Saut Reservoir, French Guiana)

NASA Astrophysics Data System (ADS)

Cailleaud, Emilie; Guérin, Frédéric; Bouillon, Steven; Sarrazin, Max; Serça, Dominique

2014-05-01

At the Petit Saut Reservoir (PSR, French Guiana, South America), vertical profiles were performed at 5 stations in the open waters (OW) and 6 stations in two shallow flooded forest (FF) areas between April 2012 and September 2013. Measurements included physico-chemical parameters, ammonium, nitrate and dissolved greenhouse gas (CO2, CH4, N2O) concentrations, dissolved and particulate organic carbon (DOC, POC) and nitrogen (PN), δ13C-POC and δ15N-PN . The diffusive fluxes were calculated from surface concentrations. The aim of this study was to estimate the spatial variations of greenhouse gas emissions at a dentrical hydroelectric reservoir located in the tropics and flooding primary forest. Twenty years after impoundment, the water column of the PSR is permanently and tightly stratified thermally in the FF whereas in the OW, the thermal gradients are not as stable. The different hydrodynamical behaviours between the two different zones have significant consequences on the biogeochemistry: oxygen barely diffuses down to the hypolimnion in the FF whereas destratification occurs sporadically during the rainy season in the OW. Although we found the same range of POC in the FF and the OW (2.5-29 μmol L-1) and 20% more DOC at the bottom of OW than in the FF (229-878 μmol L-1), CO2 and CH4 concentrations were always significantly higher in the FF (CO2: 11-1412 μmol L-1, CH4: 0.001-1015 μmol L-1) than in the OW. On average, the CO2 concentrations were 30-40% higher in the FF than in the OW and the CH4 concentrations were three times higher in the FF than in the OW. The δ13C-POC and C:N values did not suggest substantial differences in the sources of OM between the FF and OW. At all stations, POC at the bottom has an isotopic signature slightly lighter than the terrestrial OM in the surrounding forest whereas the isotopic signature of surface POM would result from phytoplankton and methanotrophs. The vertical profiles of nitrogen compounds reveal that the main source of nitrogen in the water column of the PSR is the NH4+ produced during the mineralisation of the OM at the bottom of the reservoir. In OW, the production of NO3- and N2O is enhanced compared to the FF. As a result, N2O concentrations are three times higher at the bottom of OW but surface concentrations are similar in the FF and OW. CO2 diffusive fluxes are 40% higher and CH4 diffusive fluxes are three times higher in FF (CO2: 42±20 mmol m-2 d-1 ; CH4: 0.7±1.4 mmol m-2 d-1) than in OW (CO2: 27±17 mmol m-2 d-1 ; CH4: 0.2±0.3 mmol m-2 d-1). In shallow FF, average CH4 ebullition is 3±10 mmol m-2 d-1 whereas ebullition was never observed in OW. N2O emissions did not exhibit any spatial variability (9±4 μmol m-2 d-1). At the PSR, FF which represents one third of the surface area, is responsible of half of the GHG emissions from the reservoir. This implies that the emissions from most of the tropical reservoirs flooding primary forest need to be reassessed since FF environments are usually overlooked.

Emissions of CH4 and N2O under Different Tillage Systems from Double-Cropped Paddy Fields in Southern China

PubMed Central

Zhang, Hai-Lin; Bai, Xiao-Lin; Xue, Jian-Fu; Chen, Zhong-Du; Tang, Hai-Ming; Chen, Fu

2013-01-01

Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH4) and nitrous oxide (N2O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH4 from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH4 emission among the rice growing seasons (P<0.05). However, much higher variations in N2O emission were observed across the rice growing seasons due to the vulnerability of N2O to external influences. The amount of CH4 emission in paddy fields was much higher relative to N2O emission. Conversion of CT to NT significantly reduced the cumulative CH4 emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH4 and N2O emissions over 100 years was in the order of NT

Emissions of CH4 and N2O under different tillage systems from double-cropped paddy fields in Southern China.

PubMed

Zhang, Hai-Lin; Bai, Xiao-Lin; Xue, Jian-Fu; Chen, Zhong-Du; Tang, Hai-Ming; Chen, Fu

2013-01-01

Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH4) and nitrous oxide (N2O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH4 from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH4 emission among the rice growing seasons (P<0.05). However, much higher variations in N2O emission were observed across the rice growing seasons due to the vulnerability of N2O to external influences. The amount of CH4 emission in paddy fields was much higher relative to N2O emission. Conversion of CT to NT significantly reduced the cumulative CH4 emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH4 and N2O emissions over 100 years was in the order of NT

Assessment of Pneumatic Controller Emission Measurements ...

EPA Pesticide Factsheets

Oil and Natural Gas (ONG) production facilities have the potential to emit greenhouse gases such as methane (CH4) and other hydrocarbons (HCs) to the atmosphere. ONG production sites have multiple emission sources including storage tank venting, enclosed combustion devices, engine exhaust, pneumatic controllers and uncontrolled leaks. Accounting for up to 37.8 percent of CH4 emissions, pneumatic controllers are one of the most significant sources of CH4 in ONG production field operations. Recent measurement studies used the only commercially-available high volume sampling (HVS) technology (Bacharach Hi Flow Sampler, Bacharach, Inc., New Kensington, PA) to quantify CH4 emission rates of pneumatic devices on ONG production pads and compare to inventory estimates. Other studies indicate that this HVS may malfunction, causing underestimates of emissions in certain scenarios encountered in ONG production and should not be used for some sources such as heavy emissions from condensate storage tanks. The HVS malfunction can occur on relatively large emissions, where the measured leak concentrations exceed 5%, and is ascribed to a sensor transition failure in the instrument. The HVS malfunction is believed to be exacerbated by several factors (large emission rates, amount of non-CH4 HCs in the emission stream, non-optimal HVS calibration frequency, firmware, and emission measurement coupling geometries). The degree to which HVS measurements of emissions from pneumatic co

Enhancement of farmland greenhouse gas emissions from leakage of stored CO2: simulation of leaked CO2 from CCS.

PubMed

Zhang, Xueyan; Ma, Xin; Wu, Yang; Li, Yue

2015-06-15

The effects of leaked CO2 on plant and soil constitute a key objective of carbon capture and storage (CCS) safety. The effects of leaked CO2 on trace soil gas (e.g., methane (CH4) and nitrous oxide (N2O) emissions in farmlands are not well-understood. This study simulated the effects of elevated soil CO2 on CH4 and N2O through pot experiments. The results revealed that significant increases of CH4 and N2O emissions were induced by the simulated CO2 leakages; the emission rates of CH4 and N2O were substantial, reaching about 222 and 48 times than that of the control, respectively. The absolute global warming potentials (GWPs) of the additional CH4 and N2O are considerable, but the cumulative GWPs of the additional CH4 and N2O only accounted for 0.03% and 0.06%, respectively, of the cumulative amount of leaked CO2 under high leakage conditions. The results demonstrate that leakage from CCS projects may lead to additional greenhouse gas emissions from soil; however, in general, the amount of additional CH4 and N2O emissions is negligible when compared with the amount of leaked CO2. Copyright © 2015 Elsevier B.V. All rights reserved.

Year-round CH4 and CO2 flux dynamics in two contrasting freshwater ecosystems of the subarctic

NASA Astrophysics Data System (ADS)

Jammet, Mathilde; Dengel, Sigrid; Kettner, Ernesto; Parmentier, Frans-Jan W.; Wik, Martin; Crill, Patrick; Friborg, Thomas

2017-11-01

Lakes and wetlands, common ecosystems of the high northern latitudes, exchange large amounts of the climate-forcing gases methane (CH4) and carbon dioxide (CO2) with the atmosphere. The magnitudes of these fluxes and the processes driving them are still uncertain, particularly for subarctic and Arctic lakes where direct measurements of CH4 and CO2 emissions are often of low temporal resolution and are rarely sustained throughout the entire year. Using the eddy covariance method, we measured surface-atmosphere exchange of CH4 and CO2 during 2.5 years in a thawed fen and a shallow lake of a subarctic peatland complex. Gas exchange at the fen exhibited the expected seasonality of a subarctic wetland with maximum CH4 emissions and CO2 uptake in summer, as well as low but continuous emissions of CH4 and CO2 throughout the snow-covered winter. The seasonality of lake fluxes differed, with maximum CO2 and CH4 flux rates recorded at spring thaw. During the ice-free seasons, we could identify surface CH4 emissions as mostly ebullition events with a seasonal trend in the magnitude of the release, while a net CO2 flux indicated photosynthetic activity. We found correlations between surface CH4 emissions and surface sediment temperature, as well as between diel CO2 uptake and diel solar input. During spring, the breakdown of thermal stratification following ice thaw triggered the degassing of both CH4 and CO2. This spring burst was observed in 2 consecutive years for both gases, with a large inter-annual variability in the magnitude of the CH4 degassing. On the annual scale, spring emissions converted the lake from a small CO2 sink to a CO2 source: 80 % of total annual carbon emissions from the lake were emitted as CO2. The annual total carbon exchange per unit area was highest at the fen, which was an annual sink of carbon with respect to the atmosphere. Continuous respiration during the winter partly counteracted the fen summer sink by accounting for, as both CH4 and CO2, 33 % of annual carbon exchange. Our study shows (1) the importance of overturn periods (spring or fall) for the annual CH4 and CO2 emissions of northern lakes, (2) the significance of lakes as atmospheric carbon sources in subarctic landscapes while fens can be a strong carbon sink, and (3) the potential for ecosystem-scale eddy covariance measurements to improve the understanding of short-term processes driving lake-atmosphere exchange of CH4 and CO2.

