Interpreting the variations in atmospheric methane fluxes observed above a restored wetland

DEFF Research Database (Denmark)

Herbst, Mathias; Friborg, Thomas; Ringgaard, Rasmus

2011-01-01

The eddy flux of methane (CH4) was measured over 14 months above a restored wetland in western Denmark. The average annual daily CH4 flux was 30.2mgm-2 d-1, but the daily emission rates varied considerably over time. Several factors were identified that explained some of this variation. (1) Grazing...... that the variability in the CH4 fluxes strongly affects the greenhouse gas sink strength of the restored wetland.......4 flux to soil temperature at 20cm depth was found for most of the study period, but not for parts of the summer season that coincided with a low water level in the river flowing through the wetland. (4) Additional variations in the CH4 emission rates were related to the spatial heterogeneity...

Gas seepage from Tokamachi mud volcanoes, onshore Niigata Basin (Japan): Origin, post-genetic alterations and CH{sub 4}-CO{sub 2} fluxes

Energy Technology Data Exchange (ETDEWEB)

Etiope, G., E-mail: etiope@ingv.it [Istituto Nazionale di Geofisica e Vulcanologia, via V. Murata 605, 00143 Roma (Italy); Nakada, R. [Dept. of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University (Japan); Tanaka, K. [Graduate School of Science and Engineering, Yamaguchi University (Japan); Yoshida, N. [Dept. of Environmental Chemistry and Engineering, Tokyo Institute of Technology (Japan)

2011-03-15

Research highlights: {yields} Tokamachi gas shows signals of subsurface hydrocarbon biodegradation. {yields} Hydrocarbon molecular fractionation depends on gas flux. {yields} Substantial gas emission from mud volcanoes is from invisible diffuse seepage. {yields} Global mud volcano methane emission is likely higher than 10 Mt a{sup -1}. - Abstract: Methane and CO{sub 2} emissions from the two most active mud volcanoes in central Japan, Murono and Kamou (Tokamachi City, Niigata Basin), were measured in from both craters or vents (macro-seepage) and invisible exhalation from the soil (mini- and microseepage). Molecular and isotopic compositions of the released gases were also determined. Gas is thermogenic ({delta}{sup 13}C{sub CH4} from -32.9 per mille to -36.2 per mille), likely associated with oil, and enrichments of {sup 13}C in CO{sub 2} ({delta}{sup 13}C{sub CO2} up to +28.3 per mille) and propane ({delta}{sup 13}C{sub C3H8} up to -8.6 per mille) suggest subsurface petroleum biodegradation. Gas source and post-genetic alteration processes did not change from 2004 to 2010. Methane flux ranged within the orders of magnitude of 10{sup 1}-10{sup 4} g m{sup -2} d{sup -1} in macro-seeps, and up to 446 g m{sup -2} d{sup -1} from diffuse seepage. Positive CH{sub 4} fluxes from dry soil were widespread throughout the investigated areas. Total CH{sub 4} emission from Murono and Kamou were estimated to be at least 20 and 3.7 ton a{sup -1}, respectively, of which more than half was from invisible seepage surrounding the mud volcano vents. At the macro-seeps, CO{sub 2} fluxes were directly proportional to CH{sub 4} fluxes, and the volumetric ratios between CH{sub 4} flux and CO{sub 2} flux were similar to the compositional CH{sub 4}/CO{sub 2} volume ratio. Macro-seep flux data, in addition to those of other 13 mud volcanoes, supported the hypothesis that molecular fractionation (increase of the 'Bernard ratio' C{sub 1}/(C{sub 2} + C{sub 3})) is inversely

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

Science.gov (United States)

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

Soil methane and CO2 fluxes in rainforest and rubber plantations

Science.gov (United States)

Lang, Rong; Blagodatsky, Sergey; Goldberg, Stefanie; Xu, Jianchu

2017-04-01

Expansion of rubber plantations in South-East Asia has been a land use transformation trend leading to losses of natural forest cover in the region. Besides impact on ecosystem carbon stocks, this conversion influences the dynamics of greenhouse gas fluxes from soil driven by microbial activity, which has been insufficiently studied. Aimed to understand how land use change affects the soil CO2 and CH4 fluxes, we measured surface gas fluxes, gas concentration gradient, and 13C signature in CH4 and soil organic matter in profiles in a transect in Xishuangbanna, including a rainforest site and three rubber plantation sites with age gradient. Gas fluxes were measured by static chamber method and open chamber respiration system. Soil gases were sampled from installed gas samplers at 5, 10, 30, and 75cm depth at representative time in dry and rainy season. The soil CO2 flux was comparable in rainforest and old rubber plantations, while young rubber plantation had the lowest rate. Total carbon content in the surface soil well explained the difference of soil CO2 flux between sites. All sites were CH4 sinks in dry season and uptake decreased in the order of rainforest, old rubber plantations and young rubber plantation. From dry season to rainy season, CH4 consumption decreased with increasing CH4 concentration in the soil profile at all depths. The enrichment of methane by 13CH4 shifted towards to lowerδ13C, being the evidence of enhanced CH4 production process while net surface methane flux reflected the consumption in wet condition. Increment of CH4 concentration in the profile from dry to rainy season was higher in old rubber plantation compared to rainforest, while the shifting of δ13CH4 was larger in rainforest than rubber sites. Turnover rates of soil CO2 and CH4 suggested that the 0-5 cm surface soil was the most active layer for gaseous carbon exchange. δ13C in soil organic matter and soil moisture increased from rainforest, young rubber plantation to old

Fluxes of CH4 and N2O in aspen stands grown under ambient and twice-ambient CO2

DEFF Research Database (Denmark)

Ambus, P.; Robertson, G.P.

1999-01-01

Elevated atmospheric CO2 has the potential to change below-ground nutrient cycling and thereby alter the soil-atmosphere exchange of biogenic trace gases. We measured fluxes of CH4 and N2O in trembling aspen (Populus tremuloides Michx.) stands grown in open-top chambers under ambient and twice......-ambient CO2 concentrations crossed with `high' and low soil-N conditions. Flux measurements with small static chambers indicated net CH4 oxidation in the open-top chambers. Across dates, CH4 oxidation activity was significantly (P CO2 (8.7 mu g CH4-C m(-2) h(-1)) than...... with elevated CO2 (6.5 mu g CH4-C m(-2) h(-1)) in the low N soil. Likewise, across dates and soil N treatments CH4 was oxidized more rapidly (P CO2 (9.5 mu g CH4-C m(-2) h(-1)) than in chambers with elevated CO2 (8.8 mu g CH4-C m(-2) h(-1)). Methane oxidation in soils incubated...

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

Science.gov (United States)

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.

Eddy-covariance methane flux measurements over a European beech forest

Science.gov (United States)

Gentsch, Lydia; Siebicke, Lukas; Knohl, Alexander

2015-04-01

The role of forests in global methane (CH4) turnover is currently not well constrained, partially because of the lack of spatially integrative forest-scale measurements of CH4 fluxes. Soil chamber measurements imply that temperate forests generally act as CH4 sinks. Upscaling of chamber observations to the forest scale is however problematic, if the upscaling is not constrained by concurrent 'top-down' measurements, such as of the eddy-covariance type, which provide sufficient integration of spatial variations and of further potential CH4 flux components within forest ecosystems. Ongoing development of laser absorption-based optical instruments, resulting in enhanced measurement stability, precision and sampling speed, has recently improved the prospects for meaningful eddy-covariance measurements at sites with presumably low CH4 fluxes, hence prone to reach the flux detection limit. At present, we are launching eddy-covariance CH4 measurements at a long-running ICOS flux tower site (Hainich National Park, Germany), located in a semi natural, unmanaged, beech dominated forest. Eddy-covariance measurements will be conducted with a laser spectrometer for parallel CH4, H2Ov and CO2 measurements (FGGA, Los Gatos Research, USA). Independent observations of the CO2 flux by the FGGA and a standard Infrared Gas Analyser (LI-7200, LI-COR, USA) will allow to evaluate data quality of measured CH4 fluxes. Here, we want to present first results with a focus on uncertainties of the calculated CH4 fluxes with regard to instrument precision, data processing and site conditions. In future, we plan to compare eddy-covariance flux estimates to side-by-side turbulent flux observations from a novel eddy accumulation system. Furthermore, soil CH4 fluxes will be measured with four automated chambers situated within the tower footprint. Based on a previous soil chamber study at the same site, we expect the Hainich forest site to act as a CH4 sink. However, we hypothesize that our

Landscape-level terrestrial methane flux observed from a very tall tower

Science.gov (United States)

Desai, Ankur R.; Xu, Ke; Tian, Hanqin; Weishampel, Peter; Thom, Jonthan; Baumann, Daniel D.; Andrews, Arlyn E.; Cook, Bruce D.; King, Jennifer Y.; Kolka, Randall

2015-01-01

Simulating the magnitude and variability of terrestrial methane sources and sinks poses a challenge to ecosystem models because the biophysical and biogeochemical processes that lead to methane emissions from terrestrial and freshwater ecosystems are, by their nature, episodic and spatially disjunct. As a consequence, model predictions of regional methane emissions based on field campaigns from short eddy covariance towers or static chambers have large uncertainties, because measurements focused on a particular known source of methane emission will be biased compared to regional estimates with regards to magnitude, spatial scale, or frequency of these emissions. Given the relatively large importance of predicting future terrestrial methane fluxes for constraining future atmospheric methane growth rates, a clear need exists to reduce spatiotemporal uncertainties. In 2010, an Ameriflux tower (US-PFa) near Park Falls, WI, USA, was instrumented with closed-path methane flux measurements at 122 m above ground in a mixed wetland–upland landscape representative of the Great Lakes region. Two years of flux observations revealed an average annual methane (CH4) efflux of 785 ± 75 mg CCH4 m−2 yr−1, compared to a mean CO2 sink of −80 g CCO2 m−2 yr−1, a ratio of 1% in magnitude on a mole basis. Interannual variability in methane flux was 30% of the mean flux and driven by suppression of methane emissions during dry conditions in late summer 2012. Though relatively small, the magnitude of the methane source from the very tall tower measurements was mostly within the range previously measured using static chambers at nearby wetlands, but larger than a simple scaling of those fluxes to the tower footprint. Seasonal patterns in methane fluxes were similar to those simulated in the Dynamic Land Ecosystem Model (DLEM), but magnitude depends on model parameterization and input data, especially regarding wetland extent. The model was unable to simulate short

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

Science.gov (United States)

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.

Data-Constrained Projections of Methane Fluxes in a Northern Minnesota Peatland in Response to Elevated CO2 and Warming

Science.gov (United States)

Ma, Shuang; Jiang, Jiang; Huang, Yuanyuan; Shi, Zheng; Wilson, Rachel M.; Ricciuto, Daniel; Sebestyen, Stephen D.; Hanson, Paul J.; Luo, Yiqi

2017-11-01

Large uncertainties exist in predicting responses of wetland methane (CH4) fluxes to future climate change. However, sources of the uncertainty have not been clearly identified despite the fact that methane production and emission processes have been extensively explored. In this study, we took advantage of manual CH4 flux measurements under ambient environment from 2011 to 2014 at the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experimental site and developed a data-informed process-based methane module. The module was incorporated into the Terrestrial ECOsystem (TECO) model before its parameters were constrained with multiple years of methane flux data for forecasting CH4 emission under five warming and two elevated CO2 treatments at SPRUCE. We found that 9°C warming treatments significantly increased methane emission by approximately 400%, and elevated CO2 treatments stimulated methane emission by 10.4%-23.6% in comparison with ambient conditions. The relative contribution of plant-mediated transport to methane emission decreased from 96% at the control to 92% at the 9°C warming, largely to compensate for an increase in ebullition. The uncertainty in plant-mediated transportation and ebullition increased with warming and contributed to the overall changes of emissions uncertainties. At the same time, our modeling results indicated a significant increase in the emitted CH4:CO2 ratio. This result, together with the larger warming potential of CH4, will lead to a strong positive feedback from terrestrial ecosystems to climate warming. The model-data fusion approach used in this study enabled parameter estimation and uncertainty quantification for forecasting methane fluxes.

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

Science.gov (United States)

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.

Eddy covariance flux measurements confirm extreme CH4 emissions from a Swiss hydropower reservoir and resolve their short-term variability

Directory of Open Access Journals (Sweden)

S. Sobek

2011-09-01

Full Text Available Greenhouse gas budgets quantified via land-surface eddy covariance (EC flux sites differ significantly from those obtained via inverse modeling. A possible reason for the discrepancy between methods may be our gap in quantitative knowledge of methane (CH4 fluxes. In this study we carried out EC flux measurements during two intensive campaigns in summer 2008 to quantify methane flux from a hydropower reservoir and link its temporal variability to environmental driving forces: water temperature and pressure changes (atmospheric and due to changes in lake level. Methane fluxes were extremely high and highly variable, but consistently showed gas efflux from the lake when the wind was approaching the EC sensors across the open water, as confirmed by floating chamber flux measurements. The average flux was 3.8 ± 0.4 μg C m−2 s−1 (mean ± SE with a median of 1.4 μg C m−2 s−1, which is quite high even compared to tropical reservoirs. Floating chamber fluxes from four selected days confirmed such high fluxes with 7.4 ± 1.3 μg C m−2 s−1. Fluxes increased exponentially with increasing temperatures, but were decreasing exponentially with increasing atmospheric and/or lake level pressure. A multiple regression using lake surface temperatures (0.1 m depth, temperature at depth (10 m deep in front of the dam, atmospheric pressure, and lake level was able to explain 35.4% of the overall variance. This best fit included each variable averaged over a 9-h moving window, plus the respective short-term residuals thereof. We estimate that an annual average of 3% of the particulate organic matter (POM input via the river is sufficient to sustain these large CH4 fluxes. To compensate the global warming potential associated with the CH4 effluxes from this hydropower reservoir a 1.3 to 3.7 times larger terrestrial area with net carbon dioxide uptake is needed if a European-scale compilation of grasslands, croplands and forests is taken as reference. This

CH4 fluxes across the seafloor at three district gas hydrate fields: Impacts on ocean and atmosphere chemistry

Energy Technology Data Exchange (ETDEWEB)

Kastner, M.; Bartlett, D.; MacDonald, I.; Solomon, E.

2005-07-01

The role of methane hydrate in the global methane budget is poorly documented because relatively little is known about the transport of methane through the seafloor into the ocean and atmosphere, and the extent of en route water-column methanotrophy. Pore fluids and water column samples within and adjacent to methane plumes were analyzed for methane, dissolved inorganic C (DIC), sulfide/sulfate, alkalinity, and major element concentrations, and for delta{sup 13}C-CH4 and DIC, at three distinct gas hydrate environments. The three environments are: Bush Hill (BH) in the northern Gulf of Mexico (GOM), Eel River (ER) offshore Northern California, and North and South Hydrate Ridges (HR), Cascadia, Oregon margin. The methane source at these sites ranges from mostly thermogenic at GOM to primarily biogenic at HR. At these three distinct gas hydrate environments, at all the sites a significant enrichment in {sup 13}C-CH4 along isopycnals away from the methane plumes is observed, indicating extensive aerobic bacterial methane oxidation in the water column, and correspondingly of oxygen consumption. This is principally pronounced in the mostly biogenic methane setting. The delta{sup 13}C-CH4 values range from approx. 12 to -67 , PDB, at the Hydrate Ridges, from approx. 34 to -52 at Eel River, and from approx. 41 to -67 at Bush Hill. The large variation in methane C isotope ranges between the sites suggests that major differences exist in both the rates of aerobic methane oxidation and system openness at the studied locations. Methane fluxes across the sediment/seawater interface were measured, with a flux meter, MOSQUITO (Multiple Orifice Sampler and Quantitative Injection Tracer Observers) only at BH (Solomon et al., 2005). Water column methane concentrations are on average lower at HR than at ER and GOM. Preliminary estimates suggests that aerobic oxidation is nearly complete, consumes most to all of the water column methane at HR, but at the GOM only approx. 80% to a

Landscape Controls of CH4 Fluxes in a Catchment of the Forest Tundra in Northern Siberia

Science.gov (United States)

Flessa, H.; Rodionov, A.; Guggenberger, G.; Fuchs, H.; Magdon, P.; Shibistova, O.; Zrazhevskaya, G.; Kasansky, O.; Blodau, C.

2007-12-01

Soils have the capacity to both produce and consume atmospheric methane. The direction and the size of net- CH4 exchange between soils and atmosphere is mainly controlled by the soil aeration, temperature and the amount of bioavailable organic matter. All these factors are strongly influenced by distribution and seasonal dynamics of permafrost. Thus, distribution of permafrost and the thickness of the active layer can exert strong influence on CH4 dynamics in artic and northern boreal ecosystems. We analyzed the spatial and temporal variability of net-CH4 exchange within a catchment located in the Siberian forest tundra at the eastern shore of the lower Yenissej River to constrain the current function of this region as a sink or source of atmospheric CH4 and to gain insight into the potential for climatic change to alter the rate and form of carbon cycling and CH4 fluxes in this region. Net-fluxes of CH4 were measured from July to November 2003 and from August 2006 to July 2007 on representative soils of the catchment (mineral soils with different thawing depth, soils of bog plateaux) and on a thermokarst pond. In addition, dissolved CH4 in the stream draining the catchment was determined. Field observations, classification of landscape structures from satellite images and flux measurements were combined to estimate total catchment CH4 exchange. Nearly all soils of the catchment were net-sinks of atmospheric CH4 with annual CH4-C uptake rates ranging between 1.2 and 0.2 kg ha-1 yr-1. The active layer depth was the main factor determining the size of CH4 uptake. Total net-exchange of CH4 from the catchment was dominated by ponds that covered only about 2% of the catchment area. Due to high CH4 emission from these aquatic systems, the catchment was a net source of atmospheric CH4 with a mean annual emission of approximately 170 kg CH4-C ha-1. CH4 concentration in streams draining the catchment can help to identify areas with high CH4 production. The results suggest

The Effect of Nitrogen Enrichment on C1-Cycling Microorganisms and Methane Flux in Salt Marsh Sediments

Directory of Open Access Journals (Sweden)

Irina Catherine Irvine

2012-03-01

Full Text Available Methane (CH4 flux from ecosystems is driven by C1-cycling microorganisms – the methanogens and the methylotrophs. Little is understood about what regulates these communities, complicating predictions about how global change drivers such as nitrogen enrichment will affect methane cycling. Using a nitrogen addition gradient experiment in three Southern California salt marshes, we show that sediment CH4 flux increased linearly with increasing nitrogen addition (1.23 µg CH4 m-2 d-1 for each g N m-2 yr-1 applied after seven months of fertilization. To test the reason behind this increased CH4 flux, we conducted a microcosm experiment altering both nitrogen and carbon availability under aerobic and anaerobic conditions. Methanogenesis appeared to be both nitrogen and carbon (acetate limited. N and C each increased methanogenesis by 18%, and together by 44%. In contrast, methanotrophy was stimulated by carbon (methane addition (830%, but was unchanged by nitrogen addition. Sequence analysis of the sediment methylotroph community with the methanol dehydrogenase gene (mxaF revealed three distinct clades that fall outside of known lineages. However, in agreement with the microcosm results, methylotroph abundance (assayed by qPCR and composition (assayed by T-RFLP did not vary across the experimental nitrogen gradient in the field. Together, these results suggest that nitrogen enrichment to salt marsh sediments increases methane flux by stimulating the methanogen community.

Fluxes of methane and nitrous oxide from an Indian mangrove

Energy Technology Data Exchange (ETDEWEB)

Krithika, K.; Purvaja, R.; Ramesh, R. [Anna Univ., Chennai (India). Institute for Ocean Management

2008-01-25

Methane and nitrous oxide are atmospheric trace gases and contribute about 15 and 6% respectively to the greenhouse effect. Both have a long atmospheric residence time of about 114 and 12 years respectively and since they are key compounds in the chemical reaction cycles of the troposphere and the stratosphere, their potential to directly or indirectly influence global climate is high. Fluxes of greenhouse gases, methane (CH{sub 4}) and nitrous oxide (N{sub 2}O), were measured from a mangrove ecosystem of the Cauvery delta (Muthupet) in South India. CH{sub 4} emissions were in the range between 18.99 and 37.53 mg/sq. m/d, with an average of 25.21 mg/sq. m/d, whereas N{sub 2}O emission ranged between 0.41 and 0.80 mg/sq. m/d (average of 0.62 mg/sq. m/d). The emission of CH{sub 4} and N{sub 2}O correlated positively with the number of pneumatophores. In addition to the flux measurements, different parts of the roots of Avicennia marina were quantified for CH{sub 4} concentration. Invariably in all the seasons, measured CH{sub 4} concentrations were high in the cable roots, with gradual decrease through the pneumatophores below water level and the above water level. This clearly indicates the transport of CH{sub 4} through the roots. We were able to establish that CH{sub 4} was released passively through the mangrove pneumatophores and is also a source to the atmosphere. We present some additional information on transport mechanisms of CH{sub 4} through the pneumatophores and bubble release from the mangrove ecosystems.

Environmental controls of temporal and spatial variability in CO2 and CH4 fluxes in a neotropical peatland.

Science.gov (United States)

Wright, Emma L; Black, Colin R; Turner, Benjamin L; Sjögersten, Sofie

2013-12-01

Tropical peatlands play an important role in the global storage and cycling of carbon (C) but information on carbon dioxide (CO2) and methane (CH4) fluxes from these systems is sparse, particularly in the Neotropics. We quantified short and long-term temporal and small scale spatial variation in CO2 and CH4 fluxes from three contrasting vegetation communities in a domed ombrotrophic peatland in Panama. There was significant variation in CO2 fluxes among vegetation communities in the order Campnosperma panamensis > Raphia taedigera > Cyperus. There was no consistent variation among sites and no discernible seasonal pattern of CH4 flux despite the considerable range of values recorded (e.g. -1.0 to 12.6 mg m(-2) h(-1) in 2007). CO2 fluxes varied seasonally in 2007, being greatest in drier periods (300-400 mg m(-2) h(-1)) and lowest during the wet period (60-132 mg m(-2) h(-1)) while very high emissions were found during the 2009 wet period, suggesting that peak CO2 fluxes may occur following both low and high rainfall. In contrast, only weak relationships between CH4 flux and rainfall (positive at the C. panamensis site) and solar radiation (negative at the C. panamensis and Cyperus sites) was found. CO2 fluxes showed a diurnal pattern across sites and at the Cyperus sp. site CO2 and CH4 fluxes were positively correlated. The amount of dissolved carbon and nutrients were strong predictors of small scale within-site variability in gas release but the effect was site-specific. We conclude that (i) temporal variability in CO2 was greater than variation among vegetation communities; (ii) rainfall may be a good predictor of CO2 emissions from tropical peatlands but temporal variation in CH4 does not follow seasonal rainfall patterns; and (iii) diurnal variation in CO2 fluxes across different vegetation communities can be described by a Fourier model. © 2013 John Wiley & Sons Ltd.

Improving understanding of controls on spatial variability in methane fluxes in Arctic tundra

Science.gov (United States)

Davidson, Scott J.; Sloan, Victoria; Phoenix, Gareth; Wagner, Robert; Oechel, Walter; Zona, Donatella

2015-04-01

The Arctic is experiencing rapid climate change relative to the rest of the globe, and this increase in temperature has feedback effects across hydrological and thermal regimes, plant community distribution and carbon stocks within tundra soils. Arctic wetlands account for a significant amount of methane emissions from natural ecosystems to the atmosphere and with further permafrost degradation under a warming climate, these emissions are expected to increase. Methane (CH4) is an extremely important component of the global carbon cycle with a global warming potential 28.5 times greater than carbon dioxide over a 100 year time scale (IPCC, 2013). In order to validate carbon cycle models, modelling methane at broader landscape scales is needed. To date direct measurements of methane have been sporadic in time and space which, while capturing some key controls on the spatial heterogeneity, make it difficult to accurately upscale methane emissions to the landscape and regional scales. This study investigates what is controlling the spatial heterogeneity of methane fluxes across Arctic tundra. We combined over 300 portable chamber observations from 13 micro-topographic positions (with multiple vegetation types) across three locations spanning a 300km latitudinal gradient in Northern Alaska from Barrow to Ivotuk with synchronous measurements of environmental (soil temperature, soil moisture, water table, active layer thaw depth, pH) and vegetation (plant community composition, height, sedge tiller counts) variables to evaluate key controls on methane fluxes. To assess the diurnal variation in CH4 fluxes, we also performed automated chamber measurements in one study site (Barrow) location. Multiple statistical approaches (regression tree and multiple linear regression) were used to identify key controlling variables and their interactions. Methane emissions across all sites ranged from -0.08 to 15.3 mg C-CH4 m-2 hr-1. As expected, soil moisture was the main control

Consistent regional fluxes of CH4 and CO2 inferred from GOSAT proxy XCH4 : XCO2 retrievals, 2010-2014

Science.gov (United States)

Feng, Liang; Palmer, Paul I.; Bösch, Hartmut; Parker, Robert J.; Webb, Alex J.; Correia, Caio S. C.; Deutscher, Nicholas M.; Domingues, Lucas G.; Feist, Dietrich G.; Gatti, Luciana V.; Gloor, Emanuel; Hase, Frank; Kivi, Rigel; Liu, Yi; Miller, John B.; Morino, Isamu; Sussmann, Ralf; Strong, Kimberly; Uchino, Osamu; Wang, Jing; Zahn, Andreas

2017-04-01

We use the GEOS-Chem global 3-D model of atmospheric chemistry and transport and an ensemble Kalman filter to simultaneously infer regional fluxes of methane (CH4) and carbon dioxide (CO2) directly from GOSAT retrievals of XCH4 : XCO2, using sparse ground-based CH4 and CO2 mole fraction data to anchor the ratio. This work builds on the previously reported theory that takes into account that (1) these ratios are less prone to systematic error than either the full-physics data products or the proxy CH4 data products; and (2) the resulting CH4 and CO2 fluxes are self-consistent. We show that a posteriori fluxes inferred from the GOSAT data generally outperform the fluxes inferred only from in situ data, as expected. GOSAT CH4 and CO2 fluxes are consistent with global growth rates for CO2 and CH4 reported by NOAA and have a range of independent data including new profile measurements (0-7 km) over the Amazon Basin that were collected specifically to help validate GOSAT over this geographical region. We find that large-scale multi-year annual a posteriori CO2 fluxes inferred from GOSAT data are similar to those inferred from the in situ surface data but with smaller uncertainties, particularly over the tropics. GOSAT data are consistent with smaller peak-to-peak seasonal amplitudes of CO2 than either the a priori or in situ inversion, particularly over the tropics and the southern extratropics. Over the northern extratropics, GOSAT data show larger uptake than the a priori but less than the in situ inversion, resulting in small net emissions over the year. We also find evidence that the carbon balance of tropical South America was perturbed following the droughts of 2010 and 2012 with net annual fluxes not returning to an approximate annual balance until 2013. In contrast, GOSAT data significantly changed the a priori spatial distribution of CH4 emission with a 40 % increase over tropical South America and tropical Asia and a smaller decrease over Eurasia and temperate

Observing and modeling links between soil moisture, microbes and CH4 fluxes from forest soils

Science.gov (United States)

Christiansen, Jesper; Levy-Booth, David; Barker, Jason; Prescott, Cindy; Grayston, Sue

2017-04-01

Soil moisture is a key driver of methane (CH4) fluxes in forest soils, both of the net uptake of atmospheric CH4 and emission from the soil. Climate and land use change will alter spatial patterns of soil moisture as well as temporal variability impacting the net CH4 exchange. The impact on the resultant net CH4 exchange however is linked to the underlying spatial and temporal distribution of the soil microbial communities involved in CH4 cycling as well as the response of the soil microbial community to environmental changes. Significant progress has been made to target specific CH4 consuming and producing soil organisms, which is invaluable in order to understand the microbial regulation of the CH4 cycle in forest soils. However, it is not clear as to which extent soil moisture shapes the structure, function and abundance of CH4 specific microorganisms and how this is linked to observed net CH4 exchange under contrasting soil moisture regimes. Here we report on the results from a research project aiming to understand how the CH4 net exchange is shaped by the interactive effects soil moisture and the spatial distribution CH4 consuming (methanotrophs) and producing (methanogens). We studied the growing season variations of in situ CH4 fluxes, microbial gene abundances of methanotrophs and methanogens, soil hydrology, and nutrient availability in three typical forest types across a soil moisture gradient in a temperate rainforest on the Canadian Pacific coast. Furthermore, we conducted laboratory experiments to determine whether the net CH4 exchange from hydrologically contrasting forest soils responded differently to changes in soil moisture. Lastly, we modelled the microbial mediation of net CH4 exchange along the soil moisture gradient using structural equation modeling. Our study shows that it is possible to link spatial patterns of in situ net exchange of CH4 to microbial abundance of CH4 consuming and producing organisms. We also show that the microbial

The development and validation of an unmanned aerial system (UAS) for the measurement of methane flux

Science.gov (United States)

Allen, G.; Shah, A.; Williams, P. I.; Ricketts, H.; Hollingsworth, P.; Kabbabe, K.; Bourn, M.; Pitt, J. R.; Helmore, J.; Lowry, D.; Robinson, R. A.; Finlayson, A.

2017-12-01

Emission controls for CH4are a part of the Paris Agreement and other national emissions strategies. This work represents a new method for precise quantification of point-source and facility-level methane emissions flux rates to inform both the climate science community and policymakers. In this paper, we describe the development of an integrated Unmanned Aerial System (UAS) for the measurement of high-precision in-situ CH4 concentrations. We also describe the development of a mass balance flux calculation model tailored to UAS plume sampling downwind; and the validation of this method using a known emission flux from a controlled release facility. A validation field trial was conducted at the UK Met Office site in Cardington, UK, between 31 Oct and 4 Nov 2016 using the UK National Physical Laboratory's Controlled Release Facility (CRF). A modified DJI-S900 hexrotor UAS was tethered via an inlet to a ground-based Los Gatos Ultraportable Greenhouse Gas Analyser to record geospatially-referenced methane (and carbon dioxide) concentrations. Methane fluxes from the CRF were emitted at 5 kg/hr and 10 kg/hr in a series of blind trials (fluxes were not reported to the team prior to the calculation of UAS-derived flux) for a total of 7 UAS flights, which sampled 200 m downwind of source(s), each lasting around 20 minutes. The flux calculation method was adapted for sampling considerations downwind of an emission source that has not had sufficient time to develop a Gaussian morphology. The UAS-measured methane fluxes, and representative flux uncertainty (derived from an error propagation model), were found to compare well with the controlled CH4 emission rate. For the 7 experiments, the standard error between the measured and emitted CH4 flux was found to be +/-6% with a mean bias of +0.4 kg/hr. Limits of flux sensitivity (to within 25% uncertainty) were found to extend to as little as 0.12 kg/h. Further improvements to the accuracy of flux calculation could be made by

Uncertainties in modelling CH4 emissions from northern wetlands in glacial climates: effect of hydrological model and CH4 model structure

Directory of Open Access Journals (Sweden)

J. van Huissteden

2009-07-01

Full Text Available Methane (CH4 fluxes from northern wetlands may have influenced atmospheric CH4 concentrations at climate warming phases during the last 800 000 years and during the present global warming. Including these CH4 fluxes in earth system models is essential to understand feedbacks between climate and atmospheric composition. Attempts to model CH4 fluxes from wetlands have previously been undertaken using various approaches. Here, we test a process-based wetland CH4 flux model (PEATLAND-VU which includes details of soil-atmosphere CH4 transport. The model has been used to simulate CH4 emissions from continental Europe in previous glacial climates and the current climate. This paper presents results regarding the sensitivity of modeling glacial terrestrial CH4 fluxes to (a basic tuning parameters of the model, (b different approaches in modeling of the water table, and (c model structure. In order to test the model structure, PEATLAND-VU was compared to a simpler modeling approach based on wetland primary production estimated from a vegetation model (BIOME 3.5. The tuning parameters are the CH4 production rate from labile organic carbon and its temperature sensitivity. The modelled fluxes prove comparatively insensitive to hydrology representation, while sensitive to microbial parameters and model structure. Glacial climate emissions are also highly sensitive to assumptions about the extent of ice cover and exposed seafloor. Wetland expansion over low relief exposed seafloor areas have compensated for a decrease of wetland area due to continental ice cover.

Effects of Long-Term CO2 Enrichment on Soil-Atmosphere CH4 Fluxes and the Spatial Micro-Distribution of Methanotrophic Bacteria.

Science.gov (United States)

Karbin, Saeed; Guillet, Cécile; Kammann, Claudia I; Niklaus, Pascal A

2015-01-01

Effects of elevated atmospheric CO2 concentrations on plant growth and associated C cycling have intensively been studied, but less is known about effects on the fluxes of radiatively active trace gases other than CO2. Net soil-atmosphere CH4 fluxes are determined by the balance of soil microbially-driven methane (CH4) oxidation and methanogenesis, and both might change under elevated CO2. Here, we studied CH4 dynamics in a permanent grassland exposed to elevated CO2 for 14 years. Soil-atmosphere fluxes of CH4 were measured using large static chambers, over a period of four years. The ecosystem was a net sink for atmospheric CH4 for most of the time except summer to fall when net CH4 emissions occurred. We did not detect any elevated CO2 effects on CH4 fluxes, but emissions were difficult to quantify due to their discontinuous nature, most likely because of ebullition from the saturated zone. Potential methanotrophic activity, determined by incubation of fresh sieved soil under standardized conditions, also did not reveal any effect of the CO2 treatment. Finally, we determined the spatial micro-distribution of methanotrophic activity at less than 5× atmospheric (10 ppm) and elevated (10000 ppm) CH4 concentrations, using a novel auto-radiographic technique. These analyses indicated that domains of net CH4 assimilation were distributed throughout the analyzed top 15 cm of soils, with no dependence on CH4 concentration or CO2 treatment. Our investigations suggest that elevated CO2 exerts no or only minor effects on CH4 fluxes in the type of ecosystem we studied, at least as long as soil moisture differences are small or absent as was the case here. The autoradiographic analyses further indicate that the spatial niche of CH4 oxidation does not shift in response to CO2 enrichment or CH4 concentration, and that the same type of methanotrophs may oxidize CH4 from atmospheric and soil-internal sources.

Study of the daily and seasonal atmospheric CH4 mixing ratio variability in a rural Spanish region using 222Rn tracer

Science.gov (United States)

Grossi, Claudia; Vogel, Felix R.; Curcoll, Roger; Àgueda, Alba; Vargas, Arturo; Rodó, Xavier; Morguí, Josep-Anton

2018-04-01

The ClimaDat station at Gredos (GIC3) has been continuously measuring atmospheric (dry air) mixing ratios of carbon dioxide (CO2) and methane (CH4), as well as meteorological parameters, since November 2012. In this study we investigate the atmospheric variability of CH4 mixing ratios between 2013 and 2015 at GIC3 with the help of co-located observations of 222Rn concentrations, modelled 222Rn fluxes and modelled planetary boundary layer heights (PBLHs). Both daily and seasonal changes in atmospheric CH4 can be better understood with the help of atmospheric concentrations of 222Rn (and the corresponding fluxes). On a daily timescale, the variation in the PBLH is the main driver for 222Rn and CH4 variability while, on monthly timescales, their atmospheric variability seems to depend on emission changes. To understand (changing) CH4 emissions, nocturnal fluxes of CH4 were estimated using two methods: the radon tracer method (RTM) and a method based on the EDGARv4.2 bottom-up emission inventory, both using FLEXPARTv9.0.2 footprints. The mean value of RTM-based methane fluxes (FR_CH4) is 0.11 mg CH4 m-2 h-1 with a standard deviation of 0.09 or 0.29 mg CH4 m-2 h-1 with a standard deviation of 0.23 mg CH4 m-2 h-1 when using a rescaled 222Rn map (FR_CH4_rescale). For our observational period, the mean value of methane fluxes based on the bottom-up inventory (FE_CH4) is 0.33 mg CH4 m-2 h-1 with a standard deviation of 0.08 mg CH4 m-2 h-1. Monthly CH4 fluxes based on RTM (both FR_CH4 and FR_CH4_rescale) show a seasonality which is not observed for monthly FE_CH4 fluxes. During January-May, RTM-based CH4 fluxes present mean values 25 % lower than during June-December. This seasonal increase in methane fluxes calculated by RTM for the GIC3 area appears to coincide with the arrival of transhumant livestock at GIC3 in the second half of the year.