40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment... and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O Fuel Fossil fuel-based emissions...

40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment... and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O Fuel Fossil fuel-based emissions...

40 CFR Table Aa-2 to Subpart Aa of... - Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Kraft Lime Kiln and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O AA Table AA-2 to Subpart AA of Part 98 Protection of Environment... and Calciner Emissions Factors for Fossil Fuel-Based CH4 and N2O Fuel Fossil fuel-based emissions...

On the sources of methane to the Los Angeles atmosphere.

PubMed

Wennberg, Paul O; Mui, Wilton; Wunch, Debra; Kort, Eric A; Blake, Donald R; Atlas, Elliot L; Santoni, Gregory W; Wofsy, Steven C; Diskin, Glenn S; Jeong, Seongeun; Fischer, Marc L

2012-09-04

We use historical and new atmospheric trace gas observations to refine the estimated source of methane (CH(4)) emitted into California's South Coast Air Basin (the larger Los Angeles metropolitan region). Referenced to the California Air Resources Board (CARB) CO emissions inventory, total CH(4) emissions are 0.44 ± 0.15 Tg each year. To investigate the possible contribution of fossil fuel emissions, we use ambient air observations of methane (CH(4)), ethane (C(2)H(6)), and carbon monoxide (CO), together with measured C(2)H(6) to CH(4) enhancement ratios in the Los Angeles natural gas supply. The observed atmospheric C(2)H(6) to CH(4) ratio during the ARCTAS (2008) and CalNex (2010) aircraft campaigns is similar to the ratio of these gases in the natural gas supplied to the basin during both these campaigns. Thus, at the upper limit (assuming that the only major source of atmospheric C(2)H(6) is fugitive emissions from the natural gas infrastructure) these data are consistent with the attribution of most (0.39 ± 0.15 Tg yr(-1)) of the excess CH(4) in the basin to uncombusted losses from the natural gas system (approximately 2.5-6% of natural gas delivered to basin customers). However, there are other sources of C(2)H(6) in the region. In particular, emissions of C(2)H(6) (and CH(4)) from natural gas seeps as well as those associated with petroleum production, both of which are poorly known, will reduce the inferred contribution of the natural gas infrastructure to the total CH(4) emissions, potentially significantly. This study highlights both the value and challenges associated with the use of ethane as a tracer for fugitive emissions from the natural gas production and distribution system.

On the Sources of Methane to the Los Angeles Atmosphere

NASA Technical Reports Server (NTRS)

Wennberg, Paul O.; Mui, Wilton; Fischer, Marc L.; Wunch, Debra; Kort, Eric A.; Blake, Donald R.; Atlas, Elliot L.; Santoni, Gregory W.; Wofsy, Steven C.; Diskin, Glenn S.;

Methane emissions from the Marcellus Shale in southwestern Pennsylvania and northern West Virginia based on airborne measurements

NASA Astrophysics Data System (ADS)

Ren, Xinrong; Hall, Dolly L.; Vinciguerra, Timothy; Benish, Sarah E.; Stratton, Phillip R.; Ahn, Doyeon; Hansford, Jonathan R.; Cohen, Mark D.; Sahu, Sayantan; He, Hao; Grimes, Courtney; Salawitch, Ross J.; Ehrman, Sheryl H.; Dickerson, Russell R.

2017-04-01

Natural gas production in the U.S. has increased rapidly over the past decade, along with concerns about methane (CH4) leakage (total fugitive emissions), and climate impacts. Quantification of CH4 emissions from oil and natural gas (O&NG) operations is important for establishing scientifically sound, cost-effective policies for mitigating greenhouse gases. We use aircraft measurements and a mass balance approach for three flight experiments in August and September 2015 to estimate CH4 emissions from O&NG operations in the southwestern Marcellus Shale region. We estimate the mean ± 1σ CH4 emission rate as 36.7 ± 1.9 kg CH4 s-1 (or 1.16 ± 0.06 Tg CH4 yr-1) with 59% coming from O&NG operations. We estimate the mean ± 1σ CH4 leak rate from O&NG operations as 3.9 ± 0.4% with a lower limit of 1.5% and an upper limit of 6.3%. This leak rate is broadly consistent with the results from several recent top-down studies but higher than the results from a few other observational studies as well as in the U.S. Environmental Protection Agency CH4 emission inventory. However, a substantial source of CH4 was found to contain little ethane (C2H6), possibly due to coalbed CH4 emitted either directly from coalmines or from wells drilled through coalbed layers. Although recent regulations requiring capture of gas from the completion venting step of the hydraulic fracturing appear to have reduced losses, our study suggests that for a 20 year time scale, energy derived from the combustion of natural gas extracted from this region will require further controls before it can exert a net climate benefit compared to coal.

Methane emissions from the Marcellus Shale in southwestern Pennsylvania and northern West Virginia based on airborne measurements

PubMed Central

Hall, Dolly L.; Vinciguerra, Timothy; Benish, Sarah E.; Stratton, Phillip R.; Ahn, Doyeon; Hansford, Jonathan R.; Cohen, Mark D.; Sahu, Sayantan; He, Hao; Grimes, Courtney; Salawitch, Ross J.; Ehrman, Sheryl H.; Dickerson, Russell R.

2017-01-01

Abstract Natural gas production in the U.S. has increased rapidly over the past decade, along with concerns about methane (CH4) leakage (total fugitive emissions), and climate impacts. Quantification of CH4 emissions from oil and natural gas (O&NG) operations is important for establishing scientifically sound, cost‐effective policies for mitigating greenhouse gases. We use aircraft measurements and a mass balance approach for three flight experiments in August and September 2015 to estimate CH4 emissions from O&NG operations in the southwestern Marcellus Shale region. We estimate the mean ± 1σ CH4 emission rate as 36.7 ± 1.9 kg CH4 s−1 (or 1.16 ± 0.06 Tg CH4 yr−1) with 59% coming from O&NG operations. We estimate the mean ± 1σ CH4 leak rate from O&NG operations as 3.9 ± 0.4% with a lower limit of 1.5% and an upper limit of 6.3%. This leak rate is broadly consistent with the results from several recent top‐down studies but higher than the results from a few other observational studies as well as in the U.S. Environmental Protection Agency CH4 emission inventory. However, a substantial source of CH4 was found to contain little ethane (C2H6), possibly due to coalbed CH4 emitted either directly from coalmines or from wells drilled through coalbed layers. Although recent regulations requiring capture of gas from the completion venting step of the hydraulic fracturing appear to have reduced losses, our study suggests that for a 20 year time scale, energy derived from the combustion of natural gas extracted from this region will require further controls before it can exert a net climate benefit compared to coal. PMID:28603681

Methane emissions from the Marcellus Shale in southwestern Pennsylvania and northern West Virginia based on airborne measurements.

PubMed

Ren, Xinrong; Hall, Dolly L; Vinciguerra, Timothy; Benish, Sarah E; Stratton, Phillip R; Ahn, Doyeon; Hansford, Jonathan R; Cohen, Mark D; Sahu, Sayantan; He, Hao; Grimes, Courtney; Salawitch, Ross J; Ehrman, Sheryl H; Dickerson, Russell R

2017-04-27

Natural gas production in the U.S. has increased rapidly over the past decade, along with concerns about methane (CH 4 ) leakage (total fugitive emissions), and climate impacts. Quantification of CH 4 emissions from oil and natural gas (O&NG) operations is important for establishing scientifically sound, cost-effective policies for mitigating greenhouse gases. We use aircraft measurements and a mass balance approach for three flight experiments in August and September 2015 to estimate CH 4 emissions from O&NG operations in the southwestern Marcellus Shale region. We estimate the mean ± 1 σ CH 4 emission rate as 36.7 ± 1.9 kg CH 4  s -1 (or 1.16 ± 0.06 Tg CH 4  yr -1 ) with 59% coming from O&NG operations. We estimate the mean ± 1 σ CH 4 leak rate from O&NG operations as 3.9 ± 0.4% with a lower limit of 1.5% and an upper limit of 6.3%. This leak rate is broadly consistent with the results from several recent top-down studies but higher than the results from a few other observational studies as well as in the U.S. Environmental Protection Agency CH 4 emission inventory. However, a substantial source of CH 4 was found to contain little ethane (C 2 H 6 ), possibly due to coalbed CH 4 emitted either directly from coalmines or from wells drilled through coalbed layers. Although recent regulations requiring capture of gas from the completion venting step of the hydraulic fracturing appear to have reduced losses, our study suggests that for a 20 year time scale, energy derived from the combustion of natural gas extracted from this region will require further controls before it can exert a net climate benefit compared to coal.

Methane Emissions from the Inland Waters of Alaska

NASA Astrophysics Data System (ADS)

Striegl, R. G.; Butman, D. E.; Stackpoole, S. M.; Dornblaser, M.

2017-12-01

Inland waters at high latitudes generally emit methane (CH4) continuously to the atmosphere during the open water season and build-up CH4 under ice during winter that is released over a short period following ice melt. Landscape position, stream and river size, water source, and turbulence created by water flow largely control CH4 emissions from streams and rivers. Organic carbon sources for CH4 production in lakes vary widely among lakes and landscapes and include hydrologic inputs from terrestrial sources, releases from permafrost thaw (thermokarst), and autochthonous inputs from aquatic macrophytes and algae. Lake emissions are therefore controlled by the balance between within-lake CH4 production and consumption, surface turbulence at the water-air interface, and CH4 ebullition. This creates a complex range of conditions that are difficult to characterize, where dissolved CH4 concentrations may vary by up to 4 orders of magnitude among lakes and/or within a single lake over an annual seasonal cycle. Moreover, large inputs of organic matter from permafrost thaw or other sources commonly result in high rates of bubble production and ebullition from some lakes, while other lakes have negligible ebullition. We quantified water surface areas and estimated CH4 emission rates for lakes, streams and rivers for the six major hydrologic regions of Alaska and determined that they collectively emit about 0.124 Tg C per year as CH4 to the atmosphere. Lake emissions comprise about 75% of the total. When adjusted for total land surface area in Alaska, our lake emission estimate is substantially smaller than previous global estimates for inland waters north of 50 degrees North latitude. We attribute this to incorporation of results that cover a broad range of lake conditions in interior Alaska and to new data from lakes in southwest Alaska that have very low CH4 concentration but very large surface area.

Some validation results of orbital and ground based CO and CH4 total content measurements in background and industrial regions

NASA Astrophysics Data System (ADS)

Rakitin, Vadim; Shtabkin, Yury; Elansky, Nikolai; Skorokhod, Andrey; Safronov, Alexandr; Dzhola, Anatoly

2015-04-01

The results of ground-based spectroscopic measurements of CO and CH4 total content (TC) in Moscow, Zvenigorod (53 km toward West from the Moscow center), ZOTTO station (Central Siberia) and Beijing (China) during 2010-2014 years for conditions of typical and anomalous emission rates are presented and compared with satellite TC data (the latest versions of MOPITT, AIRS, IASI products). The empiric coefficients and relationships between data of ground-based and satellite CO and CH4 total contents (TC) are discussed. The comparison demonstrated a good agreement (R2 ~ 0.6-0.9) of satellite and ground-based CO TC data in low pollution conditions and systematic underestimation of satellite CO TC (150-300 %) in condition of intense surface emissions (events of wild fires in Siberia in 2011-2012 and strong atmospheric pollutions in Beijing). The best correlation (R2 ~ 0.4) for polluted conditions of Beijing was obtained in summer time-period for averaged AIRS v.6 CO TC data for 1o*1o grid, but K=Ugrb/Ustl = 2.5, where Ugrb and Ustlare ground based and satellite diurnal TC values relatively. Under excluding of the days with low ABL heights (HABL ≥1000m selection) the correlation between satellite and ground based CO TC diurnal data increases (R2 ~ 0.7, K=1.5). Orbital AIRS CH4 total columns good enough correlate with ground-based data (R2 ~0.4-0.7). IASI CH4TC diurnal data have no correlation with AIRS and ground-based TC.

40 CFR 98.272 - GHGs to report.

Code of Federal Regulations, 2012 CFR

2012-07-01

... listed in paragraphs (a) through (f) of this section: (a) CO2, biogenic CO2, CH4, and N2O emissions from each kraft or soda chemical recovery furnace. (b) CO2, biogenic CO2, CH4, and N2O emissions from each sulfite chemical recovery combustion unit. (c) CO2, biogenic CO2, CH4, and N2O emissions from each stand...

40 CFR 98.272 - GHGs to report.

Code of Federal Regulations, 2010 CFR

2010-07-01

... listed in paragraphs (a) through (f) of this section: (a) CO2, biogenic CO2, CH4, and N2O emissions from each kraft or soda chemical recovery furnace. (b) CO2, biogenic CO2, CH4, and N2O emissions from each sulfite chemical recovery combustion unit. (c) CO2, biogenic CO2, CH4, and N2O emissions from each stand...

40 CFR 98.272 - GHGs to report.

Code of Federal Regulations, 2014 CFR

2014-07-01

... listed in paragraphs (a) through (f) of this section: (a) CO2, biogenic CO2, CH4, and N2O emissions from each kraft or soda chemical recovery furnace. (b) CO2, biogenic CO2, CH4, and N2O emissions from each sulfite chemical recovery combustion unit. (c) CO2, biogenic CO2, CH4, and N2O emissions from each stand...

40 CFR 98.272 - GHGs to report.

Code of Federal Regulations, 2013 CFR

2013-07-01

... listed in paragraphs (a) through (f) of this section: (a) CO2, biogenic CO2, CH4, and N2O emissions from each kraft or soda chemical recovery furnace. (b) CO2, biogenic CO2, CH4, and N2O emissions from each sulfite chemical recovery combustion unit. (c) CO2, biogenic CO2, CH4, and N2O emissions from each stand...

40 CFR 98.272 - GHGs to report.

Code of Federal Regulations, 2011 CFR

2011-07-01

... listed in paragraphs (a) through (f) of this section: (a) CO2, biogenic CO2, CH4, and N2O emissions from each kraft or soda chemical recovery furnace. (b) CO2, biogenic CO2, CH4, and N2O emissions from each sulfite chemical recovery combustion unit. (c) CO2, biogenic CO2, CH4, and N2O emissions from each stand...

40 CFR Table K-1 to Subpart K of... - Electric Arc Furnace (EAF) CH4 Emission Factors

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Electric Arc Furnace (EAF) CH4 Emission Factors K Table K-1 to Subpart K of Part 98 Protection of Environment ENVIRONMENTAL PROTECTION.... 98, Subpt. K, Table K-1 Table K-1 to Subpart K of Part 98—Electric Arc Furnace (EAF) CH4 Emission...

40 CFR Table K-1 to Subpart K of... - Electric Arc Furnace (EAF) CH4 Emission Factors

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Electric Arc Furnace (EAF) CH4 Emission Factors K Table K-1 to Subpart K of Part 98 Protection of Environment ENVIRONMENTAL PROTECTION.... 98, Subpt. K, Table K-1 Table K-1 to Subpart K of Part 98—Electric Arc Furnace (EAF) CH4 Emission...

40 CFR Table K-1 to Subpart K of... - Electric Arc Furnace (EAF) CH4 Emission Factors

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Electric Arc Furnace (EAF) CH4 Emission Factors K Table K-1 to Subpart K of Part 98 Protection of Environment ENVIRONMENTAL PROTECTION.... 98, Subpt. K, Table K-1 Table K-1 to Subpart K of Part 98—Electric Arc Furnace (EAF) CH4 Emission...

40 CFR Table K-1 to Subpart K of... - Electric Arc Furnace (EAF) CH4 Emission Factors

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Electric Arc Furnace (EAF) CH4 Emission Factors K Table K-1 to Subpart K of Part 98 Protection of Environment ENVIRONMENTAL PROTECTION.... 98, Subpt. K, Table K-1 Table K-1 to Subpart K of Part 98—Electric Arc Furnace (EAF) CH4 Emission...

Methane-Cycling Microbial Communities and Methane Emission in Natural and Restored Peatlands

PubMed Central

Hynninen, Anu; Nieminen, Mika; Tuomivirta, Tero T.; Tuittila, Eeva-Stiina; Nousiainen, Hannu; Kell, Dana K.; Yrjälä, Kim; Tervahauta, Arja; Fritze, Hannu

2012-01-01

We addressed how restoration of forestry-drained peatlands affects CH4-cycling microbes. Despite similar community compositions, the abundance of methanogens and methanotrophs was lower in restored than in natural sites and correlated with CH4 emission. Poor establishment of methanogens may thus explain low CH4 emissions on restored peatlands even 10 to 12 years after restoration. PMID:22752167

Straw enhanced CO2 and CH4 but decreased N2O emissions from flooded paddy soils: Changes in microbial community compositions

NASA Astrophysics Data System (ADS)

Wang, Ning; Yu, Jian-Guang; Zhao, Ya-Hui; Chang, Zhi-Zhou; Shi, Xiao-Xia; Ma, Lena Q.; Li, Hong-Bo

2018-02-01

To explore microbial mechanisms of straw-induced changes in CO2, CH4, and N2O emissions from paddy field, wheat straw was amended to two paddy soils from Taizhou (TZ) and Yixing (YX), China for 60 d under flooded condition. Illumia sequencing was used to characterize shift in bacterial community compositions. Compared to control, 1-5% straw amendment significantly elevated CO2 and CH4 emissions with higher increase at higher application rates, mainly due to increased soil DOC concentrations. In contrast, straw amendment decreased N2O emission. Considering CO2, CH4, and N2O emissions as a whole, an overall increase in global warming potential was observed with straw amendment. Total CO2 and CH4 emissions from straw-amended soils were significantly higher for YX than TZ soil, suggesting that straw-induced greenhouse gas emissions depended on soil characteristics. The abundance of C-turnover bacteria Firmicutes increased from 28-41% to 54-77% with straw amendment, thereby increasing CO2 and CH4 emissions. However, straw amendment reduced the abundance of denitrifying bacteria Proteobacteria from 18% to 7.2-13% or increased the abundance of N2O reducing bacteria Clostridium from 7.6-11% to 13-30%, thereby decreasing N2O emission. The results suggested straw amendment strongly influenced greenhouse gas emissions via alerting soil properties and bacterial community compositions. Future field application is needed to ascertain the effects of straw return on greenhouse gas emissions.

Quantifying methane emissions from coal and natural gas sources along the northwestern Appalachian

NASA Astrophysics Data System (ADS)

Barkley, Z.; Lauvaux, T.; Davis, K. J.; Fried, A.