Eddy Covariance Measurements of Methane Flux at Remote Sites with New Low-Power Lightweight Fast Gas Analyzer

Science.gov (United States)

Xu, Liukang; Burba, George; Schedlbauer, Jessica; Zona, Donatella; McDermitt, Dayle K.; Anderson, Tyler; Oberbauer, Steven; Oechel, Walter; Komissarov, Anatoly; Riensche, Brad

2010-05-01

Majority of natural methane production happens at remote unpopulated areas in ecosystems with little or no infrastructure or easily available grid power, such as arctic and boreal wetlands, tropical mangroves, etc. Present approaches for direct measurements of CH4 fluxes rely on fast closed-path analyzers, which have to work under significantly reduced pressures, and require powerful pumps and grid power. Power and labor demands may be reasons why CH4 flux is often measured at locations with good infrastructure and grid power, and not with high CH4 production. An instrument was developed to allow Eddy Covariance measurements of CH4 flux with power consumption 30-150 times below presently available technologies. This instrument, LI-7700, uses proposed extremely low-power technology would allows placing methane Eddy Covariance stations in the middle of the source (wetland, rice paddy, forest, etc.) in the absence of the grid power. This could significantly expand the Eddy Covariance CH4 flux measurements coverage, and possibly, significantly improve the budget estimates of world CH4 emissions and budget. Various prototypes of the LI-7700 were field-tested for three seasons at the remote site in middle of Everglades National Park (Florida, USA) using solar panels, at three stationary and several mobile sites during three seasons at remote Arctic wetlands near Barrow (Alaska, USA), in the tropical mangroves near La Paz (Mexico) using portable generator, and in bare agricultural field near Mead (Nebraska, USA) during 2005 through 2010. Latest data on CH4 concentration, co-spectra and fluxes, and latest details of instrumental design are examined in this presentation. Overall, hourly methane fluxes ranged from near-zero at night to about 4 mg m-2 h-1 in midday in arctic tundra. Observed fluxes were within the ranges reported in the literature for a number of wetlands in North America, including the Everglades wetlands. Diurnal patterns were similar to those measured by

LOW-POWER SOLUTION FOR EDDY COVARIANCE MEASUREMENTS OF METHANE FLUX

Science.gov (United States)

Anderson, T.; Burba, G. G.; Komissarov, A.; McDermitt, D. K.; Xu, L.; Zona, D.; Oechel, W. C.; Schedlbauer, J. L.; Oberbauer, S. F.; Riensche, B.; Allyn, D.

2009-12-01

night to about 4 mg m-2 h-1 in midday in arctic tundra. Observed fluxes were within the ranges reported in the literature for a number of wetlands in North America, including the Everglades wetlands. Diurnal patterns were similar to those measured by closed-path sensors. The LI-7700 open-path analyzer is a valuable tool for measuring long-term eddy fluxes of methane due to the good frequency response and undisturbed in-situ sampling. It enables long-term deployment of permanent, portable or mobile CH4 flux stations at remote locations with high CH4 production, because it can be powered by a solar panels or a small generator. Authors appreciate help and support provided by the LI-COR Engineering Team, Barrow Arctic Science Consortium (BASC), and numerous colleagues involved in measurements, logistics, and maintenance of the experimental field sites. This project was supported by the Small Business Innovation Research (SBIR) and Small Business Technology Transfer Program (STTR) program of the Department of Energy (DOE), Grant Number DE-FG02-05ER84283.

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

Science.gov (United States)

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.

Enhancing surface methane fluxes from an oligotrophic lake: exploring the microbubble hypothesis.

Science.gov (United States)

McGinnis, Daniel F; Kirillin, Georgiy; Tang, Kam W; Flury, Sabine; Bodmer, Pascal; Engelhardt, Christof; Casper, Peter; Grossart, Hans-Peter

2015-01-20

Exchange of the greenhouse gases carbon dioxide (CO2) and methane (CH4) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The normalized gas transfer rate for CH4 (k600,CH4) was on average 2.5 times higher than that for CO2 (k600,CO2) and consequently higher than Fickian transport. Because of its low solubility relative to CO2, the enhanced CH4 flux is possibly explained by the presence of microbubbles in the lake’s surface layer. These microbubbles may originate from atmospheric bubble entrainment or gas supersaturation (i.e., O2) or both. Irrespective of the source, we determined that an average of 145 L m(–2) d(–1) of gas is required to exit the surface layer via microbubbles to produce the observed elevated k600,CH4. As k600 values are used to estimate CH4 pathways in aquatic systems, the presence of microbubbles could alter the resulting CH4 and perhaps C balances. These microbubbles will also affect the surface fluxes of other sparingly soluble gases in inland waters, including O2 and N2.

Airborne methane remote measurements reveal heavy-tail flux distribution in Four Corners region.

Science.gov (United States)

Frankenberg, C.

2016-12-01

Methane (CH4) impacts climate as the second strongest anthropogenic greenhouse gas and air quality by influencing tropospheric ozone levels. Space-based observations have identified the Four Corners region in the Southwest United States as an area of large CH4 enhancements. We conducted an airborne campaign in Four Corners during April 2015 with the next-generation Airborne Visible/Infrared Imaging Spectrometer (near-infrared) and Hyperspectral Thermal Emission Spectrometer (thermal infrared) imaging spectrometers to better understand the source of methane by measuring methane plumes at 1- to 3-m spatial resolution. Our analysis detected more than 250 individual methane plumes from fossil fuel harvesting, processing, and distributing infrastructures, spanning an emission range from the detection limit ˜ 2 kg/h to 5 kg/h through ˜ 5,000 kg/h. Observed sources include gas processing facilities, storage tanks, pipeline leaks, natural seeps and well pads, as well as a coal mine venting shaft. Overall, plume enhancements and inferred fluxes follow a lognormal distribution, with the top 10% emitters contributing 49 to 66% to the inferred total point source flux of 0.23 Tg/y to 0.39 Tg/y. We will summarize the campaign results and provide an overview of how airborne remote sensing can be used to detect and infer methane fluxes over widespread geographic areas and how new instrumentation could be used to perform similar observations from space.

Dual stable isotopes of CH 4 from Yellowstone hot-springs suggest hydrothermal processes involving magmatic CO 2

Energy Technology Data Exchange (ETDEWEB)

Moran, James J.; Whitmore, Laura M.; Jay, Zackary J.; Jennings, Ryan deM.; Beam, Jacob P.; Kreuzer, Helen W.; Inskeep, William P.

2017-07-01

Volcanism and post-magmatism contribute both significant annual CH₄ fluxes to the atmosphere (on par with other natural sources such as forest fire and wild animal emissions) and have been implicated in past climate-change events. The Yellowstone hot spot is one of the largest volcanic systems on Earth and is known to emit methane in addition to other greenhouse gases (e.g. carbon dioxide) but the ultimate source of this methane flux has not been elucidated. Here we use dual stable isotope analysis (δ²H and δ¹³C) of CH₄(g) sampled from ten high-temperature geothermal pools in Yellowstone National Park to show that the predominant flux of CH4(g) is abiotic. The average δ¹³C and δ²H values of CH₄(g) emitted from hot springs (-26.7 (±2.4) and -236.9 (±12.0) ‰, respectively) are not consistent with biotic (microbial or thermogenic) methane sources, but are within previously reported ranges for abiotic methane production. Correlation between δ¹³C_CH4 and δ¹³C-dissolved inorganic C (DIC) also suggests that CO₂ is a parent C source for the observed CH₄(g). Moreover, CH₄-CO₂ isotopic geothermometry was used to estimate CH₄(g) formation temperatures ranging from ~ 250 - 350°C, which is just below the temperature estimated for the hydrothermal reservoir and consistent with the hypothesis that subsurface, rock-water interactions are responsible for large methane fluxes from this volcanic system. An understanding of conditions leading to the abiotic production of methane and associated isotopic signatures are central to understanding the evolutionary history of deep carbon sources on Earth.

Annual balances of CH4 and N2O from a managed fen meadow using eddy covariance flux measurements

International Nuclear Information System (INIS)

Schrier-Uijl, A.P.; Veenendaal, E.M.; Kroon, P.S.; Hensen, A.; Jonker, H.J.J.

2010-10-01

Annual terrestrial balances of methane (CH4) and nitrous oxide (N2O) are presented for a managed fen meadow in the Netherlands for 2006, 2007 and 2008, using eddy covariance (EC) flux measurements. Annual emissions derived from different methods are compared. The most accurate annual CH4 flux is achieved by gap filling EC fluxes with an empirical multivariate regression model, with soil temperature and mean wind velocity as driving variables. This model explains about 60% of the variability in observed daily CH4 fluxes. Annual N2O emissions can be separated into background emissions and event emissions due to fertilization. The background emission is estimated using a multivariate regression model also based on EC flux data, with soil temperature and mean wind velocity as driving variables. The event emissions are estimated using emission factors. The minimum direct emission factor is derived for six fertilization events by subtracting the background emission, and the IPCC default emission factor of 1% is used for the other events. In addition, the maximum direct emission factors are determined for the six events without subtracting the background emission. The average direct emission factor ranges from 1.2 to 2.8%, which is larger than the IPCC default value. Finally, the total terrestrial greenhouse gas balance is estimated at 16 Mg ha -1 year -1 in CO2-equivalents with contributions of 30, 25 and 45% by CO2, CH4 and N2O, respectively.

Environmental control of methane fluxes over a Danish peatland

Science.gov (United States)

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

Microbial and environmental controls of methane fluxes along a soil moisture gradient in a Pacific coastal temperate rainforest

DEFF Research Database (Denmark)

Christiansen, Jesper Riis; Levy-Booth, David; Prescott, Cindy E.

2016-01-01

, and nutrient availability in three typical forest types across a soil moisture gradient. CH4 displayed a spatial variability changing from a net uptake in the upland soils (3.9–46 µmol CH4 m−2 h−1) to a net emission in the wetter soils (0–90 μmol CH4 m−2 h−1). Seasonal variations of CH4 fluxes were related......Most studies of greenhouse gas fluxes from forest soils in the coastal rainforest have considered carbon dioxide (CO2), whereas methane (CH4) has not received the same attention. Soil hydrology is a key driver of CH4 dynamics in ecosystems, but the impact on the function and distribution...... of the underlying microbial communities involved in CH4 cycling and the resultant net CH4 exchange is not well understood at this scale. We studied the growing season variations of in situ CH4 fluxes, microbial gene abundances of methanotrophs (CH4 oxidizers) and methanogens (CH4 producers), soil hydrology...

Eddy covariance methane flux measurements over a grazed pasture: effect of cows as moving point sources

Science.gov (United States)

Felber, R.; Münger, A.; Neftel, A.; Ammann, C.

2015-06-01

Methane (CH4) from ruminants contributes one-third of global agricultural greenhouse gas emissions. Eddy covariance (EC) technique has been extensively used at various flux sites to investigate carbon dioxide exchange of ecosystems. Since the development of fast CH4 analyzers, the instrumentation at many flux sites has been amended for these gases. However, the application of EC over pastures is challenging due to the spatially and temporally uneven distribution of CH4 point sources induced by the grazing animals. We applied EC measurements during one grazing season over a pasture with 20 dairy cows (mean milk yield: 22.7 kg d-1) managed in a rotational grazing system. Individual cow positions were recorded by GPS trackers to attribute fluxes to animal emissions using a footprint model. Methane fluxes with cows in the footprint were up to 2 orders of magnitude higher than ecosystem fluxes without cows. Mean cow emissions of 423 ± 24 g CH4 head-1 d-1 (best estimate from this study) correspond well to animal respiration chamber measurements reported in the literature. However, a systematic effect of the distance between source and EC tower on cow emissions was found, which is attributed to the analytical footprint model used. We show that the EC method allows one to determine CH4 emissions of cows on a pasture if the data evaluation is adjusted for this purpose and if some cow distribution information is available.

Effects of plant species on soil microbial processes and CH4 emission from constructed wetlands

International Nuclear Information System (INIS)

Wang, Yanhua; Yang, Hao; Ye, Chun; Chen, Xia; Xie, Biao; Huang, Changchun; Zhang, Jixiang; Xu, Meina

2013-01-01

Methane (CH 4 ) emission from constructed wetland has raised environmental concern. This study evaluated the influence of mono and polyculture constructed wetland and seasonal variation on CH 4 fluxes. Methane emission data showed large temporal variation ranging from 0 to 249.29 mg CH 4 m −2 h −1 . Results indicated that the highest CH 4 flux was obtained in the polyculture system, planted with Phragmites australis, Zizania latifolia and Typha latifolia, reflecting polyculture system could stimulate CH 4 emission. FISH analysis showed the higher amount of methanotrophs in the profile of Z. latifolia in both mono and polyculture systems. The highest methanogens amount and relatively lower methanotrophs amount in the profile of polyculture system were obtained. The results support the characteristics of CH 4 fluxes. The polyculture constructed wetland has the higher potential of global warming. -- Highlights: ► The polyculture constructed wetland has the higher contribution to CH 4 emission. ► The CH 4 –C conversion ranged from 0 to 3.7%. ► The Z. latifolia played important roles in methanotrophs growth and CH 4 consumption. ► Major influence of T-N, TOC and plant cover on CH 4 emission was obtained. -- The polyculture constructed wetland has the higher contribution to global warming

BOREAS TGB-3 CH4 and CO2 Chamber Flux Data over NSA Upland Sites

Science.gov (United States)

Savage, Kathleen; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Moore, Tim R.

2000-01-01

The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB-3) team collected methane and carbon dioxide (CH4, CO2) chamber flux measurements at the Northern Study Area (NSA) Fen, Old Black Spruce (OBS), Young Jack Pine (YJP), and auxiliary sites along Gillam Road and the 1989 burn site. Gas samples were extracted from chambers and analyzed at the NSA lab facility approximately every 7 days during May to September 1994 and June to October 1996. The data are provided in tabular ASCII files.

Bioelectrochemical methane (CH4) production in anaerobic digestion at different supplemental voltages.

Science.gov (United States)

Choi, Kwang-Soon; Kondaveeti, Sanath; Min, Booki

2017-12-01

Microbial electrolysis cells (MECs) at various cell voltages (0.5, 0.7 1.0 and 1.5V) were operated in anaerobic fermentation. During the start-up period, the cathode potential decreased from -0.63 to -1.01V, and CH 4 generation increased from 168 to 199ml. At an applied voltage of 1.0V, the highest methane yields of 408.3ml CH 4 /g COD glucose was obtained, which was 30.3% higher than in the control tests (313.4ml CH 4 /g COD glucose). The average current of 5.1mA was generated at 1.0V at which the maximum methane yield was obtained. The other average currents were 1.42, 3.02, 0.53mA at 0.5, 0.7, and 1.5V, respectively. Cyclic voltammetry and EIS analysis revealed that enhanced reduction currents were present at all cell voltages with biocatalyzed cathode electrodes (no reduction without biofilm), and the highest value was obtained with 1V external voltage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Quantifying landscape-level methane fluxes in subarctic Finland using a multiscale approach.

Science.gov (United States)

Hartley, Iain P; Hill, Timothy C; Wade, Thomas J; Clement, Robert J; Moncrieff, John B; Prieto-Blanco, Ana; Disney, Mathias I; Huntley, Brian; Williams, Mathew; Howden, Nicholas J K; Wookey, Philip A; Baxter, Robert

2015-10-01

Quantifying landscape-scale methane (CH4 ) fluxes from boreal and arctic regions, and determining how they are controlled, is critical for predicting the magnitude of any CH4 emission feedback to climate change. Furthermore, there remains uncertainty regarding the relative importance of small areas of strong methanogenic activity, vs. larger areas with net CH4 uptake, in controlling landscape-level fluxes. We measured CH4 fluxes from multiple microtopographical subunits (sedge-dominated lawns, interhummocks and hummocks) within an aapa mire in subarctic Finland, as well as in drier ecosystems present in the wider landscape, lichen heath and mountain birch forest. An intercomparison was carried out between fluxes measured using static chambers, up-scaled using a high-resolution landcover map derived from aerial photography and eddy covariance. Strong agreement was observed between the two methodologies, with emission rates greatest in lawns. CH4 fluxes from lawns were strongly related to seasonal fluctuations in temperature, but their floating nature meant that water-table depth was not a key factor in controlling CH4 release. In contrast, chamber measurements identified net CH4 uptake in birch forest soils. An intercomparison between the aerial photography and satellite remote sensing demonstrated that quantifying the distribution of the key CH4 emitting and consuming plant communities was possible from satellite, allowing fluxes to be scaled up to a 100 km(2) area. For the full growing season (May to October), ~ 1.1-1.4 g CH4  m(-2) was released across the 100 km(2) area. This was based on up-scaled lawn emissions of 1.2-1.5 g CH4  m(-2) , vs. an up-scaled uptake of 0.07-0.15 g CH4  m(-2) by the wider landscape. Given the strong temperature sensitivity of the dominant lawn fluxes, and the fact that lawns are unlikely to dry out, climate warming may substantially increase CH4 emissions in northern Finland, and in aapa mire regions in general. © 2015 The

The effect of changing water table on methane fluxes at two Finnish mire sites

International Nuclear Information System (INIS)

Martikainen, P.J.; Nykaenen, H.; Crill, P.; Silvola, J.

1992-01-01

Methane fluxes were measured using static chamber technique on a minerotrophic fen and an ombrotrophic peat bog site located in the Lakkasuo mire complex in central Finland. Both sites consisted of a virgin area and an area drained in 1961 by ditching. The measurements in 1991 were made biweekly from spring thaw to winter freezing. During this period, the mean CH4 emission from the virgin minerotrophic site and virgin ombrotrophic site was 98 mg/m -2 d -1 and 40 mg/m -2 d -1 , respectively. The mean emission of CH 4 from the drained ombrotrophic site was 18 mg/m -2 d -1 . The drained minerotrophic site consumed methane during most of the measuring period, the average uptake was 0.13 mg/m2d. Draining had lowered the average water table by 4 cm at the ombrotrophic site and by 20 cm at minerotrophic site. The possible reasons for the different development of the water table and methane fluxes at ombrotrophic and minerotrophic sites after drainer are discussed

Continuous measurements of methane flux in two Japanese temperate forests based on the micrometeorological and chamber methods

Science.gov (United States)

Yoshikawa, K.; Ueyama, M.; Takagi, K.; Kominami, Y.

2015-12-01

Methane (CH4) budget in forest ecosystems have not been accurately quantified due to limited measurements and considerable spatiotemporal heterogeneity. In order to quantify CH4 fluxes at temperate forest at various spatiotemporal scales, we have continuously measured CH4 fluxes at two upland forests based on the micrometeorological hyperbolic relaxed eddy accumulation (HREA) and automated dynamic closed chamber methods.The measurements have been conducted at Teshio experimental forest (TSE) since September 2013 and Yamashiro forest meteorology research site (YMS) since November 2014. Three automated chambers were installed on each site. Our system can measure CH4 flux by the micrometeorological HREA, vertical concentration profile at four heights, and chamber measurements by a laser-based gas analyzer (FGGA-24r-EP, Los Gatos Research Inc., USA).Seasonal variations of canopy-scale CH4 fluxes were different in each site. CH4 was consumed during the summer, but was emitted during the fall and winter in TSE; consequently, the site acted as a net annual CH4 source. CH4 was steadily consumed during the winter, but CH4 fluxes fluctuated between absorption and emission during the spring and summer in YMS. YMS acted as a net annual CH4 sink. CH4 uptake at the canopy scale generally decreased with rising soil temperature and increased with drying condition for both sites. CH4 flux measured by most of chambers showed the consistent sensitivity examined for the canopy scale to the environmental variables. CH4 fluxes from a few chambers located at a wet condition were independent of variations in soil temperature and moisture at both sites. Magnitude of soil CH4 uptake was higher than the canopy-scale CH4 uptake. Our results showed that the canopy-scale CH4 fluxes were totally different with the plot-scale CH4 fluxes by chambers, suggesting the considerable spatial heterogeneity in CH4 flux at the temperate forests.

Fluxes of methane and nitrogen oxides in various boreal mire ecosystems. Effects of land-use activities and environmental changes

Energy Technology Data Exchange (ETDEWEB)

Martikainen, P J; Nykaenen, H; Regina, K [National Public Health Inst., Kuopio (Finland). Lab. of Environmental Microbiology; Alm, J; Silvola, J [Joensuu Univ. (Finland). Dept. of Biology

1997-12-31

Atmospheric impact of peatlands is a sum of their gas fluxes. In contrast to carbon dioxide, peatlands are net sources for methane (CH{sub 4}). Methane is an end product in the anaerobic decomposition processes and it has greater capacity to absorb infrared radiation than carbon dioxide. Most of the data on the CH{sub 4} release from northern peatlands is from North America. The total amount of methane released from wetlands is calculated to be 110 Tg yr{sup -1} of which 34 percent (38 Tg yr{sup -1}) is estimated to be emitted from the northern peatlands. Peat with high content of nitrogen is a potential source for gaseous nitrogen oxides, i.e. nitrous oxide (N{sub 2}O) and nitric oxide (NO). However, the importance of peatlands in producing these trace gases is poorly known. Nitrous oxide and nitric oxide are important components in the atmospheric chemistry and N{sub 2}O also is an effective greenhouse gas. Land-use activities and environmental changes can affect the atmospheric impacts of peatlands by modifying their biogeochemistry. This article presents a short summary of the studies whose objectives were: (1) to measure fluxes of CH{sub 4} and N{sub 2}O on wide range of natural mires in Finland, (2) to study the short- and long-term changes in fluxes of CH{sub 4}, N{sub 2}O and NO on boreal peatlands after lowering their water table. Peatlands used for agriculture, forestry and peat mining were included in the studies. The results from mires drained for forestry may reflect the possible changes in the trace gas fluxes if water table will drop in the northern peatlands as a result of drier climate, (3) to study the effects of nitrogen load on the fluxes of CH{sub 4}, N{sub 2}O and NO, (4) to identify the microbiological processes important for the fluxes of N{sub 2}O, NO and CH{sub 4}, and to study the environmental factors regulating these microbial processes

Fluxes of methane and nitrogen oxides in various boreal mire ecosystems. Effects of land-use activities and environmental changes

Energy Technology Data Exchange (ETDEWEB)

Martikainen, P.J.; Nykaenen, H.; Regina, K. [National Public Health Inst., Kuopio (Finland). Lab. of Environmental Microbiology; Alm, J.; Silvola, J. [Joensuu Univ. (Finland). Dept. of Biology

1996-12-31

Atmospheric impact of peatlands is a sum of their gas fluxes. In contrast to carbon dioxide, peatlands are net sources for methane (CH{sub 4}). Methane is an end product in the anaerobic decomposition processes and it has greater capacity to absorb infrared radiation than carbon dioxide. Most of the data on the CH{sub 4} release from northern peatlands is from North America. The total amount of methane released from wetlands is calculated to be 110 Tg yr{sup -1} of which 34 percent (38 Tg yr{sup -1}) is estimated to be emitted from the northern peatlands. Peat with high content of nitrogen is a potential source for gaseous nitrogen oxides, i.e. nitrous oxide (N{sub 2}O) and nitric oxide (NO). However, the importance of peatlands in producing these trace gases is poorly known. Nitrous oxide and nitric oxide are important components in the atmospheric chemistry and N{sub 2}O also is an effective greenhouse gas. Land-use activities and environmental changes can affect the atmospheric impacts of peatlands by modifying their biogeochemistry. This article presents a short summary of the studies whose objectives were: (1) to measure fluxes of CH{sub 4} and N{sub 2}O on wide range of natural mires in Finland, (2) to study the short- and long-term changes in fluxes of CH{sub 4}, N{sub 2}O and NO on boreal peatlands after lowering their water table. Peatlands used for agriculture, forestry and peat mining were included in the studies. The results from mires drained for forestry may reflect the possible changes in the trace gas fluxes if water table will drop in the northern peatlands as a result of drier climate, (3) to study the effects of nitrogen load on the fluxes of CH{sub 4}, N{sub 2}O and NO, (4) to identify the microbiological processes important for the fluxes of N{sub 2}O, NO and CH{sub 4}, and to study the environmental factors regulating these microbial processes

Fluxes of methane and nitrogen oxides in various boreal mire ecosystems. Effects of land-use activities and environmental changes

International Nuclear Information System (INIS)

Martikainen, P.J.; Nykaenen, H.; Regina, K.; Alm, J.; Silvola, J.

1996-01-01

Atmospheric impact of peatlands is a sum of their gas fluxes. In contrast to carbon dioxide, peatlands are net sources for methane (CH 4 ). Methane is an end product in the anaerobic decomposition processes and it has greater capacity to absorb infrared radiation than carbon dioxide. Most of the data on the CH 4 release from northern peatlands is from North America. The total amount of methane released from wetlands is calculated to be 110 Tg yr -1 of which 34 percent (38 Tg yr -1 ) is estimated to be emitted from the northern peatlands. Peat with high content of nitrogen is a potential source for gaseous nitrogen oxides, i.e. nitrous oxide (N 2 O) and nitric oxide (NO). However, the importance of peatlands in producing these trace gases is poorly known. Nitrous oxide and nitric oxide are important components in the atmospheric chemistry and N 2 O also is an effective greenhouse gas. Land-use activities and environmental changes can affect the atmospheric impacts of peatlands by modifying their biogeochemistry. This article presents a short summary of the studies whose objectives were: (1) to measure fluxes of CH 4 and N 2 O on wide range of natural mires in Finland, (2) to study the short- and long-term changes in fluxes of CH 4 , N 2 O and NO on boreal peatlands after lowering their water table. Peatlands used for agriculture, forestry and peat mining were included in the studies. The results from mires drained for forestry may reflect the possible changes in the trace gas fluxes if water table will drop in the northern peatlands as a result of drier climate, (3) to study the effects of nitrogen load on the fluxes of CH 4 , N 2 O and NO, (4) to identify the microbiological processes important for the fluxes of N 2 O, NO and CH 4 , and to study the environmental factors regulating these microbial processes

Methane emissions in Danish riparian wetlands

DEFF Research Database (Denmark)

Audet, Joachim; Johansen, Jan Ravn; Andersen, Peter Mejlhede

2013-01-01

The present study was conducted to (i) investigate parameters influencing the fluxes of the greenhouse gas methane (CH4) in Danish riparian wetlands with contrasting vegetation characteristics and (ii) develop models relating CH4 emissions to soil and/or vegetation parameters integrating the spat......The present study was conducted to (i) investigate parameters influencing the fluxes of the greenhouse gas methane (CH4) in Danish riparian wetlands with contrasting vegetation characteristics and (ii) develop models relating CH4 emissions to soil and/or vegetation parameters integrating...

Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements

Directory of Open Access Journals (Sweden)

A. Fraser

2013-06-01

Full Text Available We use an ensemble Kalman filter (EnKF, together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4 fluxes for the period June 2009–December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4 from GOSAT (Greenhouse gases Observing SATellite and/or NOAA ESRL (Earth System Research Laboratory and CSIRO GASLAB (Global Atmospheric Sampling Laboratory CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510–516 Tg yr−1, which is less than, though within the uncertainty of, the prior global flux of 529 ± 25 Tg yr−1. We find larger differences between regional prior and posterior fluxes, with the largest changes in monthly emissions (75 Tg yr−1 occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45% than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes >60° associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2 and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 10% of true values, with the exception of tropical regions where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 15% of true fluxes. We evaluate our

BOREAS TGB-5 CO2, CH4 and CO Chamber Flux Data Over the NSA

Science.gov (United States)

Burke, Roger; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor); Zepp, Richard

2000-01-01

The BOReal Ecosystem-Atmosphere Study Trace Gas Biogeochemistry (BOREAS TGB-5) team collected a variety of trace gas concentration and flux measurements at several NSA sites. This data set contains carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) chamber flux measurements conducted in 1994 at upland forest sites that experienced stand-replacement fires. These measurements were acquired to understand the impact of fires on soil biogeochemistry and related changes in trace gas exchange in boreal forest soils. Relevant ancillary data, including data concerning the soil temperature, solar irradiance, and information from nearby un-burned control sites, are included to provide a basis for modeling the regional impacts of fire and climate changes on trace gas biogeochemistry. The data are provided in tabular ASCII files.

Methane and carbon dioxide fluxes and source partitioning in urban areas: The case study of Florence, Italy

International Nuclear Information System (INIS)

Gioli, B.; Toscano, P.; Lugato, E.; Matese, A.; Miglietta, F.; Zaldei, A.; Vaccari, F.P.

2012-01-01

Long-term fluxes of CO 2 , and combined short-term fluxes of CH 4 and CO 2 were measured with the eddy covariance technique in the city centre of Florence. CO 2 long-term weekly fluxes exhibit a high seasonality, ranging from 39 to 172% of the mean annual value in summer and winter respectively, while CH 4 fluxes are relevant and don’t exhibit temporal variability. Contribution of road traffic and domestic heating has been estimated through multi-regression models combined with inventorial traffic and CH 4 consumption data, revealing that heating accounts for more than 80% of observed CO 2 fluxes. Those two components are instead responsible for only 14% of observed CH 4 fluxes, while the major residual part is likely dominated by gas network leakages. CH 4 fluxes expressed as CO 2 equivalent represent about 8% of CO 2 emissions, ranging from 16% in summer to 4% in winter, and cannot therefore be neglected when assessing greenhouse impact of cities. - Highlights: ► CH 4 and CO 2 fluxes were measured with eddy covariance in Florence city centre. ► CO 2 fluxes are dominated by winter time domestic heating combustion. ► Natural gas network leakages are responsible for 85% of observed methane emissions. ► Greenhouse impact of CH 4 accounts for 8% of CO 2 emissions. - GHG flux measurements in Florence city revealed that domestic heating and gas network leakages are the predominant contributions to CO 2 and CH 4 emissions, respectively.

Methane and Carbon Dioxide Concentrations and Fluxes in Amazon Floodplains

Science.gov (United States)

Melack, J. M.; MacIntyre, S.; Forsberg, B.; Barbosa, P.; Amaral, J. H.

2016-12-01

Field studies on the central Amazon floodplain in representative aquatic habitats (open water, flooded forests, floating macrophytes) combine measurements of methane and carbon dioxide concentrations and fluxes to the atmosphere over diel and seasonal times with deployment of meteorological sensors and high-resolution thermistors and dissolved oxygen sondes. A cavity ringdown spectrometer is used to determine gas concentrations, and floating chambers and bubble collectors are used to measure fluxes. To further understand fluxes, we measured turbulence as rate of dissipation of turbulent kinetic energy based on microstructure profiling. These results allow calculations of vertical mixing within the water column and of air-water exchanges using surface renewal models. Methane and carbon dioxide fluxes varied as a function of season, habitat and water depth. High CO2 fluxes at high water are related to high pCO2; low pCO2 levels at low water result from increased phytoplankton uptake. CO2 fluxes are highest at turbulent open water sites, and pCO2 is highest in macrophyte beds. Fluxes and pCH4 are high in macrophyte beds.

Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH4 ice core records

Science.gov (United States)

Bock, Michael; Schmitt, Jochen; Beck, Jonas; Seth, Barbara; Chappellaz, Jérôme; Fischer, Hubertus

2017-07-01

Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ13CH4 and δD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial.

Methane flux across the air-water interface - Air velocity effects

Science.gov (United States)

Sebacher, D. I.; Harriss, R. C.; Bartlett, K. B.

1983-01-01

Methane loss to the atmosphere from flooded wetlands is influenced by the degree of supersaturation and wind stress at the water surface. Measurements in freshwater ponds in the St. Marks Wildlife Refuge, Florida, demonstrated that for the combined variability of CH4 concentrations in surface water and air velocity over the water surface, CH4 flux varied from 0.01 to 1.22 g/sq m/day. The liquid exchange coefficient for a two-layer model of the gas-liquid interface was calculated as 1.7 cm/h for CH4 at air velocity of zero and as 1.1 + 1.2 v to the 1.96th power cm/h for air velocities from 1.4 to 3.5 m/s and water temperatures of 20 C.

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

Science.gov (United States)

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

Relative linkages of peatland methane and carbon dioxide fluxes with climatic, environmental and ecological parameters and their inter-comparison

Science.gov (United States)

Banerjee, Tirtha; Hommeltenberg, Janina; Roy, Avipsa; De Roo, Frederik; Mauder, Matthias

2016-04-01

Although methane (CH4) is the second most important greenhouse gas (GHG) after CO2, about 80% of its global production is biogenic (wetlands, enteric fermentation and water disposal from animals) contrary to major anthropogenic sources of most other GHGs. Although on a shorter time scale, global emissions of methane are greater (10 year time frame) or about 80% (20 year time frame) of those of carbon dioxide in terms of their influence on global warming, methane emissions have been studied much less than CO2 emissions. Lakes, reservoirs and wetlands are estimated to contribute about 15-40% to the global methane source budget, which is higher than total oceanic CH4 emission. Half of the world's wetlands are represented by peatlands which cover 3% of the global total land area. Peatlands have a thick water-logged organic soil layer (peat) made up of dead and decaying plant material. Moreover, they are carbon rich, containing twice as much stock as the entire forest biomass of the world (550 Gt carbon). When disturbed, they can become significant sources of greenhouse gas emissions. The organic carbon exposed to air due to various mechanisms can release CH4 or CO2 in the atmosphere. Thus the nature of vegetation cover, radiation environment, wind turbulence, soil characteristics, water table depth etc. are expected to be important forcings that influence the emission of CH4 or CO2 in the shorter time scale. However, long term climate change can also influence these governing factors themselves over a larger time scale, which in turn can influence the wetland GHG emissions. Thus developing a predictive framework and long term source appropriation for wetland CH4 or CO2 warrants an identification of the major environmental forcings on the CH4 or CO2 flux. In the present work, we use a simple and systematic data-analytics approach to determine the relative linkages of different climate and environmental variables with the canopy level half-hourly CH4 or CO2 fluxes over a

Background CH4 and N2O fluxes in low-input short rotation coppice

Science.gov (United States)

Görres, Carolyn-Monika; Zenone, Terenzio; Ceulemans, Reinhart

2016-04-01

Extensively managed short rotation coppice systems are characterized by low fluxes of CH4 and N2O. However due to the large global warming potential of these trace gases (GWP100: CH4: 34, N2O: 298), such background fluxes can still significantly contribute to offsetting the CO2 uptake of short rotation coppice systems. Recent technological advances in fast-response CH4 and N2O analysers have improved our capability to capture these background fluxes, but their quantification still remains a challenge. As an example, we present here CH4 and N2O fluxes from a short-rotation bioenergy plantation in Belgium. Poplars have been planted in a double-row system on a loamy sand in 2010 and coppiced in the beginning of 2012 and 2014 (two-year rotation system). In 2013 (June - November) and 2014 (April - August), the plantation's CH4 and N2O fluxes were measured in parallel with an eddy covariance tower (EC) and an automated chamber system (AC). The EC had a detection limit of 13.68 and 0.76 μmol m-2 h-1 for CH4 and N2O, respectively. The median detection limit of the AC was 0.38 and 0.08 μmol m-2 h-1 for CH4 and N2O, respectively. The EC picked up a few high CH4 emission events with daily averages >100 μmol m-2 h-1, but a large proportion of the measured fluxes were within the EC's detection limit. The same was true for the EC-derived N2O fluxes where the daily average flux was often close to the detection limit. Sporadically, some negative (uptake) fluxes of N2O were observed. On the basis of the EC data, no clear link was found between CH4 and N2O fluxes and environmental variables. The problem with fluxes within the EC detection limit is that a significant amount of the values can show the opposite sign, thus "mirroring" the true flux. Subsequently, environmental controls of background trace gas fluxes might be disguised in the analysis. As a next step, it will be tested if potential environmental drivers of background CH4 and N2O fluxes at the plantation can be

Methane fluxes from tropical coastal lagoons surrounded by mangroves, Yucatán, Mexico

Science.gov (United States)

Chuang, P.-C.; Young, M. B.; Dale, A. W.; Miller, L. G.; Herrera-Silveira, J. A.; Paytan, A.