2017-12-01

According to the EPA's 2012 gridded inventory (Maasakkers et al., 2016), more than 10% of all CH4 emissions in the U.S. are located along the western edge of the Appalachian with the majority of these emissions coming from natural gas infrastructure and coal mines. However, top-down studies of unconventional wells in southwestern Pennsylvania have found emission rates to be much higher than EPA estimates (Caulton et al., 2014, Ren et al., 2017). Furthermore, although 9 of the 10 largest sources of CH4 in the EPA Greenhouse Gas Reporting Program are coal mines located in this region, no top down studies have been performed to assess the accuracy of these enormous point sources. This study uses aircraft data from the ACT-America flight campaign in conjunction with techniques previously used to solve for CH4 emissions from the northeastern Marcellus (Barkley et al., 2017) to quantify the total CH4 flux from the western Pennsylvania/West Virginia region and constrain emissions from natural gas and coal with an upper limit for each source. We use the WRF-Chem mesoscale model at 3 km resolution to simulate CH4 enhancements from a customized emissions inventory and compare the modelled enhancements to observations from 7 flights that were downwind of coal and gas sources. Coal and natural gas emissions are adjusted in the model to minimize a cost function that accounts for the difference between the modelled and observed CH4 values, and a range of likely combinations for natural gas and coal emission rates are obtained for each flight. We then overlap this range of likely emission rates across all flights to further limit the range of possible emission rates. Influence functions created using a lagrangian particle dispersion model for segments of each flight provide information on what area emissions are being optimized for. Preliminary results find that CH4 emissions from gas and coal along the northwestern Appalachian are lower than EPA estimates by 20-50%. In particular, upper limits on CH4 emissions from unconventional natural gas are less than 1% of total production, significantly lower than previous top-down estimates in the region. Future work will use ethane data to better distinguish between coal and natural gas emissions, and expand these analyses to other study regions explored in the ACT-America aircraft campaign.

On the Discovery of CO Nighttime Emissions on Titan by Cassini/VIMS: Derived Stratospheric Abundances and Geological Implications

NASA Technical Reports Server (NTRS)

Bainesa, Kevin H.; Drossart, Pierre; Lopez-Valverde, Miguel A.; Atreya, Sushil K.; Sotin, Christophe; Momary, Thomas W.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Nicholson, Philip D.

2006-01-01

We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119-147] in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 microns. For CH3D, the prominent Q branch of the nu(2) fundamental band of CH3D near 4.55 microns is apparent. CO2 emissions from the strong nu(3) vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32 +/- 15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is similar to 2.9 +/- 1.5 x 10(exp 14) kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (similar to 0.5-1.0 Gyr), we find a mean CO atmospheric production rate of 6 +/- 3 x 10(exp 5) kg yr(exp -1). Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779-784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8 +/- 0.9 x 10(exp -4), based on an average methane surface emission rate over the past 0.5 Gyr of 1.3 x 10(exp -13) gm cm(exp -2) s(exp -1) as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi: 10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer-Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is approximately 0.02 km(exp 3) yr (exp -1), a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant geological processes reshaping the surface of Titan.

On the discovery of CO nighttime emissions on Titan by Cassini/VIMS: Derived stratospheric abundances and geological implications

USGS Publications Warehouse

Baines, K.H.; Drossart, P.; Lopez-Valverde, M. A.; Atreya, S.K.; Sotin, Christophe; Momary, T.W.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

2006-01-01

We present a quantitative analysis of CO thermal emissions discovered on the nightside of Titan by Baines et al. [2005. The atmospheres of Saturn and Titan in the near-infrared: First results of Cassini/VIMS. Earth, Moon, and Planets, 96, 119-147]. in Cassini/VIMS spectral imagery. We identify these emission features as the P and R branches of the 1-0 vibrational band of carbon monoxide (CO) near 4.65 ??m. For CH3D, the prominent Q branch of the ??2 fundamental band of CH3D near 4.55 ??m is apparent. CO2 emissions from the strong v3 vibrational band are virtually absent, indicating a CO2 abundance several orders of magnitude less than CO, in agreement with previous investigations. Analysis of CO emission spectra obtained over a variety of altitudes on Titan's nightside limb indicates that the stratospheric abundance of CO is 32??15 ppm, and together with other recent determinations, suggests a vertical distribution of CO nearly constant at this value from the surface throughout the troposphere to at least the stratopause near 300 km altitude. The corresponding total atmospheric content of CO in Titan is ???2.9??1.5??1014 kg. Given the long lifetime of CO in the oxygen-poor Titan atmosphere (???0.5-1.0 Gyr), we find a mean CO atmospheric production rate of 6??3??105 kg yr-1. Given the lack of primordial heavy noble gases observed by Huygens [Niemann et al., 2005. The abundances of constituents of Titan's atmosphere from the GCMS on the Huygens probe. Nature, 438, 779-784], the primary source of atmospheric CO is likely surface emissions. The implied CO/CH4 mixing ratio of near-surface material is 1.8??0.9??10-4, based on an average methane surface emission rate over the past 0.5 Gyr of 1.3??10-13 gm cm-2 s-1 as required to balance hydrocarbon haze production via methane photolysis [Wilson and Atreya, 2004. Current state of modeling the photochemistry of Titan's mutually dependent atmosphere and ionosphere. J. Geophys. Res. 109, E06002 Doi:10.1029/2003JE002181]. This low CO/CH4 ratio is much lower than expected for the sub-nebular formation region of Titan and supports the hypothesis [e.g., Atreya et al., 2005. Methane on Titan: photochemical-meteorological-hydrogeochemical cycle. Bull. Am. Astron. Soc. 37, 735] that the conversion of primordial CO and other carbon-bearing materials into CH4-enriched clathrate-hydrates occurs within the deep interior of Titan via the release of hydrogen through the serpentinization process followed by Fischer-Tropsch catalysis. The time-averaged predicted emission rate of methane-rich surface materials is ???0.02 km3 yr-1, a value significantly lower than the rate of silicate lava production for the Earth and Venus, but nonetheless indicative of significant active geological processes reshaping the surface of Titan. ?? 2006 Elsevier Ltd. All rights reserved.

Evaluating the relative contribution of methane oxidation to methane emissions from young floodplain soils under Alternative Irrigation Management

NASA Astrophysics Data System (ADS)

Pierreux, Sofie; Verhoeven, Elizabeth; Akter, Masuda; Sleutel, Steven; Said-Pullicino, Daniel; Romani, Marco; Boeckx, Pascal

2016-04-01

To keep the pace with a yearly growing demand for rice by 1-2%, future rice production must come primarily from high yielding irrigated rice, putting a pressure on fresh water reserves. In this context, water saving Alternative Irrigation Management (AIM) is progressively applied worldwide. By introducing repeated or mid-seasonal drainage, AIM suppresses emission of CH4, otherwise prevalent in continuously flooded rice. However, little is known about the effect of AIM on the balance of CH4 genesis and oxidation in paddy soils. We studied relevant soil parameters and CH4 emissions in continuously flooded (CF) and alternately wetted and dried (AWD) rice paddies. During a field campaign at the Castello d'Agogna experimental station (Pavia, Italy), we measured in situ CH4 oxidation and emission rates using the closed gas chamber technique with or without application of CH2F2 as a selective inhibitor of CH4 oxidation. In addition, we determined potential CH4 oxidation rates using incubated soil slurries originating from the same experimental plots. The dataset was supplemented with depth differentiated monitoring of redox potential, temperature, moisture content and soil solution parameters (DOC, Fe2+, Mn3+, mineral N and dissolved CH4). Peaks in dissolved CH4 manifested at 5 and 12.5cm depth, with much lower and equal levels at 25, 50 and 80cm depth. Also depth distributions of dissolved Fe and Mn followed this pattern, indicating that methanogenic activity was primarily confounded to the topsoil. Seasonal CH4 emissions were about halved by AWD compared to CF management. After a fast decline of in situ oxidation within the AWD treatment at the beginning of the season, CH4 oxidation percentages in CF and AWD increased until the booting stage (67DAS), reaching peak values of 83% and 69% of produced CH4, respectively. CH4 oxidation thereafter gradually declined to nearly 50% in both treatments after the final drainage (103 DAS). Seasonal trends of potential CH4 oxidation rates were alike between CF and AWD fields, except at 52 DAS, when 5cm and 25cm depth CH4 oxidation capacities from CF soil slurries exceeded those under AWD. This could firstly be explained by higher observed soil solution CH4 concentrations of CF paddies, while in mid-season dissolved CH4 was nearly absent in case of AWD. We hypothesize that a larger methanotrophic biomass was present in the CF fields, explaining the higher CH4 oxidation potential, but this requires verification by qPCR. In addition, higher NH4+ concentrations were measured under CF, which as well might have favored methanotrophic activity. Ongoing analysis of stable isotope ratios (12C/13C) in both atmospheric and subsurface gas samples will complement the specific inhibitor-based CH4 oxidation estimates. Currently, the dataset assembled during this field experiment will be used to fine-tune the biogeochemical model 'rice DNDC' (DeNitrification-DeComposition) with specific attention to DNDC's capability to simulate CH4 oxidation and depth profiles . The model revision will take into account the seasonal and depth differentiated behavior of parameters relevant to the processes of CH4 oxidation, production and emission, and hence contribute to a more precise estimation of methane emissions under AIM.

Factors affecting methane production and mitigation in ruminants.

PubMed

Shibata, Masaki; Terada, Fuminori

2010-02-01

Methane (CH(4)) is the second most important greenhouse gas (GHG) and that emitted from enteric fermentation in livestock is the single largest source of emissions in Japan. Many factors influence ruminant CH(4) production, including level of intake, type and quality of feeds and environmental temperature. The objectives of this review are to identify the factors affecting CH(4) production in ruminants, to examine technologies for the mitigation of CH(4) emissions from ruminants, and to identify areas requiring further research. The following equation for CH(4) prediction was formulated using only dry matter intake (DMI) and has been adopted in Japan to estimate emissions from ruminant livestock for the National GHG Inventory Report: Y = -17.766 + 42.793X - 0.849X(2), where Y is CH(4) production (L/day) and X is DMI (kg/day). Technologies for the mitigation of CH(4) emissions from ruminants include increasing productivity by improving nutritional management, the manipulation of ruminal fermentation by changing feed composition, the addition of CH(4) inhibitors, and defaunation. Considering the importance of ruminant livestock, it is essential to establish economically feasible ways of reducing ruminant CH(4) production while improving productivity; it is therefore critical to conduct a full system analysis to select the best combination of approaches or new technologies to be applied under long-term field conditions.

Characterization of microwave plasma CVD of diamond by mass analysis and optical emission spectroscopy

NASA Astrophysics Data System (ADS)

Weimer, Wayne A.; Johnson, Curtis E.

1990-12-01

A microwave plasma enhanced chemical vapor deposition system is characterized using optical emission spectroscopy and mass spectrometry. CH4 CH2 CH4 and CO were used as carbon source gases. The effects of 02 addition to the feed gas is examined. Emission from CH in the plasma is observed and CH4 is a stable reaction product for all carbon source gases used. 02 is fully consumed and converted to H20 and CO. Emission from C is observed for all hydrocarbon gases when 02 is added but is absent when CO is the carbon source gas. Addition of 02 also dramatically affects the relative amount of reaction products as the carbon in the system is converted to CO. 1.

Mitigating methane emission from paddy soil with rice-straw biochar amendment under projected climate change

PubMed Central

Han, Xingguo; Sun, Xue; Wang, Cheng; Wu, Mengxiong; Dong, Da; Zhong, Ting; Thies, Janice E.; Wu, Weixiang

2016-01-01

Elevated global temperatures and increased concentrations of carbon dioxide (CO2) in the atmosphere associated with climate change will exert profound effects on rice cropping systems, particularly on their greenhouse gas emitting potential. Incorporating biochar into paddy soil has been shown previously to reduce methane (CH4) emission from paddy rice under ambient temperature and CO2. We examined the ability of rice straw-derived biochar to reduce CH4 emission from paddy soil under elevated temperature and CO2 concentrations expected in the future. Adding biochar to paddy soil reduced CH4 emission under ambient conditions and significantly reduced emissions by 39.5% (ranging from 185.4 mg kg−1 dry weight soil, dws season−1 to 112.2 mg kg−1 dws season−1) under simultaneously elevated temperature and CO2. Reduced CH4 release was mainly attributable to the decreased activity of methanogens along with the increased CH4 oxidation activity and pmoA gene abundance of methanotrophs. Our findings highlight the valuable services of biochar amendment for CH4 control from paddy soil in a future that will be shaped by climate change. PMID:27090814

Gaseous emissions from outdoor concrete yards used by livestock

NASA Astrophysics Data System (ADS)

Misselbrook, T. H.; Webb, J.; Chadwick, D. R.; Ellis, S.; Pain, B. F.

Measurements of ammonia (NH 3), nitrous oxide (N 2O) and methane (CH 4) were made from 11 outdoor concrete yards used by livestock. Measurements of NH 3 emission were made using the equilibrium concentration technique while closed chambers were used to measure N 2O and CH 4 emissions. Outdoor yards used by livestock proved to be an important source of NH 3 emission. Greatest emission rates were measured from dairy cow feeding yards, with a mean of 690 mg NH 3-N m -2 h -1. Smaller emission rates were measured from sheep handling areas, dairy cow collecting yards, beef feeding yards and a pig loading area, with respective mean emission rates of 440, 280, 220 and 140 mg NH 3-N m -2 h -1. Emission rates of N 2O and CH 4 were much smaller and for CH 4, in particular, emission rates were influenced greatly by the presence or absence of dung on the measurement area.

Prediction of future methane emission from irrigated rice paddies in central Thailand under different water management practices.

PubMed

Minamikawa, Kazunori; Fumoto, Tamon; Iizumi, Toshichika; Cha-Un, Nittaya; Pimple, Uday; Nishimori, Motoki; Ishigooka, Yasushi; Kuwagata, Tsuneo

2016-10-01

There is concern about positive feedbacks between climate change and methane (CH4) emission from rice paddies. However, appropriate water management may mitigate the problem. We tested this hypothesis at six field sites in central Thailand, where the irrigated area is rapidly increasing. We used DNDC-Rice, a process-based biogeochemistry model adjusted based on rice growth data at each site to simulate CH4 emission from a rice-rice double cropping system from 2001 to 2060. Future climate change scenarios consisting of four representative concentration pathways (RCPs) and seven global climate models were generated by statistical downscaling. We then simulated CH4 emission in three water management practices: continuous flooding (CF), single aeration (SA), and multiple aeration (MA). The adjusted model reproduced the observed rice yield and CH4 emission well at each site. The simulated CH4 emissions in CF from 2051 to 2060 were 5.3 to 7.8%, 9.6 to 16.0%, 7.3 to 18.0%, and 13.6 to 19.0% higher than those from 2001 to 2010 in RCPs 2.6, 4.5, 6.0, and 8.5, respectively, at the six sites. Regionally, SA and MA mitigated CH4 emission by 21.9 to 22.9% and 53.5 to 55.2%, respectively, relative to CF among the four RCPs. These mitigation potentials by SA and MA were comparable to those from 2001 to 2010. Our results indicate that climate change in the next several decades will not attenuate the quantitative effect of water management practices on mitigating CH4 emission from irrigated rice paddies in central Thailand. Copyright © 2016 Elsevier B.V. All rights reserved.

Observations on the methane oxidation capacity of landfill soils.

PubMed

Chanton, Jeffrey; Abichou, Tarek; Langford, Claire; Spokas, Kurt; Hater, Gary; Green, Roger; Goldsmith, Doug; Barlaz, Morton A

2011-05-01

The objective of this study was to determine the role of CH(4) loading to a landfill cover in the control of CH(4) oxidation rate (gCH(4)m(-2)d(-1)) and CH(4) oxidation efficiency (% CH(4) oxidation) in a field setting. Specifically, we wanted to assess how much CH(4) a cover soil could handle. To achieve this objective we conducted synoptic measurements of landfill CH(4) emission and CH(4) oxidation in a single season at two Southeastern USA landfills. We hypothesized that percent oxidation would be greatest at sites of low CH(4) emission and would decrease as CH(4) emission rates increased. The trends in the experimental results were then compared to the predictions of two differing numerical models designed to simulate gas transport in landfill covers, one by modeling transport by diffusion only and the second allowing both advection and diffusion. In both field measurements and in modeling, we found that percent oxidation is a decreasing exponential function of the total CH(4) flux rate (CH(4) loading) into the cover. When CH(4) is supplied, a cover's rate of CH(4) uptake (gCH(4)m(-2)d(-2)) is linear to a point, after which the system becomes saturated. Both field data and modeling results indicate that percent oxidation should not be considered as a constant value. Percent oxidation is a changing quantity and is a function of cover type, climatic conditions and CH(4) loading to the bottom of the cover. The data indicate that an effective way to increase the % oxidation of a landfill cover is to limit the amount of CH(4) delivered to it. Copyright © 2010 Elsevier Ltd. All rights reserved.

CH4 emission and recovery from municipal solid waste in China.

PubMed

Xu, Xin-Hua; Yang, Yue-Ping; Wang, Da-Hui

2003-01-01

Methane ( CH4) is an important greenhouse gas and a major environmental pollutant, second only to carbon dioxide (CO2) in its contribution to potential global warming. In many cases, methane emission from landfills otherwise emitted to the atmosphere can be removed and utilized, or significantly reduced in quantity by using coat-effective management methods. The gas can also be used as a residential, commercial, or industrial fuel. Therefore, emission reduction strategies have the potential to become low cost, or even profitable. The annual growth rate of Municipal Solid Waste (MSW) output in China is 6.24%, with the highest levels found in South China, Southwest China and East China. Cities and towns are developing quickly in these regions. MSW output was only 76.36 Mt in 1991 and increased to 109.82 Mt in 1997, registering an average increase of 43.8% . In China, methane emission from landfills also increased from 5.88 Mt in 1991 to 8.46 Mt in 1997; so the recovery of methane from landfills is a profitable project.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heath, Garvin; Warner, Ethan; Steinberg, Daniel

A growing number of studies have raised questions regarding uncertainties in our understanding of methane (CH 4) emissions from fugitives and venting along the natural gas (NG) supply chain. In particular, a number of measurement studies have suggested that actual levels of CH 4 emissions may be higher than estimated by EPA" tm s U.S. GHG Emission Inventory. We reviewed the literature to identify the growing number of studies that have raised questions regarding uncertainties in our understanding of methane (CH 4) emissions from fugitives and venting along the natural gas (NG) supply chain.

Mapping methane sources and emissions over California from direct airborne flux and VOC source tracer measurements

NASA Astrophysics Data System (ADS)

Guha, A.; Misztal, P. K.; Peischl, J.; Karl, T.; Jonsson, H. H.; Woods, R. K.; Ryerson, T. B.; Goldstein, A. H.