2017-05-01

Methane concentrations in the water column and emissions to the atmosphere were determined for three tropical coastal lagoons surrounded by mangrove forests on the Yucatán Peninsula, Mexico. Surface water dissolved methane was sampled at different seasons over a period of 2 years in areas representing a wide range of salinities and anthropogenic impacts. The highest surface water methane concentrations (up to 8378 nM) were measured in a polluted canal associated with Terminos Lagoon. In Chelem Lagoon, methane concentrations were typically lower, except in the polluted harbor area (1796 nM). In the relatively pristine Celestún Lagoon, surface water methane concentrations ranged from 41 to 2551 nM. Methane concentrations were negatively correlated with salinity in Celestún, while in Chelem and Terminos high methane concentrations were associated with areas of known pollution inputs, irrespective of salinity. The diffusive methane flux from surface lagoon water to the atmosphere ranged from 0.0023 to 15 mmol CH4 m-2 d-1. Flux chamber measurements revealed that direct methane release as ebullition was up to 3 orders of magnitude greater than measured diffusive flux. Coastal mangrove lagoons may therefore be an important natural source of methane to the atmosphere despite their relatively high salinity. Pollution inputs are likely to substantially enhance this flux. Additional statistically rigorous data collected globally are needed to better consider methane fluxes from mangrove-surrounded coastal areas in response to sea level changes and anthropogenic pollution in order to refine projections of future atmospheric methane budgets.

Temporal and spatial variations of soil CO2, CH4 and N2O fluxes at three differently managed grasslands

Directory of Open Access Journals (Sweden)

D. Imer

2013-09-01

Full Text Available A profound understanding of temporal and spatial variabilities of soil carbon dioxide (CO2, methane (CH4 and nitrous oxide (N2O fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three soil greenhouse gas (GHG fluxes occur due to changes in environmental drivers as well as fertilizer applications, harvests and grazing. To assess how such changes affect soil GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400 m a.s.l. (intensively managed to 1000 m a.s.l. (moderately intensive managed to 2000 m a.s.l. (extensively managed. The alpine grassland was included to study both effects of extensive management on CH4 and N2O fluxes and the different climate regime occurring at this altitude. Temporal and spatial variabilities of soil GHG fluxes and environmental drivers on various timescales were determined along transects of 16 static soil chambers at each site. All three grasslands were N2O sources, with mean annual soil fluxes ranging from 0.15 to 1.28 nmol m−2 s−1. Contrastingly, all sites were weak CH4 sinks, with soil uptake rates ranging from −0.56 to −0.15 nmol m−2 s−1. Mean annual soil and plant respiration losses of CO2, measured with opaque chambers, ranged from 5.2 to 6.5 μmol m−2 s−1. While the environmental drivers and their respective explanatory power for soil N2O emissions differed considerably among the three grasslands (adjusted r2 ranging from 0.19 to 0.42, CH4 and CO2 soil fluxes were much better constrained (adjusted r2 ranging from 0.46 to 0.80 by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for soil N2O and CH4 fluxes. We found permanent hot spots for soil N2O emissions as well as

Global diffusive fluxes of methane in marine sediments

Science.gov (United States)

Egger, Matthias; Riedinger, Natascha; Mogollón, José M.; Jørgensen, Bo Barker

2018-06-01

Anaerobic oxidation of methane provides a globally important, yet poorly constrained barrier for the vast amounts of methane produced in the subseafloor. Here we provide a global map and budget of the methane flux and degradation in diffusion-controlled marine sediments in relation to the depth of the methane oxidation barrier. Our new budget suggests that 45-61 Tg of methane are oxidized with sulfate annually, with approximately 80% of this oxidation occurring in continental shelf sediments (methane in steady-state diffusive sediments, we calculate that 3-4% of the global organic carbon flux to the seafloor is converted to methane. We further report a global imbalance of diffusive methane and sulfate fluxes into the sulfate-methane transition with no clear trend with respect to the corresponding depth of the methane oxidation barrier. The observed global mean net flux ratio between sulfate and methane of 1.4:1 indicates that, on average, the methane flux to the sulfate-methane transition accounts for only 70% of the sulfate consumption in the sulfate-methane transition zone of marine sediments.

Methane fluxes from a wet puna ecosystem in the Peruvian Andes

Science.gov (United States)

Jones, Sam; Diem, Torsten; Priscila Huaraca Quispe, Lidia; Quispe Ccahuana, Adan Julian; Meir, Patrick; Arn Teh, Yit

2014-05-01

the seasonal scale with fluxes during the wet season almost an order of magnitude greater than those of the dry season. Mean emissions from bogs during wet and dry season were 85.0 (15.0) and 10.0 (2.0) mg C-CH4 m-2 d-1, respectively. Similarly, mean fluxes in the grassland were 0.4 (0.7) and -0.05 (0.6) mg C-CH4 m-2 d-1. These data highlight the importance of considering such Andean highlands in landscape scale source-sink inventories. In this respect, understanding the influence of differences in climatic regime found across the Andes and determining the areal extent of topographic hotspots driving methane emissions within these environments are key challenges.

Air-sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

Science.gov (United States)

Yang, Mingxi; Bell, Thomas G.; Hopkins, Frances E.; Kitidis, Vassilis; Cazenave, Pierre W.; Nightingale, Philip D.; Yelland, Margaret J.; Pascal, Robin W.; Prytherch, John; Brooks, Ian M.; Smyth, Timothy J.

2016-05-01

We present air-sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27 m above mean sea level, a.m.s.l.), each from a different period during 2014-2015. At sampling heights ≥ 18 m a.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable ( ≤ ±20 % in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air-sea exchange measurements in shelf regions. Covariance air-sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20 ± 3; 38 ± 3; 29 ± 6 µmole m-2 d-1 at 15, 18, 27 m a.m.s.l.) than during falling tides (14 ± 2; 22 ± 2; 21 ± 5 µmole m-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air-sea CH4 flux by eddy covariance to be 20 µmole m-2 d-1 over hourly timescales (4 µmole m-2 d-1 over 24 h).

Eddy Covariance Measurements of Methane Flux at a Tropical Peat Forest in Sarawak, Malaysian Borneo

Science.gov (United States)

Tang, Angela C. I.; Stoy, Paul C.; Hirata, Ryuichi; Musin, Kevin K.; Aeries, Edward B.; Wenceslaus, Joseph; Melling, Lulie

2018-05-01

Tropical biogenic sources are a likely cause of the recent increase in global atmospheric methane concentration. To improve our understanding of tropical methane sources, we used the eddy covariance technique to measure CH4 flux (FCH4) between a tropical peat forest ecosystem and the atmosphere in Malaysian Borneo over a 2-month period during the wet season. Mean daily FCH4 during the measurement period, on the order of 0.024 g C-CH4·m-2·day-1, was similar to eddy covariance FCH4 measurements from tropical rice agroecosystems and boreal fen ecosystems. A linear modeling analysis demonstrated that air temperature (Tair) was critical for modeling FCH4 before the water table breached the surface and that water table alone explained some 20% of observed FCH4 variability once standing water emerged. Future research should measure FCH4 on an annual basis from multiple tropical ecosystems to better constrain tropical biogenic methane sources.

Assessment of CH4 and N2O fluxes in a Danish Beech (Fagus sylvatica) forest and an adjacent N-fertilised barley (Hordeum vulgare)

DEFF Research Database (Denmark)

Ambus, P.; Jensen, J.M.; Prieme, A.

2001-01-01

Fluxes of CH4 and N2O were measured regularly in an agricultural field treated with 280 g m(-2) of sewage sludge. In a nearby beech forest N2O and CH4 fluxes were measured in a well-drained (dry) area and in a wet area adjacent to a drainage canal. We observed brief increases of both CH4 and N2O...... and independent of drainage status. Methane oxidation was observed all-year round in the forest cumulating to -225 mg C m(-2) and -84 mg C m(-2) in dry and wet areas. In a model experiment with incubated soil cores, nitrogen amendment (NH4Cl) and perturbation significantly reduced CH4 oxidation in the forest soil...... sludge, respectively. Four months after the sludge applications a significant effect on CO2 and NO emissions was still obvious in the field, the latter perhaps due to elevated nitrification. Nitrous oxide emission in the beech forest was about six times smaller (45 mg N m(-2)) than in the field...

Assessing Methane Fluxes in a Small Run-of-River Reservoir: The Importance of Adjacent Marshland

Science.gov (United States)

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

On the use of satellite-derived CH4 : CO2 columns in a joint inversion of CH4 and CO2 fluxes

NARCIS (Netherlands)

Pandey, S.

2015-01-01

We present a method for assimilating total column CH4 : CO2 ratio measurements from satellites for inverse modeling of CH4 and CO2 fluxes using the variational approach. Unlike conventional approaches, in which retrieved CH4 : CO2 are multiplied by model-derived total column CO2 and only the

BOREAS TGB-1 Soil CH4 and CO2 Profile Data from NSA Tower Sites

Science.gov (United States)

Crill, Patrick; Varner, Ruth K.; Hall, Forrest G. (Editor); Conrad, Sara K. (Editor)

2000-01-01

The BOREAS TGB-1 team made numerous measurements of trace gas concentrations and fluxes at various NSA sites. This data set contains methane (CH4) and carbon dioxide (CO2) concentrations in soil profiles from the NSA-OJP, NSA-OBS, NSA-YJP, and NSA-BP sites during the period of 23-May to 20-Sep-1994. The soil gas sampling profiles of CH 4 and CO 2 were completed to quantify controls on CO2 and CH4 fluxes in the boreal forest. The data are provided in tabular ASCII files.

Controls on methane concentrations and fluxes in streams draining human-dominated landscapes

Science.gov (United States)

Crawford, John T.; Stanley, Emily H.

2016-01-01

Streams and rivers are active processors of carbon, leading to significant emissions of CO2 and possibly CH4 to the atmosphere. Patterns and controls of CH4 in fluvial ecosystems remain relatively poorly understood. Furthermore, little is known regarding how major human impacts to fluvial ecosystems may be transforming their role as CH4 producers and emitters. Here, we examine the consequences of two distinct ecosystem changes as a result of human land use: increased nutrient loading (primarily as nitrate), and increased sediment loading and deposition of fine particles in the benthic zone. We did not find support for the hypothesis that enhanced nitrate loading down-regulates methane production via thermodynamic or toxic effects. We did find strong evidence that increased sedimentation and enhanced organic matter content of the benthos lead to greater methane production (diffusive + ebullitive flux) relative to pristine fluvial systems in northern Wisconsin (upper Midwest, USA). Overall, streams in a human-dominated landscape of southern Wisconsin were major regional sources of CH4 to the atmosphere, equivalent to ~20% of dairy cattle emissions, or ~50% of a landfill’s annual emissions. We suggest that restoration of the benthic environment (reduced fine deposits) could lead to reduced CH4 emissions, while decreasing nutrient loading is likely to have limited impacts to this ecosystem process.

The influence of nitrogen fertiliser rate and crop rotation on soil methane flux in rain-fed potato fields in Wuchuan County, China

International Nuclear Information System (INIS)

Wang, Liwei; Pan, Zhihua; Xu, Hui; Wang, Cheng; Gao, Lin; Zhao, Peiyi; Dong, Zhiqiang; Zhang, Jingting; Cui, Guohui; Wang, Sen; Han, Guolin; Zhao, Hui

2015-01-01

As one of the important greenhouse gases, the characteristics and principles of methane exchange characteristics in cultivated lands have become hot topics in current climate change research. This study examines the influences of nitrogen fertilisation, temperature and soil water content on methane exchange characteristic and methane exchange functional gene-pmoA gene abundance based on experimental observations of methane exchange fluxes using the static chamber–gas chromatographic method and measurements of methanotroph gene copy numbers in three growing periods by real-time PCR in rain-fed potato fields. The results indicate that the rain-fed potato fields were a CH_4 sink with an average annual methane absorption (negative emission) of 940.8 ± 103.2 g CH_4-C/ha/year. The cumulative methane absorption first exhibited flat and subsequently increasing trend with the increase of nitrogen fertilisation from 0 ~ 135 kg N·ha"−"1. Methane cumulative absorption significantly increased with the increase of temperature when temperatures were below 19.6 °C. Methane oxidation capacity (methanotroph pmoA gene copy numbers) showed an increasing and subsequently decreasing trend with the increase of soil moisture. Crop rotation was observed to increase the methane absorption in rain-fed potato fields and nearly one time higher than that under continuous cropping. A mechanism concept model of the methane exchange in rain-fed potato fields was advanced in this paper. - Highlights: • Rain-fed potato fields were a CH_4 sink. • Increased nitrogen fertilisation and temperature led to higher CH_4 absorption. • CH_4 oxidation capacity showed a parabolic trend with soil moisture increased. • Crop rotation increased CH_4 absorption one time higher than continuous cropping. • A mechanism concept model of the CH_4 exchange in potato fields was advanced.

The influence of nitrogen fertiliser rate and crop rotation on soil methane flux in rain-fed potato fields in Wuchuan County, China

Energy Technology Data Exchange (ETDEWEB)

Wang, Liwei [College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193 (China); College of Agronomy, Shenyang Agricultural University, Shenyang 110866 (China); Wuchuan Scientific Observing and Experimental Station of Agro-Environment, Ministry of Agriculture Wuchuan 011700 (China); Pan, Zhihua, E-mail: panzhihua@cau.edu.cn [College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193 (China); Wuchuan Scientific Observing and Experimental Station of Agro-Environment, Ministry of Agriculture Wuchuan 011700 (China); Xu, Hui [Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, Cheng [College of Agricultural and Biotechnology, China Agricultural University, Beijing 100193 (China); Gao, Lin [School of Resources and Environmental, Anhui Agricultural University, Hefei 230036 (China); Zhao, Peiyi [Institute of Resources Environmental and Detection Technology, Inner Mongolia Academy of Agricultural and Animal Husbandry Sciences, Huhhot 010031 (China); Wuchuan Scientific Observing and Experimental Station of Agro-Environment, Ministry of Agriculture Wuchuan 011700 (China); Dong, Zhiqiang; Zhang, Jingting; Cui, Guohui; Wang, Sen; Han, Guolin; Zhao, Hui [College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193 (China); Wuchuan Scientific Observing and Experimental Station of Agro-Environment, Ministry of Agriculture Wuchuan 011700 (China)

2015-12-15

As one of the important greenhouse gases, the characteristics and principles of methane exchange characteristics in cultivated lands have become hot topics in current climate change research. This study examines the influences of nitrogen fertilisation, temperature and soil water content on methane exchange characteristic and methane exchange functional gene-pmoA gene abundance based on experimental observations of methane exchange fluxes using the static chamber–gas chromatographic method and measurements of methanotroph gene copy numbers in three growing periods by real-time PCR in rain-fed potato fields. The results indicate that the rain-fed potato fields were a CH{sub 4} sink with an average annual methane absorption (negative emission) of 940.8 ± 103.2 g CH{sub 4}-C/ha/year. The cumulative methane absorption first exhibited flat and subsequently increasing trend with the increase of nitrogen fertilisation from 0 ~ 135 kg N·ha{sup −1}. Methane cumulative absorption significantly increased with the increase of temperature when temperatures were below 19.6 °C. Methane oxidation capacity (methanotroph pmoA gene copy numbers) showed an increasing and subsequently decreasing trend with the increase of soil moisture. Crop rotation was observed to increase the methane absorption in rain-fed potato fields and nearly one time higher than that under continuous cropping. A mechanism concept model of the methane exchange in rain-fed potato fields was advanced in this paper. - Highlights: • Rain-fed potato fields were a CH{sub 4} sink. • Increased nitrogen fertilisation and temperature led to higher CH{sub 4} absorption. • CH{sub 4} oxidation capacity showed a parabolic trend with soil moisture increased. • Crop rotation increased CH{sub 4} absorption one time higher than continuous cropping. • A mechanism concept model of the CH{sub 4} exchange in potato fields was advanced.

Ecosystem respiration, methane and nitrous oxide fluxes from ecotopes in a rewetted extracted peatland in Sweden

Directory of Open Access Journals (Sweden)

S. Jordan

2016-09-01

Full Text Available Ecosystem respiration (carbon dioxide; CO2, methane (CH4 and nitrous oxide (N2O fluxes to the atmosphere were determined using an opaque closed chamber method within various ecotopes (vegetation covered, bare peat and open water in a rewetted extracted peatland and within an adjacent open poor fen in Sweden. Ecotopes had a significant impact on CO2 and CH4 fluxes to the atmosphere. Ecosystem respiration and CH4 emissions from the bare peat site, the constructed shallow lake and the open poor fen were low but were much higher from ecotopes with Eriophorum vaginatum tussocks and Eriophorum angustifolium. A combination of vascular plant cover and high soil temperatures enhanced ecosystem respiration, while a combination of vascular plant cover, high water table levels and high soil temperatures enhanced CH4 emissions. N2O emissions contributed little to total greenhouse gas (GHG fluxes from the soil-plant-water systems to the atmosphere. However, the overall climate impact of CH4 emissions from the study area did not exceed the impact of soil and plant respiration. With regard to management of extracted peatlands, the construction of a nutrient-poor shallow lake showed great potential for lowering GHG fluxes to the atmosphere.

Flux and energy dependence of methane production from graphite due to H+ impact

International Nuclear Information System (INIS)

Davis, J.W.; Haasz, A.A.; Stangeby, P.C.

1986-06-01

Carbon is in widespread use for limiter surfaces, as well as first wall coatings in current tokamaks. Chemical erosion via methane formation, due to energetic H + impact, is expected to contribute to the total erosion rate of carbon from these surfaces. Experimental results are presented for the methane yield from pyrolytic graphite due to H + exposure, using a mass analyzed ion beam. H + energies of 0.1-3 keV and flux densities of ∼ 5x10 13 to l0 16 H + /cm 2 s were used. The measured methane yield (CH 4 /H + ) initially increases with flux density, then reaches a maximum, which is followed by a gradual decrease. The magnitude of the maximum yield and the flux density at which it occurs depends on the graphite temperature. The yields obtained at temperatures corresponding to yield maxima at specific flux densities also show an initial increase, followed by a shallow maximum and a gradual decrease as a function of flux density; the maximum occurs at ∼10 15 H + /cm 2 s. Also presented are results on the methane production dependence on ion energy over the range 0.1 to 3 keV, and graphite temperature dependence measurements

Mangroves act as a small methane source: an investigation on 5 pathways of methane emissions from mangroves

Science.gov (United States)

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 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

Air–sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

Directory of Open Access Journals (Sweden)

M. Yang

2016-05-01

Full Text Available We present air–sea fluxes of carbon dioxide (CO2, methane (CH4, momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector were made at three different sampling heights (approximately 15, 18, and 27 m above mean sea level, a.m.s.l., each from a different period during 2014–2015. At sampling heights  ≥  18 m a.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable ( ≤  ±20 % in the mean agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20 ± 3; 38 ± 3; 29 ± 6 µmole m−2 d−1 at 15, 18, 27 m a.m.s.l. than during falling tides (14 ± 2; 22 ± 2; 21 ± 5 µmole m−2 d−1, consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater. Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 µmole m−2 d−1 over hourly timescales (4 µmole m−2 d−1 over 24 h.

A Modern Automatic Chamber Technique as a Powerful Tool for CH4 and CO2 Flux Monitoring

Science.gov (United States)

Mastepanov, M.; Christensen, T. R.; Lund, M.; Pirk, N.

2014-12-01

A number of similar systems were used for monitoring of CH4 and CO2 exchange by the automatic chamber method in a range of different ecosystems. The measurements were carried out in northern Sweden (mountain birch forest near Abisko, 68°N, 2004-2010), southern Sweden (forest bog near Hässleholm, 56°N, 2007-2014), northeastern Greenland (arctic fen in Zackenberg valley, 74°N, 2005-2014), southwestern Greenland (fen near Nuuk, 64°N, 2007-2014), central Svalbard (arctic fen near Longyearbyen, 78°N, 2011-2014). Those in total 37 seasons of measurements delivered not only a large amount of valuable flux data, including a few novel findings (Mastepanov et al., Nature, 2008; Mastepanov et al., Biogeosciences, 2013), but also valuable experience with implementation of the automatic chamber technique using modern analytical instruments and computer technologies. A range of high resolution CH4 analysers (DLT-100, FMA, FGGA - Los Gatos Research), CO2 analyzers (EGM-4, SBA-4 - PP Systems; Li-820 - Li-Cor Biosciences), as well as Methane Carbon Isotope Analyzer (Los Gatos Research) has shown to be suitable for precise measurements of fluxes, from as low as 0.1 mg CH4 m-1 d-1 (wintertime measurements at Zackenberg, unpublished) to as high as 2.4 g CH4 m-1 d-1 (autumn burst 2007 at Zackenberg, Mastepanov et al., Nature, 2008). Some of these instruments had to be customized to accommodate 24/7 operation in harsh arctic conditions. In this presentation we will explain some of these customizations. High frequency of concentration measurements (1 Hz in most cases) provides a unique opportunity for quality control of flux calculations; on the other hand, this enormous amount of data can be analyzed only using highly automated algorithms. A specialized software package was developed and improved through the years of measurements and data processing. This software automates the data flow from raw concentration data of different instruments and sensors and various status records

Spatial and temporal patterns of CH4 and N2O fluxes in terrestrial ecosystems of North America during 1979–2008: application of a global biogeochemistry model

Directory of Open Access Journals (Sweden)

C. Lu

2010-09-01

Full Text Available Continental-scale estimations of terrestrial methane (CH4 and nitrous oxide (N2O fluxes over a long time period are crucial to accurately assess the global balance of greenhouse gases and enhance our understanding and prediction of global climate change and terrestrial ecosystem feedbacks. Using a process-based global biogeochemical model, the Dynamic Land Ecosystem Model (DLEM, we quantified simultaneously CH4 and N2O fluxes in North America's terrestrial ecosystems from 1979 to 2008. During the past 30 years, approximately 14.69 ± 1.64 T g C a−1 (1 T g = 1012 g of CH4, and 1.94 ± 0.1 T g N a−1 of N2O were released from terrestrial ecosystems in North America. At the country level, both the US and Canada acted as CH4 sources to the atmosphere, but Mexico mainly oxidized and consumed CH4 from the atmosphere. Wetlands in North America contributed predominantly to the regional CH4 source, while all other ecosystems acted as sinks for atmospheric CH4, of which forests accounted for 36.8%. Regarding N2O emission in North America, the US, Canada, and Mexico contributed 56.19%, 18.23%, and 25.58%, respectively, to the continental source over the past 30 years. Forests and croplands were the two ecosystems that contributed most to continental N2O emission. The inter-annual variations of CH4 and N2O fluxes in North America were mainly attributed to year-to-year climatic variability. While only annual precipitation was found to have a significant effect on annual CH4 flux, both mean annual temperature and annual precipitation were significantly correlated to annual N2O flux. The regional estimates and spatiotemporal patterns of terrestrial ecosystem CH4 and N2O fluxes in North America generated in this study provide useful information for global change research and policy making.

Soil fluxes of methane, nitrous oxide, and nitric oxide from aggrading forests in coastal Oregon

Science.gov (United States)

Erickson, Heather E.; Perakis, Steven S.

2014-01-01

Soil exchanges of greenhouse and other gases are poorly known for Pacific Northwest forests where gradients in nutrient availability and soil moisture may contribute to large variations in fluxes. Here we report fluxes of methane (CH4), nitrous oxide (N2O), and nitric oxide (NO) over multiple seasons from three naturally N-rich, aggrading forests of coastal Oregon, USA. Mean methane uptake rates (3.2 mg CH4 m−2 d−1) were high compared with forests globally, negatively related to water-filled pore space (WFPS), but unrelated to N availability or temperature. Emissions of NO (6.0 μg NO–N m−2 h−1) exceeded N2O (1.4 μg N2O–N m−2 h−1), except when WFPS surpassed 55%. Spatial variation in NO fluxes correlated positively with soil nitrate concentrations (which generally exceeded ammonium concentrations, indicating the overall high N status for the sites) and negatively with soil pH, and at one site increased with basal area of N2-fixing red alder. Combined NO and N2O emissions were greatest from the site with highest annual net N mineralization and lowest needle litterfall C/N. Our findings of high CH4 uptake and NO/N2O ratios generally >1 most likely reflect the high porosity of the andic soils underlying the widespread regenerating forests in this seasonally wet region.

Investigating the emission, dissolution, and oxidation of CH4 within and around a seep bubble plume in the Gulf of Mexico.

Science.gov (United States)

Leonte, M.; Kessler, J. D.; Socolofsky, S. A.

2016-02-01

One of the largest carbon reservoirs on the planet is stored as methane (CH4) in and below the seafloor. However, a large discrepancy exists between estimated fluxes of CH4 into the water column and CH4 fluxes from the sea surface to the atmosphere, suggesting that a significant fraction of CH4 released from seafloor seeps is dissolved and potentially removed through microbial oxidation. Here we present data investigating the fate of CH4 released from the Sleeping Dragon seep site in the Gulf of Mexico. The bubble plume was followed from the seafloor until it fully dissolved using a remotely operated vehicle (ROV). Water samples were collected by the ROV at different depths as well as lateral transects through the bubble plume. These samples were analyzed for dissolved concentrations of methane, ethane, propane, and butane as well as the 13C isotopic ratio of methane. Furthermore, seep bubbles from the seafloor were also collected and analyzed for the same properties. Based on these chemical data, the rate of CH4 emission from the seafloor, oxidation in the water column, and dissolution are investigated.

Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK

Directory of Open Access Journals (Sweden)

C. Helfter

2016-08-01

Full Text Available We report on more than 3 years of measurements of fluxes of methane (CH4, carbon monoxide (CO and carbon dioxide (CO2 taken by eddy-covariance in central London, UK. Mean annual emissions of CO2 in the period 2012–2014 (39.1 ± 2.4 ktons km−2 yr−1 and CO (89 ± 16 tons km−2 yr−1 were consistent (within 1 and 5 % respectively with values from the London Atmospheric Emissions Inventory, but measured CH4 emissions (72 ± 3 tons km−2 yr−1 were over two-fold larger than the inventory value. Seasonal variability was large for CO with a winter to summer reduction of 69 %, and monthly fluxes were strongly anti-correlated with mean air temperature. The winter increment in CO emissions was attributed mainly to vehicle cold starts and reduced fuel combustion efficiency. CO2 fluxes were 33 % higher in winter than in summer and anti-correlated with mean air temperature, albeit to a lesser extent than for CO. This was attributed to an increased demand for natural gas for heating during the winter. CH4 fluxes exhibited moderate seasonality (21 % larger in winter, and a spatially variable linear anti-correlation with air temperature. Differences in resident population within the flux footprint explained up to 90 % of the spatial variability of the annual CO2 fluxes and up to 99 % for CH4. Furthermore, we suggest that biogenic sources of CH4, such as wastewater, which is unaccounted for by the atmospheric emissions inventories, make a substantial contribution to the overall budget and that commuting dynamics in and out of central business districts could explain some of the spatial and temporal variability of CO2 and CH4 emissions. To our knowledge, this study is unique given the length of the data sets presented, especially for CO and CH4 fluxes. This study offers an independent assessment of "bottom-up" emissions inventories and demonstrates that the urban sources of CO and CO2 are well characterized in

Effects of elevated atmospheric CO2, prolonged summer drought and temperature increase on N2O and CH4 fluxes in a temperate heathland

DEFF Research Database (Denmark)

Carter, Mette Sustmann; Ambus, Per; Albert, Kristian Rost

2011-01-01

In temperate regions, climate change is predicted to increase annual mean temperature and intensify the duration and frequency of summer droughts, which together with elevated atmospheric carbon dioxide (CO2) concentrations, may affect the exchange of nitrous oxide (N2O) and methane (CH4) between...... terrestrial ecosystems and the atmosphere. We report results from the CLIMAITE experiment, where the effects of these three climate change parameters were investigated solely and in all combinations in a temperate heathland. Field measurements of N2O and CH4 fluxes took place 1–2 years after the climate...... change manipulations were initiated. The soil was generally a net sink for atmospheric CH4. Elevated temperature (T) increased the CH4 uptake by on average 10 μg C m−2 h−1, corresponding to a rise in the uptake rate of about 20%. However, during winter elevated CO2 (CO2) reduced the CH4 uptake, which...

The Extent of CH4 Emission and Oxidation in Thermogenic and Biogenic Gas Hydrate Environments

Science.gov (United States)

Kastner, M.; Solem, C.; Bartlett, D.; MacDonald, I.; Valentine, D.

2003-12-01

The role of methane hydrate in the global methane budget is poorly understood, because relatively little is known about the transport of gaseous and dissolved methane through the seafloor into the ocean, from the water column into the atmosphere, and the extent of water-column methanotrophy that occurs en route. We characterize the transport and consumption of methane in three distinct gas hydrate environments, spanning the spectrum of thermogenic and biogenic methane occurrences: Bush Hill in the Gulf of Mexico, Eel River off the coast of Northern California, and the Noth and South Hydrate Ridges on the Cascadia Oregon margin. At all the sites studied a significant enrichment in δ 13CH4 with distance along isopycnals away from the methane source is observed, indicative of extensive aerobic bacterial methane oxidation in the water column. The effects of this process are principally pronounced in the mostly biogenic methane setting, with δ 13C-CH4 measured as high as -12 permil (PDB) between North and South Hydrate Ridge. The δ 13C-CH4 values ranged from -12 to -67 permil at Hydrate Ridge, -34 to -52 permil at Eel River, and -41 to -49 permil at Bush Hill. The large variation in methane carbon isotope ranges between the sites suggest that major differences exist in both the rates of aerobic methane oxidation and system openness at the studied locations. A mean kinetic isotope fractionation factor is being determined using a closed-system Rayleigh distillation model. An approximate regional methane flux from the ocean into the atmosphere is being estimated for the Gulf of Mexico, by extrapolation of the flux value from the Bush Hill methane plume over 390 plume locations having persistent oil slicks on the ocean surface, mapped by time series satellite data.

Methane fluxes and the functional groups of methanotrophs and methanogens in a young Arctic landscape on Disko Island, West Greenland

DEFF Research Database (Denmark)

Christiansen, Jesper Riis; Barrera Romero, Alejandro Jose; Jørgensen, Niels O. G.

2015-01-01

and activity indicates that the age of an Arctic landscape is not important for the CH4 consumption but can be very important for CH4 production. Considering the prevalence of dry landscapes and contrasting ages of high Arctic soils, our results highlight that well-drained soils should not be overlooked......Arctic soils are known to be important methane (CH4) consumers and sources. This study integrates in situ fluxes of CH4 between upland and wetland soils with potential rates of CH4 oxidation and production as well as abundance and diversity of the methanotrophs and methanogens measured...... as an important component of Arctic net CH4 budget....

Methane fluxes along a salinity gradient on a restored salt marsh, Harpswell, ME

Science.gov (United States)

Gunn, Cailene; Johnson, Beverly, ,, Dr.; Dostie, Phil; Bohlen, Curtis; Craig, Matthew

2016-04-01

This study functions as a pilot project to understand the relationship between salinity and methane emissions on a recently restored salt marsh in Casco Bay, Maine. Salt marshes are dynamic and highly productive ecosystems that provide a multitude of ecosystem services including nutrient filtration, storm-water buffering and carbon sequestration. These ecosystems are highly susceptible to anthropogenic alteration. The emplacement of causeways and narrow culverts, restricts tidal flow and leads to loss of healthy salinity gradients. Consequently, numerous salt marshes have experienced increases in freshwater vegetation growth as a result of coastal population expansion. Recent restoration efforts on Long Marsh, Harpswell, ME replaced a severely undersized culvert with a larger one in February, 2014. The salinity gradient has since been restored along much of the marsh, and freshwater vegetation that encroached on the marsh platform has died back. Vegetation and salinity are key indicators and drivers of CH4 emissions on salt marshes. Using static gas chambers, we quantified CH4 fluxes along two transects at five diverse sites ranging from healthy marsh (salinity of 27 to 31 psu) with Spartina vegetation, to regions invaded by Typha and other freshwater vegetation (salinity of 0 to 4 psu). Sampling was executed in the months of July, August and October. CH4 concentrations were determined using a gas chromatograph with a flame-ionization detector. Preliminary findings suggest reintroduction of healthy tidal flows into the marsh inhibits CH4 production, where the lowest fluxes with least variability were observed at the most saline sites with Spartina vegetation. The largest range of CH4 fluxes exhibited emissions from 0.75 μmol CH4/m2/hr to 518.4 μmol CH4/m2/hr at the Typha dominated sites from July to October. Fluxes at the saltwater and brackish regions were far less variable with ranges from 0.94 μmol CH4/m2/hr to 8.2 μmol CH4/m2/hr and 2.6 to 9.5 μmol CH4/m2

Annual variation of CH4 emissions from the middle taiga in West Siberian Lowland (2005–2009: a case of high CH4 flux and precipitation rate in the summer of 2007

Directory of Open Access Journals (Sweden)

M. Sasakawa

2012-03-01

Full Text Available We described continuous measurements of CH4 and CO2 concentration obtained at two sites placed in the middle taiga, Karasevoe (KRS and Demyanskoe (DEM, in West Siberian Lowland (WSL from 2005 to 2009. Although both CH4 and CO2 accumulation (ΔCH4 and ▵CO2 during night-time at KRS in June and July 2007 showed an anomalously high concentration, higher ratios of ΔCH4/ΔCO2 compared with those in other years indicated that a considerably higher CH4 flux occurred relative to the CO2 flux. The daily CH4 flux calculated with the ratio of ΔCH4/ΔCO2 and terrestrial biosphere CO2 flux from an ecosystem model showed a maximum in July at the both sites. Although anomalously high flux was observed in June and July 2007 at KRS, only a small flux variation was observed at DEM. The high regional CH4 flux in June and July 2007 at KRS was reproduced using a process-based ecosystem model, Vegetation Integrative Simulator for Trace gases (VISIT, in response to high water table depth caused by the anomalously high precipitation during the summer of 2007.

(CH4)-C-14 Measurements in Greenland Ice: Investigating Last Glacial Termination CH4 Sources

DEFF Research Database (Denmark)

Petrenko, V. V.; Smith, A. M.; Brook, E. J.

2009-01-01

by direct cosmogenic C-14 production in ice. C-14 of CO was measured to better understand this process and correct the sample (CH4)-C-14. Corrected results suggest that wetland sources were likely responsible for the majority of the Younger Dryas-Preboreal CH4 rise.......The cause of a large increase of atmospheric methane concentration during the Younger Dryas-Preboreal abrupt climatic transition (similar to 11,600 years ago) has been the subject of much debate. The carbon-14 (C-14) content of methane ((CH4)-C-14) should distinguish between wetland and clathrate...... contributions to this increase. We present measurements of (CH4)-C-14 in glacial ice, targeting this transition, performed by using ice samples obtained from an ablation site in west Greenland. Measured (CH4)-C-14 values were higher than predicted under any scenario. Sample (CH4)-C-14 appears to be elevated...

Summary of LOX/CH4 Thruster Technology Development at NASA/MSFC

Science.gov (United States)

Greene, Sandra Elam

2015-01-01

In recent years, a variety of injectors for liquid oxygen (LOX) and methane (CH4) propellant systems have been designed, fabricated, and demonstrated with hot-fire testing at Marshall Space Flight Center (MSFC). Successful designs for liquid methane (LCH4) and gaseous methane (GCH4) have been developed. A variety of chambers, including a transpiration cooled design, along with uncooled ablatives and refractory metals, have also been hot-fire tested by MSFC for use with LOX/LCH4 injectors. Hot-fire testing has also demonstrated multiple ignition source options. Heat flux data for selected injectors has been gathered by testing with a calorimeter chamber. High performance and stable combustion have been demonstrated, along with designs for thrust levels ranging from 500 to 7,000 lbf. The newest LOX/CH4 injector and chamber developed by MSFC have been fabricated with additive manufacturing techniques and include unique design features to investigate regenerative cooling with methane. This low cost and versatile hardware offers a design for 4,000 lbf thrust and will be hot-fire tested at MSFC in 2015. Its design and operation can easily be scaled for use in systems with thrust levels up to 25,000 lbf.