2013-12-01

Quantifying the contributions of methane (CH4) emissions from anthropogenic sources in the Central Valley of California is important for validation of the statewide greenhouse gas (GHG) inventory and subsequent AB32 law implementation. The state GHG inventory is largely based on activity data and emission factor based estimates. The 'bottom-up' emission factors for CH4 have large uncertainties and there is a lack of adequate 'top-down' measurements to characterize emission rates. Emissions from non-CO2 GHG sources display spatial heterogeneity and temporal variability, and are thus, often, poorly characterized. The Central Valley of California is an agricultural and industry intensive region with large concentration of dairies and livestock operations, active oil and gas fields and refining operations, as well as rice cultivation all of which are known CH4 sources. In order to gain a better perspective of the spatial distribution of major CH4 sources in California, airborne measurements were conducted aboard a Twin Otter aircraft for the CABERNET (California Airborne BVOC Emissions Research in Natural Ecosystems Transects) campaign, where the driving research goal was to understand the spatial distribution of biogenic VOC emissions. The campaign took place in June 2011 and encompassed over forty hours of low-altitude and mixed layer airborne CH4 and CO2 measurements alongside coincident VOC measurements. Transects during eight unique flights covered much of the Central Valley and its eastern edge, the Sacramento-San Joaquin delta and the coastal range. We report direct quantification of CH4 fluxes using real-time airborne Eddy Covariance measurements. CH4 and CO2 were measured at 1-Hz data rate using an instrument based on Cavity Ring Down Spectroscopy (CRDS) along with specific VOCs (like isoprene, methanol, acetone etc.) measured at 10-Hz using Proton Transfer Reaction Mass Spectrometer - Eddy Covariance (PTRMS-EC) flux system. Spatially resolved eddy covariance fluxes were obtained using the virtual disjunct eddy covariance method and from Wavelet Analysis along flight tracks flown in the mixed layer. Preliminary analysis of mixing ratio measurements indicate that high concentrations of CH4 occur consistently while flying above the Central Valley that are correlated to large enhancements of methanol which is an important dairy and livestock emissions tracer. The elevated CH4 mixing ratios along the eastern edge of the San Joaquin Valley highlight the contribution of topography and emissions transport to local ambient levels of CH4. Large enhancements of CH4, benzene and toluene are also observed while flying over the oil production facilities in western part of Kern county (state's top oil producing county, 10% of US production) suggesting the likelihood of fugitive emissions in the region. VOC tracer analysis is used to evaluate the source of high CH4 emissions encountered along the eastern edge of the central Sacramento valley where fugitive emissions from natural gas fields and cultivation of rice are likely sources. Plumes from biomass burning, landfills and refineries encountered during different flights are also investigated. Eddy covariance based CH4 flux estimates are derived for various sources and compared with ';bottom-up' inventory estimates to verify/validate the CA methane inventory for major sources.

Quantification of Methane and Nitrous Oxide Emissions from Wastewater Collection Systems (Cincinnati, Ohio, USA)

NASA Astrophysics Data System (ADS)

Fries, A. E.; Townsend-Small, A.; Shuster, W.; Schifman, L. A.

2016-12-01

Greenhouse gas emissions from urban areas is an emerging topic in environmental science, but source apportionment of these emissions, particularly for methane (CH4) and nitrous oxide (N2O), is still underway. Here we present an analysis of CH4 and N2O sources from urban pipelines in Cincinnati, Ohio, USA. Leaks from manholes and sewer grates in Cincinnati are found by using a Bascom Turner Gas Rover to indicate CH4 enhancements, along with spatial data for CH4 enhancements at street level from previously published work. When possible, the atmospheric flux of CH4 and N2O of these leaks are quantified by using a flux chamber method. Source apportionment is determined by using carbon and hydrogen stable isotope ratios (13C and D) and CH4 to N2O ratios. Biogenic CH4 has a δ13C of approximately -55‰ and δD of approximately -270‰, whereas thermogenic CH4 has a δ13C of approximately -45‰ and δD of approximately -150‰. Biogenic CH4 may also co-occur with N2O, whereas thermogenic natural gas does not contain N2O. Contrary to our expectations, we found a portion of CH4 enhancements that are biogenic CH4, presumably from sewer gas, whereas most studies have assumed them to be natural gas leaks. In the future we will be working on determining the exact proportion of biogenic and thermogenic CH4 in street leaks and further quantifying CH4 and N2O emissions throughout Cincinnati. Our work indicates that CH4 leaks in cities may be a mixture of sewer gas and natural gas, especially in cities like Cincinnati where natural gas pipelines have been replaced with less leak-prone pipe materials.

CO2 and CH4 fluxes along a latitudinal transect in Northern Alaska using eddy covariance technique in challenging conditions: first results of a long term experiment in the Arctic tundra

NASA Astrophysics Data System (ADS)

Moreaux, V.; Oechel, W. C.; Losacco, S.; McEwing, R.; Murphy, P.; Zona, D.

2013-12-01

Being one of the most sensitive regions on earth, the Arctic is likely to be one of the most affected by global change. Physical changes (drying, snow cover, active layer depth, permafrost thawing, etc.) could create feedbacks in the release of greenhouse gas to the atmosphere. Correlated to the significant increase in air temperature, changes in trace gas balance have already been reported (Oechel et al. 1998). Carbon (C) is currently trapped as organic matter in the permafrost that underlies much of the Arctic. C represents about 30-50% of the global belowground organic carbon pool (Tarnocai et al.2009, Zona et al. 2012). Stored organic matter can form the substrate for significant release of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Ubiquitous arctic wetlands are additional sources of CH4 and CO2 to the atmosphere (Melton et al. 2013). CO2 is important because of the magnitude of its fluxes, and CH4 is of interest since its global warming potential is 23 times higher than the CO2 over a 100-year time horizon. CH4 is produced by the decomposition of dead plant material in anaerobic soils, especially in tundra ponds. Methane release is mostly influenced by temperature, water table, and active layer depth. The spatial and temporal variability results in very large uncertainties of current CH4 fluxes from the Arctic. The sporadic studies available create a generally inadequate baseline from which to determine a change in emissions from this critical and sensitive environment. Here we initiate a large scale, continuously monitored, study of CO2 and CH4 budgets from tundra ecosystems across a latitudinal gradient of more than 400 km. Our main questions for this study are: (i) does the release of CO2 and CH4 from biological and geothermal processes exceed the sink of greenhouse gases from active vegetation and surface organisms? (ii) How does this balance behave over latitudinal and environmental gradients? The observations presented are the result of the first year of a new long-term study that includes the results of the upgrading of 5 sites in Northern Alaska across a latitudinal transect (Barrow, Atqasuk, and Ivotuk) and across a moisture gradient (Barrow) in the Arctic. These sites are equipped with different eddy covariance systems to follow CO2 and CH4 fluxes, combined with a full data set of meteorological and soil measurements. The study summarizes a full analysis of energy balance, CO2 and CH4 fluxes correlated to changes in meteorological and soil conditions on the 5 sites of the transect. Based on the results available, CH4 fluxes averaged approximatively 8 mgC m-2 d-1 in the north (Barrow) to 13 mgC m-2 d-1 in the south (Ivotuk). In between these two sites, a daily value of about 20 mgC m-2 d-1 in the wetter, vegetated drained lake basin was observed. Surprisingly, from our preliminary data investigation, the southernmost and warmer site (Ivotuk) did not present the highest CH4 emission, which instead was the highest in the 200 km north site (Atqasuk) with a mean daily value of 25 mgC m-2 d-1. The importance of fall season CH4 emissions will also be presented and their importance relative to summertime emissions.

Evaluation of modelled methane emissions over northern peatland sites

NASA Astrophysics Data System (ADS)

Gao, Yao; Burke, Eleanor; Chadburn, Sarah; Raivonen, Maarit; Susiluoto, Jouni; Vesala, Timo; Aurela, Mika; Lohila, Annalea; Aalto, Tuula

2017-04-01

Methane (CH4) is a powerful greenhouse gas, with approximately 34 times the global warming potential of carbon dioxide (CO2) over a century time horizon (IPCC, 2013). The strong sensitivity of methane emissions to environmental factors has led to concerns about potential positive feedbacks to climate change. Evaluation of the ability of the process-based land surface models of earth system models (ESMs) in simulating CH4 emission over peatland is needed for more precise future predictions. In this study, two peatland sites of poor and rich soil nutrient conditions, in southern and northern Finland respectively, are adopted. The measured CH4 fluxes at the two sites are used to evaluate the CH4 emissions simulated by the land surface model (JULES) of the UK Earth System model and by the Helsinki peatland methane emission model (HIMMELI), which is developed at Finnish Meteorological Institute and Helsinki University. In JULES, CH4 flux is simply related to soil temperature, wetland fraction and effective substrate availability. However, HIMMELI has detailed descriptions of microbial and transport processes for simulating CH4 flux. The seasonal dynamics of CH4 fluxes at the two sites are relatively well captured by both models, but model biases exist. Simulated CH4 flux is sensitive to water table depth (WTD) at both models. However, the simulated WTD is limited to be below ground in JULES. It is also important to have the annual cycle of LAI correct when coupling JULES with HIMMELI.

Spatial and temporal variability of greenhouse gas emissions from a small and shallow temperate lake

NASA Astrophysics Data System (ADS)

Praetzel, Leandra; Schmiedeskamp, Marcel; Broder, Tanja; Hüttemann, Caroline; Jansen, Laura; Metzelder, Ulrike; Wallis, Ronya; Knorr, Klaus-Holger; Blodau, Christian

2017-04-01

Small inland waters (< 1 km2) have recently been discovered as significant sources and sinks in the global carbon cycle because they cover larger areas than previously assumed and exhibit a higher metabolic activity than larger lakes. They are further expected to be susceptible to changing climate conditions. So far, little is known about the spatial and temporal variability of carbon dioxide (CO2) and methane (CH4) emissions and in-lake dynamics of CH4 production and oxidation in small, epilimnetic lakes in the temperate zone. Of particular interest is the potential occurrence of "hot spots" and "hot moments" that could contribute significantly to total emissions. To address this knowledge gap, we determined CO2 and CH4 emissions and dynamics to identify their controlling environmental factors in a polymictic small (1.4 ha) and shallow (max. depth approx. 1.5 m) crater lake ("Windsborn") in the Eifel uplands in south-west Germany. As Lake Windsborn has a small catchment area (8 ha) and no surficial inflows, it serves well as a model system for the identification of factors and processes controlling emissions. In 2015, 2016 and 2017 we measured CO2 and CH4 gas fluxes with different techniques across the sediment/water and water/atmosphere interface. Atmospheric exchange was measured using mini-chambers equipped with CO2 sensors and with an infra-red greenhouse gas analyzer for high temporal resolution flux measurements. Ebullition of CH4 was quantified with funnel traps. Sediment properties were examined using pore-water peepers. All measurements were carried out along a transect covering both littoral and central parts of the lake. Moreover, a weather station on a floating platform in the center of the lake recorded meteorological data as well as CO2 concentration in different depths of the water column. So far, Lake Windsborn seems to be a source for both CO2 and CH4 on an annual scale. CO2 emissions generally increased from spring to summer. Even though CO2 uptake could be observed during some periods in spring and fall, CO2 emissions in the summer exceeded the uptake. CO2 and CH4 emissions also appeared to be spatially variable between littoral areas and the inner lake. Shallow areas turned out to be "hot spots" of CO2 emissions whereas CH4 emissions were - against our expectations - highest in the center of the lake. Moreover, CH4 ebullition contributed substantially to total CH4 emissions. Our results show the importance of spatially and temporally highly resolved long-term measurements of greenhouse gas emissions and of potential controlling factors to address diurnal, seasonal and inter-annual variability as well as possible feedbacks to climate change.

Economic Analysis of Planting Forests on Rice Lands in Texas: Sequestering Carbon and Avoiding Methane Production

NASA Astrophysics Data System (ADS)

Kronrad, G. D.; Huang, C.

2005-12-01

Global climate change is predicted due to increases in greenhouse gasses (i.e. CO2, CH4, CFCs, N2O, O3) in the atmosphere caused by human activities. The atmospheric concentration of methane (CH4), which absorbs and retains heat 21 times more effectively than CO2, has increased. Anaerobic bacterial activity in rice paddies constitutes one of major emission sources of CH4. The rice fields of Texas, for example, accounted for an annual CH4 emission of between 1.1 and 1.6 million tons of CO2 equivalent between 1990 and 2000. Converting marginal rice fields to forests plantations will remove CO2 from the atmosphere, sequester carbon in the forests and prevent the production of CH4. Therefore, carbon credits can be claimed for the carbon sequestered and the avoidance of CH4 production. Analyses were conducted to calculate the amount of carbon sequestered and methane avoided, and the profitability, measured in net present worth (NPW), of managing loblolly pine plantation for 1) timber production only, 2) the dual products of timber products and carbon credits in forests planted on marginal agricultural and unused pastureland and 3) the dual products of timber and carbon storage in forests planted on marginal rice lands. Calculations were performed using three discount rates, three site qualities and five prices for carbon credits. The results indicate that on average quality land, using a discount rate of 8 percent, forests planted on marginal agricultural and unused pastureland earn a NPW of 346 per acre from timber production only; a NPW of 438 per acre from timber and carbon credits (54.4 tons of carbon sequestered), assuming carbon is worth 10 per ton, during one rotation (32 years). The profitability of forest management increases due to the inclusion of carbon credits. The profitability of planting forests on marginal rice fields is even higher, earning a NPW of 566 per acre from timber and carbon credits (54.4 tons of C sequestered and 33.3 tons of C emission avoided).

Ice core δD(CH4) record precludes marine hydrate CH4 emissions at the onset of Dansgaard-Oeschger events

NASA Astrophysics Data System (ADS)

Bock, M.; Schmitt, J.; Möller, L.; Spahni, R.; Blunier, T.; Fischer, H.

2010-12-01

Air enclosures in polar ice cores represent the only direct paleoatmospheric archive (besides firn air) and show that atmospheric CH4 concentrations changed in concert with northern hemisphere temperature during both glacial/interglacial transitions as well as rapid climate changes (Dansgaard-Oeschger events). For stadials and interstadials during Marine Isotope Stage 3 concentration jumps of 100 - 200 ppbv within a few decades are observed. A concentration gradient with higher values in the northern versus the southern hemisphere during warm stages was reconstructed from ice core methane data from Greenland and Antarctica. This gradient indicates additional methane emissions during warm periods located in the northern hemisphere. However, the underlying processes for these changes are still not well understood. With tropical and boreal wetlands, biomass burning, thermokarst lakes, ruminants, termites, UV-induced emissions from organic matter and marine gas hydrates all contributing to the natural atmospheric CH4 level, an unambiguous source attribution remains difficult. Also changes in the methane sinks can modify the tropospheric CH4 budget, as trace gases like volatile organic compounds are competing for the major reactant - the OH radical. Additionally, the changing global atmospheric methane concentration itself feeds back on its lifetime. Together with the CH4 interhemispheric gradient, stable hydrogen and carbon isotopic studies on methane (δD(CH4) and δ13CH4) in ice cores allow to constrain individual CH4 source/sink changes. Here we present clear evidence from the North Greenland Ice Core Project ice core based on the hydrogen isotopic composition of methane δD(CH4) that clathrates did not cause atmospheric methane concentration to rise at the onset of Dansgaard-Oeschger (DO) events 7 and 8 (34 - 41 kilo years before present), however, we can not exclude that they played a minor role during and at the end of an interstadial. Box modeling supports boreal wetland emissions as the most likely explanation for the interstadial increase, strengthening from ~6 to ~30 Tg CH4 yr-1 from stadial to interstadial conditions, respectively. Our steady state model results suggest constant background clathrate emissions for the investigated time slices (~25 Tg CH4 yr-1). Tropical wetland emissions strengthened only moderately for the long interstadial 8 (from ~84 to ~118 Tg CH4 yr-1) and biomass burning emissions show slightly higher values during the interstadial time slices (~55 to ~60 versus ~45 Tg CH4 yr-1 in the stadial). Moreover, our data show that δD(CH4) dropped 500 years before the onset of DO 8, with CH4 concentration rising only slightly. This can be explained by an early climate response of boreal wetlands, which carry the strongly depleted isotopic signature of high-latitude precipitation at that time. Reference: Bock et al., 2010, Science, 328, p1686

Mitigating effects of ex situ application of rice straw on CH4 and N2O emissions from paddy-upland coexisting system

PubMed Central

Wang, Wei; Wu, Xiaohong; Chen, Anlei; Xie, Xiaoli; Wang, Yunqiu; Yin, Chunmei

2016-01-01

The in situ application of rice straw enhances CH4 emissions by a large margin. The ex situ application of rice straw in uplands, however, may mitigate total global warming potential (GWP) of CH4 and N2O emissions from paddy-upland coexisting systems. To evaluate the efficiency of this practice, two field trials were conducted in rice-rice-fallow and maize-rape cropping systems, respectively. Year-round measurements of CH4 and N2O emissions were conducted to evaluate the system-scaled GWP. The results showed that CH4 accounted for more than 98% of GWP in paddy. Straw removal from paddy decreased 44.7% (302.1 kg ha−1 yr−1) of CH4 emissions and 51.2% (0.31 kg ha−1 yr−1) of N2O emissions, thus decreased 44.8% (7693 kg CO2-eqv ha−1 yr−1) of annual GWP. N2O accounted for almost 100% of GWP in upland. Straw application in upland had insignificant effects on CH4 and N2O emissions, which increased GWP only by 91 kg CO2-eqv ha−1 yr−1. So, the transfer of straw from paddy to upland could decrease GWP by 7602 kg CO2-eqv ha−1 yr−1. Moreover, straw retention during late rice season contributed to 88.2% of annual GWP increment. It is recommended to transfer early rice straw to upland considering GWP mitigation, nutrient recycling and labor cost. PMID:27869209

Mitigating effects of ex situ application of rice straw on CH4 and N2O emissions from paddy-upland coexisting system

NASA Astrophysics Data System (ADS)

Wang, Wei; Wu, Xiaohong; Chen, Anlei; Xie, Xiaoli; Wang, Yunqiu; Yin, Chunmei

2016-11-01

The in situ application of rice straw enhances CH4 emissions by a large margin. The ex situ application of rice straw in uplands, however, may mitigate total global warming potential (GWP) of CH4 and N2O emissions from paddy-upland coexisting systems. To evaluate the efficiency of this practice, two field trials were conducted in rice-rice-fallow and maize-rape cropping systems, respectively. Year-round measurements of CH4 and N2O emissions were conducted to evaluate the system-scaled GWP. The results showed that CH4 accounted for more than 98% of GWP in paddy. Straw removal from paddy decreased 44.7% (302.1 kg ha-1 yr-1) of CH4 emissions and 51.2% (0.31 kg ha-1 yr-1) of N2O emissions, thus decreased 44.8% (7693 kg CO2-eqv ha-1 yr-1) of annual GWP. N2O accounted for almost 100% of GWP in upland. Straw application in upland had insignificant effects on CH4 and N2O emissions, which increased GWP only by 91 kg CO2-eqv ha-1 yr-1. So, the transfer of straw from paddy to upland could decrease GWP by 7602 kg CO2-eqv ha-1 yr-1. Moreover, straw retention during late rice season contributed to 88.2% of annual GWP increment. It is recommended to transfer early rice straw to upland considering GWP mitigation, nutrient recycling and labor cost.

Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling

NASA Astrophysics Data System (ADS)

Pisso, Ignacio; Myhre, Cathrine Lund; Platt, Stephen Matthew; Eckhardt, Sabine; Hermansen, Ove; Schmidbauer, Norbert; Mienert, Jurgen; Vadakkepuliyambatta, Sunil; Bauguitte, Stephane; Pitt, Joseph; Allen, Grant; Bower, Keith; O'Shea, Sebastian; Gallagher, Martin; Percival, Carl; Pyle, John; Cain, Michelle; Stohl, Andreas

2017-04-01

Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (FAAM) and a ship (Helmer Hansen) during the Summer 2014, and for Zeppelin Observatory for the full year. We present a model-supported analysis of the atmospheric CH4 mixing ratios measured by the different platforms. To address uncertainty about where CH4 emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH4 emission areas. We found small differences between the CH4 mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH4 fluxes. The CH4 flux during the campaign was small, with an upper limit of 2.5 nmol / m s in the stability model scenario. The Zeppelin Observatory data for 2014 suggests CH4 fluxes from the Svalbard continental platform below 0.2 Tg/yr . All estimates are in the lower range of values previously reported.

N2O and CH4-emissions from energy crops - Can the use of organic fertilizers in form of biogas digestate be considered as a real alternative? Results from a three and a half year multi-site field study of energy crops fertilized with biogas digestate in so

NASA Astrophysics Data System (ADS)

Heintze, Gawan

2016-04-01

Gawan Heintze1,2, Matthias Drösler1, Ulrike Hagemann3and Jürgen Augustin3 1University of Applied Sciences Weihenstephan-Triesdorf, Chair of Vegetation Ecology, Weihenstephaner Berg 4, 85354 Freising, Germany 2Technische Universität München, Chair of Plant Nutrition, Emil-Ramann-Str. 2, 85354 Freising, Germany 3Leibniz Centre for Agricultural Landscape Research (ZALF), Eberswalder Straße 84, 15374 Müncheberg, Germany Together with industrial process-related emissions (8.1%) the actual GHG emissions from agriculture (7.5% - 70 million tones (Mt) of carbon dioxide (CO2)-equivalents) representing after energy-related emissions from combustion processes of fossil fuels (83.7%) the second largest budget of the Germany-wide total emissions per year. To reduce the EU's CO2 emissions by 20% by 2020 the cultivation of energy crops for biogas production, ideally coupled to a subsequent return of the resulting residues in form of biogas digestate is intended as one key element in the pathway of renewable energy production. Despite an increasing cultivation of energy crops for the production of biogas aiming to reduce the overall climate impact of the agricultural sector, it is still largely unknown how the application of ammonia-rich organic digestate effects field N2O emissions. Therefore, the collaborative research project "potential for reducing the release of climate-relevant trace gases in the cultivation of energy crops for the production of biogas" was launched. The main objective of the study was to determine an improved process understanding and to quantify the influence of mineral nitrogen fertilization, biogas digestate application, crop type and crop rotation, to gain precise and generalizable statements on the exchange of trace gases like nitrous oxide (N2O) and methane (CH4) on the resulting climate impact. Gas fluxes of N2O and CH4 were measured for three and a half years on two differently managed sites in maize monoculture with different applied organic N amounts and in a crop rotation system called FFA and FFB with same amounts of applied N but three different forms of N application (mineral N, mineral+organic N, organic N). The annual cumulative N2O exchange rates in maize monoculture showed a clear dependence on the amount of applied organic fertilizer. Average annual cumulative exchange rates ranged from 1.65 ± 0.74 kg N ha-1 yr-1 to 11.03 ± 1.63 kg N ha-1 y-1explainable by a twice as high amount of N compared to the conventional fertilized site. The average annual cumulative CH4 exchange rates in maize monoculture varied between -1.2 ± 0.46 kg C ha-1 yr-1 and 3.75 ± 0.48 kg C ha-1 y-1with measured CH4 fluxes around zero between the fertilizing events, indicating a minor role. For FFA and FFB the average annual cumulative N2O exchange rates ranged from 1.45 ± 0.18 kg N ha-1 yr-1 to 3.5 ± 1.1 kg N ha-1 y-1and 1.37 ± 0.57 kg N ha-1 yr-1 to 1.71 ± 0.29 kg N ha-1 y-1 andshowed lower values to comparable treatments in the maize monoculture especially indicating the different management effects. Determined average annual cumulative CH4 exchange rates ranged from 0.19 ± 0.6 kg C ha-1 yr-1 to 0.21 ± 0.45 kg C ha-1 yr-1and -0.8 ± 0.7 kg C ha-1 y-1 to 1 ± 0.6 kg C ha-1 y-1 and played as well a minor role. Altogether, biogas digestate can be seen as a suitable alternative if the amounts of applied N selected appropriately in combination with a customized management.

Effects of nitrogen fertilisation rate and maturity of grass silage on methane emission by lactating dairy cows.

PubMed

Warner, D; Hatew, B; Podesta, S C; Klop, G; van Gastelen, S; van Laar, H; Dijkstra, J; Bannink, A

2016-01-01

Grass silage is typically fed to dairy cows in temperate regions. However, in vivo information on methane (CH(4)) emission from grass silage of varying quality is limited. We evaluated the effect of two rates of nitrogen (N) fertilisation of grassland (low fertilisation (LF), 65 kg of N/ha; and high fertilisation (HF), 150 kg of N/ha) and of three stages of maturity of grass at cutting: early maturity (EM; 28 days of regrowth), mid maturity (MM; 41 days of regrowth) and late maturity (LM; 62 days of regrowth) on CH(4) production by lactating dairy cows. In a randomised block design, 54 lactating Holstein-Friesian dairy cows (168±11 days in milk; mean±standard error of mean) received grass silage (mainly ryegrass) and compound feed at 80 : 20 on dry matter basis. Cows were adapted to the diet for 12 days and CH(4) production was measured in climate respiration chambers for 5 days. Dry matter intake (DMI; 14.9±0.56 kg/day) decreased with increasing N fertilisation and grass maturity. Production of fat- and protein-corrected milk (FPCM; 24.0±1.57 kg/day) decreased with advancing grass maturity but was not affected by N fertilisation. Apparent total-tract feed digestibility decreased with advancing grass maturity but was unaffected by N fertilisation except for an increase and decrease in N and fat digestibility with increasing N fertilisation, respectively. Total CH(4) production per cow (347±13.6 g/day) decreased with increasing N fertilisation by 4% and grass maturity by 6%. The smaller CH(4) production with advancing grass maturity was offset by a smaller FPCM and lower feed digestibility. As a result, with advancing grass maturity CH(4) emission intensity increased per units of FPCM (15.0±1.00 g CH(4)/kg) by 31% and digestible organic matter intake (33.1±0.78 g CH(4)/kg) by 15%. In addition, emission intensity increased per units of DMI (23.5±0.43 g CH(4)/kg) by 7% and gross energy intake (7.0±0.14% CH(4)) by 9%, implying an increased loss of dietary energy with advancing grass maturity. Rate of N fertilisation had no effect on CH(4) emissions per units of FPCM, DMI and gross energy intake. These results suggest that despite a lower absolute daily CH(4) production with a higher N fertilisation rate, CH(4) emission intensity remains unchanged. A significant reduction of CH(4) emission intensity can be achieved by feeding dairy cows silage of grass harvested at an earlier stage of maturity.

Year-round simulated methane emissions from a permafrost ecosystem in Northeast Siberia

NASA Astrophysics Data System (ADS)

Castro-Morales, Karel; Kleinen, Thomas; Kaiser, Sonja; Zaehle, Sönke; Kittler, Fanny; Kwon, Min Jung; Beer, Christian; Göckede, Mathias

2018-05-01

Wetlands of northern high latitudes are ecosystems highly vulnerable to climate change. Some degradation effects include soil hydrologic changes due to permafrost thaw, formation of deeper active layers, and rising topsoil temperatures that accelerate the degradation of permafrost carbon and increase in CO2 and CH4 emissions. In this work we present 2 years of modeled year-round CH4 emissions into the atmosphere from a Northeast Siberian region in the Russian Far East. We use a revisited version of the process-based JSBACH-methane model that includes four CH4 transport pathways: plant-mediated transport, ebullition and molecular diffusion in the presence or absence of snow. The gas is emitted through wetlands represented by grid cell inundated areas simulated with a TOPMODEL approach. The magnitude of the summertime modeled CH4 emissions is comparable to ground-based CH4 fluxes measured with the eddy covariance technique and flux chambers in the same area of study, whereas wintertime modeled values are underestimated by 1 order of magnitude. In an annual balance, the most important mechanism for transport of methane into the atmosphere is through plants (61 %). This is followed by ebullition ( ˜ 35 %), while summertime molecular diffusion is negligible (0.02 %) compared to the diffusion through the snow during winter ( ˜ 4 %). We investigate the relationship between temporal changes in the CH4 fluxes, soil temperature, and soil moisture content. Our results highlight the heterogeneity in CH4 emissions at landscape scale and suggest that further improvements to the representation of large-scale hydrological conditions in the model will facilitate a more process-oriented land surface scheme and better simulate CH4 emissions under climate change. This is especially necessary at regional scales in Arctic ecosystems influenced by permafrost thaw.

40 CFR 98.323 - Calculating GHG emissions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... systems (metric tons CH4). CH4V = Quarterly CH4 liberated from each ventilation monitoring point (metric... vent holes are collected, you must calculate the quarterly CH4 liberated from the ventilation system... CH4 liberated from a ventilation monitoring point (metric tons CH4). V = Volumetric flow rate for the...