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

Science.gov (United States)

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

The Effect of Different Organic Manures Treatments on Methane Emission from Single-cropping Paddy Fields%不同种类有机肥施用对一季稻田CH4排放的影响

Institute of Scientific and Technical Information of China (English)

吴家梅; 纪雄辉; 彭华; 霍莲杰; 刘勇; 朱坚

2011-01-01

Methane emission fluxes from single-cropping paddy fields with application different fertilization treatments were studied by using the static chamber-gas chromatograph techniques with manual method. Results showed that the treatments with application fertilizer increased methane emission compared with no fertilizer treatments (NF). Seasonal average methane emission flux of the incorporation of rice straw and mineral fertilizer( RS) was 31.04 mg·m-2·h-1 which increased by 326.4%( P<0.05) and 211.7% compared with that of the mineral fertilized MF) and incorporation of pig manure and mineral fertilizer( PM), respectively. Seasonal average methane emission flux from the incorporation of chicken manure and the mineral fertilizer( CM) increased by 140.4%( P<0.05) and 75.7%(P<0.05) as compared with MF and PM, respectively. The results indicated there was the obvious influence for RS and CM to methane emission. However, there was no significant difference between NF and PM. According to the analysis of related environmental factors, there was significant correlation between methane emission fluxes and the soil temperature at S cm depth, and the same as the soil Eh. No significant correlation was found between CH4 flux and water depth. The unit yield of Global warming Potential (GWP) in PM treatment was 0.83 kg·kg-1 which suggested PM was a better recommend fertilization during the rice growth. The application of PM took the slight advantages not only in reducing the GWP but also in improving the grain yield.%选取不同施肥处理的一季中稻田为研究对象,采用静态箱-气相色谱法对一季稻CH4排放通量进行手动观测.结果表明,与不施肥相比,各施肥处理CH4平均排放通量均有不同程度增加.其中稻草还田+化肥处理(稻草处理)CH4平均排放通量为31.04mg· m-2· h-1,比化肥处理和猪粪+化肥处理(猪粪处理)分别增加326.4％( P＜0.05)和211.7％(P＜0.05),�

The variation of methane flux rates from boreal tree species at the beginning of the growing season

Science.gov (United States)

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

Fluxes of greenhouse gases CH{sub 4}, CO{sub 2} and N{sub 2}O on some peat mining areas in Finland

Energy Technology Data Exchange (ETDEWEB)

Nykaenen, H; Martikainen, P J [National Public Health Inst., Kuopio (Finland). Dept. of Biology; Silvola, J; Alm, J [Joensuu Univ. (Finland). Dept. of Biology

1997-12-31

The increase in concentration of greenhouse gases (CO{sub 2}, CH{sub 4} and N{sub 2}O) in atmosphere is associated with burning of fossil fuels and also changes in biogeochemistry due to land use activities. Virgin peatlands are globally important stores of carbon and sources of CH4. Peatland drainage changes the processes in carbon and nitrogen cycles responsible for the fluxes of CO{sub 2}, CH{sub 4} and N{sub 2}O. Preparing of peatlands for peat mining greatly change their biogeochemical processes. Effective drainage decreases water table and allows air to penetrate deep into peat profile. Aerobic conditions inhibit activities of anaerobic microbes, including the methanogens, whereas aerobic processes like methane oxidation are stimulated. Destruction of vegetation cover stops the carbon input to peat. In Finland the actual peat mining area is 0.05 x 106 hectares and further 0.03 x 106 hectares have been prepared or are under preparation for peat mining. The current total peatland area in the world used for mining is 0.94 x 106 ha and the area already mined is 1.15 x 106 ha. In this presentation fluxes of greenhouse gases (CH{sub 4}, CO{sub 2} and N{sub 2}O) on some mires under peat mining are reported and compared with those on natural mires and with the emissions from peat combustion. (15 refs.)

Fluxes of greenhouse gases CH{sub 4}, CO{sub 2} and N{sub 2}O on some peat mining areas in Finland

Energy Technology Data Exchange (ETDEWEB)

Nykaenen, H.; Martikainen, P.J. [National Public Health Inst., Kuopio (Finland). Dept. of Biology; Silvola, J.; Alm, J. [Joensuu Univ. (Finland). Dept. of Biology

1996-12-31

The increase in concentration of greenhouse gases (CO{sub 2}, CH{sub 4} and N{sub 2}O) in atmosphere is associated with burning of fossil fuels and also changes in biogeochemistry due to land use activities. Virgin peatlands are globally important stores of carbon and sources of CH4. Peatland drainage changes the processes in carbon and nitrogen cycles responsible for the fluxes of CO{sub 2}, CH{sub 4} and N{sub 2}O. Preparing of peatlands for peat mining greatly change their biogeochemical processes. Effective drainage decreases water table and allows air to penetrate deep into peat profile. Aerobic conditions inhibit activities of anaerobic microbes, including the methanogens, whereas aerobic processes like methane oxidation are stimulated. Destruction of vegetation cover stops the carbon input to peat. In Finland the actual peat mining area is 0.05 x 106 hectares and further 0.03 x 106 hectares have been prepared or are under preparation for peat mining. The current total peatland area in the world used for mining is 0.94 x 106 ha and the area already mined is 1.15 x 106 ha. In this presentation fluxes of greenhouse gases (CH{sub 4}, CO{sub 2} and N{sub 2}O) on some mires under peat mining are reported and compared with those on natural mires and with the emissions from peat combustion. (15 refs.)

Seasonal variations in methane fluxes in response to summer warming and leaf litter addition in a subarctic heath ecosystem

Science.gov (United States)

Pedersen, Emily Pickering; Elberling, Bo; Michelsen, Anders

2017-08-01

Methane (CH4) is a powerful greenhouse gas controlled by both biotic and abiotic processes. Few studies have investigated CH4 fluxes in subarctic heath ecosystems, and climate change-induced shifts in CH4 flux and the overall carbon budget are therefore largely unknown. Hence, there is an urgent need for long-term in situ experiments allowing for the study of ecosystem processes over time scales relevant to environmental change. Here we present in situ CH4 and CO2 flux measurements from a wet heath ecosystem in northern Sweden subjected to 16 years of manipulations, including summer warming with open-top chambers, birch leaf litter addition, and the combination thereof. Throughout the snow-free season, the ecosystem was a net sink of CH4 and CO2 (CH4 -0.27 mg C m-2 d-1; net ecosystem exchange -1827 mg C m-2 d-1), with highest CH4 uptake rates (-0.70 mg C m-2 d-1) during fall. Warming enhanced net CO2 flux, while net CH4 flux was governed by soil moisture. Litter addition and the combination with warming significantly increased CH4 uptake rates, explained by a pronounced soil drying effect of up to 32% relative to ambient conditions. Both warming and litter addition also increased the seasonal average concentration of dissolved organic carbon in the soil. The site was a carbon sink with a net uptake of 60 g C m-2 over the snow-free season. However, warming reduced net carbon uptake by 77%, suggesting that this ecosystem type might shift from snow-free season sink to source with increasing summer temperatures.

Four-year measurement of methane flux over a temperate forest with a relaxed eddy accumulation method

Science.gov (United States)

Sakabe, A.; Kosugi, Y.; Ueyama, M.; Hamotani, K.; Takahashi, K.; Iwata, H.; Itoh, M.

2013-12-01

Forests are generally assumed to be an atmospheric methane (CH4) sink (Le Mer and Roger, 2001). However, under Asian monsoon climate, forests are subject to wide spatiotemporal range in soil water status, where forest soils often became water-saturated condition heterogeneously. In such warm and humid conditions, forests may act as a CH4 source and/or sink with considerable spatiotemporal variations. Micrometeorological methods such as eddy covariance (EC) method continuously measure spatially-representative flux at a canopy scale without artificial disturbance. In this study, we measured CH4 fluxes over a temperate forest during four-year period using a CH4 analyzer based on tunable diode laser spectroscopy detection with a relaxed eddy accumulation (REA) method (Hamotani et al., 1996, 2001). We revealed the amplitude and seasonal variations of canopy-scale CH4 fluxes. The REA method is the attractive alternative to the EC method to measure trace-gas flux because it allows the use of analyzers with an optimal integration time. We also conducted continuous chamber measurements on forest floor to reveal spatial variations in soil CH4 fluxes and its controlling processes. The observations were made in an evergreen coniferous forest in central Japan. The site has a warm temperate monsoon climate with wet summer. Some wetlands were located in riparian zones along streams within the flux footprint area. For the REA method, the sonic anemometer (SAT-550, Kaijo) was mounted on top of the 29-m-tall tower and air was sampled from just below the sonic anemometer to reservoirs according to the direction of vertical wind velocity (w). After accumulating air for 30 minutes, the air in the reservoirs was pulled into a CO2/H2O gas analyzer (LI-840, Li-Cor) and a CH4 analyzer (FMA-200, Los Gatos Research). Before entering the analyzers, the sampled air was dried using a gas dryer (PD-50 T-48; Perma Pure Inc.). The REA flux is obtained from the difference in the mean concentrations

Thermodynamic calculations in the system CH4-H2O and methane hydrate phase equilibria

Science.gov (United States)

Circone, S.; Kirby, S.H.; Stern, L.A.

2006-01-01

Using the Gibbs function of reaction, equilibrium pressure, temperature conditions for the formation of methane clathrate hydrate have been calculated from the thermodynamic properties of phases in the system CH4-H 2O. The thermodynamic model accurately reproduces the published phase-equilibria data to within ??2 K of the observed equilibrium boundaries in the range 0.08-117 MPa and 190-307 K. The model also provides an estimate of the third-law entropy of methane hydrate at 273.15 K, 0.1 MPa of 56.2 J mol-1 K-1 for 1/n CH4??H 2O, where n is the hydrate number. Agreement between the calculated and published phase-equilibria data is optimized when the hydrate composition is fixed and independent of the pressure and temperature for the conditions modeled. ?? 2006 American Chemical Society.

Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO2 levels: The added value of the isotope (δ13C and δ18O CO2; δ13C and δD CH4) approach

International Nuclear Information System (INIS)

Widory, D.; Proust, E.; Bellenfant, G.; Bour, O.

2012-01-01

Highlights: ► Comparison of the isotope and mass balance approaches to evaluate the level of methane oxidation within a landfill. ► The level of methane oxidation is not homogenous under the landfill cover and is strongly correlated to the methane flux. ► Isotope tracking of the contribution of the methane oxidation to the CO 2 concentrations in the ambient air. - Abstract: We are presenting here a multi-isotope approach (δ 13 C and δ 18 O of CO 2 ; δ 13 C and δD of CH 4 ) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through a landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO 2 levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH 4 oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH 4 is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH 4 oxidation by the methanotrophic bacteria. δ 13 C of CO 2 samples taken at different heights (from below the cover up to 8 m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.

CO2 and CH4 fluxes in a Spartina salt marsh and brackish Phragmites marsh in Massachusetts

Science.gov (United States)

Tang, J.; Wang, F.; Kroeger, K. D.; Gonneea, M. E.

2017-12-01

Coastal salt marshes play an important role in global and regional carbon cycling. Tidally restricted marshes reduce salinity and provide a habitat suitable for Phragmites invasion. We measured greenhouse gas (GHG) emissions (CO2 and CH4) continuously with the eddy covariance method and biweekly with the static chamber method in a Spartina salt marsh and a Phragmites marsh on Cape Cod, Massachusetts, USA. We did not find significant difference in CO2 fluxes between the two sites, but the CH4 fluxes were much higher in the Phragmites site than the Spartina marsh. Temporally, tidal cycles influence the CO2 and CH4 fluxes in both sites. We found that the salt marsh was a significant carbon sink when CO2 and CH4 fluxes were combined. Restoring tidally restricted marshes will significantly reduce CH4 emissions and provide a strong ecosystem carbon service.

CO2 Reforming of CH4 by Atmospheric Pressure Abnormal Glow Plasma

International Nuclear Information System (INIS)

Chen Qi; Dai Wei; Tao Xumei; Yu Hui; Dai Xiaoyan; Yin Yongxiang

2006-01-01

A novel plasma atmospheric pressure abnormal glow discharge was used to investigate synthesis gas production from reforming methane and carbon dioxide. Special attentions were paid to the discharge characteristics and CH 4 , CO 2 conversion, H 2 , CO selectivity, and ratio of H 2 /CO varied with the changing of discharging power, the total flux, and the ratio of CH 4 /CO 2 . Experiments were performed in wider operation variables, the discharging power of 240 to 600 W, the CH 4 /CO 2 of 0.2 to 1.0 and the total flux of 140 to 500 mL/min. The experiments showed that the conversion of CH 4 and CO 2 was up to 91.9% and 83.2%, the selectivity of CO and H 2 was also up to 80% and 90% and H 2 /CO mole ratio was 0.2 to 1.2, respectively. A brief analysis for discharge characteristics and the experimental results were given

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Directory of Open Access Journals (Sweden)

S. Hartery

2018-01-01

Full Text Available 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.

Estimating regional-scale methane flux and budgets using CARVE aircraft measurements over Alaska

Science.gov (United States)

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.

Temporal and spatial variations of soil carbon dioxide, methane, and nitrous oxide fluxes in a Southeast Asian tropical rainforest

Science.gov (United States)

Itoh, M.; Kosugi, Y.; Takanashi, S.; Hayashi, Y.; Kanemitsu, S.; Osaka, K.; Tani, M.; Nik, A. R.

2010-09-01

To clarify the factors controlling temporal and spatial variations of soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes, we investigated these gas fluxes and environmental factors in a tropical rainforest in Peninsular Malaysia. Temporal variation of CO2 flux in a 2-ha plot was positively related to soil water condition and rainfall history. Spatially, CO2 flux was negatively related to soil water condition. When CO2 flux hotspots were included, no other environmental factors such as soil C or N concentrations showed any significant correlation. Although the larger area sampled in the present study complicates explanations of spatial variation of CO2 flux, our results support a previously reported bipolar relationship between the temporal and spatial patterns of CO2 flux and soil water condition observed at the study site in a smaller study plot. Flux of CH4 was usually negative with little variation, resulting in the soil at our study site functioning as a CH4 sink. Both temporal and spatial variations of CH4 flux were positively related to the soil water condition. Soil N concentration was also related to the spatial distribution of CH4 flux. Some hotspots were observed, probably due to CH4 production by termites, and these hotspots obscured the relationship between both temporal and spatial variations of CH4 flux and environmental factors. Temporal variation of N2O flux and soil N2O concentration was large and significantly related to the soil water condition, or in a strict sense, to rainfall history. Thus, the rainfall pattern controlled wet season N2O production in soil and its soil surface flux. Spatially, large N2O emissions were detected in wet periods at wetter and anaerobic locations, and were thus determined by soil physical properties. Our results showed that, even in Southeast Asian rainforests where distinct dry and wet seasons do not exist, variation in the soil water condition related to rainfall history controlled the

Variability in concentrations and fluxes of methane in the Indian estuaries

Digital Repository Service at National Institute of Oceanography (India)

Rao, G.D.; Sarma, V.V.S.S.

and aerobic conditions in the sediments and water column (Abril and Iversen 2002; Valentine, 2011). In total marine CH4 emission to atmosphere, estuaries, coastal areas and continental shelves account a large fraction (75%) (Bange et al., 1994; Middelburg... and lagoons of Ivory Coast (West Africa). Biogeochemistry 100, 21-37 Krithika, K., R. Purvaja, and R. Ramesh. 2008. Fluxes of methane and nitrous oxide from an Indian mangrove. Current Science 94: 218-224. Mau, S., D.L.Valentine, J.F.Clark, J.Reed, R...

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

Science.gov (United States)

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

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

Directory of Open Access Journals (Sweden)

Y. A. Teh

2017-08-01

Full Text Available 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

Application of Relaxed Eddy Accumulation (REA) method to estimate CO2 and CH4 surface fluxes in the city of Krakow, southern Poland.

Science.gov (United States)

Zimnoch, Miroslaw; Gorczyca, Zbigniew; Pieniazek, Katarzyna; Jasek, Alina; Chmura, Lukasz; Rozanski, Kazimierz

2013-04-01

There is a growing interest in the recent years in studies aimed at quantifying carbon cycling in urban centres. Worldwide migration of human population from rural to urban areas and corresponding growth of extensive urban agglomerations and megacities leads to intensification of anthropogenic emissions of carbon and strong disruption of natural carbon cycle on these areas. Therefore, a deeper understanding of the carbon "metabolism" of such regions is required. Apart of better quantification of surface carbon fluxes, also a thorough understanding of the functioning of biosphere under strong anthropogenic influence is needed. Nowadays, covariance methods are widely applied for studying gas exchange between the atmosphere and the Earth's surface. Relaxed Eddy Accumulation method (REA), combined with the CO2 and CH4 CRDS analyser allows simultaneous measurements of surface fluxes of carbon dioxide and methane within the chosen footprint of the detection system, thus making possible thorough characterisation of the overall exchange of those gases between the atmosphere and the urban surface across diverse spatial and temporal scales. Here we present preliminary results of the study aimed at quantifying surface fluxes of CO2 and CH4 in Krakow, southern Poland. The REA system for CO2 and CH4 flux measurements has been installed on top of a 20m high tower mounted on the roof of the faculty building, close to the city centre of Krakow. The sensors were installed ca 42 m above the local ground. Gill Windmaster-Pro sonic anemometer was coupled with self-made system, designed by the Poznan University of Life Sciences, Poland, for collecting air samples in two pairs of 10-liter Tedlar bags, and with Picarro G2101-i CRDS analyser. The air was collected in 30-min intervals. The CO2 and CH4 mixing ratios in these cumulative downdraft and updraft air samples were determined by the CRDS analyser after each sampling interval. Based on the measured mixing ratios difference and the

CO2 and CH4 fluxes from oil palm plantations in Sumatra, Indonesia: effects of palm age and environmental conditions

Science.gov (United States)

Meijide, A.; Hassler, E.; Corre, M. D.; June, T.; Sabajo, C.; Veldkamp, E.; Knohl, A.

2015-12-01

Global increasing demand of palm oil is leading to the expansion of oil palm plantations, particularly in SE Asia, which in Sumatran lowlands has resulted in a 21% forest area loss. Large photosynthesis rates are expected for oil palms, due to their high growth and yield production. However, there is very limited information on their effect on carbon dioxide (CO2) fluxes and their sink or source strength at ecosystem scale. For methane (CH4) fluxes, research has mainly focused in oil palm plantations located on peatlands, but no information is available at ecosystem level from plantations on mineral soils. With the aim of studying CO2 fluxes during the non-productive and productive phases of oil palm cultivation, an eddy covariance (EC) tower was installed in a 2 year old oil palm plantation, where it was measuring for 8 months, and was subsequently moved to a 12 year old plantation, both in the province of Jambi, Sumatra. The EC system consisted of a Licor 7500A and an ultrasonic Metek anemometer, operating at 10 Hz, installed on a 7m and 22m tower respectively. In the 12 year old plantation, the tower was also equipped with a Los Gatos FGGA-24EP, to assess CH4 fluxes. Chamber measurements were also carried out to obtain information on respiration and CH4 fluxes from the soil. Radiation was the major driver controlling net carbon uptake, while soil moisture did not play a significant role. Average net ecosystem exchange in the hours of the day with higher radiation for the whole measurement period was 10 μmol m-2 s-1 for the 2 year old plantation and -22 μmol m-2 s-1 in the 12 year old. The analysis of the cumulative fluxes show that the non-productive plantation was a carbon source of around 636 g CO2 m-2 during the 8 months of measurements, while in the productive period, it acted as a strong carbon sink (-794 g CO2 m-2 yr-1). Methane uptake was observed in the soil in both plantations and also for the whole ecosystem in the 12 year old one, but its

Estimation of Atmospheric Methane Surface Fluxes Using a Global 3-D Chemical Transport Model

Science.gov (United States)

Chen, Y.; Prinn, R.

2003-12-01

Accurate determination of atmospheric methane surface fluxes is an important and challenging problem in global biogeochemical cycles. We use inverse modeling to estimate annual, seasonal, and interannual CH4 fluxes between 1996 and 2001. The fluxes include 7 time-varying seasonal (3 wetland, rice, and 3 biomass burning) and 3 steady aseasonal (animals/waste, coal, and gas) global processes. To simulate atmospheric methane, we use the 3-D chemical transport model MATCH driven by NCEP reanalyzed observed winds at a resolution of T42 ( ˜2.8° x 2.8° ) in the horizontal and 28 levels (1000 - 3 mb) in the vertical. By combining existing datasets of individual processes, we construct a reference emissions field that represents our prior guess of the total CH4 surface flux. For the methane sink, we use a prescribed, annually-repeating OH field scaled to fit methyl chloroform observations. MATCH is used to produce both the reference run from the reference emissions, and the time-dependent sensitivities that relate individual emission processes to observations. The observational data include CH4 time-series from ˜15 high-frequency (in-situ) and ˜50 low-frequency (flask) observing sites. Most of the high-frequency data, at a time resolution of 40-60 minutes, have not previously been used in global scale inversions. In the inversion, the high-frequency data generally have greater weight than the weekly flask data because they better define the observational monthly means. The Kalman Filter is used as the optimal inversion technique to solve for emissions between 1996-2001. At each step in the inversion, new monthly observations are utilized and new emissions estimates are produced. The optimized emissions represent deviations from the reference emissions that lead to a better fit to the observations. The seasonal processes are optimized for each month, and contain the methane seasonality and interannual variability. The aseasonal processes, which are less variable, are

Optical sensor system for time-resolved quantification of methane densities in CH4-fueled spark ignition engines.

Science.gov (United States)

Golibrzuch, Kai; Digulla, Finn-Erik; Bauke, Stephan; Wackerbarth, Hainer; Thiele, Olaf; Berg, Thomas

2017-08-01

We present the development and the first application of an optical sensor system that allows single-cycle determination of methane (CH 4 ) concentration inside internal combustion (IC) engines. We use non-dispersive infrared absorption spectroscopy to detect the CH 4 density with a time resolution up to 33 μs at acquisition rates of 30 kHz. The measurement scheme takes advantage of the strong temperature dependence of the absorption band applying two detection channels for CH 4 that detect different spectral regions of the ν 3 anti-symmetric C-H-stretch absorption. The strategy allows the simultaneous determination of fuel concentration as well as gas temperature. We show the proof-of-concept by validation of the measurement strategy in static pressure cell experiments as well as its application to a methane-fueled IC engine using a modified spark plug probe. Our results clearly demonstrate that it is crucial to determine the CH 4 temperature in the probe volume. Due to thermal influences of the sensor probe, the temperature needed to calculate the desired quantities (fuel density, fuel concentration) significantly differs from the gas phase temperature in the rest of the combustion chamber and estimations from standard thermodynamic models, e.g., polytropic compression, will fail.

Fluxes of Methane and Carbon Dioxide from a Subarctic Lake

DEFF Research Database (Denmark)

Jammet, Mathilde Manon

) and carbon dioxide (CO2) with the atmosphere. Yet uncertainties in the magnitude and drivers of these fluxes remain, partly due to a lack of direct observations covering all seasons of the year, but also because of the diversity in measurement methods that often miss components of the transport processes......Ongoing climate warming is expected to affect the carbon functioning of subarctic ecosystems. Lakes and wetlands, which are common ecosystems of the high northern latitudes, are of utmost interest in this context because they exchange large amounts of the climate-forcing gases methane (CH4......-out and the release of CH4 and CO2 was established. These results underline the crucial importance of shoulder seasons in the annual carbon emissions from seasonally frozen lakes. Overall, the lake was an important annual source of carbon to the atmosphere, partially compensating the higher, annual sink function...

Nitrous oxide and methane fluxes in six different land use systems in the Peruvian Amazon

Science.gov (United States)

Palm, C. A.; Alegre, J. C.; Arevalo, L.; Mutuo, P. K.; Mosier, A. R.; Coe, R.

2002-12-01

The contribution of different land-use systems in the humid tropics to increasing atmospheric trace gases has focused on forests, pastures, and crops with few measurements from managed, tree-based systems that dominate much of the landscape. This study from the Peruvian Amazon includes monthly nitrous oxide and methane fluxes from two cropping systems, three tree-based systems, and a 23-year secondary forest control. Average N2O fluxes from the cropping systems were two to three times higher than the secondary forest control (9.1 μg N m-2 h-1), while those of the tree-based systems were similar to the secondary forest. Increased fluxes in the cropping systems were attributed to N fertilization, while fluxes from the tree-based systems were related to litterfall N. Average CH4 consumption was reduced by up to half that of the secondary forest (-30.0 μg C m-2 h-1) in the tree-based and low-input cropping systems. There was net CH4 production in the high-input cropping system. This switch to net production was a result of increased bulk density and increased soil respiration resulting in anaerobic conditions. Reduced rates of N2O emissions, similar CH4 consumption, and high C sequestration rates in these tree-based systems compared with mature forests, coupled with the large area of these systems in the humid tropics, may partially offset the past effects of deforestation on increased atmospheric trace gas concentrations. In contrast, cropping systems with higher N2O emissions, substantially reduced CH4 consumption or even net CH4 emissions, and little C sequestration exacerbate those effects.

Temporal variations in methane emissions from emergent aquatic macrophytes in two boreonemoral lakes.

Science.gov (United States)

Milberg, Per; Törnqvist, Lina; Westerberg, Lars M; Bastviken, David

2017-07-01

Methane (CH 4 ) emissions via emergent aquatic macrophytes can contribute substantially to the global CH 4 balance. We addressed temporal variability in CH 4 flux by using the static chamber approach to quantify fluxes from plots dominated by two species considered to differ in flux transport mechanisms ( Phragmites australis , Carex rostrata ). Temporal variability in daily mean emissions from early June to early October was substantial. The variable that best explained this variation was air temperature. Regular and consistent diel changes were absent and therefore less relevant to include when estimating or modelling CH 4 emissions. Methane emissions per m 2 from nearby plots were similar for Phragmites australis and Carex rostrata indicating that CH 4 production in the system influenced emissions more than the species identity. This study indicates that previously observed diel patterns and species-effects on emissions require further evaluation to support improved local and regional CH 4 flux assessments.

Fluxed of nitrous oxide and methane in a lake border ecosystem in northern Germany

Energy Technology Data Exchange (ETDEWEB)

Rusch, H.; Rembges, D.; Papke, H.; Rennenberg, H. [Fraunhofer Inst. for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany)

1995-12-31

Methane and nitrous oxide are radiatively active trace gases. This accounts for approximately 20 % of the total anticipated greenhouse effect. The atmospheric mixing ratio of both gases has increased significantly during the last decades at a rate of 0.25 % yr{sup -l} for N{sub 2}O and a rate of 1 % yr{sup -1} for CH{sub 4}. Whether this increase is caused by enhanced biogenic production of both gases or is due to decreased global sinks, has not been definitely elucidated. Soils are an important source of methane and nitrous oxide. Natural wetlands, e.g., have a similar global source strength of methane as rice paddies. On the other hand, well aerated grasslands have been shown to be a sink for atmospheric methane due to methane oxidation. Nitrous oxide is emitted by a wide range of soil types. Its rate of emission is strongly enhanced by nitrogen fertilization. In the present study, fluxes of methane and nitrous oxide were determined in a lake border ecosystem along a toposequence from reed to dry pasture. The aim of this study was to characterize the influence of soil type, land use and season on the flux rates of these greenhouse gases. (author)

Fluxed of nitrous oxide and methane in a lake border ecosystem in northern Germany

Energy Technology Data Exchange (ETDEWEB)

Rusch, H; Rembges, D; Papke, H; Rennenberg, H [Fraunhofer Inst. for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany)

1996-12-31

Methane and nitrous oxide are radiatively active trace gases. This accounts for approximately 20 % of the total anticipated greenhouse effect. The atmospheric mixing ratio of both gases has increased significantly during the last decades at a rate of 0.25 % yr{sup -l} for N{sub 2}O and a rate of 1 % yr{sup -1} for CH{sub 4}. Whether this increase is caused by enhanced biogenic production of both gases or is due to decreased global sinks, has not been definitely elucidated. Soils are an important source of methane and nitrous oxide. Natural wetlands, e.g., have a similar global source strength of methane as rice paddies. On the other hand, well aerated grasslands have been shown to be a sink for atmospheric methane due to methane oxidation. Nitrous oxide is emitted by a wide range of soil types. Its rate of emission is strongly enhanced by nitrogen fertilization. In the present study, fluxes of methane and nitrous oxide were determined in a lake border ecosystem along a toposequence from reed to dry pasture. The aim of this study was to characterize the influence of soil type, land use and season on the flux rates of these greenhouse gases. (author)

Identifying sources of methane sampled in the Arctic using δ13C in CH4 and Lagrangian particle dispersion modelling.

Science.gov (United States)

Cain, Michelle; France, James; Pyle, John; Warwick, Nicola; Fisher, Rebecca; Lowry, Dave; Allen, Grant; O'Shea, Sebastian; Illingworth, Samuel; Jones, Ben; Gallagher, Martin; Welpott, Axel; Muller, Jennifer; Bauguitte, Stephane; George, Charles; Hayman, Garry; Manning, Alistair; Myhre, Catherine Lund; Lanoisellé, Mathias; Nisbet, Euan

2016-04-01

An airmass of enhanced methane was sampled during a research flight at ~600 m to ~2000 m altitude between the North coast of Norway and Svalbard on 21 July 2012. The largest source of methane in the summertime Arctic is wetland emissions. Did this enhancement in methane come from wetland emissions? The airmass was identified through continuous methane measurements using a Los Gatos fast greenhouse gas analyser on board the UK's BAe-146 Atmospheric Research Aircraft (ARA) as part of the MAMM (Methane in the Arctic: Measurements and Modelling) campaign. A Lagrangian particle dispersion model (the UK Met Office's NAME model) was run backwards to identify potential methane source regions. This was combined with a methane emission inventory to create "pseudo observations" to compare with the aircraft observations. This modelling was used to constrain the δ13C CH4 wetland source signature (where δ13C CH4 is the ratio of 13C to 12C in methane), resulting in a most likely signature of -73‰ (±4‰7‰). The NAME back trajectories suggest a methane source region of north-western Russian wetlands, and -73‰ is consistent with in situ measurements of wetland methane at similar latitudes in Scandinavia. This analysis has allowed us to study emissions from remote regions for which we do not have in situ observations, giving us an extra tool in the determination of the isotopic source variation of global methane emissions.

Methane Provenance Determined by CH2D2 and 13CH3D Abundances

Science.gov (United States)

Kohl, I. E.; Giunta, T.; Warr, O.; Ash, J. L.; Ruffine, L.; Sherwood Lollar, B.; Young, E. D.

2017-12-01

Determining the provenance of naturally occurring methane gases is of major interest to energy companies and atmospheric climate modelers, among others. Bulk isotopic compositions and other geochemical tracers sometimes fail to provide definitive determinations of sources of methane due to complications from mixing and complicated chemical pathways of origin. Recent measurements of doubly-substituted isotopologues of methane, CH2D2 (UCLA) and 13CH3D (UCLA, CalTech, and MIT) have allowed for major improvements in sourcing natural methane gases. Early work has focused on formation temperatures obtained when the relative abundances of both doubly-substituted mass-18 species are consistent with internal equilibrium. When methane gases do not plot on the thermodynamic equilibrium curve in D12CH2D2 vs D13CH3D space, temperatures determined from D13CH3D values alone are usually spurious, even when appearing reasonable. We find that the equilibrium case is actually rare and almost exclusive to thermogenic gases produced at temperatures exceeding 100°C. All other relevant methane production processes appear to generate gases that are not in isotopologue-temperature equilibrium. When gases show departures from equilibrium as determined by the relationship between CH2D2 and 13CH3D abundances, data fall within empirically defined fields representing formation pathways. These fields are thus far consistent between different geological settings and and between lab experiments and natural samples. We have now defined fields for thermogenic gas production, microbial methanogenesis, low temperature abiotic (Sabatier) synthesis and higher temperature FTT synthesis. The majority of our natural methane data can be explained by mixing between end members originating within these production fields. Mixing can appear complex, resulting in both hyper-clumped and anti-clumped isotopologue abundances. In systems where mixtures dominate and end-members are difficult to sample, mixing models

Annual variation of CH{sub 4} emissions from the middle taiga in West Siberian Lowland (2005-2009): a case of high CH{sub 4} flux and precipitation rate in the summer of 2007

Energy Technology Data Exchange (ETDEWEB)

Sasakawa, M.; Ito, A.; Machida, T. (Center for Global Environmental Research, National Inst. for Environmental Studies, Tsukuba (Japan)), Email: sasakawa.motoki@nies.go.jp; Tsuda, N. (Global Environmental Forum, Bunkyo-ku Tokyo (Japan)); Niwa, Y. (Meteorological Research Inst., Tsukuba (Japan)); Davydov, D.; Fofonov, A.; Arshinov, M. (V.E. Zuev Inst. of Atmospheric Optics, Russian Academy of Sciences, Siberian Branch, Tomsk (Russian Federation))

2012-03-15

We described continuous measurements of CH{sub 4} and CO{sub 2} concentration obtained at two sites placed in the middle taiga, Karasevoe (KRS) and Demyanskoe (DEM), in West Siberian Lowland (WSL) from 2005 to 2009. Although both CH{sub 4} and CO{sub 2} accumulation (DELTACH{sub 4} and DELTACO{sub 2}) during night-time at KRS in June and July 2007 showed an anomalously high concentration, higher ratios of DELTACH{sub 4}/DELTACO{sub 2} compared with those in other years indicated that a considerably higher CH{sub 4} flux occurred relative to the CO{sub 2} flux. The daily CH{sub 4} flux calculated with the ratio of DELTACH{sub 4}/DELTACO{sub 2} and terrestrial biosphere CO{sub 2} flux from an ecosystem model showed a maximum in July at the both sites. Although anomalously high flux was observed in June and July 2007 at KRS, only a small flux variation was observed at DEM. The high regional CH{sub 4} flux in June and July 2007 at KRS was reproduced using a process-based ecosystem model, Vegetation Integrative Simulator for Trace gases (VISIT), in response to high water table depth caused by the anomalously high precipitation during the summer of 2007

Russian boreal peatlands dominate the natural European methane budget

International Nuclear Information System (INIS)

Schneider, Julia; Jungkunst, Hermann F; Wolf, Ulrike; Schreiber, Peter; Kutzbach, Lars; Gazovic, Michal; Miglovets, Mikhail; Mikhaylov, Oleg; Grunwald, Dennis; Erasmi, Stefan; Wilmking, Martin

2016-01-01

About 60% of the European wetlands are located in the European part of Russia. Nevertheless, data on methane emissions from wetlands of that area are absent. Here we present results of methane emission measurements for two climatically different years from a boreal peatland complex in European Russia. Winter fluxes were well within the range of what has been reported for the peatlands of other boreal regions before, but summer fluxes greatly exceeded the average range of 5–80 mg CH 4 m −2 d −1 for the circumpolar boreal zone. Half of the measured fluxes ranged between 150 and 450 mg CH 4 m −2 d −1 . Extrapolation of our data to the whole boreal zone of European Russia shows that theses emissions could amount to up to 2.7 ± 1.1 Tg CH 4 a −1 , corresponding to 69% of the annual emissions from European wetlands or 33% of the total annual natural European methane emission. In 2008, climatic conditions corresponded to the long term mean, whereas the summer of 2011 was warmer and noticeably drier. Counterintuitively, these conditions led to even higher CH 4 emissions, with peaks up to two times higher than the values measured in 2008. As Russian peatlands dominate the areal extend of wetlands in Europe and are characterized by very high methane fluxes to the atmosphere, it is evident, that sound European methane budgeting will only be achieved with more insight into Russian peatlands. (letter)

Concurrent enrichment in δD and δ13C in CH4 within stems of aquatic plants relative to methane within sediments

International Nuclear Information System (INIS)

Chanton, J.P.; Showers, W.J.

1991-01-01

13 CH 4 enrichment in methane within the stems of aquatic macrophytes relative to methane held within the sediments has been demonstrated previously. Hypotheses offered to explain this phenomenon include methane oxidation, production and transport effects (Chanton et al., Geophys. Res. Lett. 16, 799, 1989). The authors report here concurrent enrichment of δD and δ 13 C ranging from 36-59 per-thousand and 5.8-11.5 per-thousand respectively for methane within stems relative to methane within the sediments in a stand of Pontederia cordata. This sympathetic variation of H and C isotopes serves to eliminate the production hypothesis as an explanation of the effects observed. If production effects were responsible for the 13 CH 4 enrichment within macrophyte stems, H and C isotopes would have been expected to vary antipathetically (Whiticar et al., Geochim. Cosmochim. Acta, 50, 693, 1986)

Cold season emissions dominate the Arctic tundra methane budget

Science.gov (United States)

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.

Methane Carbon Isotopic Composition Reveals Changing Production Pathways Across a Gradient of Permafrost Thaw

Science.gov (United States)

Rocci, K.; Burke, S. A.; Clariza, P.; Malhotra, A.; McCalley, C. K.; Verbeke, B. A.; Werner, S. L.; Roulet, N. T.; Varner, R. K.

2017-12-01

Methane (CH4) emission in areas of discontinuous permafrost may increase with warming temperatures resulting in a positive feedback to climate change. Characterizing the production pathways of CH4, which may be inferred by measuring carbon isotopes, can help determine underlying mechanistic changes. We studied CH4 flux and isotopic composition of porewater (δ13C-CH4) in a sub-arctic peatland in Abisko, Sweden to understand controls on these factors across a thaw gradient during four growing seasons. Methane chamber flux measurements and porewater samples were collected in July 2013, and over the growing seasons of 2014 to 2016. Samples were analyzed on a Gas Chromatograph with a Flame Ionization Detector for CH4 concentrations and a Quantum Cascade Laser for carbon isotopes. Increased emission rates and changing isotopic signatures were observed across the thaw gradient throughout the growing season. While CH4 flux increased with increases in temperature and shallower water table, δ13C-CH4 exhibited a seasonal pattern that did not correlate with measured environmental variables, suggesting dependence on other factors. The most significant controlling factor for both flux and isotopic signature was plant community composition, specifically, the presence of graminoid species. Graminoid cover increases with thaw stage so both CH4 emissions and δ13C-CH4 are likely to increase in a warmer world, suggesting a shift toward the acetoclastic pathway of methane production.

Remote Sensing and Sea-Truth Measurements of Methane Flux to the Atmosphere (HYFLUX project)

Energy Technology Data Exchange (ETDEWEB)

Ian MacDonald

2011-05-31

, respectively. Based on the contemporaneous wind speeds at this site, contemporary estimates of the diffusive fluxes from the mixed layer to the atmosphere for methane, ethane, and propane are 26.5, 2.10, and 2.78 {micro}mol/m{sup 2}d, respectively. Continuous measurements of air and sea surface concentrations of methane were made to obtain high spatial and temporal resolution of the diffusive net sea-to-air fluxes. The atmospheric methane fluctuated between 1.70 ppm and 2.40 ppm during the entire cruise except for high concentrations (up to 4.01 ppm) sampled during the end of the occupation of GC600 and the transit between GC600 and GC185. Results from interpolations within the survey areas show the daily methane fluxes to the atmosphere at the three sites range from 0.744 to 300 mol d-1. Considering that the majority of seeps in the GOM are deep (>500 m), elevated CH{sub 4} concentrations in near-surface waters resulting from bubble-mediated CH4 transport in the water column are expected to be widespread in the Gulf of Mexico.

Methane and carbon dioxide fluxes over a lake: comparison between eddy covariance, floating chambers and boundary layer method

Directory of Open Access Journals (Sweden)

K.-M. Erkkilä

2018-01-01

Full Text Available Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2 and methane (CH4 to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, kCC (introduced by Cole and Caraco, 1998, for calculating diffusive flux with the boundary layer method (BLM. We compared CH4 and CO2 fluxes from BLM with kCC and two other gas transfer velocities (kTE and kHE, which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC and floating chamber (FC fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajärvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model kTE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajärvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference

Influence of transient flooding on methane fluxes from subtropical pastures

Science.gov (United States)

Seasonally flooded subtropical pastures are major methane (CH4) sources, where transient flooding drives episodic and high-magnitude emissions from the underlying landscape. Understanding the mechanisms that drive these patterns is needed to better understand pasture CH4 emissions and their response...

Methane flux from boreal peatlands

International Nuclear Information System (INIS)

Crill, P.; Bartlett, K.; Roulet, N.

1992-01-01

The peatlands in the boreal zone (roughly 45 deg - 60 degN) store a significant reservoir of carbon, much of which is potentially available for exchange with the atmosphere. The anaerobic conditions that cause these soils to accumulate carbon also makes wet, boreal peatlands significant sources of methane to the global troposphere. It is estimated that boreal wetlands contribute approximately 19.5 Tg methane per year. The data available on the magnitude of boreal methane emissions have rapidly accumulated in the past twenty years. This paper offers a short review of the flux measured (with range roughly 1 - 2000 mg methane/m2d), considers environmental controls of the flux and briefly discusses how climate change might affect future fluxes

The influence of cockchafer larvae on net soil methane fluxes under different vegetation types - a mesocosm study

Science.gov (United States)

Görres, Carolyn-Monika; Kammann, Claudia; Chesmore, David; Müller, Christoph

2017-04-01

The influence of land-use associated pest insects on net soil CH4 fluxes has received little attention thus far, although e.g. soil-dwelling Scarabaeidae larvae are qualitatively known to emit CH4. The project "CH4ScarabDetect" aims to provide the first quantitative estimate of the importance of soil-dwelling larvae of two important European agricultural and forest pest insect species - the common cockchafer (Melolontha melolontha) and the forest cockchafer (M. hippocastani) - for net soil CH4 fluxes. Here we present a mesocosm study within "CH4ScarabDetect" which tests the influence of different abundances of common cockchafer larvae on net soil CH4 fluxes under different vegetation types. In August 2016, 27 PVC boxes with a base area of 50 cm x 50 cm and a height of 40 cm were buried in planting beds previously used for cultivating vegetables. The bottom of each box was filled with a 10 cm thick layer of loam which was then covered with a 25 cm thick layer of loamy sand. The soil was hand-sieved prior to filling the boxes to remove any macrofauna. The mesocosms were planted with either turf, carrots or a combination of both. Of the resulting nine replicates per vegetation type, six were infested with one cockchafer larvae each in November 2016. In three of these infested mesocosms, the larvae abundance will be further increased to three in May 2017. This mesocosm study will continue until October 2017 during which measurements of net soil CH4 fluxes will be conducted with the chamber flux method twice per month. For the in situ separation of gross CH4 production and gross CH4 oxidation, the chamber method will be combined with a 13CH4 isotope pool dilution technique. Methane concentrations and their isotopic signatures in the collected gas samples will be analysed with a state-of-the-art CRDS analyzer (cavity ring-down spectroscopy, G2201-i) equipped with the Small Sample Isotope Module 2 - A0314 (Picarro Inc., USA). Different combinations of larvae abundance and

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

NARCIS (Netherlands)

Peltola, O.; Hensen, A.; Helfter, C.; Belelli Marchesini, L.; Bosveld, F.C.; Bulk, van de W.C.M.; Elbers, J.A.; Haapanala, S.; Holst, J.; Laurila, T.; Lindroth, A.; Nemitz, E.; Röckmann, T.; Vermeulen, A.T.; Mammarella, I.

2014-01-01

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements : the InGOS inter-comparison field experiment

NARCIS (Netherlands)

Peltola, O.; Hensen, A.; Helfter, C.; Belelli Marchesini, L.; Bosveld, F. C.; Van Den Bulk, W. C M; Elbers, J. A.; Haapanala, S.; Holst, J.; Laurila, T.; Lindroth, A.; Nemitz, E.; Röckmann, T.; Vermeulen, A. T.; Mammarella, I.

2014-01-01

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

NARCIS (Netherlands)

Peltola, O.; Hensen, A.; Helfter, C.; Belelli Marchesini, L.; Bosveld, F. C.; Van Den Bulk, W. C. M.; Elbers, J. A.; Haapanala, S.; Holst, J.; Laurila, T.; Lindroth, A.; Nemitz, E.; Röckmann, T.; Vermeulen, A. T.; Mammarella, I.

2014-01-01

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimize the effect of varying

Environmental and microbial factors influencing methane and nitrous oxide fluxes in Mediterranean cork oak woodlands: trees make a difference.

Science.gov (United States)

Shvaleva, Alla; Siljanen, Henri M P; Correia, Alexandra; Costa E Silva, Filipe; Lamprecht, Richard E; Lobo-do-Vale, Raquel; Bicho, Catarina; Fangueiro, David; Anderson, Margaret; Pereira, João S; Chaves, Maria M; Cruz, Cristina; Martikainen, Pertti J

2015-01-01

Cork oak woodlands (montado) are agroforestry systems distributed all over the Mediterranean basin with a very important social, economic and ecological value. A generalized cork oak decline has been occurring in the last decades jeopardizing its future sustainability. It is unknown how loss of tree cover affects microbial processes that are consuming greenhouse gases in the montado ecosystem. The study was conducted under two different conditions in the natural understory of a cork oak woodland in center Portugal: under tree canopy (UC) and open areas without trees (OA). Fluxes of methane and nitrous oxide were measured with a static chamber technique. In order to quantify methanotrophs and bacteria capable of nitrous oxide consumption, we used quantitative real-time PCR targeting the pmoA and nosZ genes encoding the subunit of particulate methane mono-oxygenase and catalytic subunit of the nitrous oxide reductase, respectively. A significant seasonal effect was found on CH4 and N2O fluxes and pmoA and nosZ gene abundance. Tree cover had no effect on methane fluxes; conversely, whereas the UC plots were net emitters of nitrous oxide, the loss of tree cover resulted in a shift in the emission pattern such that the OA plots were a net sink for nitrous oxide. In a seasonal time scale, the UC had higher gene abundance of Type I methanotrophs. Methane flux correlated negatively with abundance of Type I methanotrophs in the UC plots. Nitrous oxide flux correlated negatively with nosZ gene abundance at the OA plots in contrast to that at the UC plots. In the UC soil, soil organic matter had a positive effect on soil extracellular enzyme activities, which correlated positively with the N2O flux. Our results demonstrated that tree cover affects soil properties, key enzyme activities and abundance of microorganisms and, consequently net CH4 and N2O exchange.

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

Science.gov (United States)

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

Microtopography and methane flux in boreal peatlands, northern Ontario, Canada

International Nuclear Information System (INIS)

Bubier, J.; Costello, A.; Moore, T.R.; Roulet, N.T.; Savage, K.

1993-01-01

Peatlands act as a major sink of carbon dioxide and a source of methane. Fluxes of methane were measured by a static chamber technique at hummock, hollow, and lawn microtopographic locations in 12 peatland sites near Cochrane, northern Ontario, from May to October 1991. Average fluxes (mg/m 2 /d) were 2.3 at hummocks, 44.4 at hollows, and 15.6 at lawns. Methane flux was negatively correlated with average water table position based on the 36 locations, with hummocks having a smaller flux than hollows or lawns, where the water table depth was <25 cm. Peat samples from a bog hummock and hollow failed to produce methane during anaerobic incubations in the laboratory; samples from a poor fen hollow produced <1.4 μg/g/d. The production decreased with depth but was greater than the rates observed during incubation of samples from an adjacent hummock. Rates of methane consumption during aerobic incubations ranged from 1 to 55 μg/g/d and were greatest in the surface layers and decreased with depth. Differences in methane emissions between hummocks and hollows appear to be controlled primarily by greater methane production rates in hollows compared with hummocks. Of secondary importance are the capacity of the peat profiles to consume methane during its transport to the peat surface and warmer temperatures at the water table beneath hollows compared with hummocks. 29 refs., 4 figs., 2 tabs

Gross photosynthesis explains the ‘artificial bias’ of methane fluxes by static chamber (opaque versus transparent) at the hummocks in a boreal peatland

International Nuclear Information System (INIS)

Luan, Junwei; Wu, Jianghua

2014-01-01

The closed chamber technique has been widely employed to detect methane emissions, despite little being known about whether the absence or presence of light will impact the flux estimation. Here, we employed a laser greenhouse gas analyzer with an opaque—transparent chamber pair to measure the methane emission rate in a boreal peatland complex. Microtopography (i.e., hummocks and hollows) in natural and drained peatlands, and plant communities (i.e., grasses and shrubs) in a pasture converted from natural peatlands, were considered to cover the local heterogeneity. Our results indicated that opaque chambers (0.58–0.78 g CH 4 m −2 during the growing season) measured a significantly higher (∼2–3 times) methane emission at the hummocks than transparent chambers (∼0.24 g CH 4 m −2 ); however, a similar phenomenon was not found at the hollows or at other measurement plots. Gross photosynthesis explained 44%–47% of the temporal variation of the ‘artificial bias’ (the difference in methane flux obtained by the opaque versus transparent chambers) at the hummocks. Additionally, both water table depth and surface soil moisture significantly explained spatial variations of methane emissions. Our study suggests that microtopography has a significant influence on the artificial bias in methane emission estimation and the artificial properties of a chamber (transparency/opacity) method can be vitally important in some cases (i.e., hummocks), and negligible in others (i.e., hollows). The observed connection between the photosynthesis process and the ‘artificial bias’ of closed chambers (opaque versus transparent) can be used to improve methane flux modeling. Separate parameterization schemes are needed for methane transportation under the presence or absence of light. (paper)

Methane emissions from a freshwater marsh in response to experimentally simulated global warming and nitrogen enrichment

DEFF Research Database (Denmark)

Flury, Sabine; McGinnis, Daniel Frank; Gessner, Mark O.

2010-01-01

We determined methane (CH4) emissions in a field enclosure experiment in a littoral freshwater marsh under the influence of experimentally simulated warming and enhanced nitrogen deposition. Methane emissions by ebullition from the marsh composed of Phragmites australis were measured with funnel ...... to the atmosphere, even when they occupy only relatively small littoral areas. More detailed investigations are clearly needed to assess whether global warming and nitrogen deposition can have climate feedbacks by altering methane fluxes from these wetlands.  ......We determined methane (CH4) emissions in a field enclosure experiment in a littoral freshwater marsh under the influence of experimentally simulated warming and enhanced nitrogen deposition. Methane emissions by ebullition from the marsh composed of Phragmites australis were measured with funnel...... traps deployed in a series of enclosures for two 3 week periods. Diffusive fluxes were estimated on the basis of measured CH4 concentrations and application of Fick's law. Neither diffusive nor ebullitive fluxes of methane were significantly affected by warming or nitrate enrichment, possibly because...

Natural gas facility methane emissions: measurements by tracer flux ratio in two US natural gas producing basins

Directory of Open Access Journals (Sweden)

Tara I. Yacovitch

2017-11-01

Full Text Available Methane (CH4 emission rates from a sample of natural gas facilities across industry sectors were quantified using the dual tracer flux ratio methodology. Measurements were conducted in study areas within the Fayetteville shale play, Arkansas (FV, Sept–Oct 2015, 53 facilities, and the Denver-Julesburg basin, Colorado, (DJ, Nov 2014, 21 facilities. Distributions of methane emission rates at facilities by type are computed and statistically compared with results that cover broader geographic regions in the US (Allen et al., 2013, Mitchell et al., 2015. DJ gathering station emission rates (kg CH4 hr–1 are lower, while FV gathering and production sites are statistically indistinguishable as compared to these multi-basin results. However, FV gathering station throughput-normalized emissions are statistically lower than multi-basin results (0.19% vs. 0.44%. This implies that the FV gathering sector is emitting less per unit of gas throughput than would be expected from the multi-basin distribution alone. The most common emission rate (i.e. mode of the distribution for facilities in this study is 40 kg CH4 hr–1 for FV gathering stations, 1.0 kg CH4 hr–1 for FV production pads, and 11 kg CH4 hr–1 for DJ gathering stations. The importance of study design is discussed, including the benefits of site access and data sharing with industry and of a scientist dedicated to measurement coordination and site choice under evolving wind conditions.

Methane oxidation associated to submerged brown-mosses buffers methane emissions from Siberian polygonal peatlands

Science.gov (United States)

Liebner, Susanne; Zeyer, Josef; Knoblauch, Christian

2010-05-01

Circumpolar peatlands store roughly 18 % of the globally stored carbon in soils [based on 1, 2]. Also, northern wetlands and tundra are a net source of methane (CH4), an effective greenhouse gas (GHG), with an estimated annual CH4 release of 7.2% [3] or 8.1% [4] of the global total CH4 emission. Although it is definite that Arctic tundra significantly contributes to the global methane emissions in general, regional variations in GHG fluxes are enormous. CH4 fluxes of polygonal tundra within the Siberian Lena Delta, for example, were reported to be low [5, 6], particularly at open water polygonal ponds and small lakes [7] which make up around 10 % of the delta's surface. Low methane emissions from polygonal ponds oppose that Arctic permafrost thaw ponds are generally known to emit large amounts of CH4 [8]. Combining tools of biogeochemistry and molecular microbiology, we identified sinks of CH4 in polygonal ponds from the Lena Delta that were not considered so far in GHG studies from Arctic wetlands. Pore water CH4 profiling in polygonal ponds on Samoylov, a small island in the central part of the Lena Delta, revealed a pronounced zone of CH4 oxidation near the vegetation surface in submerged layers of brown-mosses. Here, potential CH4 oxidation was an order of magnitude higher than in non-submerged mosses and in adjacent bulk soil. We could additionally show that this moss associated methane oxidation (MAMO) is hampered when exposure of light is prevented. Shading of plots with submerged Scorpidium scorpioides inhibited MAMO leading to higher CH4 concentrations and an increase in CH4 fluxes by a factor of ~13. Compared to non-submerged mosses, the submerged mosses also showed significantly lower δ13C values indicating that they use carbon dioxide derived from methane oxidation for photosynthesis. Applying stable isotope probing of DNA, type II methanotrophs were identified to be responsible for the oxidation of CH4 in the submerged Scorpidium scorpioides. Our

Ecosystem level methane fluxes from tidal freshwater and brackish marshes of the Mississippi River Delta: Implications for coastal wetland carbon projects

Science.gov (United States)

Holm, Guerry O.; Perez, Brian C.; McWhorter, David E.; Krauss, Ken W.; Johnson, Darren J.; Raynie, Richard C.; Killebrew, Charles J.

2016-01-01

Sulfate from seawater inhibits methane production in tidal wetlands, and by extension, salinity has been used as a general predictor of methane emissions. With the need to reduce methane flux uncertainties from tidal wetlands, eddy covariance (EC) techniques provide an integrated methane budget. The goals of this study were to: 1) establish methane emissions from natural, freshwater and brackish wetlands in Louisiana based on EC; and 2) determine if EC estimates conform to a methane-salinity relationship derived from temperate tidal wetlands with chamber sampling. Annual estimates of methane emissions from this study were 62.3 g CH4/m2/yr and 13.8 g CH4/m2/yr for the freshwater and brackish (8–10 psu) sites, respectively. If it is assumed that long-term, annual soil carbon sequestration rates of natural marshes are ~200 g C/m2/yr (7.3 tCO2e/ha/yr), healthy brackish marshes could be expected to act as a net radiative sink, equivalent to less than one-half the soil carbon accumulation rate after subtracting methane emissions (4.1 tCO2e/ha/yr). Carbon sequestration rates would need case-by-case assessment, but the EC methane emissions estimates in this study conformed well to an existing salinity-methane model that should serve as a basis for establishing emission factors for wetland carbon offset projects.

Carbon dioxide, methane and nitrous oxide fluxes from a fire chronosequence in subarctic boreal forests of Canada.

Science.gov (United States)

Köster, Egle; Köster, Kajar; Berninger, Frank; Aaltonen, Heidi; Zhou, Xuan; Pumpanen, Jukka

2017-12-01

Forest fires are one of the most important natural disturbances in boreal forests, and their occurrence and severity are expected to increase as a result of climate warming. A combination of factors induced by fire leads to a thawing of the near-surface permafrost layer in subarctic boreal forest. Earlier studies reported that an increase in the active layer thickness results in higher carbon dioxide (CO 2 ) and methane (CH 4 ) emissions. We studied changes in CO 2 , CH 4 and nitrous oxide (N 2 O) fluxes in this study, and the significance of several environmental factors that influence the greenhouse gas (GHG) fluxes at three forest sites that last had fires in 2012, 1990 and 1969, and we compared these to a control area that had no fire for at least 100years. The soils in our study acted as sources of CO 2 and N 2 O and sinks for CH 4 . The elapsed time since the last forest fire was the only factor that significantly influenced all studied GHG fluxes. Soil temperature affected the uptake of CH 4 , and the N 2 O fluxes were significantly influenced by nitrogen and carbon content of the soil, and by the active layer depth. Results of our study confirm that the impacts of a forest fire on GHGs last for a rather long period of time in boreal forests, and are influenced by the fire induced changes in the ecosystem. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluating the performance of commonly used gas analysers for methane eddy covariance flux measurements: the InGOS inter-comparison field experiment

Science.gov (United States)

Peltola, O.; Hensen, A.; Helfter, C.; Belelli Marchesini, L.; Bosveld, F. C.; van den Bulk, W. C. M.; Elbers, J. A.; Haapanala, S.; Holst, J.; Laurila, T.; Lindroth, A.; Nemitz, E.; Röckmann, T.; Vermeulen, A. T.; Mammarella, I.

2014-06-01

The performance of eight fast-response methane (CH4) gas analysers suitable for eddy covariance flux measurements were tested at a grassland site near the Cabauw tall tower (Netherlands) during June 2012. The instruments were positioned close to each other in order to minimise the effect of varying turbulent conditions. The moderate CH4 fluxes observed at the location, of the order of 25 nmol m-2 s-1, provided a suitable signal for testing the instruments' performance. Generally, all analysers tested were able to quantify the concentration fluctuations at the frequency range relevant for turbulent exchange and were able to deliver high-quality data. The tested cavity ringdown spectrometer (CRDS) instruments from Picarro, models G2311-f and G1301-f, were superior to other CH4 analysers with respect to instrumental noise. As an open-path instrument susceptible to the effects of rain, the LI-COR LI-7700 achieved lower data coverage and also required larger density corrections; however, the system is especially useful for remote sites that are restricted in power availability. In this study the open-path LI-7700 results were compromised due to a data acquisition problem in our data-logging setup. Some of the older closed-path analysers tested do not measure H2O concentrations alongside CH4 (i.e. FMA1 and DLT-100 by Los Gatos Research) and this complicates data processing since the required corrections for dilution and spectroscopic interactions have to be based on external information. To overcome this issue, we used H2O mole fractions measured by other gas analysers, adjusted them with different methods and then applied them to correct the CH4 fluxes. Following this procedure we estimated a bias of the order of 0.1 g (CH4) m-2 (8% of the measured mean flux) in the processed and corrected CH4 fluxes on a monthly scale due to missing H2O concentration measurements. Finally, cumulative CH4 fluxes over 14 days from three closed-path gas analysers, G2311-f (Picarro Inc

Megafauna and frozen soil: the drivers of atmospheric CH4 dynamics

Science.gov (United States)

Zimov, N.; Zimov, S. A.

2010-12-01

During the last deglaciation (LD) a strong increase in atmospheric methane (CH4) concentrations occurred simultaneously with a rise in Greenland temperatures indicating that in the north, during this time period, strong CH4 sources “awakened”, as additionally documented by the appearance of a strong gradient between northern (Greenland) and southern (Antarctica) hemisphere atmospheric CH4 concentrations. This rise could not be caused by wetland expansion. A reconstruction of peatland formation dynamics has indicated that wetlands on Earth were few in LD and only actively expanded 10,000 yr BP, after atmospheric CH4 concentrations began to decline. Destabilization of methane clathrates also could not be the source for atmospheric CH4 increase. Geological CH4 (including methane clathrates) has the highest deuterium content (δD) among all of the known sources of CH4 while atmospheric CH4 δD values determined for the LD were record low. To explain recorded atmospheric CH4 and its isotopic dynamics required a strong northern source, which was active only during the LD and that provided very low δD CH4 values. Such a source is permafrost thawing under anaerobic conditions (or better stated soils of mammoth steppe-tundra ecosystems). Permafrost thawing is the strongest, among known, wetland sources (usually over 100g CH4/m2yr) and has a unique isotopic signature (δD = -400 per mil (-338 to -479 per mil), δ13C = -73 per mil (-58 to -99 per mil)). The main sources of atmospheric CH4 have different isotopic signatures (δ13C, δD). The isotopic content of atmospheric CH4 is a simple function of the weight average for all of the sources. Inclusion of permafrost source into a budget model of the atmospheric methane and its isotopes allowed us to reconstruct the dynamics of methane’s main sources. Model indicated geological source to be negligible as in LGM so and in LD and Holocene. During the glaciation, the largest methane source was megafauna, whose 1.4

Land-use change effects on fluxes and isotopic composition of CO2 and CH4 in Panama, and possible insights into the atmospheric H2 cycle

Science.gov (United States)

Pendall, E.; Schwendenmann, L.; Potvin, C.

2003-12-01

Land-use changes in tropical regions are believed to release a quantity of C to the atmosphere which is similar in magnitude to the entire "missing" sink for anthropogenic CO2. Our research attempts to evaluate carbon cycling in three land-cover systems in central Panama: cow pasture, native tree plantation, and undisturbed moist forest. In this ongoing project, we are collecting samples of air from profiles in the stable, nocturnal boundary layer, which is dominated by ecosystem respiration. Samples are analyzed for CO2 and its isotopes, CH4 and its C isotopic composition, N2O, H2, CO, and SF6. We use a flux-gradient method to estimate ecosystem-scale fluxes of trace gases from soil to the atmosphere. Keeling plot intercepts reflect the respiratory contribution of C3 and C4 biomass under contrasting land cover systems, and how this varies with pronounced wet-dry seasonal cycles. C isotopes of methane and gradients of molecular hydrogen provide insight into the source of methane production from pasture and plantation soils. Rainforest soils, in contrast, are sinks for both atmospheric methane and hydrogen. The process oriented nature of this field experiment will contribute to parameterization of carbon cycle models at a variety of spatial scales.

Anaerobic methane oxidation rates at the sulfate-methane transition in marine sediments from Kattegat and Skagerrak (Denmark)

International Nuclear Information System (INIS)

Iversen, N.; Jorgensen, B.B.

1985-01-01

Concomitant radiotracer measurements were made of in situ rates of sulfate reduction and anaerobic methane oxidation in 2-3-m-long sediment cores. Methane accumulated to high concentrations (> 1 mM CH 4 ) only below the sulfate zone, at 1 m or deeper in the sediment. Sulfate reduction showed a broad maximum below the sediment surface and a smaller, narrow maximum at the sulfate-methane transition. Methane oxidation was low (0.002-0.1 nmol CH 4 cm -3 d -1 ) throughout the sulfate zone and showed a sharp maximum at the sulfate-methane transition, coinciding with the sulfate reduction maximum. Total anaerobic methane oxidation at two stations was 0.83 and 1.16 mmol CH 4 m -2 d -1 , of which 96% was confined to the sulfate-methane transition. All the methane that was calculated to diffuse up into the sulfate-methane transition was oxidized in this zone. The methane oxidation was equivalent to 10% of the electron donor requirement for the total measured sulfate reduction. A third station showed high sulfate concentrations at all depths sampled and the total methane oxidation was only 0.013 mmol m -2 d -1 . From direct measurements of rates, concentration gradients, and diffusion coefficients, simple calculations were made of sulfate and methane fluxes and of methane production rates

Investigating CH4 production in an oxic plant-soil system -a new approach combining isotopic labelling (13C) and inhibitors

Science.gov (United States)

Lenhart, Katharina; Keppler, Frank

2017-04-01

Typically, aerated soil are net sinks of atmospheric methane (CH4), being highest in native ecosystems (pristine forests > managed forests > grasslands > crop fields). However, this does not exclude a simultaneous endogenic CH4 production in the plant-soil system, which cannot be detected simply via CH4 flux measurements. Methanogenic archaea producing CH4 under anoxic conditions were thought to be the only biotic source of CH4 in the soil. However, until recently a non-archaeal pathway of CH4 formation is known where CH4 is produced under oxic conditions in plants (Keppler et al. 2006) and fungi (Lenhart et al. 2012). Additionally, abiotic formation of CH4 from soil organic matter was reported (Jugold et al. 2012) and may be ubiquitous in terrestrial ecosystems. The major goal of this project was to determine soil endogenic CH4 sources and to estimate their contribution to the endogenic CH4 production. Especially the effect of plants and fungi on soil CH4 production was investigated. Therefore, a series of experiments was carried out on field fresh soil collected in a grassland and a forest ecosystem under controlled laboratory conditions. By combining selective inhibitors and 13C labelling, CH4 production rates of several CH4 sources were quantified. The major difficulty was to detect the comparatively small flux of CH4 production against the background of the high CH4 consumption rates due to methanotrophic bacteria. Therefore, we supplemented bare soil and soil with vegetation with selective inhibitors and 13C labelled substrates in a closed chamber system. In a first step, CH4 production was determined by the inhibition of CH4 oxidizing bacteria with Difluoromethane (DFM, 2ml l-1). In the following, a 13C labelled substrate (either CO2, Acetate, or Methionine -S-CH3 labelled) was added in combination with a specific inhibitor -either for archaeal methanogenesis (Bromoethanesulfonate), bacteria (Streptomycin), or fungi (Captan, Cycloheximide). Gas samples were

Sources of atmospheric methane from coastal marine wetlands

International Nuclear Information System (INIS)

Harriss, R.C.; Sebacher, D.I.; Bartlett, K.B.; Bartlett, D.S.

1982-01-01

Biological methanogenesis in wetlands is believed to be one of the major sources of global tropospheric methane. The present paper reports measurements of methane distribution in the soils, sediments, water and vegetation of coastal marine wetlands. Measurements, carried out in the salt marshes Bay Tree Creek in Virginia and Panacea in northwest Florida, reveal methane concentrations in soils and sediments to vary with depth below the surface and with soil temperature. The fluxes of methane from marsh soils to the atmosphere at the soil-air interface are estimated to range from -0.00067 g CH 4 /sq m per day (methane sink) to 0.024 g CH 4 /sq m per day, with an average value of 0.0066 g CH 4 /sq m per day. Data also demonstrate the important role of tidal waters percolating through marsh soils in removing methane from the soils and releasing it to the atmosphere. The information obtained, together with previous studies, provides a framework for the design of a program based on in situ and remote sensing measurements to study the global methane cycle

Effects of phosphorus addition on nitrogen cycle and fluxes of N2O and CH4 in tropical tree plantation soils in Thailand

Directory of Open Access Journals (Sweden)

Taiki Mori

2017-04-01

Full Text Available An incubation experiment was conducted to test the effects of phosphorus (P addition on nitrous oxide (N2O emissions and methane (CH4 uptakes, using tropical tree plantation soils in Thailand. Soil samples were taken from five forest stands—Acacia auriculiformis, Acacia mangium, Eucalyptus camaldulensis, Hopea odorata, and Xylia xylocarpa—and incubated at 80% water holding capacity. P addition stimulated N2O emissions only in Xylia xylocarpa soils. Since P addition tended to increase net ammonification rates in Xylia xylocarpa soils, the stimulated N2O emissions were suggested to be due to the stimulated nitrogen (N cycle by P addition and the higher N supply for nitrification and denitrification. In other soils, P addition had no effects on N2O emissions or soil N properties, except that P addition tended to increase the soil microbial biomass N in Acacia auriculiformis soils. No effects of P addition were observed on CH4 uptakes in any soil. It is suggested that P addition on N2O and CH4 fluxes at the study site were not significant, at least under laboratory conditions.

Methane oxidation and methane fluxes in the ocean surface layer and deep anoxic waters

Science.gov (United States)

Ward, B. B.; Kilpatrick, K. A.; Novelli, P. C.; Scranton, M. I.

1987-01-01

Measured biological oxidation rates of methane in near-surface waters of the Cariaco Basin are compared with the diffusional fluxes computed from concentration gradients of methane in the surface layer. Methane fluxes and oxidation rates were investigated in surface waters, at the oxic/anoxic interface, and in deep anoxic waters. It is shown that the surface-waters oxidation of methane is a mechanism which modulates the flux of methane from marine waters to the atmosphere.

Methane, carbon dioxide and nitrous oxide fluxes in soil profile under a winter wheat-summer maize rotation in the North China Plain.

Directory of Open Access Journals (Sweden)

Yuying Wang

Full Text Available The production and consumption of the greenhouse gases (GHGs methane (CH4, carbon dioxide (CO2 and nitrous oxide (N2O in soil profile are poorly understood. This work sought to quantify the GHG production and consumption at seven depths (0-30, 30-60, 60-90, 90-150, 150-200, 200-250 and 250-300 cm in a long-term field experiment with a winter wheat-summer maize rotation system, and four N application rates (0; 200; 400 and 600 kg N ha(-1 year(-1 in the North China Plain. The gas samples were taken twice a week and analyzed by gas chromatography. GHG production and consumption in soil layers were inferred using Fick's law. Results showed nitrogen application significantly increased N2O fluxes in soil down to 90 cm but did not affect CH4 and CO2 fluxes. Soil moisture played an important role in soil profile GHG fluxes; both CH4 consumption and CO2 fluxes in and from soil tended to decrease with increasing soil water filled pore space (WFPS. The top 0-60 cm of soil was a sink of atmospheric CH4, and a source of both CO2 and N2O, more than 90% of the annual cumulative GHG fluxes originated at depths shallower than 90 cm; the subsoil (>90 cm was not a major source or sink of GHG, rather it acted as a 'reservoir'. This study provides quantitative evidence for the production and consumption of CH4, CO2 and N2O in the soil profile.

CO2 and CH4 fluxes of contrasting pristine bogs in southern Patagonia (Tierra del Fuego, Argentina)

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Münchberger, Wiebke; Blodau, Christian; Kleinebecker, Till; Pancotto, Veronica

2015-04-01

South Patagonian peatlands cover a wide range of the southern terrestrial area and thus are an important component of the terrestrial global carbon cycle. These extremely southern ecosystems have been accumulating organic material since the last glaciation up to now and are - in contrast to northern hemisphere bogs - virtually unaffected by human activities. So far, little attention has been given to these pristine ecosystems and great carbon reservoirs which will potentially be affected by climate change. We aim to fill the knowledge gap in the quantity of carbon released from these bogs and in what controls their fluxes. We study the temporal and spatial variability of carbon fluxes in two contrasting bog ecosystems in southern Patagonia, Tierra del Fuego. Sphagnum-dominated bog ecosystems in Tierra del Fuego are similar to the ones on the northern hemisphere, while cushion plant-dominated bogs can almost exclusively be found in southern Patagonia. These unique cushion plant-dominated bogs are found close to the coast and their occurrence changes gradually to Sphagnum-dominated bogs with increasing distance from the coast. We conduct closed chamber measurements and record relevant environmental variables for CO2 and CH4 fluxes during two austral vegetation periods from December to April. Chamber measurements are performed on microforms representing the main vegetation units of the studied bogs. Gas concentrations are measured with a fast analyzer (Los Gatos Ultraportable Greenhouse Gas Analyzer) allowing to accurately record CH4 fluxes in the ppm range. We present preliminary results of the carbon flux variability from south Patagonian peat bogs and give insights into their environmental controls. Carbon fluxes of these two bog types appear to be highly different. In contrast to Sphagnum-dominated bogs, cushion plant-dominated bogs release almost no CH4 while their CO2 flux in both, photosynthesis and respiration, can be twice as high as for Sphagnum

Biogeochemical controls on microbial CH4 and CO2 production in Arctic polygon tundra

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Zheng, J.

2016-12-01

Accurately simulating methane (CH4) and carbon dioxide (CO2) emissions from high latitude soils is critically important for reducing uncertainties in soil carbon-climate feedback predictions. The signature polygonal ground of Arctic tundra generates high level of heterogeneity in soil thermal regime, hydrology and oxygen availability, which limits the application of current land surface models with simple moisture response functions. We synthesized CH4 and CO2 production measurements from soil microcosm experiments across a wet-to dry permafrost degradation gradient from low-centered (LCP) to flat-centered (FCP), and high-centered polygons (HCP) to evaluate the relative importance of biogeochemical processes and their response to warming. More degraded polygon (HCP) showed much less carbon loss as CO2 or CH4, while the total CO2 production from FCP is comparable to that from LCP. Maximum CH4 production from the active layer of LCP was nearly 10 times that of permafrost and FCP. Multivariate analyses identifies gravimetric water content and organic carbon content as key predictors for CH4 production, and iron reduction as a key regulator of pH. The synthesized data are used to validate the geochemical model PHREEQC with extended anaerobic organic substrate turnover, fermentation, iron reduction, and methanogenesis reactions. Sensitivity analyses demonstrate that better representations of anaerobic processes and their pH dependency could significantly improve estimates of CH4 and CO2 production. The synthesized data suggest local decreases in CH4 production along the polygon degradation gradient, which is consistent with previous surface flux measurements. Methane oxidation occurring through the soil column of degraded polygons contributes to their low CH4 emissions as well.

Management practices and controls on methane emissions from sub-tropical wetlands

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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

Large emissions from floodplain trees close the Amazon methane budget

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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.

Large emissions from floodplain trees close the Amazon methane budget.

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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.

Static Vented Chamber and Eddy Covariance Methane Flux Comparisons in Mid-South US Rice

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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.

Fluxes of CH4 and CO2 from soil and termite mounds in south Sudanian savanna of Burkina Faso (West Africa)

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Brümmer, Christian; Papen, Hans; Wassmann, Reiner; Brüggemann, Nicolas

2009-03-01

The contribution of West African savanna ecosystems to global greenhouse gas budgets is highly uncertain. In this study we quantified soil-atmosphere CH4 and CO2 fluxes in the southwest of Burkina Faso from June to September 2005 and from April to September 2006 at four different agricultural fields planted with sorghum (n = 2), cotton, and peanut and at a natural savanna site with termite (Cubitermes fungifaber) mounds. During the rainy season both CH4 uptake and CH4 emission were observed in the savanna, which was on average a CH4 source of 2.79 and 2.28 kg CH4-C ha-1 a-1 in 2005 and 2006, respectively. The crop sites were an average CH4 sink of -0.67 and -0.70 kg CH4-C ha-1 a-1 in the 2 years, without significant seasonal variation. Mean annual soil respiration ranged between 3.86 and 5.82 t CO2-C ha-1 a-1 in the savanna and between 2.50 and 4.51 t CO2-C ha-1 a-1 at the crop sites. CH4 emission from termite mounds was 2 orders of magnitude higher than soil CH4 emissions, whereas termite CO2 emissions were of the same order of magnitude as soil CO2 emissions. Termite CH4 and CO2 release in the savanna contributed 8.8% and 0.4% to the total soil CH4 and CO2 emissions, respectively. At the crop sites, where termite mounds had been almost completely removed because of land use change, termite fluxes were insignificant. Mound density-based upscaling of termite CH4 fluxes resulted in a global termite CH4 source of 0.9 Tg a-1, which corresponds to 0.15% of the total global CH4 budget of 582 Tg a-1, hence significantly lower than those obtained previously by biomass-based calculations. This study emphasizes that land use change, which is of high relevance in this region, has particularly affected soil CH4 fluxes in the past and might still do so in the future.

The influence of nitrogen fertiliser rate and crop rotation on soil methane flux in rain-fed potato fields in Wuchuan County, China.

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Wang, Liwei; Pan, Zhihua; Xu, Hui; Wang, Cheng; Gao, Lin; Zhao, Peiyi; Dong, Zhiqiang; Zhang, Jingting; Cui, Guohui; Wang, Sen; Han, Guolin; Zhao, Hui

2015-12-15

As one of the important greenhouse gases, the characteristics and principles of methane exchange characteristics in cultivated lands have become hot topics in current climate change research. This study examines the influences of nitrogen fertilisation, temperature and soil water content on methane exchange characteristic and methane exchange functional gene-pmoA gene abundance based on experimental observations of methane exchange fluxes using the static chamber-gas chromatographic method and measurements of methanotroph gene copy numbers in three growing periods by real-time PCR in rain-fed potato fields. The results indicate that the rain-fed potato fields were a CH4 sink with an average annual methane absorption (negative emission) of 940.8±103.2 g CH4-C/ha/year. The cumulative methane absorption first exhibited flat and subsequently increasing trend with the increase of nitrogen fertilisation from 0~135 kg N·ha(-1). Methane cumulative absorption significantly increased with the increase of temperature when temperatures were below 19.6 °C. Methane oxidation capacity (methanotroph pmoA gene copy numbers) showed an increasing and subsequently decreasing trend with the increase of soil moisture. Crop rotation was observed to increase the methane absorption in rain-fed potato fields and nearly one time higher than that under continuous cropping. A mechanism concept model of the methane exchange in rain-fed potato fields was advanced in this paper. Copyright © 2015 Elsevier B.V. All rights reserved.

Global Methane Biogeochemistry

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Reeburgh, W. S.

2003-12-01

. Methane absorbs infrared radiation in the troposphere, as do CO2 and H2O, and is an important greenhouse gas (Lacis et al., 1981; Ramanathan et al., 1985).A number of review articles on atmospheric CH4 have appeared during the last 15 years. Cicerone and Oremland (1988) reviewed evidence for the temporal atmospheric increase, updated source estimates in the global CH4 budget, and placed constraints on the global budget, emphasizing that the total is well constrained, but that the constituent sources may be uncertain by a factor of 2 or more. This paper was part of a special section in Global Biogeochemical Cycles that resulted from a 1987 American Chemical Society Symposium, "Atmospheric Methane: Formation and Fluxes form the Biosphere and Geosphere." Tyler (1991) and Wahlen (1993) emphasized new information on stable isotopes of CH4 and 14CH4, respectively. Several reviews deal with the microbially mediated CH4 oxidation. King (1992) reviewed the ecology of microbial CH4 oxidation, emphasizing the important role of this process in global CH4 dynamics. R. S. Hanson and T. E. Hanson (1996) reviewed the physiology and taxonomy of methylotrophic bacteria, their role in the global carbon cycle, and the ecology of methanotrophic bacteria. Conrad (1996) reviewed the role of soils and soil microbial communities as controllers of CH4 fluxes, as well as those of H2, CO, OCS, N2O, and NO. Two meetings focusing on CH4 biogeochemistry were held in 1991: an NATO Advanced Science Workshop held at Mt. Hood, OR, and the Tenth International Symposium on Environmental Biogeochemistry (ISEB). A dedicated issue of Chemosphere (26(1-4), 1993) contains contributions from the NATO workshop; two additional volumes (Khalil, 1993 and Khalil, 2000) contain a report of the workshop and updates of important topics. Contributions to the ISEB meeting are presented in Oremland (1993). Wuebbles and Hayhoe (2002) reviewed the effects of CH4 on atmospheric chemistry and examined the direct and indirect

Improving accuracy and precision of ice core δD(CH4 analyses using methane pre-pyrolysis and hydrogen post-pyrolysis trapping and subsequent chromatographic separation

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M. Bock

2014-07-01

Full Text Available Firn and polar ice cores offer the only direct palaeoatmospheric archive. Analyses of past greenhouse gas concentrations and their isotopic compositions in air bubbles in the ice can help to constrain changes in global biogeochemical cycles in the past. For the analysis of the hydrogen isotopic composition of methane (δD(CH4 or δ2H(CH4 0.5 to 1.5 kg of ice was hitherto used. Here we present a method to improve precision and reduce the sample amount for δD(CH4 measurements in (ice core air. Pre-concentrated methane is focused in front of a high temperature oven (pre-pyrolysis trapping, and molecular hydrogen formed by pyrolysis is trapped afterwards (post-pyrolysis trapping, both on a carbon-PLOT capillary at −196 °C. Argon, oxygen, nitrogen, carbon monoxide, unpyrolysed methane and krypton are trapped together with H2 and must be separated using a second short, cooled chromatographic column to ensure accurate results. Pre- and post-pyrolysis trapping largely removes the isotopic fractionation induced during chromatographic separation and results in a narrow peak in the mass spectrometer. Air standards can be measured with a precision better than 1‰. For polar ice samples from glacial periods, we estimate a precision of 2.3‰ for 350 g of ice (or roughly 30 mL – at standard temperature and pressure (STP – of air with 350 ppb of methane. This corresponds to recent tropospheric air samples (about 1900 ppb CH4 of about 6 mL (STP or about 500 pmol of pure CH4.

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

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A. F. Sabrekov

2017-08-01

Full Text Available 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.

Controls for multi-scale temporal variation in methane flux of a subtropical tidal salt marsh

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Li, H.

2016-12-01

Coastal wetlands provide critical carbon sequestration benefits, yet the production of methane (CH4) from these ecosystems can vary by an order of magnitude based on environmental and biological factors. Eddy covariance (EC) measurements for methane flux (FCH4) were performed in a subtropical tidal salt marsh of eastern China over 20 months. Spectral analysis techniques including the continuous wavelet transform, the wavelet coherence, the partial wavelet coherence and the multiple wavelet coherence were employed to analyze the periodicities and the main regulating factors of FCH4 in the tidal salt marsh. The annual budget of methane was 17.8 g C-CH4 m-2 yr-1, which was relatively high compared to those of most reported from inland wetland sites. In non-growing season, release of ebullition was the dominant driving mechanism for variability of FCH4 from hourly to monthly scales. There was no single dominant factor at short-term scale (half-day to 1-day) in growing season. It is worthwhile to note that tide was one of the most important factors regulating FCH4 at short time scale (half-day to 1-day). In comparison, the contribution of temperature to FCH4 at a short time scale (half-day to 1-day) was small due to its narrow range. In addition, plant-modulated transport and gross primary production also contributed to FCH4 at multiple temporal scales in this densely vegetated marsh, especially at weekly to monthly scales. Due to the complex interactive influences of tidal dynamics, temperature fluctuation, plant productivity, plant-mediated transport and release of ebullition on FCH4 exhibited no clear pattern of diurnal variation, but instead was highly variable.

Diurnal patterns of methane flux from a seasonal wetland: mechanisms and methodology

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Bansal, Sheel; Tangen, Brian; Finocchiaro, Raymond

2018-01-01

Methane emissions from wetlands are temporally dynamic. Few chamber-based studies have explored diurnal variation in methane flux with high temporal replication. Using an automated sampling system, we measured methane flux every 2.5 to 4 h for 205 diel cycles during three growing seasons (2013–2015) from a seasonal wetland in the Prairie Pothole Region of North America. During ponded conditions, fluxes were generally positive (i.e., methanogenesis dominant, 10.1 ± 0.8 mg m−2 h−1), had extreme range of variation (from −1 to 70 mg m−2 h−1), and were highest during late day. In contrast, during dry conditions fluxes were very low and primarily negative (i.e., oxidation dominant, −0.05 ± 0.002 mg m−2 h−1), with the highest (least negative) fluxes occurring at pre-dawn. During semi-saturated conditions, methane fluxes also were very low, oscillated between positive and negative values (i.e., balanced between methanogenesis and methane oxidation), and exhibited no diel pattern. Methane flux was positively correlated with air temperature during ponded conditions (r = 0.57) and negatively during dry conditions (r = −0.42). Multiple regression analyses showed that temperature, light and water-filled pore space explained 72% of variation in methane flux. Methane fluxes are highly temporally dynamic and follow contrasting diel patterns that are dependent on dominant microbial processes influenced by saturation state.

Carbon dioxide and methane fluxes from arctic mudboils

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Wilson, K.S.; Humphreys, E.R.

2010-01-01

Carbon-rich ecosystems in the Arctic have large stores of soil carbon. However, small changes in climate have the potential to change the carbon (C) balance. This study examined how changes in ecosystem structure relate to differences in the exchange of greenhouse gases, notably carbon dioxide (CO 2 ) and methane (CH 4 ), between the atmosphere and soil. In particular, it examined low-center mudboils to determine the influence that this distinct form of patterned ground in the Arctic may have on the overall C balance of Tundra ecosystems. The net ecosystem exchange of carbon dioxide (NEE) was measured along with methane efflux along a 35-m transect intersecting two mudboils in a wet sedge fen in Canada's Southern Arctic during the summer of 2008. Mudboil features revealed significant variations in vegetation, soil temperature and thaw depth, and soil organic matter content along this transect. Variations in NEE were attributed to changes in the amount of vascular vegetation, but CO 2 and CH 4 effluxes were similar among the two mudboil and the sedge fen sampling areas. The study showed that vegetation played a key role in limiting temporal variations in CH 4 effluxes through plant mediated transport in both mudboil and sedge fen sampling areas. The negligible vascular plant colonization in one of the mudboils was likely due to more active frost heave processes. Growth and decomposition of cryptogamic organisms along with inflow of dissolved organic C and warmer soil temperatures may have been the cause of the rather high CO 2 and CH 4 efflux in this mudboil area.

Effects of permafrost thaw on CO2 and CH4 exchange in a western Alaska peatland chronosequence

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Carmel E. Johnston,; Stephanie A. Ewing,; Harden, Jennifer W.; Ruth K. Varner,; Wickland, Kimberly P.; Koch, Joshua C.; Fuller, Christopher C.; Manies, Kristen L.; M. Torre Jorgenson,

2014-01-01

Permafrost soils store over half of global soil carbon (C), and northern frozen peatlands store about 10% of global permafrost C. With thaw, inundation of high latitude lowland peatlands typically increases the surface-atmosphere flux of methane (CH4), a potent greenhouse gas. To examine the effects of lowland permafrost thaw over millennial timescales, we measured carbon dioxide (CO2) and CH4 exchange along sites that constitute a ~1000 yr thaw chronosequence of thermokarst collapse bogs and adjacent fen locations at Innoko Flats Wildlife Refuge in western Alaska. Peak CH4exchange in July (123 ± 71 mg CH4–C m−2 d−1) was observed in features that have been thawed for 30 to 70 (peatlands, particularly those developed on poorly drained mineral substrates, are a key locus of elevated CH4 emission to the atmosphere that must be considered for a complete understanding of high latitude CH4 dynamics.

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Weld County Colorado using δ13CH4 analysis

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Rella, C.; Jacobson, G. A.; Crosson, E.; Sweeney, C.; Karion, A.; Petron, G.

2012-12-01

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Given that the global warming potential of methane is many times greater than that of carbon dioxide (Forster et al. 2007), the importance of quantifying methane emissions becomes clear. Companion presentations at this meeting describe efforts to quantify the overall methane emissions in two separate gas producing areas in Colorado and Utah during intensive field campaigns undertaken in 2012. A key step in the process of assessing the emissions arising from natural gas production activities is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One method for assessing the contribution of these different sources is stable isotope analysis. In particular, the δ13CH4 signature of natural gas (-37 permil) is significantly different that the signature of other significant sources of methane, such as landfills or ruminants (-50 to -70 permil). In this paper we present measurements of δ13CH4 in Colorado in Weld County, a region of intense natural gas production, using a mobile δ13CH4¬ analyzer capable of high-precision measurements of the stable isotope ratio of methane at ambient levels. This analyzer was used to make stable isotope measurements at a fixed location near the center of the gas producing region, from which an overall isotope ratio for the regional emissions is determined. In addition, mobile measurements in the nocturnal boundary layer have been made, over a total distance of 150 km throughout Weld County, allowing spatially resolved measurements of this isotope signature. Finally, this analyzer was used to quantify the isotopic signature of those individual sources (natural gas fugitive emissions, concentrated animal feeding operations, and landfills) that constitute the majority of methane emissions in this region, by making

Combining tracer flux ratio methodology with low-flying aircraft measurements to estimate dairy farm CH4 emissions

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Daube, C.; Conley, S.; Faloona, I. C.; Yacovitch, T. I.; Roscioli, J. R.; Morris, M.; Curry, J.; Arndt, C.; Herndon, S. C.

2017-12-01

Livestock activity, enteric fermentation of feed and anaerobic digestion of waste, contributes significantly to the methane budget of the United States (EPA, 2016). Studies question the reported magnitude of these methane sources (Miller et. al., 2013), calling for more detailed research of agricultural animals (Hristov, 2014). Tracer flux ratio is an attractive experimental method to bring to this problem because it does not rely on estimates of atmospheric dispersion. Collection of data occurred during one week at two dairy farms in central California (June, 2016). Each farm varied in size, layout, head count, and general operation. The tracer flux ratio method involves releasing ethane on-site with a known flow rate to serve as a tracer gas. Downwind mixed enhancements in ethane (from the tracer) and methane (from the dairy) were measured, and their ratio used to infer the unknown methane emission rate from the farm. An instrumented van drove transects downwind of each farm on public roads while tracer gases were released on-site, employing the tracer flux ratio methodology to assess simultaneous methane and tracer gas plumes. Flying circles around each farm, a small instrumented aircraft made measurements to perform a mass balance evaluation of methane gas. In the course of these two different methane quantification techniques, we were able to validate yet a third method: tracer flux ratio measured via aircraft. Ground-based tracer release rates were applied to the aircraft-observed methane-to-ethane ratios, yielding whole-site methane emission rates. Never before has the tracer flux ratio method been executed with aircraft measurements. Estimates from this new application closely resemble results from the standard ground-based technique to within their respective uncertainties. Incorporating this new dimension to the tracer flux ratio methodology provides additional context for local plume dynamics and validation of both ground and flight-based data.

Verification of Agricultural Methane Emission Inventories

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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.

New optical method for heat flux measurements in stagnation point laminar methane/air flames and hydrogen/methane/air flames using thermographic phosphors

Energy Technology Data Exchange (ETDEWEB)

Elmnefi, Mohamed Salem

2010-11-24

In the present study, a new optical method was implemented to study the heat transfer from flat stagnation point flames which can be regarded as one-dimensional in the central part. Premixed methane-air flames and hydrogen-methane-air flames were investigated. The effects of burner-to-plate distance and the fresh gas mixture velocity on heat transfer were examined. Experiments were performed using light induced phosphorescence from thermographic phosphors to study the wall temperatures and heat fluxes of nearly one-dimensional flat premixed flames impinging upward normally on a horizontal water cooled circular flat plate. The investigated flames were stoichiometric, lean and rich laminar methane/air flames with different equivalence ratios of {phi} =1, {phi} = 0.75 and {phi} = 1.25 and stoichiometric laminar hydrogen/methane/air flames. Mixtures of air with 10, 25, 50 and 75 % hydrogen in methane (CH{sub 4}) as well as a pure hydrogen flames at ambient pressure were investigated. The central part of this plate was an alumina ceramic plate coated from both sides with chromium doped alumina (ruby) and excited with a Nd:YAG laser or a green light emitting diode (LED) array to measure the wall temperature from both sides and thus the heat flux rate from the flame. The outlet velocity of the gases was varied from 0.1 m/s to 1.2 m/s. The burner to plate distance ranged from 0.5 to 2 times the burner exit diameter (d = 30 mm).The accuracy of the method was evaluated. The measured heat flux indicate the change of the flame stabilization mechanism from a burner stabilized to a stagnation plate stabilized flame. The results were compared to modeling results of a one dimensional stagnation point flow, with a detailed reaction mechanism. In order to prove the model, also measured gas phase temperatures by OH LIF for a stoichiometric stagnation point flame were discussed. It turns out that the flame stabilization mechanism and with it the heat fluxes change from low to high

Observations on the methane oxidation capacity of landfill soils

Science.gov (United States)

Field data and two independent models indicate that landfill cover methane (CH4) oxidation should not be considered as a constant 10% or any other single value. Percent oxidation is a decreasing exponential function of the total methane flux rate into the cover and is also dependent on climate and c...

Comparison of chamber and eddy covariance-based CO2 and CH4 emission estimates in a heterogeneous grass ecosystem on peat

International Nuclear Information System (INIS)

Schrier-Uijl, A.P.; Berendse, F.; Veenendaal, E.M.; Kroon, P.S.; Hensen, A.; Leffelaar, P.A.

2010-08-01

Fluxes of methane (CH4) and carbon dioxide (CO2) estimated by empirical models based on small-scale chamber measurements were compared to large-scale eddy covariance (EC) measurements for CH4 and to a combination of EC measurements and EC-based models for CO2. The experimental area was a flat peat meadow in the Netherlands with heterogeneous source strengths for both greenhouse gases. Two scenarios were used to assess the importance of stratifying the landscape into landscape elements before up-scaling the fluxes measured by chambers to landscape scale: one took the main landscape elements into account (field, ditch edge ditch), the other took only the field into account. Non-linear regression models were used to up-scale the chamber measurements to field emission estimates. EC CO2 respiration consisted of measured night time EC fluxes and modeled day time fluxes using the Arrhenius model. EC CH4 flux estimate was based on daily averages and the remaining data gaps were filled by linear interpolation. The EC and chamber-based estimates agreed well when the three landscape elements were taken into account with 16.5% and 13.0% difference for CO2 respiration and CH4, respectively. However, both methods differed 31.0% and 55.1% for CO2 respiration and CH4 when only field emissions were taken into account when up-scaling chamber measurements to landscape scale. This emphasizes the importance of stratifying the landscape into landscape elements. The conclusion is that small-scale chamber measurements can be used to estimate fluxes of CO2 and CH4 at landscape scale if fluxes are scaled by different landscape elements.

Australian methane fluxes

International Nuclear Information System (INIS)

Williams, D.J.

1990-01-01

Estimates are provided for the amount of methane emitted annually into the atmosphere in Australia for a variety of sources. The sources considered are coal mining, landfill, motor vehicles, natural gas suply system, rice paddies, bushfires, termites, wetland and animals. This assessment indicates that the major sources of methane are natural or agricultural in nature and therefore offer little scope for reduction. Nevertheless the remainder are not trival and reduction of these fluxes could play a significant part in any Australian action on the greenhouse problem. 19 refs., 7 tabs., 1 fig

Changes of soil carbon dioxide, methane, and nitrous oxide fluxes in relation to land use/cover management.

Science.gov (United States)

Kooch, Yahya; Moghimian, Negar; Bayranvand, Mohammad; Alberti, Giorgio

2016-06-01

Conversions of land use/cover are associated with changes in soil properties and biogeochemical cycling, with implications for carbon (C), nitrogen (N), and trace gas fluxes. In an attempt to provide a comprehensive evaluation of the significance of different land uses (Alnus subcordata plantation, Taxodium distichum plantation, agriculture, and deforested areas) on soil features and on the dynamics of greenhouse gas (GHG) fluxes at local scale, this study was carried out in Mazandaran province, northern Iran. Sixteen samples per land use, from the top 10 cm of soil, were taken, from which bulk density, texture, water content, pH, organic C, total N, microbial biomass of C and N, and earthworm density/biomass were determined. In addition, the seasonal changes in the fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) were monitored over a year. Our results indicated that the different land uses were different in terms of soil properties and GHG fluxes. Even though the amount of the GHG varied widely during the year, the highest CO2 and CH4 fluxes (0.32 mg CO2 m(-2) day(-1) and 0.11 mg CH4 m(-2) day(-1), respectively) were recorded in the deforested areas. N2O flux was higher in Alnus plantation (0.18 mg N2O m(-2) day(-1)) and deforested areas (0.17 mg N2O m(-2) day(-1)) than at agriculture site (0.05 mg N2O m(-2) day(-1)) and Taxodium plantation (0.03 mg N2O m(-2) day(-1)). This study demonstrated strong impacts of land use change on soil-atmosphere trace gas exchanges and provides useful observational constraints for top-down and bottom-up biogeochemistry models.

Potential for negative emissions of greenhouse gases (CO2, CH4 and N2O) through coastal peatland re-establishment: Novel insights from high frequency flux data at meter and kilometer scales

Science.gov (United States)

Windham-Myers, Lisamarie; Bergamaschi, Brian; Anderson, Frank; Knox, Sara; Miller, Robin; Fujii, Roger

2018-04-01

High productivity temperate wetlands that accrete peat via belowground biomass (peatlands) may be managed for climate mitigation benefits due to their global distribution and notably negative emissions of atmospheric carbon dioxide (CO2) through rapid storage of carbon (C) in anoxic soils. Net emissions of additional greenhouse gases (GHG)—methane (CH4) and nitrous oxide (N2O)—are more difficult to predict and monitor due to fine-scale temporal and spatial variability, but can potentially reverse the climate mitigation benefits resulting from CO2 uptake. To support management decisions and modeling, we collected continuous 96 hour high frequency GHG flux data for CO2, CH4 and N2O at multiple scales—static chambers (1 Hz) and eddy covariance (10 Hz)—during peak productivity in a well-studied, impounded coastal peatland in California’s Sacramento Delta with high annual rates of C fluxes, sequestering 2065 ± 150 g CO2 m‑2 y‑1 and emitting 64.5 ± 2.4 g CH4 m‑2 y‑1. Chambers (n = 6) showed strong spatial variability along a hydrologic gradient from inlet to interior plots. Daily (24 hour) net CO2 uptake (NEE) was highest near inlet locations and fell dramatically along the flowpath (‑25 to ‑3.8 to +2.64 g CO2 m‑2 d‑1). In contrast, daily net CH4 flux increased along the flowpath (0.39 to 0.62 to 0.88 g CH4 m‑2 d‑1), such that sites of high daily CO2 uptake were sites of low CH4 emission. Distributed, continuous chamber data exposed five novel insights, and at least two important datagaps for wetland GHG management, including: (1) increasing dominance of CH4 ebullition fluxes (15%–32% of total) along the flowpath and (2) net negative N2O flux across all sites as measured during a 4 day period of peak biomass (‑1.7 mg N2O m‑2 d‑1 0.51 g CO2 eq m‑2 d‑1). The net negative emissions of re-established peat-accreting wetlands are notably high, but may be poorly estimated by

A 4 U Laser Heterodyne Radiometer for Methane (CH4) and Carbon Dioxide (CO2) Measurements from an Occultation-Viewing CubSat

Science.gov (United States)

Wilson, Emily L.; DiGregorio, A. J.; Riot, Vincent J.; Ammons, Mark S.; Bruner, WIlliam W.; Carter, Darrell; Mao, Jianping; Ramanathan, Anand; Strahan, Susan E.; Oman, Luke D.;

CO2 and CH4 exchange by Phragmites australis under different climates

Science.gov (United States)

Serrano Ortiz, Penélope; Chojnickic, Bogdan H.; Sánchez-Cañete, Enrique P.; Kowalska, Natalia; López-Ballesteros, Ana; Fernández, Néstor; Urbaniak, Marek; Olejnik, Janusz; Kowalski, Andrew S.

2015-04-01

The key role of wetlands regarding global warming is the resulting balance between net CO2 assimilation, via photosynthesis, and CO2 and CH4 emissions, given the potential to release stored carbon, because of the high temperature sensitivity of heterotrophic soil respiration and anoxic conditions. However, it is still unknown whether wetlands will convert from long-term carbon sinks to sources as a result of climate change and other anthropogenic effects such as land use changes. Phragmites australis is one of the most common species found in wetlands and is considered the most globally widespread and productive plant species in this type of ecosystem. In this context, the main objective of this study is to analyse the GHG exchange (CO2 and CH4) of two wetlands with Phragmites australis as the dominant species under different climates using the eddy covariance (EC) technique. The first site, Padul, is located in southern Spain, with a sub-humid warm climate, characterised by a mean annual temperature of 16°C and annual precipitation of ca. 470 mm, with a very dry summer. The second site, Rzecin is located in Poland with a mean annual temperature of 8°C, and annual precipitation around 600mm with no dry season. The Padul EC station is equipped with two infrared gas analysers to measure CO2 and CH4 fluxes (LI-7200 and LI-7700 respectively) while the Rzecin EC station has the same CH4 sensor as Padul, but also a sensor measuring both GHG fluxes (DLT-100 Fast Methane Analyser, Los Gatos). In this study, we present: i) the results of a CH4 analyser inter-comparison campaign (LI-7700 vs. Los Gatos), ii) a comparative analysis of the functional behaviour of respiration and photosynthesis in both sites testing relationships between CO2 fluxes measured with the EC technique and meteorological variables such as temperature and direct or diffuse radiation and iii) the CH4 dynamicsat both sites by identifying, when possible, annual, seasonal and diurnal patterns.

Summer fluxes of atmospheric greenhouse gases N{sub 2}O, CH{sub 4} and CO{sub 2} from mangrove soil in South China

Energy Technology Data Exchange (ETDEWEB)

Chen, G.C. [Department of Biology and Chemistry, City University of Hong Kong, Hong Kong SAR (China); Tam, N.F.Y., E-mail: bhntam@cityu.edu.hk [Department of Biology and Chemistry, City University of Hong Kong, Hong Kong SAR (China); Ye, Y. [State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian (China)

2010-06-01

The atmospheric fluxes of N{sub 2}O, CH{sub 4} and CO{sub 2} from the soil in four mangrove swamps in Shenzhen and Hong Kong, South China were investigated in the summer of 2008. The fluxes ranged from 0.14 to 23.83 {mu}mol m{sup -2} h{sup -1}, 11.9 to 5168.6 {mu}mol m{sup -2} h{sup -1} and 0.69 to 20.56 mmol m{sup -2} h{sup -1} for N{sub 2}O, CH{sub 4} and CO{sub 2}, respectively. Futian mangrove swamp in Shenzhen had the highest greenhouse gas fluxes, followed by Mai Po mangrove in Hong Kong. Sha Kong Tsuen and Yung Shue O mangroves in Hong Kong had similar, low fluxes. The differences in both N{sub 2}O and CH{sub 4} fluxes among different tidal positions, the landward, seaward and bare mudflat, in each swamp were insignificant. The N{sub 2}O and CO{sub 2} fluxes were positively correlated with the soil organic carbon, total nitrogen, total phosphate, total iron and NH{sub 4}{sup +}-N contents, as well as the soil porosity. However, only soil NH{sub 4}{sup +}-N concentration had significant effects on CH{sub 4} fluxes.

SOIL 222Rn CONCENTRATION, CO2 AND CH4 FLUX MEASUREMENTS AROUND THE JWALAMUKHI AREA OF NORTH-WEST HIMALAYAS, INDIA.

Science.gov (United States)

Kumar, Arvind; Walia, Vivek; Yang, Tsanyao Frank; Fu, Ching-Chou; Singh, Surinder; Bajwa, Bikramjit Singh; Arora, Vishal

2016-10-01

Soil 222 Rn concentration, CO 2 and CH 4 flux measurements were conducted around the Jwalamukhi area of North-West Himalayas, India. During this study, around 37 soil gas points and flux measurements were taken with the aim to assure the suitability of this method in the study of fault zones. For this purpose, RAD 7 (Durridge, USA) was used to monitor radon concentrations, whereas portable diffuse flux meter (West Systems, Italy) was used for the CO 2 and CH 4 flux measurements. The recorded radon concentration varies from 6.1 to 34.5 kBq m -3 with an average value of 16.5 kBq m -3 The anomalous value of radon concentrations was recorded between Jwalamukhi thrust and Barsar thrust. The recorded average of CO 2 and CH 4 flux were 11.8 and 2.7 g m -2 day -1 , respectively. The good correlation between anomalous CO 2 flux and radon concentrations has been observed along the fault zone in the study area, suggesting that radon migration is dependent on CO 2 . © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

BOREAS TF-04 CO2 and CH4 Chamber Flux Data from the SSA

Data.gov (United States)

National Aeronautics and Space Administration — ABSTRACT: Contains fluxes of carbon dioxide and methane across the soil-air interface in four ages of jack pine forest at the Southern Study Area. Gross and net flux...

Linking rhizospheric CH₄ oxidation and net CH₄ emissions in an arctic wetland based on ¹³CH₄ labeling of mesocosms

DEFF Research Database (Denmark)

Nielsen, Cecilie Skov; Michelsen, Anders; Ambus, Per

2017-01-01

Aims: Poorly drained arctic ecosystems are potential large emitters of methane (CH4) due to their high soil organic carbon content and low oxygen availability. In wetlands, aerenchymatous plants transport CH4 from the soil to the atmosphere, but concurrently transport O2 to the rhizosphere, which...... may lead to oxidation of CH4. The importance of the latter process is largely unknown for arctic plant species and ecosystems. Here, we aim to quantify the subsurface oxidation of CH4 in a waterlogged arctic ecosystem dominated by Carex aquatilis ssp. stans and Eriophorum angustifolium, and evaluate...... during three weeks after addition of 13C-enriched CH4 below the mesocosm. Results: Most of the recovered 13C label (>98 %) escaped the ecosystem as CH4, while less than 2 % was oxidized to 13CO2. Conclusions: It is concluded that aerenchymatous plants control the overall CH4 emissions but, as a transport...

Tropical rainforest methane consumption during the El Niño of 2015-16

Science.gov (United States)

Aronson, E. L.; Dierick, D.; Botthoff, J.; Swanson, A. C.; Allen, M. F.

2016-12-01

Tropical forests sequester up to 40% of the anthropogenic and natural carbon exchanged with the atmosphere. Even though soils are the largest pool of terrestrial carbon, relatively little is known about the methane consumption capacity of tropical forest soils. Under high water, low oxygen (anaerobic) conditions, carbon decomposed is respired as methane (CH4) by methanogen microorganisms. During dry seasons, deeper rainforest soils remain wet, but dry at the surface. Since molecule for molecule the global warming potential of CH4 is two orders of magnitude greater than CO2, the relative production and sequestration of CO2 versus CH4 in tropical rainforests has a large impact on global climate trends. In 2015-16, the globe experienced an unusually strong ENSO event, which impacted the tropics. Atypical ENSO climatic events such as this include drought in tropical forests of Central America. We hypothesized that ENSO controls much of the year-to-year variability in the global CH4 cycle, primarily by turning the tropical forest from a strong annual source for CH4 during the La Niña or normal rainy season, to a year-round sink for CH4 during El Niño events. Further, we hypothesized that during a strong El Niño event, the unusually dry conditions of the tropical rainy season lead to the methanotrophs in these soils consuming large amounts of CH4. In order to investigate these predictions, CH4 flux was measured in three campaigns in March, during peak ENSO impact, as well as May and July 2016, at the La Selva Biological Station, Costa Rica. Fluxes were measured in eight paired plots, each with four collars. The collars measure 20 cm diameter by 12 cm in length, inserted into the soil, with a collar height of around 8 cm, in February 2016, a month before the first field campaign. Air samples were injected into pre-evacuated exetainers, and analyzed by gas chromatograph within 72 h. We found an average CH4 sink of -0.018 mg m-2 h-1. This flux is roughly four times lower

A 4 U laser heterodyne radiometer for methane (CH4) and carbon dioxide (CO2) measurements from an occultation-viewing CubeSat

International Nuclear Information System (INIS)

Wilson, Emily L; Oman, Luke D; DiGregorio, A J; Garner, Richard M; Riot, Vincent J; Ammons, Mark S; Bruner, William W; Carter, Darrell; Mao, Jianping; Ramanathan, Anand; Strahan, Susan E; Hoffman, Christine

2017-01-01

We present a design for a 4 U (20 cm  ×  20 cm  ×  10 cm) occultation-viewing laser heterodyne radiometer (LHR) that measures methane (CH 4 ), carbon dioxide (CO 2 ) and water vapor (H 2 O) in the limb that is designed for deployment on a 6 U CubeSat. The LHR design collects sunlight that has undergone absorption by the trace gas and mixes it with a distributive feedback (DFB) laser centered at 1640 nm that scans across CO 2 , CH 4 , and H 2 O absorption features. Upper troposphere/lower stratosphere measurements of these gases provide key inputs to stratospheric circulation models: measuring stratospheric circulation and its variability is essential for projecting how climate change will affect stratospheric ozone. (paper)

A 4 U laser heterodyne radiometer for methane (CH4) and carbon dioxide (CO2) measurements from an occultation-viewing CubeSat

Science.gov (United States)

Wilson, Emily L.; DiGregorio, A. J.; Riot, Vincent J.; Ammons, Mark S.; Bruner, William W.; Carter, Darrell; Mao, Jianping; Ramanathan, Anand; Strahan, Susan E.; Oman, Luke D.; Hoffman, Christine; Garner, Richard M.

2017-03-01

We present a design for a 4 U (20 cm  ×  20 cm  ×  10 cm) occultation-viewing laser heterodyne radiometer (LHR) that measures methane (CH4), carbon dioxide (CO2) and water vapor (H2O) in the limb that is designed for deployment on a 6 U CubeSat. The LHR design collects sunlight that has undergone absorption by the trace gas and mixes it with a distributive feedback (DFB) laser centered at 1640 nm that scans across CO2, CH4, and H2O absorption features. Upper troposphere/lower stratosphere measurements of these gases provide key inputs to stratospheric circulation models: measuring stratospheric circulation and its variability is essential for projecting how climate change will affect stratospheric ozone.

Implications of Representative Concentration Pathway 4.5 Methane Emissions to Stabilize Radiative Forcing

Energy Technology Data Exchange (ETDEWEB)

Emanuel, William R.; Janetos, Anthony C.

2013-02-01

Increases in the abundance of methane (CH4) in the Earth’s atmosphere are responsible for significant radiative forcing of climate change (Forster et al., 2007; Wuebbles and Hayhoe, 2002). Since 1750, a 2.5 fold increase in atmospheric CH4 contributed 0.5 W/m2 to direct radiative forcing and an additional 0.2 W/m2 indirectly through changes in atmospheric chemistry. Next to water and carbon dioxide (CO2), methane is the most abundant greenhouse gas in the troposphere. Additionally, CH4 is significantly more effective as a greenhouse gas on a per molecule basis than is CO2, and increasing atmospheric CH4 has been second only to CO2 in radiative forcing (Forster et al., 2007). The chemical reactivity of CH4 is important to both tropospheric and stratospheric chemistry. Along with carbon monoxide, methane helps control the amount of the hydroxyl radical (OH) in the troposphere where oxidation of CH4 by OH leads to the formation of formaldehyde, carbon monoxide, and ozone.

Biogeochemical cycles at the sulfate-methane transition zone (SMTZ) and geochemical characteristics of the pore fluids offshore southwestern Taiwan

Science.gov (United States)

Hu, Ching-Yi; Frank Yang, Tsanyao; Burr, George S.; Chuang, Pei-Chuan; Chen, Hsuan-Wen; Walia, Monika; Chen, Nai-Chen; Huang, Yu-Chun; Lin, Saulwood; Wang, Yunshuen; Chung, San-Hsiung; Huang, Chin-Da; Chen, Cheng-Hong

2017-11-01

In this study, we used pore water dissolved inorganic carbon (DIC), SO42-, Ca2+ and Mg2+ gradients at the sulfate-methane transition zone (SMTZ) to estimate biogeochemical fluxes for cored sediments collected offshore SW Taiwan. Net DIC flux changes (ΔDIC-Prod) were applied to determine the proportion of sulfate consumption by organic matter oxidation (heterotrophic sulfate reduction) and anaerobic oxidation of methane (AOM), and to determine reliable CH4 fluxes at the SMTZ. Our results show that SO42- profiles are mainly controlled by AOM rather than heterotrophic sulfate reduction. Refinement of CH4 flux estimates enhance our understanding of methane abundance from deep carbon reservoirs to the SMTZ. Concentrations of chloride (Cl-), bromide (Br-) and iodide (I-) dissolved in pore water were used to identify potential sources that control fluid compositions and the behavior of dissolved ions. Constant Cl- concentrations throughout ∼30 m sediment suggest no influence of gas hydrates for the compositions within the core. Bromide (Br-) and Iodine (I-) concentrations increase with sediment depth. The I-/Br- ratio appears to reflect organic matter degradation. SO42- concentrations decrease with sediment depth at a constant rate, and sediment depth profiles of Br- and I- concentrations suggests diffusion as the main transport mechanism. Therefore diffusive flux calculations are reasonable. Coring sites with high CH4 fluxes are more common in the accretionary wedge, amongst thrust faults and fractures, than in the passive continental margin offshore southwestern Taiwan. AOM reactions are a major sink for CH4 passing upward through the SMTZ and prevent high methane fluxes in the water column and to the atmosphere.

Uncertainties in modelling CH4 emissions from northern wetlands in glacial climates: the role of vegetation parameters

Directory of Open Access Journals (Sweden)

J. van Huissteden

2011-10-01

Full Text Available Marine Isotope Stage 3 (MIS 3 interstadials are marked by a sharp increase in the atmospheric methane (CH4 concentration, as recorded in ice cores. Wetlands are assumed to be the major source of this CH4, although several other hypotheses have been advanced. Modelling of CH4 emissions is crucial to quantify CH4 sources for past climates. Vegetation effects are generally highly generalized in modelling past and present-day CH4 fluxes, but should not be neglected. Plants strongly affect the soil-atmosphere exchange of CH4 and the net primary production of the vegetation supplies organic matter as substrate for methanogens. For modelling past CH4 fluxes from northern wetlands, assumptions on vegetation are highly relevant since paleobotanical data indicate large differences in Last Glacial (LG wetland vegetation composition as compared to modern wetland vegetation. Besides more cold-adapted vegetation, Sphagnum mosses appear to be much less dominant during large parts of the LG than at present, which particularly affects CH4 oxidation and transport. To evaluate the effect of vegetation parameters, we used the PEATLAND-VU wetland CO2/CH4 model to simulate emissions from wetlands in continental Europe during LG and modern climates. We tested the effect of parameters influencing oxidation during plant transport (fox, vegetation net primary production (NPP, parameter symbol Pmax, plant transport rate (Vtransp, maximum rooting depth (Zroot and root exudation rate (fex. Our model results show that modelled CH4 fluxes are sensitive to fox and Zroot in particular. The effects of Pmax, Vtransp and fex are of lesser relevance. Interactions with water table modelling are significant for Vtransp. We conducted experiments with different wetland vegetation types for Marine Isotope Stage 3 (MIS 3 stadial and interstadial climates and the present-day climate, by coupling PEATLAND-VU to high resolution climate model simulations for Europe. Experiments assuming

Uncertainties in modelling CH4 emissions from northern wetlands in glacial climates: the role of vegetation parameters

Science.gov (United States)

Berrittella, C.; van Huissteden, J.

2011-10-01

Marine Isotope Stage 3 (MIS 3) interstadials are marked by a sharp increase in the atmospheric methane (CH4) concentration, as recorded in ice cores. Wetlands are assumed to be the major source of this CH4, although several other hypotheses have been advanced. Modelling of CH4 emissions is crucial to quantify CH4 sources for past climates. Vegetation effects are generally highly generalized in modelling past and present-day CH4 fluxes, but should not be neglected. Plants strongly affect the soil-atmosphere exchange of CH4 and the net primary production of the vegetation supplies organic matter as substrate for methanogens. For modelling past CH4 fluxes from northern wetlands, assumptions on vegetation are highly relevant since paleobotanical data indicate large differences in Last Glacial (LG) wetland vegetation composition as compared to modern wetland vegetation. Besides more cold-adapted vegetation, Sphagnum mosses appear to be much less dominant during large parts of the LG than at present, which particularly affects CH4 oxidation and transport. To evaluate the effect of vegetation parameters, we used the PEATLAND-VU wetland CO2/CH4 model to simulate emissions from wetlands in continental Europe during LG and modern climates. We tested the effect of parameters influencing oxidation during plant transport (fox), vegetation net primary production (NPP, parameter symbol Pmax), plant transport rate (Vtransp), maximum rooting depth (Zroot) and root exudation rate (fex). Our model results show that modelled CH4 fluxes are sensitive to fox and Zroot in particular. The effects of Pmax, Vtransp and fex are of lesser relevance. Interactions with water table modelling are significant for Vtransp. We conducted experiments with different wetland vegetation types for Marine Isotope Stage 3 (MIS 3) stadial and interstadial climates and the present-day climate, by coupling PEATLAND-VU to high resolution climate model simulations for Europe. Experiments assuming dominance of

Methane Fluxes and Consumption in an Oil Sands Tailings End Pit Lake

Science.gov (United States)

Slater, G. F.; Goad, C.; Arriaga, D.; Risacher, F.; Morris, P.; Lindsay, M. B.; Mumford, K. G.; Warren, L. A.

2017-12-01

End pit lakes are engineered freshwater lakes designed to reclaim land impacted by surface mining activities via establishment of a functioning ecosystem where biogeochemical cycling mitigates release of hazardous components either by stabilization or biodegradation. End pit lakes provide unique opportunities to gain insight into microbial nutrient cycling under extreme levels of impact that can be applicable to a range of levels of anthropogenic impacts and issues. This study focuses on microbial CH4 cycling in the underlying fluid fine tailings (FFT) and surface waters of Base Mine Lake (BML), the first full demonstration of end pit lake reclamation in the Athabasca Oil Sands Region (AOSR) of northern Alberta, Canada. Over two field seasons (2015 and 2016) BML was thermally stratified, turning over in spring and fall. Oxygen concentrations in the epilimnion (70 to 80 % saturation) decreased steeply through the metalimnion to 3% saturation in the hypolimnion. Conversely, CH4 concentrations were highest in the hypolimnion of BML (25 to 140 µM) with the highest values being observed at the FFT/Water interface. Concentrations decreased to 1-2 µM at the metalimnion and further decreased to < 0.5 µM in the epilimnion. CH4 δ13C in FFT porewater indicated production via fermentative pathways. FFT settlement and dewatering of 0.73 to 1.0 m/yr results in advection of an estimated 1x107 to 2x107 moles/yr CH4 into the surface water, circa an order of magnitude greater than the 3x106 moles/year estimated for molecular diffusion. Calculated fluxes of dissolved CH4 from the FFT into the hypolimnion were 4 orders of magnitude higher than those from the hypolimnion to the metalimnion, indicating a significant sink for CH4 within the hypolimnion limiting upward dissolved CH4 transport. Dissolution of CH4 from bubbles released from the FFT may be contributing to the observed epilimnion concentrations. CH4 δ13C in the hypolimnion showed only minimal enrichment with decreasing

Growing season CH4 and N2O fluxes from a subarctic landscape in northern Finland; from chamber to landscape scale

Science.gov (United States)

Dinsmore, Kerry J.; Drewer, Julia; Levy, Peter E.; George, Charles; Lohila, Annalea; Aurela, Mika; Skiba, Ute M.

2017-02-01

Subarctic and boreal emissions of CH4 are important contributors to the atmospheric greenhouse gas (GHG) balance and subsequently the global radiative forcing. Whilst N2O emissions may be lower, the much greater radiative forcing they produce justifies their inclusion in GHG studies. In addition to the quantification of flux magnitude, it is essential that we understand the drivers of emissions to be able to accurately predict climate-driven changes and potential feedback mechanisms. Hence this study aims to increase our understanding of what drives fluxes of CH4 and N2O in a subarctic forest/wetland landscape during peak summer conditions and into the shoulder season, exploring both spatial and temporal variability, and uses satellite-derived spectral data to extrapolate from chamber-scale fluxes to a 2 km × 2 km landscape area.From static chamber measurements made during summer and autumn campaigns in 2012 in the Sodankylä region of northern Finland, we concluded that wetlands represent a significant source of CH4 (3.35 ± 0.44 mg C m-2 h-1 during the summer campaign and 0.62 ± 0.09 mg C m-2 h-1 during the autumn campaign), whilst the surrounding forests represent a small sink (-0.06 ± zero across both ecosystems.We found a weak negative relationship between CH4 emissions and water table depth in the wetland, with emissions decreasing as the water table approached and flooded the soil surface and a positive relationship between CH4 emissions and the presence of Sphagnum mosses. Temperature was also an important driver of CH4 with emissions increasing to a peak at approximately 12 °C. Little could be determined about the drivers of N2O emissions given the small magnitude of the fluxes.A multiple regression modelling approach was used to describe CH4 emissions based on spectral data from PLEIADES PA1 satellite imagery across a 2 km × 2 km landscape. When applied across the whole image domain we calculated a CH4 source of 2.05 ± 0.61 mg C m-2 h-1. This was

Effect of summer throughfall exclusion, summer drought, and winter snow cover on methane fluxes in a temperate forest soil

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Borken, W.; Davidson, E.A.; Savage, K.; Sundquist, E.T.; Steudler, P.

2006-01-01

Soil moisture strongly controls the uptake of atmospheric methane by limiting the diffusion of methane into the soil, resulting in a negative correlation between soil moisture and methane uptake rates under most non-drought conditions. However, little is known about the effect of water stress on methane uptake in temperate forests during severe droughts. We simulated extreme summer droughts by exclusion of 168 mm (2001) and 344 mm (2002) throughfall using three translucent roofs in a mixed deciduous forest at the Harvard Forest, Massachusetts, USA. The treatment significantly increased CH4 uptake during the first weeks of throughfall exclusion in 2001 and during most of the 2002 treatment period. Low summertime CH4 uptake rates were found only briefly in both control and exclusion plots during a natural late summer drought, when water contents below 0.15 g cm-3 may have caused water stress of methanotrophs in the A horizon. Because these soils are well drained, the exclusion treatment had little effect on A horizon water content between wetting events, and the effect of water stress was smaller and more brief than was the overall treatment effect on methane diffusion. Methane consumption rates were highest in the A horizon and showed a parabolic relationship between gravimetric water content and CH4 consumption, with maximum rate at 0.23 g H2O g-1 soil. On average, about 74% of atmospheric CH4 was consumed in the top 4-5 cm of the mineral soil. By contrast, little or no CH4 consumption occurred in the O horizon. Snow cover significantly reduced the uptake rate from December to March. Removal of snow enhanced CH4 uptake by about 700-1000%, resulting in uptake rates similar to those measured during the growing season. Soil temperatures had little effect on CH4 uptake as long as the mineral soil was not frozen, indicating strong substrate limitation of methanotrophs throughout the year. Our results suggest that the extension of snow periods may affect the annual rate

Tropospheric radiative forcing of CH4

International Nuclear Information System (INIS)

Grossman, A.S.; Grant, K.E.

1994-04-01

We have evaluated the tropospheric radiative forcing of CH 4 in the 0-3000 cm -1 wavenumber range and compared this with prior published calculations. The atmospheric test cases involved perturbed methane scenarios in both a McClatchey mid latitude, summer, clear sky approximation, model atmosphere, as well as a globally and seasonally averaged model atmosphere containing a representative cloud distribution. The scenarios involved pure CH 4 radiative forcing and CH 4 plus a mixture of H 2 O, CO 2 , O 3 , and N 2 O. The IR radiative forcing was calculated using a correlated k-distribution transmission model. The major purposes of this paper are to first, use the correlated k-distribution model to calculate the tropospheric radiative forcing for CH 4 , as the only radiatively active gas, and in a mixture with H 2 O, CO 2 , O 3 , and N 2 O, for a McClatchey mid-latitude summer, clear-sky model atmosphere, and to compare the results to those obtained in the studies mentioned above. Second, we will calculate the tropospheric methane forcing in a globally and annually averaged atmosphere with and without a representative cloud distribution in order to validate the conjecture given in IPCC (1990) that the inclusion of clouds in the forcing calculations results in forcing values which are approximately 20 percent less than those obtained using clear sky approximations

Implications for carbon processing beneath the Greenland Ice Sheet from dissolved CO2 and CH4 concentrations of subglacial discharge

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Pain, A.; Martin, J.; Martin, E. E.

2017-12-01

Subglacial carbon processes are of increasing interest as warming induces ice melting and increases fluxes of glacial meltwater into proglacial rivers and the coastal ocean. Meltwater may serve as an atmospheric source or sink of carbon dioxide (CO2) or methane (CH4), depending on the magnitudes of subglacial organic carbon (OC) remineralization, which produces CO2 and CH4, and mineral weathering reactions, which consume CO2 but not CH4. We report wide variability in dissolved CO2 and CH4 concentrations at the beginning of the melt season (May-June 2017) between three sites draining land-terminating glaciers of the Greenland Ice Sheet. Two sites, located along the Watson River in western Greenland, drain the Isunnguata and Russell Glaciers and contained 1060 and 400 ppm CO2, respectively. In-situ CO2 flux measurements indicated that the Isunnguata was a source of atmospheric CO2, while the Russell was a sink. Both sites had elevated CH4 concentrations, at 325 and 25 ppm CH4, respectively, suggesting active anaerobic OC remineralization beneath the ice sheet. Dissolved CO2 and CH4 reached atmospheric equilibrium within 2.6 and 8.6 km downstream of Isunnguata and Russell discharge sites, respectively. These changes reflect rapid gas exchange with the atmosphere and/or CO2 consumption via instream mineral weathering. The third site, draining the Kiagtut Sermiat in southern Greenland, had about half atmospheric CO2 concentrations (250 ppm), but approximately atmospheric CH4 concentrations (2.1 ppm). Downstream CO2 flux measurements indicated ingassing of CO2 over the entire 10-km length of the proglacial river. CO2 undersaturation may be due to more readily weathered lithologies underlying the Kiagtut Sermiat compared to Watson River sites, but low CH4 concentrations also suggest limited contributions of CO2 and CH4 from OC remineralization. These results suggest that carbon processing beneath the Greenland Ice Sheet may be more variable than previously recognized

New accurate theoretical line lists of 12CH4 and 13CH4 in the 0-13400 cm-1 range: Application to the modeling of methane absorption in Titan's atmosphere

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Rey, Michaël; Nikitin, Andrei V.; Bézard, Bruno; Rannou, Pascal; Coustenis, Athena; Tyuterev, Vladimir G.

2018-03-01

The spectrum of methane is very important for the analysis and modeling of Titan's atmosphere but its insufficient knowledge in the near infrared, with the absence of reliable absorption coefficients, is an important limitation. In order to help the astronomer community for analyzing high-quality spectra, we report in the present work the first accurate theoretical methane line lists (T = 50-350 K) of 12CH4 and 13CH4 up to 13400 cm-1 ( > 0.75 μm). These lists are built from extensive variational calculations using our recent ab initio potential and dipole moment surfaces and will be freely accessible via the TheoReTS information system (http://theorets.univ-reims.fr, http://theorets.tsu.ru). Validation of these lists is presented throughout the present paper. For the sample of lines where upper energies were available from published analyses of experimental laboratory 12CH4 spectra, small empirical corrections in positions were introduced that could be useful for future high-resolution applications. We finally apply the TheoRetS line list to model Titan spectra as observed by VIMS and by DISR, respectively onboard Cassini and Huygens. These data are used to check that the TheoReTS line lists are able to model observations. We also make comparisons with other experimental or theoretical line lists. It appears that TheoRetS gives very reliable results better than ExoMol and even than HITRAN2012, except around 1.6 μm where it gives very similar results. We conclude that TheoReTS is suitable to be used for the modeling of planetary radiative transfer and photometry. A re-analysis of spectra recorded by the DISR instrument during the descent of the Huygens probe suggests that the CH4 mixing ratio decreases with altitude in Titan's stratosphere, reaching a value of ∼10-2 above the 110 km altitude.

Assessment of winter fluxes of CO2 and CH4 in boreal forest soils of central Alaska estimated by the profile method and the chamber method: a diagnosis of methane emission and implications for the regional carbon budget

International Nuclear Information System (INIS)

Kim, Yongwon; Ueyama, Masahito; Harazono, Yoshinobu; Tanaka, Noriyuki; Nakagawa, Fumiko; Tsunogai, Urumu

2007-01-01

This research was carried out to estimate the winter fluxes of CO 2 and CH 4 using the concentration profile method and the chamber method in black spruce forest soils in central Alaska during the winter of 2004/5. The average winter fluxes of CO 2 and CH 4 by chamber and profile methods were 0.24 ± 0.06 (SE; standard error) and 0.21 ± 0.06 gCO 2 -C/m2/d, and 21.4 ± 5.6 and 21.4 ± 14 μgCH 4 -C/m2/hr. This suggests that the fluxes estimated by the two methods are not significantly different based on a one-way ANOVA with a 95% confidence level. The hypothesis on the processes of CH 4 transport/production/emission in underlying snow-covered boreal forest soils is proven by the pressure differences between air and in soil at 30 cm depth. The winter CO 2 emission corresponds to 23% of the annual CO 2 emitted from Alaska black spruce forest soils, which resulted in the sum of mainly root respiration and microbial respiration during the winter based on the (delta) 13 CO 2 of -2.25%. The average wintertime emissions of CO 2 and CH 4 were 49 ± 13 gCO 2 -C/m 2 /season and 0.11 ± 0.07 gCH 4 -C/m 2 /season, respectively. This implies that winter emissions of CO 2 and CH 4 are an important part of the annual carbon budget in seasonally snow-covered terrain of typical boreal forest soils

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

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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

Fluxes of N2O and CH4 from forest and grassland lysimeter soils in response to simulated climate change

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Weymann, Daniel; Brueggemann, Nicolas; Puetz, Thomas; Vereecken, Harry

2015-04-01

Central Europe is expected to be exposed to altered temperature and hydrological conditions, which will affect the vulnerability of nitrogen and carbon cycling in soils and thus production and fluxes of climate relevant trace gases. However, knowledge of the response of greenhouse gas fluxes to climate change is limited so far, but will be an important basis for future climate projections. Here we present preliminary results of an ongoing lysimeter field study which aims to assess the impact of simulated climate change on N2O and CH4 fluxes from a forest and a fertilized grassland soil. The lysimeters are part of the Germany-wide research infrastructure TERENO, which investigates feedbacks of climate change to the pedosphere on a long-term scale. Lysimeters (A = 1m2) were established in 2010 at high elevated sites (HE, 500 and 600 m.a.s.l.) and subsequently transferred along an altitudinal gradient to a low elevated site (LE, 100 m.a.s.l.) within the Eifel / Lower Rhine Valley Observatory in Western Germany, thereby resulting in a temperature increase of 2.3 K whereas precipitation decreased by 160 mm during the present study period. Systematic monitoring of soil-atmosphere exchange of N2O and CH4 based on weekly manual closed chamber measurements at HE and LE sites has started in August 2013. Furthermore, we routinely determine dissolved N2O and CH4 concentrations in the seepage water using a headspace equilibration technique and record water discharge in order to quantify leaching losses of both greenhouse gases. Cumulative N2O fluxes clearly responded to simulated climate change conditions and increased by 250 % and 600 % for the forest and the grassland soil, respectively. This difference between the HE and LE sites was mainly caused by an exceptionally heavy precipitation event in July 2014 which turned the LE site sustainably to a consistently higher emission level. Nonetheless, emissions remained rather small and ranged between 20 and 40 μg m-2 h-1. In

Comprehensive effects of a sedge plant on CH4 and N2O emissions in an estuarine marsh

Science.gov (United States)

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.

Eddy covariance methane measurements at a Ponderosa pine plantation in California

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T. Röckmann

2009-11-01

Full Text Available Long term methane flux measurements have been mostly performed with plant or soil enclosure techniques on specific components of an ecosystem. New fast response methane analyzers make it possible to use the eddy covariance (EC technique instead. The EC technique is advantageous because it allows continuous flux measurements integrating over a larger and more representative area including the complete ecosystem, and allows fluxes to be observed as environmental conditions change naturally without disturbance. We deployed the closed-path Fast Methane analyzer (FMA from Los Gatos Research Ltd and demonstrate its performance for EC measurements at a Ponderosa pine plantation at the Blodgett Forest site in central California. The fluctuations of the CH₄ concentration measured at 10 Hz appear to be small and their standard deviation is comparable to the magnitude of the signal noise (±5 ppbv. Consequently, the power spectra typically have a white noise signature at the high frequency end (a slope of +1. Nevertheless, in the frequency range important for turbulent exchange, the cospectra of CH₄ compare very well with all other scalar cospectra confirming the quality of the FMA measurements are good for the EC technique. We furthermore evaluate the complications of combined open and closed-path measurements when applying the Webb-Pearman-Leuning (WPL corrections (Webb et al., 1980 and the consequences of a phase lag between the water vapor and methane signal inside the closed path system. The results of diurnal variations of CH₄ concentrations and fluxes are summarized and compared to the monthly results of process-based model calculations.

Spartina alterniflora alters ecosystem DMS and CH4 emissions and their relationship along interacting tidal and vegetation gradients within a coastal salt marsh in Eastern China

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Wang, Jinxin; Wang, Jinshu

2017-10-01

Invasive Spartina alterniflora accumulates organic carbon rapidly and can utilize a wide range of potential precursors for dimethyl sulfide (DMS) production, as well as a wide variety of methanogenic substrates. Therefore, we predicted that S. alterniflora invasion would alter the relationships between DMS and methane (CH4) fluxes along the interacting gradients of tidal influence and vegetation, as well as the ecosystem-atmosphere exchange of DMS and CH4. In this study, we used static flux chambers to measure DMS and CH4 fluxes in August (growing season) and December (non-growing season) of 2013, along creek and vegetation transects in an Eastern Chinese coastal salt marsh. S. alterniflora invasion dramatically increased DMS and CH4 emission rates by 3.8-513.0 and 2.0-127.1 times the emission rates within non-vegetated regions and regions populated with native species, respectively, and significantly altered the spatial distribution of DMS and CH4 emissions. We also observed a substantial amount of variation in the DMS and CH4 fluxes along the elevation gradient in the salt marsh studied. A significant relationship between DMS and CH4 fluxes was observed, with the CH4 flux passively related to the DMS flux. The correlation between CH4 and DMS emissions along the vegetation transects was more significant than along the tidal creek. In the S. alterniflora salt marsh, the relationship between DMS and CH4 fluxes was more significant than within any other salt marsh. Additionally, CH4 emissions within the S. alterniflora salt marsh were more sensitive to the variation in DMS emissions than within any other vegetation zone. The spatial variability in the relationship observed between DMS and CH4 fluxes appears to be at least partly due to the alteration of substrates involved in DMS and CH4 by S. alterniflora invasion. In the S. alterniflora salt marsh, methanogenesis was more likely to be derived from non-competitive substrates than competitive substrates, but within

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

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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.

Year-round methane emissions from permafrost in a North-east Siberian region

Science.gov (United States)

Castro-Morales, Karel; Kaiser, Sonja; Kleinen, Thomas; Kwon, Min Jung; Kittler, Fanny; Zaehle, Sönke; Beer, Christian; Göckede, Mathias

2017-04-01

(max. 2 mg CH4 m-2 d-1) when the thickness of the snow layer starts to melt or accumulate, respectively. The performance of the model was evaluated by comparing the modeled total methane emissions from a section of the Kolyma river floodplain near Chersky, against methane fluxes obtained from eddy covariance (for 2014 and 2015) and chambers (for June - August 2014) measured in the same area. Model results agree well with observations, with the highest emissions during August each year with 92.3 mg CH4 m-2 d-1 from eddy fluxes, 72.5 mg CH4 m-2 d-1 from chambers and 79.0 mg CH4 m-2 d-1 from the model in 2014, while 64.4 mg CH4 m-2 d-1 from eddy and 66.3 mg CH4 m-2 d-1 from the model in August 2015. The model underestimates winter emissions by up to 15 mg CH4 m-2 d-1, however a better agreement is observed in April 2014. To understand the shortcomings of the model against observations, the heterogeneity between model grid cells will be discussed.

One year of continuous measurements of soil CH4 and CO2 fluxes in a Japanese cypress forest: Temporal and spatial variations associated with Asian monsoon rainfall

OpenAIRE

Sakabe, Ayaka; Kosugi, Yoshiko; Takahashi, Kenshi; Itoh, Masayuki; Kanazawa, Akito; Makita, Naoki; Ataka, Mioko

2015-01-01

We examined the effects of Asian monsoon rainfall on CH[4] absorption of water-unsaturated forest soil. We conducted a 1 year continuous measurement of soil CH[4] and CO[2] fluxes with automated chamber systems in three plots with different soil characteristics and water content to investigate how temporal variations in CH[4] fluxes vary with the soil environment. CH[4] absorption was reduced by the “Baiu” summer rainfall event and peaked during the subsequent hot, dry period. Although CH[4] ...

Impact of the heatwave in 2003 on the summer CH4 and N2O budget of a spruce forest ecosystem: A four-year comparison

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Lamers, M.; Fiedler, S.; Jungkunst, H. F.; Stahr, K.; Streck, T.

2009-04-01

Both CH4 and N2O reduction and oxidation are highly sensitive to variation in soil moisture. Significant changes of net CH4 and total N2O fluxes from soils can therefore be expected to accompany redistribution for precipitation in the course of climate change where more extreme events are predicted for the future. The extreme summer drought in 2003 offered the unique opportunity to study the impact of such events on the emission of greenhouse gases, such as methane or nitrous oxide, under field conditions. The main objective of the present study was to evaluate the impact of the summer drought in 2003 on the net methane and nitrous oxide budget of a spruce forest ecosystem (South-West Germany) with large variation in soil drainage. During the summers of 2000-2004 we measured net CH4 and N2O fluxes (bi)-weekly using the closed-chamber technique for six different soil types ranging from well-aerated Cambisols to poorly drained Gleysols and a wet Histosol. With regard to CH4 the extreme summer draught (1) did not elevate net CH4-sink function of soils, but (2) highly reduced net CH4-source strength and (3) reversed the net CH4 source of the investigated catchment into a sink. In all four summers investigated, net ecosystem exchange of CH4 was found only in the hydromorphic soils but not in the dominant well-aerated soils. This highlighted the key role of hydromorphic soils for the investigated pedodiverse system. With regard to N2O the summer draught in 2003 significantly reduced N2O emissions at least for the Humic Gleysol and the Sapric Histosol and hence markedly reduced the net N2O source strength of the investigated ecosystem.

Prediction CH4 Emissions from the Wetlands in the Sanjiang Plain of Northeastern China in the 21st Century.

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Tingting Li

Full Text Available The Sanjiang Plain has been experienced significant wetland loss due to expanded agricultural activities, and will be potentially restored by the China National Wetland Conservation Action Plan (NWCP in future. The objective of this study is to evaluate the impact of future climate warming and wetland restoration on wetland CH4 emissions in northeast China. We used an atmosphere-vegetation interaction model (AVIM2 to drive a modified biogeophysical model (CH4MODwetland, and projected CH4 flux variations from the Sanjiang Plain wetlands under different Representative Concentration Pathway scenarios throughout the 21st century. Model validation showed that the regressions between the observed and simulated CH4 fluxes by the modified model produced an R2 of 0.49 with a slope of 0.87 (p<0.001, n = 237. According to the AVIM2 simulation, the net primary productivity of the Sanjiang Plain wetlands will increase by 38.2 g m-2 yr-1, 116.6 g m-2 yr-1 and 250.4 g m-2 yr-1 under RCP 2.6, RCP 4.5 and RCP 8.5, respectively, by the end of this century. For RCP 2.6, 4.5 and 8.5 scenarios, the CH4 fluxes will increase by 5.7 g m-2 yr-1, 57.5 g m-2 yr-1 and 112.2 g m-2 yr-1. Combined with the wetland restoration, the regional emissions will increase by 0.18‒1.52 Tg. The CH4 emissions will be stimulated by climate change and wetland restoration. Regional wetland restoration planning should be directed against different climate scenarios in order to suppress methane emissions.

Validation of farm-scale methane emissions using nocturnal boundary layer budgets

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J. Stieger

2015-12-01

Full Text Available This study provides the first experimental validation of Swiss agricultural methane emission estimates at the farm scale. We measured CH4 concentrations at a Swiss farmstead during two intensive field campaigns in August 2011 and July 2012 to (1 quantify the source strength of livestock methane emissions using a tethered balloon system and (2 to validate inventory emission estimates via nocturnal boundary layer (NBL budgets. Field measurements were performed at a distance of 150 m from the nearest farm buildings with a tethered balloon system in combination with gradient measurements at eight heights on a 10 m tower to better resolve the near-surface concentrations. Vertical profiles of air temperature, relative humidity, CH4 concentration, wind speed, and wind direction showed that the NBL was strongly influenced by local transport processes and by the valley wind system. Methane concentrations showed a pronounced time course, with highest concentrations in the second half of the night. NBL budget flux estimates were obtained via a time–space kriging approach. Main uncertainties of NBL budget flux estimates were associated with nonstationary atmospheric conditions and the estimate of the inversion height zi (top of volume integration. The mean NBL budget fluxes of 1.60 ± 0.31 μg CH4 m-2 s-1 (1.40 ± 0.50 and 1.66 ± 0.20 μg CH4 m-2 s-1 in 2011 and 2012 respectively were in good agreement with local inventory estimates based on current livestock number and default emission factors, with 1.29 ± 0.47 and 1.74 ± 0.63 μg CH4 m-2 s-1 for 2011 and 2012 respectively. This indicates that emission factors used for the national inventory reports are adequate, and we conclude that the NBL budget approach is a useful tool to validate emission inventory estimates.

Validation of farm-scale methane emissions using nocturnal boundary layer budgets

Science.gov (United States)

Stieger, J.; Bamberger, I.; Buchmann, N.; Eugster, W.

2015-12-01

This study provides the first experimental validation of Swiss agricultural methane emission estimates at the farm scale. We measured CH4 concentrations at a Swiss farmstead during two intensive field campaigns in August 2011 and July 2012 to (1) quantify the source strength of livestock methane emissions using a tethered balloon system and (2) to validate inventory emission estimates via nocturnal boundary layer (NBL) budgets. Field measurements were performed at a distance of 150 m from the nearest farm buildings with a tethered balloon system in combination with gradient measurements at eight heights on a 10 m tower to better resolve the near-surface concentrations. Vertical profiles of air temperature, relative humidity, CH4 concentration, wind speed, and wind direction showed that the NBL was strongly influenced by local transport processes and by the valley wind system. Methane concentrations showed a pronounced time course, with highest concentrations in the second half of the night. NBL budget flux estimates were obtained via a time-space kriging approach. Main uncertainties of NBL budget flux estimates were associated with nonstationary atmospheric conditions and the estimate of the inversion height zi (top of volume integration). The mean NBL budget fluxes of 1.60 ± 0.31 μg CH4 m-2 s-1 (1.40 ± 0.50 and 1.66 ± 0.20 μg CH4 m-2 s-1 in 2011 and 2012 respectively) were in good agreement with local inventory estimates based on current livestock number and default emission factors, with 1.29 ± 0.47 and 1.74 ± 0.63 μg CH4 m-2 s-1 for 2011 and 2012 respectively. This indicates that emission factors used for the national inventory reports are adequate, and we conclude that the NBL budget approach is a useful tool to validate emission inventory estimates.

Evaluation of methane oxidation activity in waste biocover soil during landfill stabilization.

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He, Ruo; Wang, Jing; Xia, Fang-Fang; Mao, Li-Juan; Shen, Dong-Sheng

2012-10-01

Biocover soil has been demonstrated to have high CH(4) oxidation capacity and is considered as a good alternative cover material to mitigate CH(4) emission from landfills, yet the response of CH(4) oxidation activity of biocover soils to the variation of CH(4) loading during landfill stabilization is poorly understood. Compared with a landfill cover soil (LCS) collected from Hangzhou Tianziling landfill cell, the development of CH(4) oxidation activity of waste biocover soil (WBS) was investigated using simulated landfill systems in this study. Although a fluctuation of influent CH(4) flux occurred during landfill stabilization, the WBS covers showed a high CH(4) removal efficiency of 94-96% during the entire experiment. In the LCS covers, the CH(4) removal efficiencies varied with the fluctuation of CH(4) influent flux, even negative ones occurred due to the storage of CH(4) in the soil porosities after the high CH(4) influent flux of ~137 gm(-2) d(-1). The lower concentrations of O(2) and CH(4) as well as the higher concentration of CO(2) were observed in the WBS covers than those in the LCS covers. The highest CH(4) oxidation rates of the two types of soil covers both occurred in the bottom layer (20-30 cm). Compared to the LCS, the WBS showed higher CH(4) oxidation activity and methane monooxygenase activity over the course of the experiment. Overall, this study indicated the WBS worked well for the fluctuation of CH(4) influent flux during landfill stabilization. Copyright © 2012 Elsevier Ltd. All rights reserved.

Spatiotemporal dynamics of carbon dioxide and methane fluxes from agricultural and restored wetlands in the California Delta

Science.gov (United States)

Hatala, Jaclyn Anne

The Sacramento-San Joaquin Delta in California was drained for agriculture and human settlement over a century ago, resulting in extreme rates of soil subsidence and release of CO2 to the atmosphere from peat oxidation. Because of this century-long ecosystem carbon imbalance where heterotrophic respiration exceeded net primary productivity, most of the land surface in the Delta is now up to 8 meters below sea level. To potentially reverse this trend of chronic carbon loss from Delta ecosystems, land managers have begun converting drained lands back to flooded ecosystems, but at the cost of increased production of CH4, a much more potent greenhouse gas than CO2. To evaluate the impacts of inundation on the biosphere-atmophere exchange of CO2 and CH4 in the Delta, I first measured and analyzed net fluxes of CO2 and CH4 for two continuous years with the eddy covariance technique in a drained peatland pasture and a recently re-flooded rice paddy. This analysis demonstrated that the drained pasture was a consistent large source of CO2 and small source of CH 4, whereas the rice paddy was a mild sink for CO2 and a mild source of CH4. However more importantly, this first analysis revealed nuanced complexities for measuring and interpreting patterns in CO2 and CH4 fluxes through time and space. CO2 and CH4 fluxes are inextricably linked in flooded ecosystems, as plant carbon serves as the primary substrate for the production of CH4 and wetland plants also provide the primary transport pathway of CH4 flux to the atmosphere. At the spatially homogeneous rice paddy during the summer growing season, I investigated rapid temporal coupling between CO2 and CH4 fluxes. Through wavelet Granger-causality analysis, I demonstrated that daily fluctuations in growing season gross ecosystem productivity (photosynthesis) exert a stronger control than temperature on the diurnal pattern in CH4 flux from rice. At a spatially heterogeneous restored wetland site, I analyzed the spatial coupling

How to oxidize atmospheric CH4? - A challenge for the future

International Nuclear Information System (INIS)

Chazelas, Bruno; Leger, Alain; Ollivier, Marc

2006-01-01

Methane is an active Greenhouse effect gas whose concentration will likely increase in the future. The possible destabilisation of CH 4 clathrates (hydrates) due to anthropogenic climate warming, and the resulting outgasing of methane, could lead to a major increase of the global Greenhouse effect, with dramatic consequences for Humanity. For these reasons, the study of possible countermeasures should be actively considered. Here, we suggest taking advantage of the thermodynamic instability of CH 4 in air, and search for ways to oxidize it

Effects of Boreal Lake Wetlands on Atmospheric 13CH3D and 12CH2D2

Science.gov (United States)

Haghnegahdar, M. A.; Kohl, I. E.; Schauble, E. A.; Walter Anthony, K. M.; Young, E. D.

2017-12-01

Recently, we developed a theoretical model to investigate the potential use of 13CH3D and 12CH2D2 as tools for tracking atmospheric methane budget. We used electronic structure methods to estimate kinetic isotope fractionations associated with the major sink reactions of CH4 in air (reactions with •OH and Cl•), and literature data with reconnaissance measurements of the relative abundances of 13CH3D and 12CH2D2 to estimate the compositions of the largest atmospheric sources. Here we present new methane rare isotopologue data from boreal wetlands, comprising one of the most important sources, in order to evaluate the robustness of the model. Boreal wetlands (>55° N) account for more than half of the wetland area in the Northern hemisphere. We analyzed methane samples from high latitude lakes representing different geographical regions, geological and ecological contexts, methane fluxes, and isotopic signatures. Using clumped isotopes of CH4 we are able to determine the likely production mechanism for natural CH4 samples. So far, all of our analyzed samples except one plot in the microbial pure-culture methanogenesis field (Young et al. 2017) with ranges of -0.2‰ to +1.2‰ for Δ13CH3D, and -29.6‰ to -18.2‰ for Δ12CH2D2. These compositions are far from equilibrium. The one exception, from Lake Doughnut, Alaska, exhibits Δ13CH3D and Δ12CH2D2 values of +5.2‰ and +18.7‰, respectively, which fall near ambient thermodynamic equilibrium values. This may be an effect of methanotrophy. Mean Δ13CH3D and Δ12CH2D2 for all lake samples are +1.7‰ and -15.4‰ respectively, compared to our original estimate of +6.1‰ and +21.2‰ for the wetland methane source based on an assumption of equilibrium. If we assume that these samples are representative of the overall wetland source, Δ13CH3D decreases by 0.8‰ and Δ12CH2D2 decreases by 0.6‰ in our model of bulk atmospheric methane. Δ13CH3D and Δ12CH2D2 values of air (including •OH and Cl• sink

The H2/CH4 ratio during serpentinization cannot reliably identify biological signatures.

Science.gov (United States)

Huang, Ruifang; Sun, Weidong; Liu, Jinzhong; Ding, Xing; Peng, Shaobang; Zhan, Wenhuan

2016-09-26

Serpentinization potentially contributes to the origin and evolution of life during early history of the Earth. Serpentinization produces molecular hydrogen (H 2 ) that can be utilized by microorganisms to gain metabolic energy. Methane can be formed through reactions between molecular hydrogen and oxidized carbon (e.g., carbon dioxide) or through biotic processes. A simple criterion, the H 2 /CH 4 ratio, has been proposed to differentiate abiotic from biotic methane, with values approximately larger than 40 for abiotic methane and values of serpentinization experiments at 200 °C and 0.3 kbar. However, it is not clear whether the criterion is applicable at a wider range of temperatures. In this study, we performed sixteen experiments at 311-500 °C and 3.0 kbar using natural ground peridotite. Our results demonstrate that the H 2 /CH 4 ratios strongly depend on temperature. At 311 °C and 3.0 kbar, the H 2 /CH 4 ratios ranged from 58 to 2,120, much greater than the critical value of 40. By contrast, at 400-500 °C, the H 2 /CH 4 ratios were much lower, ranging from 0.1 to 8.2. The results of this study suggest that the H 2 /CH 4 ratios cannot reliably discriminate abiotic from biotic methane.

The H2/CH4 ratio during serpentinization cannot reliably identify biological signatures

Science.gov (United States)

Huang, Ruifang; Sun, Weidong; Liu, Jinzhong; Ding, Xing; Peng, Shaobang; Zhan, Wenhuan

2016-09-01

Serpentinization potentially contributes to the origin and evolution of life during early history of the Earth. Serpentinization produces molecular hydrogen (H2) that can be utilized by microorganisms to gain metabolic energy. Methane can be formed through reactions between molecular hydrogen and oxidized carbon (e.g., carbon dioxide) or through biotic processes. A simple criterion, the H2/CH4 ratio, has been proposed to differentiate abiotic from biotic methane, with values approximately larger than 40 for abiotic methane and values of serpentinization experiments at 200 °C and 0.3 kbar. However, it is not clear whether the criterion is applicable at a wider range of temperatures. In this study, we performed sixteen experiments at 311-500 °C and 3.0 kbar using natural ground peridotite. Our results demonstrate that the H2/CH4 ratios strongly depend on temperature. At 311 °C and 3.0 kbar, the H2/CH4 ratios ranged from 58 to 2,120, much greater than the critical value of 40. By contrast, at 400-500 °C, the H2/CH4 ratios were much lower, ranging from 0.1 to 8.2. The results of this study suggest that the H2/CH4 ratios cannot reliably discriminate abiotic from biotic methane.

Low methane flux from a constructed boreal wetland

Science.gov (United States)

Clark, M. G.; Humphreys, E.; Carey, S. K.

2016-12-01

The Sandhill Fen Watershed project in northern Alberta, Canada, is a pilot study in reconstructing a mixed upland and lowland boreal plain ecosystem. The physical construction of the 50 ha area was completed in 2012 and revegetation programs, through planting and seeding, began that same year and continued into 2013. Since then, the vegetation has developed a substantial cover over the reclaimed soil and peat substrates used to cap the engineered topography constructed from mine tailings. To monitor the dynamics of carbon cycling processes in this novel ecosystem, near weekly gas chamber measurements of methane fluxes were carried out over 3 growing seasons. Soil moisture, temperature and ion flux measurements, using Plant Root Simulator probes, were also collected alongside the gas flux plots. In the 3rd season, a transect was established in the lowlands along a moisture gradient to collect continuous reduction-oxidation potential measurements along with these other variables. Overall, methane effluxes remained low relative to what is expected for rewetted organic substrates. However, there is a trend over time towards increasing methane gas emissions that coincides with increasing fluxes of reduced metal ions and decreasing fluxes of sulphate in the fully saturated substrates. The suppressed levels of methane fluxes are possibly due to naturally occurring high levels of sulphate in the donor materials used to cap the ecosystem construction.

Year-round simulated methane emissions from a permafrost ecosystem in Northeast Siberia

Science.gov (United States)

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.

Year-round simulated methane emissions from a permafrost ecosystem in Northeast Siberia

Directory of Open Access Journals (Sweden)

K. Castro-Morales

2018-05-01

Full Text Available 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.

Agricultural peatland restoration: effects of land-use change on greenhouse gas (CO2 and CH4) fluxes in the Sacramento-San Joaquin Delta.

Science.gov (United States)

Knox, Sara Helen; Sturtevant, Cove; Matthes, Jaclyn Hatala; Koteen, Laurie; Verfaillie, Joseph; Baldocchi, Dennis

2015-02-01

Agricultural drainage of organic soils has resulted in vast soil subsidence and contributed to increased atmospheric carbon dioxide (CO2) concentrations. The Sacramento-San Joaquin Delta in California was drained over a century ago for agriculture and human settlement and has since experienced subsidence rates that are among the highest in the world. It is recognized that drained agriculture in the Delta is unsustainable in the long-term, and to help reverse subsidence and capture carbon (C) there is an interest in restoring drained agricultural land-use types to flooded conditions. However, flooding may increase methane (CH4) emissions. We conducted a full year of simultaneous eddy covariance measurements at two conventional drained agricultural peatlands (a pasture and a corn field) and three flooded land-use types (a rice paddy and two restored wetlands) to assess the impact of drained to flooded land-use change on CO2 and CH4 fluxes in the Delta. We found that the drained sites were net C and greenhouse gas (GHG) sources, releasing up to 341 g C m(-2) yr(-1) as CO2 and 11.4 g C m(-2) yr(-1) as CH4. Conversely, the restored wetlands were net sinks of atmospheric CO2, sequestering up to 397 g C m(-2) yr(-1). However, they were large sources of CH4, with emissions ranging from 39 to 53 g C m(-2) yr(-1). In terms of the full GHG budget, the restored wetlands could be either GHG sources or sinks. Although the rice paddy was a small atmospheric CO2 sink, when considering harvest and CH4 emissions, it acted as both a C and GHG source. Annual photosynthesis was similar between sites, but flooding at the restored sites inhibited ecosystem respiration, making them net CO2 sinks. This study suggests that converting drained agricultural peat soils to flooded land-use types can help reduce or reverse soil subsidence and reduce GHG emissions. © 2014 John Wiley & Sons Ltd.

CH4 emissions from European Major Population Centers: Results from aircraft-borne CH4 in-situ observations during EMeRGe-Europe campaign 2017

Science.gov (United States)

Roiger, A.; Klausner, T.; Schlager, H.; Ziereis, H.; Huntrieser, H.; Baumann, R.; Eirenschmalz, L.; Joeckel, P.; Mertens, M.; Fisher, R.; Bauguitte, S.; Young, S.; Andrés Hernández, M. D.

2017-12-01

Urban environments represent large and diffuse area sources of CH4 including emissions from pipeline leaks, industrial/sewage treatment plants, and landfills. However, there is little knowledge about the exact magnitude of these emissions and their contribution to total anthropogenic CH4. Especially in the context of an urbanizing world, a better understanding of the methane footprint of urban areas is crucial, both with respect to mitigation and projection of climate impacts. Aircraft-borne in-situ measurements are particularly useful to both quantify emissions from such area sources, as well as to study their impact on the regional distribution. However, airborne CH4 observations downstream of European cities are especially sparse.Here we report from aircraft-borne CH4 in-situ measurements as conducted during the HALO aircraft campaign EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) in July 2017, which was led by the University of Bremen, Germany. During seven research flights, emissions from a variety of European (Mega)-cities were probed at different altitudes from 3km down to 500m, including measurements in the outflows of London, Rome, Po Valley, Ruhr and Benelux. We will present and compare the CH4 distribution measured downstream of the various studied urban hot-spots. With the help of other trace gas measurements (including e.g. CO2, CO, O3, SO2), observed methane enhancements will be attributed to the different potential source types. Finally, by the combination of in-situ measurements and regional model simulations using the EMAC-MECO(n) model, the contribution of emissions from urban centers to the regional methane budget over Europe will be discussed.

Methane Transmission and Oxidation throughout the Soil Column from Three Central Florida Sites

Science.gov (United States)

Bond-Lamberty, B. P.; Fansler, S.; Becker, K. E.; Hinkle, C. R.; Bailey, V. L.

2015-12-01

When methane (CH4) is generated in anoxic soil sites, it may be subsequently re-oxidized to carbon dioxide (CO2). Understanding the controls on, and magnitudes of, these processes is necessary to accurately represent greenhouse gas production and emission from soils. We used a laboratory incubation to examine the influence of variable conditions on methane transmission and oxidation, and identify critical reaction zones throughout the soil column. Sandy soils were sampled from three different sites at Disney Wilderness Preserve (DWP), Florida, USA: a depression marsh characterized by significant surface organic matter accumulation, a dry pine flatwood site with water intrusion and organic horizon at depth (200+ cm); and an intermediate-drainage site. Contiguous, 30-cm long cores were sampled from N=4 random boreholes at each site, from the surface to the water table (varying from 90 to 240 cm). In the lab, each core was monitored for 50 hours to quantify baseline (pretreatment) gas fluxes before injection with 6 ml CH4 (an amount commensurate with previous field collar measurements) at the base of each core. We then monitored CH4 and CO2 evolution for 100 hours after injection, calculating per-gas and total C evolution. Methane emissions spiked ~10 hours after injection for all cores, peaking at 0.001 μmol/g soil/hr, ~30x larger than pre-injection flux rates. On a C basis, CO2 emissions were orders of magnitude larger, and rose significantly after injection, with elevated rates generally sustained throughout the incubation. Cores from the depression marsh and shallower depths had significantly higher fluxes of both gases. We estimate that 99.1% of the original CH4 injection was oxidized to CO2. These findings suggest either that the methane measured in the field at DWP originates from within a few centimeters of the surface, or that it is produced in much larger quantities deeper in the profile before most is subsequently oxidized. This highlights the need for

CO2, CH4 and N2O fluxes from soil of a burned grassland in Central Africa

Directory of Open Access Journals (Sweden)

R. Valentini

2010-11-01

Full Text Available The impact of fire on soil fluxes of CO2, CH4 and N2O was investigated in a tropical grassland in Congo Brazzaville during two field campaigns in 2007–2008. The first campaign was conducted in the middle of the dry season and the second at the end of the growing season, respectively one and eight months after burning. Gas fluxes and several soil parameters were measured in each campaign from burned plots and from a close-by control area preserved from fire. Rain events were simulated at each campaign to evaluate the magnitude and duration of the generated gas flux pulses. In laboratory experiments, soil samples from field plots were analysed for microbial biomass, net N mineralization, net nitrification, N2O, NO and CO2 emissions under different water and temperature soil regimes. One month after burning, field CO2 emissions were significantly lower in burned plots than in the control plots, the average daily CH4 flux shifted from net emission in the unburned area to net consumption in burned plots, no significant effect of fire was observed on soil N2O fluxes. Eight months after burning, the average daily fluxes of CO2, CH4 and N2O measured in control and burned plots were not significantly different. In laboratory, N2O fluxes from soil of burned plots were significantly higher than fluxes from soil of unburned plots only above 70% of maximum soil water holding capacity; this was never attained in the field even after rain simulation. Higher NO emissions were measured in the lab in soil from burned plots at both 10% and 50% of maximum soil water holding capacity. Increasing the incubation temperature from 25 °C to 37 °C negatively affected microbial growth, mineralization and nitrification activities but enhanced N2O and CO2 production. Results indicate that fire did not increase post-burning soil GHG emissions in this tropical grasslands characterized by acidic, well drained and nutrient-poor soil.

Global diffusive fluxes of methane in marine sediments

NARCIS (Netherlands)

Egger, M.; Riedinger, N.; Mogollón, J.M.; Jørgensen, B.B.

2018-01-01

Anaerobic oxidation of methane provides a globally important, yet poorly constrained barrier for the vast amounts of methane produced in the subseafloor. Here we provide a global map and budget of the methane flux and degradation in diffusion-controlled marine sediments in relation to the depth of

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

Science.gov (United States)

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

Acclimation of methane production weakens ecosystem response to climate warming in a northern peatland

Science.gov (United States)

MA, S.; Huang, Y.; Jiang, J.; Ricciuto, D. M.; Hanson, P. J.; Luo, Y.

2017-12-01

Warming-induced increases in greenhouse gases from terrestrial ecosystems represent a positive feedback to twenty-first-century climate warming, but the magnitude of this stimulatory effect remains uncertain. Acclimation of soil respiration and photosynthesis have been found to slow down the feedback due to the substrate limitation and thermal adaptation. However, acclimation of ecosystem methane emission to climate warming has not been well illustrated, despite that methane is directly responsible for approximately 20% of global warming since pre-industrial time. In this study, we used the data-model fusion approach to explore the potential acclimation of methane emission to climate warming. We assimilated CH4 static chamber flux data at the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) experimental site into the ecosystem model, TECO_SPRUCE. The SPRUCE project has been conducted to study the responses of northern peatland to climate warming (+0, +2.25, +4.5, +6.75, +9 °C) and elevated atmospheric CO2 concentration (+0 and +500 ppm). The warming treatments were initiated from June 2014. We estimated parameter values using environmental and flux data in those five warming treatment levels from 2014 to 2016 for the acclimation study. The key parameters that were estimated for methane emissions are the potential ratio of CO2 converted to CH4 (r_me), Q10 for CH4 production (Q10_pro), maximum oxidation rate (Omax) and the factor of transport ability at plant community level (Tveg). Among them, r_me and Q10_pro were well constrained in each treatment plot. Q10 decreased from 3.33 (control) to 1.22 (+9˚C treatment) and r_me decreased from 0.675 (control) to 0.505 (+9˚C treatment). The acclimation will dampen the warming effect on methane production and emission. Current ecosystem models assumed constant Q10 for CH4 production and CH4/CO2 conversion ratio in the future warmed climate. The assumption is likely to overestimate the methane

Measurement of N2O and CH4 soil fluxes from garden, agricultural and natural soils using both closed and open chamber systems coupled with high-precision CRDS analyzer

Science.gov (United States)

He, Yonggang; Jacobson, Gloria; Alexander, Chris; Fleck, Derek; Hoffnagel, John; Del Campo, Bernardo; Rella, Chris

2013-04-01

Studying the emission and uptake of greenhouse gases from soil is essential for understanding, adapting to and ultimately mitigating the effects of climate change. To-date, majority of such studies have been focused on carbon dioxide (CO2 ) , however, in 2006 the EPA estimated that "Agricultural activities currently generate the largest share, 63 percent, of the world's anthropogenic non-carbon dioxide (non-CO2) emissions (84 percent of nitrous oxide [N2O] and 52 percent of methane[CH4]), and make up roughly 15 percent of all anthropogenic greenhouse gas emissions" (Prentice et al., 2001). Therefore, enabling accurate N2O and CH4 flux measurements in the field are clearly critical to our ability to better constrain carbon and nitrogen budgets, characterize soil sensitivities, agricultural practices, and microbial processes like denitrification and nitrification. To aide in these studies, Picarro has developed a new analyzer based on its proven, NIR technology platform, which is capable of measuring both N2O and CH4 down to ppb levels in a single, field-deployable analyzer. This analyzer measures N2O with a 1-sigma, precision of 3.5 ppb and CH4 with a 1-sigma precision of 3ppb on a 5 minute average. The instrument also has extremely low drift to enable accurate measurements with infrequent calibrations. The data rate of the analyzer is on the order of 5 seconds in order to capture fast, episodic emission events. One of the keys to making accurate CRDS measurements is to thoroughly characterize and correct for spectral interfering species. This is especially important for closed system soil chambers used on agricultural soils where a variety of soil amendments may be applied and gases not usually present in ambient air could concentrate to high levels. In this work, we present the results of analyzer interference testing and corrections completed for the interference of carbon dioxide, methane, ammonia, ethane, ethylene, acetylene, and water on N2O. In addition, we

Sensitivity of Global Methane Bayesian Inversion to Surface Observation Data Sets and Chemical-Transport Model Resolution

Science.gov (United States)

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

2017-12-01

Methane is the second most important greenhouse gas after carbon dioxide. In efforts to control emissions, a careful examination of the methane budget and source strengths is required. To determine methane surface fluxes, Bayesian methods are often used to provide top-down constraints. Inverse modeling derives unknown fluxes using observed methane concentrations, a chemical transport model (CTM) and prior information. The Bayesian inversion reduces prior flux uncertainties by exploiting information content in the data. While the Bayesian formalism produces internal error estimates of source fluxes, systematic or external errors that arise from user choices in the inversion scheme are often much larger. Here we examine model sensitivity and uncertainty of our inversion under different observation data sets and CTM grid resolution. We compare posterior surface fluxes using the data product GLOBALVIEW-CH4 against the event-level molar mixing ratio data available from NOAA. GLOBALVIEW-CH4 is a collection of CH4 concentration estimates from 221 sites, collected by 12 laboratories, that have been interpolated and extracted to provide weekly records from 1984-2008. Differently, the event-level NOAA data records methane mixing ratios field measurements from 102 sites, containing sampling frequency irregularities and gaps in time. Furthermore, the sampling platform types used by the data sets may influence the posterior flux estimates, namely fixed surface, tower, ship and aircraft sites. To explore the sensitivity of the posterior surface fluxes to the observation network geometry, inversions composed of all sites, only aircraft, only ship, only tower and only fixed surface sites, are performed and compared. Also, we investigate the sensitivity of the error reduction associated with the resolution of the GEOS-Chem simulation (4°×5° vs 2°×2.5°) used to calculate the response matrix. Using a higher resolution grid decreased the model-data error at most sites, thereby

Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula.

Science.gov (United States)

Lara, Mark J; McGuire, A David; Euskirchen, Eugenie S; Tweedie, Craig E; Hinkel, Kenneth M; Skurikhin, Alexei N; Romanovsky, Vladimir E; Grosse, Guido; Bolton, W Robert; Genet, Helene

2015-04-01

The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO2 and CH4 flux data were collected for the summers of 2006-2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO2 uptake occurs at -902.3 10(6) gC-CO2 day(-1) (uncertainty using 95% CI is between -438.3 and -1366 10(6) gC-CO2 day(-1)) and CH4 flux at 28.9 10(6) gC-CH4 day(-1) (uncertainty using 95% CI is between 12.9 and 44.9 10(6) gC-CH4 day(-1)), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO2 and CH4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO2 uptake (-166.9 10(6) gC-CO2 day(-1)) and CH4 flux (2.8 10(6) gC-CH4 day(-1)) with geomorphic change from low

Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula

Science.gov (United States)

Lara, Mark J.; McGuire, A. David; Euskirchen, Eugénie S.; Tweedie, Craig E.; Hinkel, Kenneth M.; Skurikhin, Alexei N.; Romanovsky, Vladimir E.; Grosse, Guido; Bolton, W. Robert; Genet, Helene

2015-01-01

The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO2 and CH4 flux data were collected for the summers of 2006–2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO2 uptake occurs at -902.3 106gC-CO2 day−1(uncertainty using 95% CI is between −438.3 and −1366 106gC-CO2 day−1) and CH4 flux at 28.9 106gC-CH4 day−1(uncertainty using 95% CI is between 12.9 and 44.9 106gC-CH4 day−1), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO2 and CH4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO2uptake (−166.9 106gC-CO2 day−1) and CH4 flux (2.8 106gC-CH4 day−1) with geomorphic change from

Preparation of CH4 for 14C measurements

International Nuclear Information System (INIS)

Cechova, A.; Grgula, M.; Povinec, P.; Sivo, A.

1988-01-01

An improved method of methane preparation from wood samples is described. It consists of the preparation of α-cellulose to secure a complete removal of contamination from the wood, its combustion to the form of CO 2 and the preparation of CH 4 in a new designed hydrogenation converter. Purified methane is suitable as a gas filling of the proportional counter. (author). 1 fig., 16 ref

Methane bubbling from northern lakes: present and future contributions to the global methane budget.

Science.gov (United States)

Walter, Katey M; Smith, Laurence C; Chapin, F Stuart

2007-07-15

Large uncertainties in the budget of atmospheric methane (CH4) limit the accuracy of climate change projections. Here we describe and quantify an important source of CH4 -- point-source ebullition (bubbling) from northern lakes -- that has not been incorporated in previous regional or global methane budgets. Employing a method recently introduced to measure ebullition more accurately by taking into account its spatial patchiness in lakes, we estimate point-source ebullition for 16 lakes in Alaska and Siberia that represent several common northern lake types: glacial, alluvial floodplain, peatland and thermokarst (thaw) lakes. Extrapolation of measured fluxes from these 16 sites to all lakes north of 45 degrees N using circumpolar databases of lake and permafrost distributions suggests that northern lakes are a globally significant source of atmospheric CH4, emitting approximately 24.2+/-10.5Tg CH4yr(-1). Thermokarst lakes have particularly high emissions because they release CH4 produced from organic matter previously sequestered in permafrost. A carbon mass balance calculation of CH4 release from thermokarst lakes on the Siberian yedoma ice complex suggests that these lakes alone would emit as much as approximately 49000Tg CH4 if this ice complex was to thaw completely. Using a space-for-time substitution based on the current lake distributions in permafrost-dominated and permafrost-free terrains, we estimate that lake emissions would be reduced by approximately 12% in a more probable transitional permafrost scenario and by approximately 53% in a 'permafrost-free' Northern Hemisphere. Long-term decline in CH4 ebullition from lakes due to lake area loss and permafrost thaw would occur only after the large release of CH4 associated thermokarst lake development in the zone of continuous permafrost.

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

Science.gov (United States)

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

2013-01-01

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 CO...

Laboratory-scale measurements of N2O and CH4 emissions from hybrid poplars (Populus deltoides x Populus nigra).

Science.gov (United States)

McBain, M C; Warland, J S; McBride, R A; Wagner-Riddle, C

2004-12-01

The purpose of this study was to determine whether or not young hybrid poplar (Populus deltoides x Populus nigra) could transport landfill biogas internally from the root zone to the atmosphere, thereby acting as conduits for landfill gas release. Fluxes of methane (CH4) and nitrous oxide (N2O) from the seedlings to the atmosphere were measured under controlled conditions using dynamic flux chambers and a tunable diode laser trace gas analyser (TDLTGA). Nitrous oxide was emitted from the seedlings, but only when extremely high soil N2O concentrations were applied to the root zone. In contrast, no detectable emissions of CH4 were measured in a similar experimental trial. Visible plant morphological responses, characteristic of flood-tolerant trees attempting to cope with the negative effects of soil hypoxia, were observed during the CH4 experiments. Leaf chlorosis, leaf abscission and adventitious roots were all visible plant responses. In addition, seedling survival was observed to be highest in the biogas 'hot spot' areas of a local municipal solid waste landfill involved in this study. Based on the available literature, these observations suggest that CH4 can be transported internally by Populus deltoides x Populus nigra seedlings in trace amounts, although future research is required to fully test this hypothesis.

Hydrothermal waste package interactions with methane-containing basalt groundwater

International Nuclear Information System (INIS)

McGrail, B.P.

1984-11-01

Hydrothermal waste package interaction tests with methane-containing synthetic basalt groundwater have shown that in the absence of gamma radiolysis, methane has little influence on the glass dissolution rate. Gamma radiolysis tests at fluxes of 5.5 x 10 5 and 4.4 x 10 4 R/hr showed that methane-saturated groundwater was more reducing than identical experiments where Ar was substituted for CH 4 . Dissolved methane, therefore, may be beneficial to the waste package in limiting the solubility of redox sensitive radionuclides such a 99 Tc. Hydrocarbon polymers known to form under the irradiation conditions of these tests were not produced. The presence of the waste package constituents apparently inhibited the formation of the polymers, however, the mechanism which prevented their formation was not determined

Methane fluxes and inventories in the accretionary prism of southwestern Taiwan

Science.gov (United States)

Lin, L. H.; Chen, N. C.; Yang, T. F.; Hong, W. L.; Chen, H. W.; Chen, H. C.; Hu, C. Y.; Huang, Y. C.; Lin, S.; Su, C. C.; Liao, W. Z.; Sun, C. H.; Wang, P. L.; Yang, T.; Jiang, S. Y.; Liu, C. S.; Wang, Y.; Chung, S. H.

2017-12-01

Sediments distributed across marine and terrestrial realms represent the largest methane reservoir on Earth. The degassing of methane facilitated through either geological structures or perturbation would contribute significantly to global climatic fluctuation and elemental cycling. The exact fluxes and processes governing methane production, consumption and transport in a geological system remain largely unknown in part due to the limited coverage and access of samples. In this study, more than 200 sediment cores were collected from offshore and onshore southwestern Taiwan and analyzed for their gas and aqueous geochemistry. These data combined with published data and existing parameters of subduction system were used to calculate methane fluxes across different geochemical transitions and to develop scenarios of mass balance to constrain deep microbial and thermogenic methane production rates within the Taiwanese accretionary prism. The results showed that high methane fluxes tend to be associated with structural features, suggesting a strong structural control on methane transport. A significant portion of ascending methane (>50%) was consumed by anaerobic oxidation of methane at most sites. Gas compositions and isotopes revealed a transition from the predominance of microbial methane in the passive margin to thermogenic methane at the upper slope of the active margin and onshore mud volcanoes. Methane production and consumption at shallow depths were nearly offset with a small fraction of residual methane discharged into seawater or the atmosphere. The flux imbalance arose primarily from the deep microbial and thermogenic production and could be likely accounted for by the sequestration of methane into hydrate forms, and clay absorption.

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

Science.gov (United States)

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.

Calibrating the sqHIMMELI v1.0 wetland methane emission model with hierarchical modeling and adaptive MCMC

Science.gov (United States)

Susiluoto, Jouni; Raivonen, Maarit; Backman, Leif; Laine, Marko; Makela, Jarmo; Peltola, Olli; Vesala, Timo; Aalto, Tuula

2018-03-01

Estimating methane (CH4) emissions from natural wetlands is complex, and the estimates contain large uncertainties. The models used for the task are typically heavily parameterized and the parameter values are not well known. In this study, we perform a Bayesian model calibration for a new wetland CH4 emission model to improve the quality of the predictions and to understand the limitations of such models.The detailed process model that we analyze contains descriptions for CH4 production from anaerobic respiration, CH4 oxidation, and gas transportation by diffusion, ebullition, and the aerenchyma cells of vascular plants. The processes are controlled by several tunable parameters. We use a hierarchical statistical model to describe the parameters and obtain the posterior distributions of the parameters and uncertainties in the processes with adaptive Markov chain Monte Carlo (MCMC), importance resampling, and time series analysis techniques. For the estimation, the analysis utilizes measurement data from the Siikaneva flux measurement site in southern Finland. The uncertainties related to the parameters and the modeled processes are described quantitatively. At the process level, the flux measurement data are able to constrain the CH4 production processes, methane oxidation, and the different gas transport processes. The posterior covariance structures explain how the parameters and the processes are related. Additionally, the flux and flux component uncertainties are analyzed both at the annual and daily levels. The parameter posterior densities obtained provide information regarding importance of the different processes, which is also useful for development of wetland methane emission models other than the square root HelsinkI Model of MEthane buiLd-up and emIssion for peatlands (sqHIMMELI). The hierarchical modeling allows us to assess the effects of some of the parameters on an annual basis. The results of the calibration and the cross validation suggest that

Role of meteorology in simulating methane seasonal cycle and growth rate

Science.gov (United States)

Ghosh, A.; Patra, P. K.; Ishijima, K.; Morimoto, S.; Aoki, S.; Nakazawa, T.

2012-12-01

Methane (CH4) is the second most important anthropogenically produced greenhouse gas whose radiative effect is comparable to that of carbon dioxide since the preindustrial time. Methane also contributes to formation of tropospheric ozone and water vapor in the stratosphere, further increasing its importance to the Earth's radiative balance. In the present study, model simulation of CH4 for three different emission scenarios has been conducted using the CCSR/NIES/FRCGC Atmospheric General Circulation Model (AGCM) based Chemistry Transport Model (ACTM) with and without nudging of meteorological parameters for the period of 1981-2011. The model simulations are compared with measurements at monthly timescale at surface monitoring stations. We show the overall trends in CH4 growth rate and seasonal cycle at most measurement sites can be fairly successfully modeled by using existing knowledge of CH4 flux trends and seasonality. Detailed analysis reveals the model simulation without nudging has greater seasonal cycle amplitude compared to observation as well as the model simulation with nudging. The growth rate is slightly overestimated for the model simulation without nudging. For better representation of regional/global flux distribution pattern and strength in the future, we are exploring various dynamical and chemical aspects in the forward model with and without nudging.

Greenhouse gas fluxes of a shallow lake in south-central North Dakota, USA

Science.gov (United States)

Tangen, Brian; Finocchiaro, Raymond; Gleason, Robert A.; Dahl, Charles F.

2016-01-01

Greenhouse gas (GHG) fluxes of aquatic ecosystems in the northern Great Plains of the U.S. represent a significant data gap. Consequently, a 3-year study was conducted in south-central North Dakota, USA, to provide an initial estimate of GHG fluxes from a large, shallow lake. Mean GHG fluxes were 0.02 g carbon dioxide (CO2) m−2 h−1, 0.0009 g methane (CH4) m−2 h−1, and 0.0005 mg nitrous oxide (N2O) m−2 h−1. Fluxes of CO2 and CH4 displayed temporal and spatial variability which is characteristic of aquatic ecosystems, while fluxes of N2O were consistently low throughout the study. Comparisons between results of this study and published values suggest that mean daily fluxes of CO2, CH4, and N2O fromLong Lakewere low, particularly when compared to the well-studied prairie pothole wetlands of the region. Similarly, cumulative seasonal CH4 fluxes, which ranged from 2.68–7.58 g CH4 m−2, were relatively low compared to other wetland systems of North America. The observed variability among aquatic ecosystems underscores the need for further research.

Carbon-13 isotopic abundance and concentration of atmospheric methane for background air in the Southern and Northern Hemispheres from 1978 to 1989

International Nuclear Information System (INIS)

Stevens, C.M.; Sepanski; Morris, L.J.

1995-03-01

Atmospheric methane (CH 4 ) may become an increasingly important contributor to global warming in future years. Its atmospheric concentration has risen, doubling over the past several hundred years, and additional methane is thought to have a much greater effect on climate, on a per molecule basis, than additional C0 2 at present day concentrations (Shine et al. 1990). The causes of the increase of atmospheric CH 4 have been difficult to ascertain because of a lack of quantitative knowledge of the fluxes (i.e., net emissions) from the numerous anthropogenic and natural sources. The goal of CH 4 isotopic studies is to provide a constraint (and so reduce the uncertainties) in estimating the relative fluxes from the various isotopically distinct sources, whose combined fluxes must result in the measured atmospheric isotopic composition, after the fractionating effect of the atmospheric removal process is considered. In addition, knowledge of the spatial and temporal changes in the isotopic composition of atmospheric CH 4 , along with estimates of the fluxes from some of the major sources, makes it possible to calculate growth rates for sources whose temporal emissions trends would be difficult to measure directly

Disproportionation and thermochemical sulfate reduction reactions in S-H20-Ch4 and S-D2O-CH4 systems from 200 to 340 °C at elevated pressures

Science.gov (United States)

Yuan, Shunda; Chou, I-Ming; Burruss, Robert A.

2013-01-01

Elemental sulfur, as a transient intermediate compound, by-product, or catalyst, plays significant roles in thermochemical sulfate reduction (TSR) reactions. However, the mechanisms of the reactions in S-H2O-hydrocarbons systems are not clear. To improve our understanding of reaction mechanisms, we conducted a series of experiments between 200 and 340 °C for S-H2O-CH4, S-D2O-CH4, and S-CH4-1m ZnBr2 systems in fused silica capillary capsules (FSCC). After a heating period ranging from 24 to 2160 hours (hrs), the quenched samples were analyzed by Raman spectroscopy. Combined with the in situ Raman spectra collected at high temperatures and pressures in the S-H2O and S-H2O-CH4 systems, our results showed that (1) the disproportionation of sulfur in the S-H2O-CH4 system occurred at temperatures above 200 °C and produced H2S, SO42-, and possibly trace amount of HSO4-; (2) sulfate (and bisulfate), in the presence of sulfur, can be reduced by methane between 250 and 340 °C to produce CO2 and H2S, and these TSR temperatures are much closer to those of the natural system (2O-CH4 system may take place simultaneously, with TSR being favored at higher temperatures; and (4) in the system S-D2O-CH4, both TSR and the competitive disproportionation reactions occurred simultaneously at temperatures above 300 °C, but these reactions were very slow at lower temperatures. Our observation of methane reaction at 250 °C in a laboratory time scale suggests that, in a geologic time scale, methane may be destroyed by TSR reactions at temperatures > 200 °C that can be reached by deep drilling for hydrocarbon resources.

Methane Flux and Authigenic Carbonate in Shallow Sediments Overlying Methane Hydrate Bearing Strata in Alaminos Canyon, Gulf of Mexico

Directory of Open Access Journals (Sweden)

Joseph P. Smith

2014-09-01

Full Text Available In June 2007 sediment cores were collected in Alaminos Canyon, Gulf of Mexico across a series of seismic data profiles indicating rapid transitions between the presence of methane hydrates and vertical gas flux. Vertical profiles of dissolved sulfate, chloride, calcium, magnesium, and dissolved inorganic carbon (DIC concentrations in porewaters, headspace methane, and solid phase carbonate concentrations were measured at each core location to investigate the cycling of methane-derived carbon in shallow sediments overlying the hydrate bearing strata. When integrated with stable carbon isotope ratios of DIC, geochemical results suggest a significant fraction of the methane flux at this site is cycled into the inorganic carbon pool. The incorporation of methane-derived carbon into dissolved and solid inorganic carbon phases represents a significant sink in local carbon cycling and plays a role in regulating the flux of methane to the overlying water column at Alaminos Canyon. Targeted, high-resolution geochemical characterization of the biogeochemical cycling of methane-derived carbon in shallow sediments overlying hydrate bearing strata like those in Alaminos Canyon is critical to quantifying methane flux and estimating methane hydrate distributions in gas hydrate bearing marine sediments.